Interview with Warren Anderson

0:00 It's quarter past two in the afternoon of the 10th of February, 2000. I'm speaking with Warren Anderson. So, mostly I just kind of wanted to learn more about work that you're doing these days. And I had a first question in mind, but since you just mentioned taking notes for one of the LIGO committees, or one of the LSE committees, I was going to add a further question that I had, which is how much of these kind of committee type of meetings, and I know a lot of teleconferencing goes on, and how much of that kind of thing you find yourself doing these days? So, well, okay, so let me address that question. You might want to just shut the door because the hallway is noisy sometimes. So since I've been here, I've been part of the LIGO Scientific Collaboration Group here on Bruce's Memorandum of Understanding. So, the particular, so the LSC is broken up into, I think, or has, I think, six committees right now. Three hardware committees and three software committees. And Bruce is the head of one of the software committees, the Astrophysical Source Identification and Signature Subgroup, which Alan came up with the acronym ASIS. So he came up with this name for it, so that he envisioned the acronym, I think, being pronounced ASES, which he sort of felt reflected the nature of our committee work. But at the end of the day, Bruce decided that it would be more appropriate to pronounce it ACEs. so anyways the UWM group in particular is heavily involved in ACES because Bruce is the head honcho and so it's easiest for him to just you know ask one of the local members here to do something that needs to be done and I'm the secretary of that this year

2:30 it was Ana Flanagan last year and in March it's going to be somebody else I don't know who yet but it's not going to be me because I find that Taking the notes is somewhat distracting during the meetings. I find that because I'm at the keyboard, I can't spend as much time thinking about the implications of what people are saying as much and trying to ask meaningful questions. But what I find really time-consuming is getting everything tidied up in such a way that it can be put on a web page. We have a web page for the group. So I post the minutes there. complete with links to, you know, when somebody says, oh, I've just posted my latest results on GRQC. You know, I look them up and link them and that sort of thing. So it just, it takes about a day after every meeting to get that done. But that's really my only, my only sort of administrative commitment to the LSC. So, and like I say, it's only for a year. Alan organizes the meetings for ACES Patrick is the ACES webmaster and administers the we have a major domo mailing group that he administers as well so there's lots of lots of sort of tasks involved and everybody pitches in but right now it's very UWM dominated And I think that's just been a matter of convenience, but Bruce is trying now to push it out into the community, into the other members of the community more, because it's just not a good thing for a group that involves many institutions to have most of its administration done in one group. How many institutions are there that are really quite active in ATSIS? So, there's, so Penn State has been quite active. Anna Flanagan at Cornell, Joe Romano's group down in Brownsville. There's a group at Florida State that's quite involved.

5:00 So, and that's, you know, those are just the ones that come immediately to mind. There's actually considerably more than that, including things like KIPP's group, which was once sort of the center of activity and now is kind of peripheral, but still, I mean, they, you know, So when Kip has something to say, it's still very important. It's just that his interests have moved somewhat towards quantum non-demolition interferometers and that sort of thing. He feels like there's enough people in this game already. I think his, as I understand it, his goal was always to push people into the voids. And once he gets the void filled, then he looks for the next void. He's like the field martian or something. Well, yeah. So that's, so yeah, the number of institutions probably is around, well, 10 to 15 that are quite active in ACEs. And how frequent are the meetings? um the meetings have been um not so frequently frequent lately and and i i think there's two reasons for that one is that uh one is that there hasn't been well i think they both boil down to essentially the same thing which is that we have gotten to the point where people need to deliver code that's written to the LIL specifications that you heard us talking about at the group meeting this morning, which is the official LIGO standard for software that's going to interface with its data analysis and acquisition systems. So right now, there's less to report because people are not trying to think up better algorithms to do detection or new types of sources we can look for, that sort of thing.

7:30 They're busy just trying to write code to the standard, and of course, that takes quite a while. meetings have tapered off. There'll be one next Tuesday, and that will be the first one in quite a while. But at one time, we were having about two meetings a month. And are they primarily teleconferences? Yeah, they were primarily teleconferences. We look, you know, when there's something that most people in the gravitational wave data analysis business will be at, like one of the LIGO scientific collaborations or one of the gravitational wave data analysis workshops or an Amaldi meeting or something like that, a LISA workshop, then there will often be attached to that an extra few days of meetings for the ACES group, for those people who are interested. But, so, basically, we meet in person two or three times a year, and then typically there'll be maybe twice or three times that many phone-run conferences. What did LALs get? LAL, the LIGO algorithm library or LSC algorithm library. So when people are writing code for this new standard, does that mostly mean at the moment rewriting old code that's been really rewritten? So it can mean either. So a lot of the stuff, so GRASP, of course, has huge amounts of routines written up to the standard for data analysis already. And so there is a considerable amount of work going into updating some of those things, the ones that are particularly useful. but I think for instance for the people who are more interested in writing diagnostics and characterization algorithms for the instruments not looking for sources just trying to figure out what's going on with the interferometer

10:00 I think there are quite a few things in that where People have not written code specific, you know, where sort of things that work for other sorts of experiments might be around, but nobody's written code with interferometers in mind. And so the first real attempt to write something for interferometer-type data will be done at the standard rather than upgrading something. So the data comes out of the interferometers in something called frames, which basically give you sort of a short window time snap of all the information coming out of the interferometer and all the different environmental channels and everything. And while GRASP is already set up to handle those and now it will be a matter of updating the GRASP code that handles those to the LAL standards, I think the detector characterization groups and probably a few of the data analysis groups of the source search groups won't have written anything that handles frames and so they'll be incorporating and they'll be incorporating that sort of technology in with the LAL. Right. The, I was just curious as to, well, how, I guess, previous to this LAL, the whole GRASP package and that form, a kind of standard that people were using. Yeah, so, I mean, it was a, there was sort of a, It was because Bruce was not very, you know, didn't say in order to be included in GRASP, your software has to have the following features. In fact, having written some stuff for Grasp, I don't think Bruce actually looked at how it was written necessarily at all.

12:30 I mean, in my case, he might have, just because I was working for him, he wanted to see what was in there. But in general, I think, you know, if you sent him something, he would put it in, he'd maybe run it. So everything came as a set of routines with some example programs that used the routines to do something maybe interesting, maybe not interesting. But just gave a sort of a template of how the routines were supposed to be used and what they might be useful for. And so I think he'd run the example programs, make sure that, you know, there was no segmentation faults or anything like that. As long as it ran, it sort of got included in GRASP. But yeah, it's sort of, I think people in our group think of having written things, you know, to a GRASP standard, which just means it works. And now we're looking at upgrading it to the LAL standard, which is significantly more strenuous in its requirements. All functions must take exactly four arguments, which are structures, all data types. They've redefined all the data types. You don't use floats and ints anymore. You use real fours and real eights. So what's the main necessity for a higher level of standard? I mean, obviously, what were the problems that were being foreseen that were going to arise? So I'm not probably the ideal person to ask about this. The people down in the LIGO laboratory at Caltech, Kent Blackburn and Albert Lazariner, would have much better answers to this, I think. But essentially I imagine it was just things like somebody defining a global variable in their code at some point and then somebody else having a local variable with the same name that suddenly got changed by this other person's code

15:00 because he had had it as a global variable and that sort of thing. So, I mean, people are writing routines that will be called by other people's routines, and the stack could get quite large as far as the hierarchy of who's calling whom. And I think the general idea was just that unless you have some sort of standard so that you know what the other person has done in at least some general term, beforehand, that it's almost impossible to make sure that you're not going to do something in the piece of code that you write that may call his code or may be called by his code that won't conflict with what he's doing. I guess one thing I was thinking of, putting it more appropriately from your end as opposed to the people setting the standard, given the situation is it the situation at present that you know there already were big problems developing or foreseeable with the standard that GRASP had? No I don't think there was any problems with the standard it works so far there were problems with GRASP I mean you know I have on any you know on a few occasions done something with one of the GRASP routines that I thought and it didn't end up working perfectly, and I went in and found out what had happened with the routine, and it had not taken into account some possibility that I was actually implementing in my code in how it could, in the values it could be passed or something, and so it failed to work properly without any error messages or anything. But these things did occur. The grasp is at us still on a small enough scale that, you know, I can phone up somebody and say, I just tried to use your code. I ran into the following problem. Do you have any idea what's going on? Or I just figured out what's going on and, you know, you should probably check for such and such in the future.

17:30 But for instance, even the memory allocation statements in a lot of the code are not checked for their return. So if there's not enough memory on the computer to allocate that next array that you need for your FFT routine or whatever it is that you're writing, you'll get back a null pointer. And if you don't check to see if the pointer is null on return, you know you'll go ahead and and and try and access memory that's that's not available and get a segmentation fault and can take a while to track that down if you if you have to go through a lot of a lot of people's different routines before you figure out so so there were some small problems I don't think there was anything major yet, but I certainly understand why LIGO wants to have an overall standard for the software that they're going to implement. Sure. Especially, I suppose, if you have more and more people. I think the main problem is just that, you know, GRASP was a fairly confined effort in the sense that um there were lots of contributors but they were all people whose names i i would recognize and and who i could phone or or get in contact with easily and say you know yeah what's up with what's up with this or they could do the same for me and and and ligo i don't think could rely on having that as a model for what the what the software writing community would be like so Yeah. Nor would you want to. I mean, you don't want to be, you know, processing the data that's coming out, and you can barely process it in real time, and then somebody hasn't checked their memory allocation and is returning a null pointer, and the software analysis system is coming to a screeching halt. Well, from the other extreme, does it seem, you know, on the receiving end, as it were, of the new standard, that it's needlessly fussy? So, I'm definitely not the person to ask about this because of the people in this group, I think I have written the least LAL code, being none at this point.

20:00 But I hear that, actually, my feeling on this, just with that caveat that I haven't actually used it, It is not so much that the standards are draconian so much as that there are situations which have not been, which people are finding arise, which haven't been envisioned necessarily by the original committee who drafted the standards. and so they're finding that they can't accommodate these situations within the standard and they'd like to have the standard modified. And so this is leading to this conflicting set of requirements that on one hand you want something that's flexible so that it can change to meet new needs that are being discovered for it. On the other hand, you know, nobody wants to have the standard change after they've just finished writing 2,000 lines of code and have to go back and change the code to be realigned with how the standard has changed. Yeah, sure. So again, another question leading up on this, whether you have a feeling for it or not, general area is I'm trying to get a feel for whether it's the standard is mostly necessary, you know, having a standard is mostly necessary because you're going to have kind of a central code or, you know, that's been, say, mostly written, I don't know, by the LIGO lab or whatever, and then all of the other people involved are going to be writing ancillary bits that will hook on to that in a way, or whether, and they can all be relatively independent of each other as long as they all more or less work with the central one, or whether in fact, you know, it's actually necessary for all many bits or different bits of code written by many different people to actually work properly together. So I think the second model is the one that's currently being envisioned by people, but But it's a little bit difficult to figure out because I think the actual policies for distribution of, for how analysis tasks will be handled.

22:30 whether data will be farmed out to anybody who wants to run their own analysis looking for particular things or whether it will all have to be done at a central location. I think that's still somewhat fuzzy, although it seems to be coming down on the side of everybody doing it at a central location. So basically, you submit your software and a proposal to use it to LIGO, and they fit it into their system, and if the proposal is accepted, basically, sort of thing. So, from that point of view, it looks like it's probably going to be necessary that all these different, you know, that you have many people writing different little bits, but that it has to fit snugly into some predefined slot that's available for it. And you mentioned that up to now, say, working with Grasp and that kind of thing, where you have a fairly large number of contributors, but everyone knows each other to a greater lesser extent. So does that actually turn out to be a fairly smooth way to work at the level of the kind of software that you're writing here, that as long as you actually can just ring up somebody and check something, it's fairly easy to keep everything going together, or is that kind of fairly frustrating? No, I mean, the problems, so, I mean, especially being here, almost all the problems I've encountered, it hasn't even been a matter of ringing up somebody. It's been a matter of going down the hallway and saying, I just used your such and such routine and got this strange behavior. So, I think, I don't think that there's anything, I think it's been a very easy model to use for me.

25:00 I wouldn't want to speak to what the experience has been like, you know, at other places. But since there's such a critical mass of people here, as long as you're at the one side. because I ask the question because talking to a lot of the American Relative View people there certainly does seem to be a fairly I get the impression that there's a fairly big split between being physically in the one place where you really see somebody all the time and having to cooperate or collaborate with somebody who's somewhere else Right, so yeah, I think we're certainly shifting from one of those paradigms to the other. But we have the advantage of having the LIGO laboratory as sort of a central agency that can organize that kind of thing, whereas I'm not sure. I don't know that much about the numerical relativity community, but I'm not sure there's anybody who can say, you know, these are the standards we're going to implement, and if you're going to write software, Yeah, that's a different set of . Has there been much collaboration between the different groups within the LSE already? For instance, I gather that for doing code for hierarchical searches, that's sort of a responsibility that's split between here and CARD. Right. Does that mean much day-to-day thing, or is it still possible, even when you're working on broadly the same thing, to divide it up into? Right. So I think the experience here has been, and again, because I haven't been directly involved with it, Julian, for instance, might be a better person to consult. But my understanding has been that they basically, what Cardiff is going to provide is sort of the template spacing parts of the code. So, you know, how do you break up the parameter space for optimal? So what they're going to tell you is what templates need to be generated in a bank

27:30 and how many there will be, for instance. And so here they can write, they're writing code, you know, with some routine get template bank, which will take some arguments. and they probably have to agree on what are the relevant arguments but I think that's such a natural thing that it's not even necessary probably to consult on it to know what level of a hierarchical search you're at how deep you're going and what sort of ultimate overlap you're going to need so basically they're just writing code that will have some get template bank statement in it and then Cardiff will eventually supply a routine that that statement calls. But for the purposes right now, it's not too important. So first of all, I think this is the only source-searching algorithm that has been sort of divided up in this way. I think all the other ones have been more or less farmed out independently. And in this particular case, they've broken it up in such a way that there doesn't have to be that close collaboration. And in fact, I don't think there is, you know, I don't think they have weekly teleconferences trying to make sure that the organization on both sides is the same. I think it's more like, you know, an occasional email saying this is where we're at, where are you at, you know, basically. Just as an aside, that was kind of another comparison, I think, with the numerical relativity side where they don't seem to be as able to farm things out. And my impression is that part of the problem there is, you know, it's not so clear cut ahead of time how to solve a problem. so it's not such an easy job that's one of the things the model that's been followed here is actually kind of interesting in that what's happened is there was sort of a

30:00 the first step was somebody identified a source as being interesting Then somebody comes along and develops an algorithm which would be good for searching for that kind of source. Then somebody, usually the person who came up with the algorithm, implements it at sort of a functional grasp kind of level. And then finally we're at a stage now where really all the scientific work, if you like, has been done, and we just have the technical job of changing that into something that's going to work with the LIGO. But it's not nearly so much a sort of synergistic development of things as numerical relativity has. Well, to switch to a personal question, you were discussing yesterday in the process of looking for jobs and so on. You know, from what you spoke about, it sounds like you're just staying in the general area of this sort of field of gravitational waves and gravitational wave detection. Yeah, I'd like to spend, you know, at least half my time for most of my research career doing that, I think. So is that kind of personal preference because that's, you know, something you're enjoying right now, something that seems exciting? Or is it also, you know, because that's sort of in relativity terms where the jobs are, or accommodation? of those things um so i i was saying yesterday too that that um i was finding things like quantum so you know my phd is in quantum fields and curved backgrounds and in particular uh involved with thought experiments where you lower a box filled with some sort of quantized field towards a black hole and it turns out that the box will float above the black hole if you lower it sort of

32:30 in an adiabatic manner towards the black hole. At some point the quantum state inside the black hole develops negative energy and eventually the negative energy is sufficient that the net energy of the system is zero and so there is no longer any attraction of this zero energy object towards the black hole and it just floats above the horizon. Well this is a really cool idea and not my idea, it was originally Bill Unruh and Bob Wald's idea but I sort of extended it and that's the sort of thing that got me interested in gravitational physics in the first place is there are all these counterintuitive, amazing things that sort of stretch your imagination beyond what it might normally do. But at the same time, after working in that for quite a while, I started feeling like I was making statements about things that would never be tested in the laboratory. And in some sense, it's unfulfilling to just keep doing things that are, of which you're not, you can't get a firm grasp of what the relevance is. I mean, what exactly is the relevance of the fact that these things float above black holes when you'll never make one? You'll never make such an apparatus. And, you know, it's cool from a purely philosophical point of view. but not of any practical interest. And so I was looking for some way to get involved in things that had a more observational or experimental bent to them. And I think given my choice of all things that I could have done that would have involved that,

35:00 I might have looked at different things in sort of modeling astrophysics-y kind of things as an interest and whatnot. not but at the end of the day because gravitate you know because this is a very I think the gravitational community is about to is on the threshold of of entering into a new era the excitement of being part of that and the fact you know also obviously the fact that there are lots of opportunities to become involved at the ground floor was was probably what swayed me towards that rather than looking at explanations of why pulsars have glitches or that sort of thing. Interesting. Well, you mentioned also yesterday that what you've been working on the last couple of weeks is radiation reactions. So I was curious as to what you're doing in that line. Okay, so this is basically, so I gave a talk in Ireland on some stuff I was doing with Ana Flanagan. I don't know if you were there for that or... I was there, although right this minute I can't recollect what the detail of the talks. That's fine, I can explain that just so that you have some reference point. It's the same work as that. Adrian Ottewell has pointed out to us a way of doing a calculation that we were doing in a much easier manner, something that was 30 pages of calculation has become three pages of calculation. That's good. And not so much because it's a better way of doing it as because he just recognized that what we were doing was something that was already in the quantum field theory literature, so quantizing gravitons, basically, and said, well, you know, why go through all this calculation that you're doing when you can just sort of crib the results from the quantum field theory community?

37:30 So basically the idea is the following We know that it's easy to find the retarded Green's function For a gravitational field Easy might be a misnomer But we know at least in principle how to do it It's trivial But what we don't know is how to get the retarded part And so, sorry, not the retarded part, but the tail part. So for radiation reaction, it's the tail that's important. You calculate the retarded Green's function, you throw away the so-called direct piece that basically tells you about the cell field of the particle and only look at the so-called tail piece, which tells you about how the particle sourced itself in its past, but not at its present. And so the idea is that, and this was an idea that developed at the first, well, I think Alan Wiseman probably had it even before the first Capra Ranch meeting that was actually held at Kappa Ranch. But at that meeting, we discussed gravitational radiation reaction at some length in an even more informal way than we did in Ireland. And eventually there seemed to be some consensus towards this idea that what one should optimally do is in the zone near where the particle is now, that, so in the zone near where the particle is now, that's where you can use quantum field theory methods or known methods to write down the Green's function in what's called the Hadamard form. and once you've written something in Hadamard form you've basically divided it into two terms the retarded reads function into two terms one of which is the direct part and one of which is the tail part so you just throw away the direct part and you're done

40:00 but you can only do that basically in a normal neighborhood of the particle of the present position of the particle So that's great for getting rid of this divergence that would occur normally if you integrated the contribution of the retarded greens function right up to the particle because when you integrate it right up to the particle, there's still this direct part that's going to come in. But you can't do the things far away from the particle with that. neighborhood of the particle. But far away from the particle, the idea goes that you could just do a mode sum, and with some partial mode sum, you would, you know, if the mode sum converges quickly enough, with some partial mode sum, you could get most of the retarded Green's function. And because you're far away from the particle, you know, you're farther away from the particle now that you've moved outside the normal neighborhood, the direct part will not contribute so strongly. I mean, in fact, it actually vanishes, but in a partial mode, it won't completely vanish because it's only when you take the mode expansion of the entire direct piece that you find that it vanishes in the paths of the particle. Any partial mode sum will have some contribution from the direct piece and some contribution from the tail piece, but the idea is if you're far enough away from the particle, even a partial mode sum will be dominated by the tail piece and the direct piece, which you know has to vanish when you take the full mode sum, will be sufficiently small that it will create manageable errors so so the idea is just to break it into these two zones one where where you can deal with with the direct piece you know in a straightforward manner but have but can't extend it very far and another where you can extend it over almost the whole manifold, but you can't deal with the direct piece very well, at least in the vicinity of the particle. And these are complementary views, and you just match the, try and do

42:30 some matching of the solution in some buffer zone, and get an entire radiation reaction force from the distant history and the recent history by combining these. So that's what And when we were at Capra Ranch, people, you know, practically the last thing we did was somebody, people said, well, I'd be interested in working on this aspect. And somebody else said, I'd be interested in working on that aspect. And I had worked on Huygens Principle for my master's thesis, Huygens Principle and Curved Backgrounds. and that turned out to require some Hadamard, some basically putting the solution to the wave equation into a Hadamard form and then doing expansions, normal neighborhood expansions of pieces of it. So I thought, well, I've already got some background with that. doing near field, and Ana Flanagan had also said that he was interested in doing that part of the calculation, so basically we ended up teaming up out of the Capper Ranch thing to work on that, and then after Adrian saw our partial results in Ireland, he came up with an improvement to what we were doing, so this thing now is at the point where basically I'm checking my calculation one more time. I've got Adrian's calculation, and I'll make sure that our answers agree, and I'm going to be writing it up in the next few weeks and sending it off to my collaborators. So that part's pretty much done. And then there's another radiation reaction idea that Pat Brady had that I've been working on with him, but that's sort of on the back burner right now So he's got other things he needs to get out first, and of course he's teaching right now, so things go a little bit more slowly. So is this approach, especially with this labor-saving suggestion of Adrian's, looking very practical from a point of view?

45:00 Well, so the near-field part is very practical. Well, I shouldn't say that, actually. The problem is that you do, basically what you do is you do an expansion of the normal neighbourhood of the tailpiece. Should I interrupt for a second? How is the normal neighbourhood defined? Okay, the normal neighbourhood is the, so given a point on a manifold, the normal neighbourhood is the set of all points for which there is a unique geodesic connecting the central point, the point you started with, with the point in the neighborhood. So you take a point, and then the set of all the points that are connected to that point by a unique geodesic is the normal neighborhood. Okay. So what is that? So what is that? Is that like a neighborhood in which there's no... So it's like as far as you can go away from that point without encountering a caustic. Okay. Anyway, so go on. Okay, so... Okay. Now I forgot what the question was. Well, we were discussing how practical... Oh, how practical it is, right. So it's an expansion, and basically what it's an expansion in is the distance back that you're going from the present position of the particle along its world line. So we can... So it's three pages to calculate that second order in the distance from the particle and it turns out that at zeroth order there's no contribution and you would sort of expect that because you don't expect to get radiation reaction over a vanishingly small portion of the particle's trajectory and it turns out also that at first order it vanishes so there is no

47:30 there is no part of the radiation reaction force that increases linearly as you move from the particle's present position backwards. But there is a quadratic, there's a second order contribution, and presumably there will be higher order contributions as well. The second order contribution is three-page calculation. The third order contribution. We've basically looked at doing this problem in two parts. One is, can you tell what kind of terms exist? Basically, any terms in one of these normal neighborhood expansions will be constructed out of local properties in the space-time, or local quantities in the space-time and local quantities associated with the particle. And so, in a vacuum space-time, for instance, there are sufficiently few quantities that you can write down sort of... You could basically make a list of all the different coefficients to this distance part that could exist. Well, at each order, there's actually an infinite number of possible coefficients, but because you can just keep stacking, say, more and more vial tensors, contracting more and more vial tensors together to get some bigger and bigger coefficient, but at some point you start seeing that there's no way to stack another one on without it vanishing identically. So it limits the size by that kind of argument. So basically, you can construct a list of all the possible things that could appear as coefficients at a given order. And the order determines what the dimensionality of the coefficient is because the acceleration has got a dimension of 1 over length and the distance back has a dimension of length. So, for instance, at second order, you need something that relates 1 over length to a length squared. to have a 1 over length cubed dimension coefficient does. So you construct all the things that have dimension 1 over length cubed, and you find that there's only one thing that you can construct that doesn't vanish identically.

50:00 And then at the next order, at third order, so distance back cubed, you would be looking for something that had dimension 1 over length to the fourth, and you construct all the things there's eight, I think, of them. And that's as far as we've gone. You could, in principle, keep going, but the further you go, the more possibilities there are for constructing things of that dimensionality, and so the harder it is to check and see which ones vanish identically and which ones don't. But then there's still a matter of some overall numerical coefficient. so you know what the sort of geometric coefficient is but you don't know what numerical factor that comes into the expansion with and so for that you have to fall back on these quantum field theory techniques to expand the tail part and while you're doing that you can also check that only those sort of geometric quantities that you expected to be there actually do occur So what we've done is we've got a three-page calculation for the numerical coefficient and a very short argument for the geometric coefficient for the second-order term. For the third-order term, we've got a somewhat longer argument for geometric coefficients. Adrian apparently has produced some 20 or so pages of calculation for the numerical coefficient, but he actually had to extend results that were in the literature in order to do that. So how well is it working? The answer is it depends how many terms you need, and we don't know that yet. so if you if you need second order things are looking really good if you need third order things are looking pretty good if you have to go up to eighth order in order to to get something that matches well with this mode expansion further back then then then this is completely impractical so that's probably going to be the main criterion how much you need to match that's right and that That would be the criterion for the mode expansion, too, and that's, of course, the other part

52:30 of the calculation which I don't think anybody has gotten going well on yet. Alan was going to work on that, and I think he's sort of got some preliminary results in that direction, but I don't think he's really sort of stepped up to that plate for game day yet. He's sort of still at the warm-up stage for it. And so that's another, I mean, knowing what the radiation reaction from some part of the path is not so particularly interesting unless you have some way of finding the radiation reaction from the rest of the path. And so if Alan can't do the distant past of the world line with some reasonable number of terms in the mode expansion, then again we're going to be stuck. So things are looking good, but I wouldn't want to say that this is going to solve the radiation reaction problem or anything like that. Yeah, I think that's a good way of saying it. We're making progress, which is always an encouraging sign. So we haven't encountered the brick wall on this approach yet. But I always think of research like mining. I always think of research as an analogy of research as mining. You've got this big mountain in front of you, and you know that there's these gemstones hidden in it, you know, deep in the core somewhere. And so you pick a likely place, you start picking away, you come across some you know granite outcropping or something that's too hard and so you sort of have to veer off the path a little bit and hope you can get back on and then you eventually get where you're going and maybe you know there wasn't something where you expected it to be or maybe along the way you find some vein of something else that's even

55:00 better than what you were looking for it's not a bad metaphor it's not a bad metaphor and sometimes you just come up to a place where no matter what you try you can't get any deeper you still think there's something back there but you don't know how to get to it and it seems like radiation reaction has been one of those really well guarded gems at the center of the mountain where people have tried all sorts of different angles and had trouble you know, getting the result. I mean, there's been good success with getting the, getting sort of the formal form of the result, but actually saying the radiation reaction force on, you know, particle A on trajectory B in space-time C is this four vector. I mean, that's something that's been, that seems to have closed a lot of doors to people, so, which is why we have Capro Ranch talks coming from all sorts of different angles at it. Yeah, sure. Yeah, it's been a difficult one. Because when I was, started in Kip's group, the first thing he said for me to do was to look away and look at implementing this GALSA form, this paper long ago and I remember spending the whole first summer looking through this paper and deciding it was a crock that wasn't really going to be the way you wanted to do it at all and of course now, ten years later almost, everyone is still looking for everything and it is a much more hopeful sign that there are actually, I mean at the time that was about the only paper that existed so at least there are plenty of ideas now and people actually pushing them forward well and it's one of those things where you know you're getting you're getting sort of partial you know this I'd say when this paper is done it will be a partial result in the right direction Hughes has the circular orbits in Kerr that get you information, it's not clear that you can push that to more interesting cases, but at least it gives you some feeling for what's

57:30 going on. That's right. Yeah, that's another good point too, because what we decided way back then was, well, okay, let's go back and do this Schwarzfield case, you know, it's the same sort of general philosophy, Right. And Alan's got static charges outside of Schwartz-Trobe black holes and stuff. So everybody's sort of pushing at it, pushing in the boundaries from various angles. Whether anybody's going to reach the goal or not is not there. Well, another thing that we were talking about yesterday that was interesting, and that's something that I keep feeling I should get a handle on, it's kind of, one hesitates to ask people about sensitive issues, is this whole business of, that you were mentioning, kind of internal jealousies within the LSC and that kind of thing. Right. Well, I think, so basically, basically I think there's a number of factors that make this a much more political situation than I've ever been in before. One is that, obviously, there's a sort of a larger community involved than I've been involved in with Earth before, and all working towards a common goal. The goals are very specific. So the second thing is the goals are very specific. And so it's not a matter of, you know, research in general in the gravitational community has been, you know, well, I had this idea to do something and this other guy got to it first, but that's fine because I've been working on this other thing that's going to pan out. So, you know, there's enough there for everybody here because the goals are very well defined. I think there's much more an issue with, you know, if somebody gets recognition for that thing that I was working on, And that's one more substantial piece of all the interesting things there are gone.

1:00:00 And the third thing is simply that I think the stakes are higher. I mean, one of the things that attracted me to gravitational waves, as I was saying is the fact that this is a burgeoning young field and I think that the gravitational community in some sense is on the verge of having sort of a revolution in it in that we'll hopefully have strong field data soon that will provide very firm guidelines for directions for theory to push. also that will hopefully uncover new astrophysical phenomena that nobody knew about, you know, and open up the playing field for people to come up with speculation, you know, which gravitational physicists are really good at, that actually can be tested against the data. So I think that's going to be a new way that the gravitational wave community works. because because of that i think a lot of people feel that way because um that that this will be sort of a revolution and and and and this is someplace where you know conceivably uh there there will be uh books written about how how gravity changed and and and you know somebody will have to be central some people will have to be central figures in that story and so because that's such a big story to be a central figure in it and one that will gain you a lot of recognition, the stakes are high so the fact that the goals are narrow and the stakes are high and the community is large I think just leads to a much more political atmosphere than I'm used to and probably than most of us are used to. And it's interesting because this is not a new thing to physics. I think particle physicists and astronomer astrophysics people

1:02:30 have probably had things like this for a considerable amount of time. Sure. And probably lots of other physicists as well, but the ones that we're now coming into contact are the particle with, the gravitational communities coming in contact with, are the particle physicists and the astrophysicists. And they seem to be much more climatized, that kind of environment. But for us, I think it's sort of a new horizon. And so there seems to be some tensions involved at times with how things are going. And so I'm, in particular, I think there, so this is, this is, this I definitely want to know about if you're going to use it directly. But in particular, I think Sam, Finn, and Bruce have had some internal tension between them. And some of that has been quite overt. There's been emails exchanged recently through this mailing list for ASIS where Bruce has sent out a list of people who have taken on tasks that need to be completed and scheduled conferences, teleconferences for discussions about how these tasks are going and whether the milestones will be met. and Sam has sent out an email saying you've listed me in your last three emails you've listed me as being responsible or having taken on a certain task I told you several months ago that I was not going to be able to take on that task and please remove me from your list of people who have taken on tasks and Bruce has written back saying well no one else was taking on the task and I thought you might get interested in it again of some external conflict that you see, but I think there's been even more going on behind

1:05:00 the scenes. And so now I'm in the situation where I've been working with one of the people I'm going to be, I've accepted a job to work with the other party in the situation. So So I think it's a sign that things aren't too bad, that everybody seems to be quite happy that I'm going to be going from one group to the other. So obviously things are not too politicized, so politicized that you can't possibly take go to another group with them. Or you couldn't possibly be trusted if you came from the one group to be part of the other group. But, you know, that was, I think that was something that I, that is an issue that I'm going to be aware of in going from one group to another. Anyways, that there has been some tension in the past and that I have to keep my eyes open to make sure that I don't somehow end up in the middle of a future tension. Right. So it hadn't, you know, sort of general politicized aperture isn't enough to make things down most of the time? Yeah, well, it's hard to say how. So like I say, you know, a lot of it goes on sort of, well, what for me is behind the scenes. I think, you know, I'm a post-doc. I don't get to sit in on the places where the very weighty matters are discussed. But I think there has been certainly an uncomfortable amount for me of politicization. So, I think there are, to use another metaphor, I think that there are people in the sandbox who feel that others should be given the label, you know, does not play well with other children.

1:07:30 I was curious as to, if you had an impression over what kind of issues these sort of rivalries have tended to develop over, you know, for instance, I had the impression that the analysis of the 40-meter prototype data was a bone contention at one point, but I have no idea what the actual issue was. So, again, for me, the primary, the only issue that I know that arose from that, and actually I shouldn't even know, the only issue that I've heard rumors about arising from that, But, well, I guess it's one issue with maybe two parts. One is that I understand, although I've never heard Sam say it, but I've heard that he felt that he had made a significant contribution to how the data was analyzed, the statistical analysis in that paper, and felt that other people who were on the author list had made less of a contribution towards the end product and therefore felt that he had been slighted by not being included on the author list. um on the uh as a second part to that perhaps uh after that paper was published um a paper appeared by sam on the bulletin board saying that that this there was a that the statistical analysis that was done was not as did not put as strong limits on on the event rate in the galaxy what the goal of that paper was, as another statistical method might have done,

1:10:00 or another specific analysis would do, and outlined that. And there was some feeling here that, A, the 40-meter paper had been circulated quite substantially before it had been posted. And so if there was a problem with the statistical analysis, they would have appreciated having heard about it before they had published the paper. And secondly, that if there was going to be some criticism of the analysis that had been done, or at least some statement that there was a better way of doing it, that in a community like the LIGO Scientific Collaboration, they would have expected to have been given advance warning and been allowed to discuss the results with SAM before they came into their office and looked at GRQC and found that there was a paper there. So the net result of that, I think, has been quite positive, or at least has the potential to be quite positive because the result right now is still uncertain. But I think what happened after that was that the group here contacted Sam about the paper and in specific Patrick, Jolien, and Alan and discussed Sam's ideas and their ideas back and forth and it looks like, so there's a manuscript right now that's got all four people as authors with sort of an expanded discussion of how these statistical analyses should be done. That's gone back and forth a few times,

1:12:30 and neither side has been particularly happy with the drafts that the other side has put out, but at least there's communication back and forth. So that could all work out quite well, But this is the kind of thing that seems to be... So these are the kind of issues that seem to be arising in the community. Right. Yeah, so as you say, friends on the one hand, who author lists her perennial book contention. Right. And in fact, that's, you know, LIGO eventually will... So... There was an authorship policy paper passed around a couple of years ago as sort of a starting place to discuss the situation of authorship. I think there is a policy now. I haven't seen a final draft of a paper about it, but that just might be because I haven't read the right things. But apparently there is some group called the LIGO-1 Collaboration, assist people in the LIGO laboratory, in other members of the LIGO scientific collaboration. And it's essentially meant to be a list that encompasses all the people who have made contributions, significant contributions, to getting the initial phase of LIGO working. So all the instrumental people who did work on the instrument itself, on developing new technologies for the instrument as well as the data analysis people and the detector characterization people, everybody who will have made a significant contribution. And apparently everybody who falls on this LIGO 1 collaboration list will be included on all publications that come out of LIGO about data. But this particular paper, which involved LIGO data, data from the 40-meter prototype, was sort of, in some sense, preceded that policy. And so there was a lot of, or I shouldn't say there was a lot of, there was some uncertainty in exactly how that should work.

1:15:00 And I should mention that, in fairness to Bruce, I think what happened at one point was that the paper was posted and made known to all the members of the LSC, and anybody who felt that they should have been included on the author list but weren't. And I have to admit that I think Bruce in particular was thinking about the experimentalists who had been involved with the 40-meter data that he might not have known about. But anybody who felt that they should have been included but weren't, and anybody whose name was on there and didn't want to be associated with it, were given the opportunity to make that known. And I'm sure Bruce had no problem with taking names of people off who didn't want to have their name on it. I'm not sure what his policy was for including names that, from people who, I mean, you know, I don't think you could, I don't think you could just, well, maybe you could. I'm not sure if you, you know, if somebody who he had never, never heard of before, nor had anybody else ever heard of before, could just say, yeah, I'd like to be an author on that, But you might have had to actually, you know, at least mention what your contribution was. Sure. But... It certainly was an effort to make it as inclusive as possible. Yeah, I think there was an effort to make it as inclusive as possible, so... Well, it's very interesting for me to get the background. And actually, Alan was saying to me yesterday, or did I have any gems of wisdom to impart from studying, say, the Grand Challenge people and things like that, and for what it's worth, they went through, I think, tremendous eruptions along similar lines, and I think much worse probably. So, and I did, except I can't say any details because I sworn to secrecy, but there was a case in that instance, without giving anything away, of a people, of somebody going as a postdoc from one group to another where there was a certain amount of rivalry, and there being a very uncomfortable situation, I think.

1:17:30 but the good news is that in that instance probably everyone could have been forewarned that there was going to be a problem because when this person went from one group to the other the group he was going from was telling him not to impart any information about certain topics of information in the new group so I guess assuming you're not being told anything like that I don't think there's I actually don't feel I mean, I feel that I do have to be aware that there's a situation where I could potentially end up sort of with divided loyalties and sort of caught in the middle of someplace that I don't want to be. I don't feel that there's any pressure from outside to get myself in trouble. I just feel that I have to watch that I don't get myself in trouble all by myself. But in fact, I think everybody in my case has thought that things were great, that this was a great idea. And I'm also a little bit aware that if I'm willing to take a little bit of risk about getting caught in the middle, that I can also, you know, perhaps provide a conduit between the two groups so that things are not as, so that, you know, so that each side does hear the other's point of view and there's not this sort of uncomfortable. But, you know, I mean, it would be a difficult situation for me instance, I had been at Penn State when Sam was writing a paper on criticizing the, or I shouldn't really use the word criticizing because he didn't say that what they had done

1:20:00 was wrong. All he said was there was a different way of doing it that would give better results. But, you know, had he given a seminar about that at Penn State or talked to me about it and then said, you know, but you can't say anything to the Milwaukee group about it, that would have been an uncomfortable situation for me because the people here are, I mean, in one particular case, Patrick is, you know, we went to grad school together. He was my best man at my wedding, so he's one of my closest friends, and that would have been an extremely difficult situation. Yeah, no, you can see these difficult situations arising, but as you say, the dynamic between the various groups obviously is relatively healthy if, you know, if you do have collaborative efforts still on. Right. Well, I think at the end of the day, you know, there's still, I mean, there is jockeying for position. ways about that you know everybody would like to be doing the most important things get the most recognition you know have their name appear high up on the list of of people who made this all work and given that there's been you know pretty much since before I got involved talk about about the fact that there could be Nobel Prizes involved with the first detection of gravitational waves. You know, you can see why there's this need to try and stay in the limelight as much as possible. But I think at the end of the day, everybody does realize that there's not going to be a limelight the job gets done. Right now, I don't know how anyone else feels, but I feel like things are rushing along at a crazy pace. The people who are constructing the instruments are making progress at a much greater rate than the people who are designing the software to operate

1:22:30 with it, and it's almost a little overwhelming, you know, the amount that the data analysis people need to get done in the next little while. And so, so, you're really being put under the hammer by the experimenters in that sense that they're setting up fast pace. Yeah, well, they're not doing anything that they didn't say they were going to do. I mean, they're not pushing ahead of schedule or anything, but I think, you know, just, again, all this gravitational theorists who are used to working at our own pace are maybe not used to getting things going. and I don't know that we're behind or anything. It's just that this sort of external pressure to have such and such done by a certain time is kind of a bit unusual. Usually it's self-imposed pressure. Oh, I better get that paper out before I write my next grant proposal or I better get that paper out before I look for the next postdoc or whatever it is. But in this case, it's, you've got to get this done before the detector goes on. Um, but at the same time, the, um, at the same, well, I suppose given the, um, I mean my impression is, well, I suppose to begin with, you know, actually when I started in Kipp's group, the, uh, one of the very first group meetings I was at, he came out with a list of stuff that, this is what we ought to do, the last three minutes paper. So, previous to that, you know, there was no group, previous to around that time, there was no group working on closely LIGO-related issues. And for a long time there was really Kipps Group and the Cardiff Group, say. And then in recent years it's been here and Cardiff and, you know, a couple of other places. Given the amount of work as you see it is the the amount of people who've been working up to now with that you know if they all continue flat out in the next year or two will that sort of suffice or do you think it has to be you know more and more people have to come in I don't know but we might need a little bit more I think

1:25:00 Things are fairly well in hand as far as doing it. The only thing is how much the deadlines will slide. I mean, I think we have the manpower to do it, but there's also another issue that's unique in my experience in the gravity community to this particular project, which is that, for instance, right now, the work that needs to be done is, so there's two issues. One is that I think people would have to work pretty much all out to get it done. And so if you happen to get, you know, happen to have an interesting thought on black hole entropy or radiation reaction or whatever, you know, I've been so far in a position where where I've been able to sort of barter that I can spend half my time doing other things. Ideally, for the project, I should be spending all my time doing data analysis. But, so, that's one thing. The other thing is that, so people don't tend to do, so people don't tend to, you know, So, for instance, Aina continues to write papers about various other things as well as data analysis. And I don't think you could stop him from doing that. So that's one of the issues. The other is that we're at a point now where, like I said, a lot of the, you know, even designing data analysis algorithms is somewhat technical and less scientific. compared to what we're used to but but right now we're talking about specific implementations of the algorithms which is very technical and so uh as a postdoc or a grad student it's it's hard to see it's a it will be a change in paradigm uh to have people get recognition for doing for you know writing software that does what needs to be done even in the face of the fact that it might not be publishable

1:27:30 it's not like you've come up with anything new you've just written some code that does something that somebody else wrote a paper about and so I don't know if that recognition is going to come people will still feel the need to try and make sure that they've got some minimum number of publications coming out every year. I still feel that pressure. And, for instance, a lot of the jobs that I'm applying to, the tenure-track positions, are in Canada. Canada's not involved with LIGO. The universities there don't care that I spent the last two years developing the backbone of, not that I have, the last two years developing the backbone of LIGO data analysis but had got no publications out of it, all they'd see is no publications on my CV. They wouldn't care. They might get some letters of recommendation saying, this guy's a great software guru and has done this important work. I don't know how impressed they'd be by that. I mean, what they want is somebody who's going to publish papers. Yeah, sure. So that's still a concern to me. And so the idea of throwing myself wholeheartedly into LIGO is a little bit daunting because what's that going to do to my career in the future? And I think it's even more of an issue for grad students, although maybe not so much at this point. Maybe we're developing enough of a gravitational wave circuit now, of a data analysis circuit that people can go from here to Penn State to Brownsville to AEI, Cardiff. By that time, if you're not done post-docing, you'll wish you were. Sure, but as you say, when you want to get a permanent job, it's a different way. Yeah. So it's a, it's a, you know, these are sort of new, new angles that, that, that people are having to figure out as they go along. And I have to say, I was interviewing at LIGO a couple weeks ago, and one of my main concerns about interviewing there was, you know, as much as the LSC in general needs manpower to devote itself to relatively intellectually poor and unrecognized tasks,

1:30:00 um LIGO is probably in in a great much greater need of that kind of thing and and uh you know one of my great fears about about um the a potential offer from LIGO was will I be able to actually pursue other things that will lead to publications or will I be spending all my time in their basement in Livingston, you know, programming 10,000 lines of code per year into some data analysis workstation, and they seem to be somewhat aware of this issue and encouraging people to take advantage of, especially at Caltech and MIT, the people who they hired to go to those places, taking advantage of the fact that you're part of a vibrant research institution and trying to spread tendrils into other things. So they're aware of the problem? Yeah, they're aware of it, and they did have encouragement. At the end of the day, it was not clear to me whether or not they would feel... I guess I had this concern that although they might genuinely want to promote this sort of idea that the pressures to get things done in time would just eventually overwhelm any good intentions. Sure. Well, it's certainly a pretty true worry to have. I can certainly say, from my own point of view, that you hear a great deal about this buzzword multidisciplinarity, and so you might think that somebody in my position would be really in a good spot to take advantage of that. But what you usually find out is that people talk about multidisciplinarity, and then in the next breath they say, yeah, but we really wish you just did the one thing. just concentrate couldn't you be multidisciplinary in just the one discipline yeah you seem to it's nice to have somebody

1:32:30 with such a diverse background but you don't seem to be publishing that many physics papers So anyway, the upshot is it certainly would be nice to have more bodies around the place to take on all of these. Yeah, I certainly, people have asked me in the last year or so, it seems like everybody's getting involved in LIGO, is there still room for people to get involved? And I think there's lots of room for people to get involved, especially if you want to get involved in, you know, sort of in a 50-50 capacity with something else. But I really feel like I've got the best of all possible worlds right now because I do get, you know, I get to do the floating boxes and the coding and, you know, I get to be part of LIGO, but I don't have to, you know, lay my life on the LIGO altar and hope for the best. And given that, as you say, it seems to have been possible in this instance to sort of divide up the task, Probably, you know, if you did absorb, if the Aussie was lucky and hordes of people poved in the view to help out with the task, it would probably not be in a terribly difficult manner assimilating them in some sense. Right. I think, actually, because I've been looking for jobs recently, I've had to, you know, for the first time in my life, write sort of research and teaching proposals. and one of the statements that I made so I had some of the more senior people here take a look at what I had written and one statement that I made in particular really caught people's eyes and they actually encouraged me to move it to the very front of my research proposal And that was that LIGO data analysis research is ideal for graduate students because it exposes them to an international community of people, puts them on the cutting edge of one of the most exciting experiments around these days,

1:35:00 and requires relatively little initial knowledge to get involved in. I mean, the learning curve to do data analysis is not huge. You just, you know, you have to understand Fourier transforms and various things. But it's not like getting involved in string theory where, you know, I'd probably have to drop out of all the other things I do and study string theory for two years in order to get up to the speed where I could publish something that anybody cared about. That's a good point. So I really think that the opportunities right now are huge. The effort is small. The payback is large. Yeah, that's a good point. Part of a generally good outlook. Well, thanks very much. No problem.