Interview with Nils Andersson

0:00 How many mini-discs do you fill up in a day, then? A fair few, and I'm going through loads of mini-discs at the moment because I'm making copies of everything that I've done, which is taking me a long while to get around to because I only have one mini-disc player. But it's an obvious thing to do since it's fun to spend so much time and other people's time making the damn things in the first place. You don't want to lose it always. So what do you do with it after you tape them? Do you sort of transcribe them in some sense as well? that's right what I've done up to now is I make partial transcripts a combination of notes and transcripts that is I go through it and I make notes and then actually transcribe bits that I think I would want to see written down I think I have a little bit of money now so I'm actually going to try and get somebody to transcribe them for me, a few of them anyway professionally but I think that's a difficult problem because of course they're going to hear all of these arcane relativity terms and not know what to quite do with them. That is the difficult thing. That's why I find it intriguing, absolutely intriguing for someone to do it. It's very interesting. I haven't been following a lot with Harry's stuff, but I think it's really interesting. Yeah. And it's very funny to read a description of your subject, if you like, different language with a different intention just say oh that's peculiar is that the way that it was yeah yeah it's quite it is interesting yeah and i i quite enjoy reading some of harris papers just for that reason that it gives an interesting viewpoint um i think he does a good job too of getting you know of describing something that's really there i mean it's recognizable to somebody who's been there, I think, at the same time. Anyway, so I'd better speak to my usual incantation and say that it's the 23rd of February 2000 at 3 o'clock and I'm speaking with Niels Anderson. We're going to see if he's changed his mind for two hours. Quick test. Well, one of the things I was interested in talking about is this, which is something we've already talked about a bit off the air, as it were, but about this European network that's being set up in the American Relativity field.

2:30 So, and just for the purposes of the tape recorder, you were saying, you gave me a list earlier of the groups that are involved. Okay, so, taking the risk of being wrong. That's okay. It's us. Southampton, Portsmouth, Paris, Jena, the Potsdam-Golm AEI, Trieste, the Cesar in Trieste, Rome and Thessaloniki, and then in Spain, Palma and Valencia. I think there should be ten, but I'm not. I have Rome, Thessaloniki, Palma, Valencia, Southampton, Portsmouth, Paris, Potsdam, I'm confused, it's probably not very good, is it? Spain, England, France, Germany. Maybe it's just nine then. One, two, three, four, five. Oh, there's just nine. Okay. Four, five. Trieste that's number 10 okay so that's a big group that's even in terms of number of places it's similar actually to the Grand Challenge I think yes but it's different in the sense that we are not funded mainly to work on one big project I mean the project is like an umbrella which is gravitational wave sources in a way but we're not funded to say that we're going to collide black holes and everyone is going to be happy and do it together the focus here is on

5:00 you know this European Union mobility of research and young researchers so the idea is that you have number of students and postdocs that move from one European country to get a job or take up a studentship in another European country. And then it's all tied together by the research network. So in that sense the focus is very much on the students and postdocs not very much at all on things like computing resources or anything like that. We don't get hardly any money at all for those kinds of things. It's very much for the postdocs. I suppose one could argue that it's quite a good model in the sense that one of the impressions I get looking at the history of GR, which always was a field with only a few groups, is how much cross-fertilization went on between groups and postdocs moving. Yes, I think that's right. I think this is potentially could be very, very good indeed, certainly for European relativists. The problem, of course, is that it's completely out of the normal scale. I think if you start adding up how many postdocs exist outside, say, Potsdam right now in Europe, it's probably not going to be There's certainly not going to be an order of magnitude larger than this. It's going to be this order of magnitude. So what we're talking about, I think, is almost doubling the numbers. And so the obvious logistical problems are, you know, where do we find the candidates? And that's where today, I mean, that's where we're sitting. we have some very strong applicants but we don't have enough of them to sort of be able to have a proper selection process I think at the moment if we were to have a discussion it's going to be more like a tug of war saying well yeah you want that guy but I want that guy too so it's going to be interesting to see in the next couple of days what emerges I think some lateral creative thinking is in order now we'll see

7:30 well obviously as you say any time you make such a big jump in the numbers especially since you have to choose Europeans I think that's another thing it's obvious the postdoc circuit in Europe is so small compared to the American one. If we were to include Americans here, we would probably have had five times as many applicants easily. Actually, I think it's interesting. You can compare Carsten's postdoc that was advertised at the same time. He had for that one job, 21 applicants all to come here and we had for the EU network, 14 so there's 14 applicants for 7 jobs, and 21 for 1 and 21 is a good number for Europe but it's a very small number for it if it were an American postal so the scales are just completely different one has to sort of understand that so I think actually people are being too optimistic about the network being you know attracting a huge number of people and we we were worried about it several people were worried about it a long time ago but that's not the reason being worried about it I think is not a reason to think that well we shouldn't do it it just makes the situation now a little bit tricky but sure whatever happens I mean the truth is that there are several reasons we could fill all the jobs with good candidates we just might have to change a little bit of what the idea is of what we're going to do in the various groups I mean but that's fine I think So there's enough flexibility there to tailor what groups will work on depending on who's available? Normally we have a research program but I which one always would have of course which is under to be controlled by the different partners in the network so for example we're part we're in control of one particular part of the numerical relativity bit and we're also partly in control of dynamics of rotating stars so these are two of the corner stones

10:00 that we're working towards sort of corner projects and then Potsdam is very much in charge of developing this thing called cactus and so on. Paris is in charge of post-Newtonian expansions for gravitational waves and stuff. So we have these different facets that are sort of sub-parts to the overall structure which people are in charge of normally. But I think if it were to turn out that we're not going to do this part, this guy at some other place is going to do it instead, that's not a problem at all. So, in terms of the overall goals of the network, as you were saying, it's not so closely tied to just one monolithic project, but it's very broadly... Basically, I would say that the project is actually not very ambitious at all, although, of course, now that you're getting on tape, I'll probably have to eat those words later on. But it's not very ambitious at all in the sense that the things we are committed to doing are things that we are working on anyway as groups. It doesn't mean that we would succeed in doing them in three years without these postdocs and students, right? But they are projects that we are very much interested in working on anyway. And it's not as if if we hadn't got this money, we would stop working on these things. it's more in the sense it's more in the way that given this money we can actually push these much harder and in that sense they're different from the grand challenges in the states where they sort of have a big project with one single goal more or less where they say that after six months you can review us and we're going to have reached this milestone will present this to you on that date. We haven't really said that. And also, the focus isn't exclusively, say, on numerical relativity, like the Paris group would be just looking at post-entoning expansions, and it's not in any way tied to what the Potsdam group are doing. Well, no, it's not tied strongly. Of course, all these things are tied together loosely

12:30 the Potsdam group if they want to do neutron star collisions they need post-Newtonian initial data or post-Newtonian wave extraction the exact way that they are tied I think they aren't really decided they will be hammered out I believe in a couple of meetings with all the participants where we actually sit down and talk plans are they what exactly out of these dreams you know which of these dreams are we going to be able to um to work on i mean sure and there's also i suppose if therefore some rooms or particular collaborations that develop within the context yeah which i suppose you'd expect depending on which postdocs go from where Yeah, that's right. Absolutely. So that's another factor, of course, in thinking about who's going to go where. So in Southampton, for instance, part of it will be the Cauchy characteristic matching approach to radiation. That's the, um, numerical part of it. And then also the things like gravitational waves for neutron stars. Which is, I mean, it is a key, obviously for me it's a key problem, but then I have funding, PPARC funding for E.ON for another two and a half years and that is going to be done in collaboration with the Thessaloniki group and they have they're going to have this EU postdoc plus one more from other funding sources. So that part of the project is in very good shape even without anyone in Southampton anyone else in Southampton is good. So you're not dependent on getting it? No, I'm not dependent on that at all. Of course there are candidates here that would be interesting to have, but that's a different story. So our main focus is to find someone

15:00 numerical. And so the Greek group, that's Coquitage. Yeah. Does that happen in Portsmouth? Are they sort of working on certain things? so Portsmouth is there because Philippus Papadopoulos moved to Portsmouth last year well this year actually no last, sorry, this academic year but last year in September so he was a part of it through the Potsdam he came out of Potsdam so he sort of got involved there and then we extended it to provide funding for one student So he is going to work on similar things in a way. I think maybe more tuned towards fluids, like hydrodynamics and things like that. And who's that, Jena? Jena is Gerhard Schaeffer. So that's likely to be rather post-Newtonian. Yeah, he's Ibanez, I think. So that's also relativistic hydrodynamics. He was one of them. He's assumed that Louis Bell. Might have been, yeah. I think his name is on there. There's necessarily Bell, D'Amour, Darwell, Ibanez. Oh, it could be, yes. It could be right, yeah. I think he's on there. Anyway, that's just the only place I've heard. I'm trying to get my thing on. in Trieste? Well, Trieste, of course, Dennis Sharma used to be in Trieste, but he died. So now in Trieste, it's pretty much John Miller, part-time, half-time in Oxford and half-time in Trieste. So their situation, I think, is a little bit uncertain, given that Dennis Sharma was such a strong character, and now without that sort of leader figure, it's hard to say what will happen to that part of the because it's very much an astrophysics institute with a few people doing relativity and it's hard to see to say right now what will happen if they're going to sort of downscale

17:30 on the relativity or not and then who's that wrong? Valeria Ferrari and so there's also money for people to visit quite a lot of networking money as they call it travel so you mentioned that there were two previous bids for a network that failed there just seemed to be the way the third one was written or was it just sort of I was only involved in this one the last one but in doing that in being involved it was written basically last spring May, June and when we started looking at it you know you look at the actual writing not so much the science that they promised to do or anything like that but the actual writing was appalling and it was not very convincing at all and so i think the only difference the difference between being almost successful but failing which is what the situation was for the first two um and this one which was almost unsuccessful but succeeding the difference was simply that there were different people writing it, mainly Ed Seidel coordinated it and me and Costas wrote large chunks of it and I think that did make a difference in the presentation and I think in particular what was important was Ed's vast experience of getting the Grand Challenge money basically knowing which buttons to tweak to make it look nice. You know what I mean. How do we get the big money, not just pocket change? So I think that experience is crucial. And obviously, I mean, for small research groups, that is a difficult thing.

20:00 is what experience do we have in getting millions of whatever the currency might be except the Italians oh the Italians or the Indians no the Indians never get a million even if it's not worth anything so I think that was a subtle difference but it shifted it since Seidel had the experience of being part of these That was a huge benefit to this. So actually, is there a sense in which the network could be sort of a big center of Potsdam with the other groups sort of orbiting around it, or is it probably not likely to say? Well, I think you could rephrase that question and ask, is there any way that that's not going to happen? Right. I don't know the answer I think it would be very unfortunate if that were to be the case but I think from a practical point of view it's going to be true that the small groups are the ones that really benefit from this because we are the ones that for us, one more postdoc makes a huge difference there's one more person in a group that's smaller than say 10 whereas in Potsdam postdoc, well there's one more postdoc in an institute that is topping 50 it's not the same scale for us this is life or death kind of thing, we're almost a critical whereas for them it's not a big deal so in that sense I think this is more important for the smaller groups whether it's going to be everyone just being a little satellite to Potsdam as far as practical matters go on I really don't know. It's hard to say, isn't it? Of course, maybe not, at least for many of the groups, since, as you say, what they're interested in is quite diverse. So, for instance, if you're interested in power modes or post-intuitive expansions, then you might have your own collaborations.

22:30 well that don't necessarily involve Potsdam I think that's the thing personally I don't mind if Potsdam were to be the centrepiece and everyone else were to be playing the second fiddle doesn't matter at all I think as long as the moment when I will start getting a bit queasy is the moment when the suggestions that are going to come that oh there is an important result coming out of this group we all write the paper with everyone in the network as author, that's the moment when I will think that we've become a little bit too much like the Grand Challenges. Right, I don't think they have big problems that way. Well but you were not in one of the groups either. I can tell you from within the WashU group that there were people there that were very unhappy with that. I mean there were people like from the NCSA and then Paul Walker for example when he left there were two reasons I think that he left Relativity to going to Wall Street, one was money which is obvious very talented programmer why not the second one that he was seriously pissed off with the way that things were being done and that basically dated back to, you've probably seen it, there's a science article from the Grand Challenge about the pair of pants black hole collision that was entirely Paul's work and he was not even an author on the paper he was told by, or basically it was decreed from the top within the Grand Challenge that this was going to be a paper with only the principal investigators and when you see things like that I think it is I find it scary you know in that kind of collaboration that people can just say well look I will decide who did this work for posterity I didn't like that at all and we had several discussions in the WashU group because And the attitude that was taken there, again from sort of the top, was that every group paper should be in alphabetical order, no matter who did the work.

25:00 And that's, well, I'm fine if you're like me, so you'll always end up first. you know if you're talking about a graduate student who presents his thesis work that was done more or less with him doing all the work and maybe the supervisor being a part of it to then write it up and have to put ten names on the paper and figuring out that oh whoops my surname begins with a W that's a bit unfortunate so I'm last author on my own I think that if you look at the way that relativity was done as you said, small groups of people, small collaborations friends working together, suddenly having this almost experimental physics strategy where everyone in a screwdriver authors the paper and the author list is longer than the paper itself that's a large step and I think a lot of people were not very happy when these groups started doing that. I mean, if it is genuinely sort of the centerpiece of the grand challenge, you know, we have collided black holes, yes, aren't we good, then fine, it's just a press release, right? But when it comes down to who actually did the work and who should get the detailed credit for the clever idea or something like that, I think it's not a good sign when, say, for their work by being shoved aside or being put into if they did all the work, actual work if they put in an author list with 10, 15 other people who did nothing I don't like it at all, so if we ever get to that point I'll be very unhappy So actually based on had you been at Wash U and seen some of the dynamics, internal dynamics the Grand Challenge would you actually feel that there's more potential for conflict over issues of, you know, authorship and so on than, say, just over resources and money? I mean, is it actually not such a hard job to divide up the postdocs, as it were, as it is to divide up the credit? Well, I probably reserve judgment on both guys.

27:30 I think I was in a fortunate position at WashU because I was not a member of the numerical group, as it were, although I could have been if I wanted to. Sometimes it's very useful to opt, to stand on the sidelines and just sort of be a bit facetious about everything that's going on. But I do think that one has to be very careful about dividing and giving credit in science, especially when you're dealing in the American system. The European is slightly different, but not much. you have to make sure that your students given, I mean they're given very small financial rewards and they have to work like crazy to get a thesis out the pressure is really on, it's a difficult thing to do if you on top of that make them unhappy and not give them credit for things they actually have done I think then you will almost rob them of everything they could have rights to claims in my view that's very very important you know what it's like it's a sort of self esteem to make people aware of the fact that you do appreciate what they're doing you appreciate the fact that they work hard and you appreciate they get and I don't think it probably naively but I don't think it ought to be that difficult I mean for example if some students work it doesn't matter alphabetical order on a paper if you have 15 authors then fine but put this guy first why not what's so difficult about that at one level I don't think the number of authors really matter but I think it is important for example if Ian and all the rest of us were to write a paper we probably will do on his thesis work where my input for example would be very small facilitating discussions and helping out in general then it would be was an Anderson Jones blah blah blah paper. It has to be a Jones et al.

30:00 Right. Sure. There's a subtle difference, but I think that sort of signals that, you know, that's you know, that the difference that is signaled by actually changing alphabetical order in our field is quite subtle. Well, I think it is. It's interesting. Not only that, funny enough, I was just discussing it with my wife this morning or yesterday, because the whole business of having a large number of collaborators, some of whom contributed tangentially because they did something, did a favour, as it were, and then of course you had the person who really did the work, so they're the first author, whereas like you, I come from this tradition where it's alphabetical order because it used to just always be the group of friends working together, and of course she was saying that, well, I could just never understand this alphabetical order business, what happens if, and of course but obviously there is a change in the field now where you get these bigger groups and then you have to ask the questions and then it will become who's number one ok so number one might be easy but number two, three, four, five as compared to six, seven, eight how do you rank people I can see that being difficult because we're dealing with people that have different ideas, perhaps, of themselves and their contributions and their importance. I mean, basically, well, you know the answer's better than I do, some possible answer's better than I do, why people do science. Why do we do this? Why punish yourself for no money, no respect in society, no rewards at all? Why would you want to do that? ten years and then what? I think that drives clearly if you want to be a scientist it's kind of a peculiar you have to have some personality quirk I think some ambition either it is an ambition to learn or it is an ambition to well just ambition ambition to contribute contribute to history whatever it is. And if you put a large number of people like that together, it's inevitable, I think, that there's going to be clashes, personality clashes, and stuff like that.

32:30 Yeah, sure. Something I've got to check, actually, it's funny that it's never dawned on me really until now, the last three minutes paper in Caltech, which was really right at the beginning that's an interesting example you end up with people being on papers for no very good reason I'm on that paper and in the actual paper that's published there's nothing to do with me originally I was in a couple of footnotes and then in the long process of getting it published I think they disappeared but somehow my name stayed in there nobody really cared but what interests me It started out in an early draft, and I don't know if I might still have it around somewhere, as Apostolatis at all, but it ended up as Cutler at all, because it was decided that Kurt, I guess, had made the biggest contribution or whatever. so I think there must have been because certainly in Kip's group it always used to be alphabetical or some type of thing so obviously it had to be it was decided in that case to depart from that practice I know several examples of similar things papers kind of meander along or maybe two papers being married into one and then some authors being dropped because they decide they don't want to be a part of it and then they come at a later stage it's always a bit of a circus I think it is difficult but I think it is important to be aware of the fact that people could have quite different opinions about how things should be done and I think if it were to come to a crunch happy to budge in any direction but it doesn't mean that I wouldn't have my own opinion of what would be fair but I don't know I think I just hope that this network is not going to be able to create what the grand challenges in the states have managed people that have decided they will never ever be able to work together I think that would be a bit unfortunate

35:00 I guess at the same time the Grand Challenge also seems to have in my distance impression created certain smaller fragments It's quite interesting to look at what happened to the various participants for example my impression was, say the Black Hole Grand Challenge Cornell came out of it almost weaker than what they went into it, whereas a place like Penn State came out of it with flying colors. Texas went into it pretty strong, but came out of it quite weak. I mean, my impression, of course. That's an interesting point. it's interesting if one could try to piece that together you know whose reputation was enhanced by this and whose was not if that's the purpose of the exercise I mean there's a different different story of course but I don't it's absolutely clear that not every group benefited maximally I think so yeah that's an interesting point and I suppose it could be a similar experience So at Potsdam are sort of both the numerical group and the relativistic astrophysics group, if you want a better term, involved in the network itself as it has? it's hard to say to be completely honest because the way it was done was we have a number of projects I think the relativistic astrophysics projects are very much what me, Costas Calcutas and Valeria Ferrari are working on in some shape or form and then there's the fluids you know the relativistic fluids things groups are doing. All of these overlap in some sense with interests of people at Potsdam, but there was no detailed discussion about who exactly in Potsdam would be involved in the day-to-day work of the network, apart from Ed. So in that sense, my impression is

37:30 is that the network is run from the Potsdam Numerical Relativity Group. But, I mean, hopefully other people there will take an interest as well. I would expect that. Is there much of any connection with the European actual detection detector groups? No. Not written into the strategy. So that means there's nothing formalized. think we would be foolish if we were not to take this as an opportunity because given that we have travel money etc to organize some joint events or to see to it that we take part in in their meetings in some shape or form because after all i mean we are getting close to actually having machines that are up and running yeah whether they will see anything. It's a different story. So I think it would be good if we could do that. And then what about with the groups interested in data analysis? Is that sort of, again, written into the network thing? No, but I think it would be natural to, again, it would be natural to work on a little bit on that, given that, say, Carstus-Cocatus has done some data analysis, in Potsdam, they've got a strong group, and Cardiff is very close to my connections. So I think we, again, it would be natural for us to discuss with these people. in fact that's I think there is a really urgent need for almost like a workshop where two questions are being asked one by Mr. Theory and one by Mr. Detector three questions and one by Mr. Detector the theory guys will say look what is it you need from me

40:00 what is it I have to provide you in order to convince you that a source is important. And the data analysis tells, says, well, what is it you want from me? That is, what is it I have to tell you about my data analysis, signal search tools and all that, in order to help you sort of tweak your models, put them in the right context? And the same for the detector person. What is it you want from me? I mean, what should I tell you about my machine, in order that you understand what we can and what we can't do? and I think even though there's been so many meetings the three communities still not the three but the detector analysis and the detector people obviously talk to each other but I think there's still a sort of cross communication between theorists and the detector people probably not within LIGO because they've got the LIGO science collaboration which includes both sides in a big way. But I think for the European detectors, it's, I don't know, for GEO, it's probably not fair to say that because they have their own data analysis and source people in Potsdam. But for people like me and this group and other groups in Europe, they aren't actually tied up with one of the detector collaborations. I think we are a bit on the fringe in that sense, Not necessarily, I think we should do something about that. Well, do you, you know, assuming the detectors do see something the anticipated being, you know, having a really dramatic influence on the kind of work that you do? Well, let me give you two answers. When they see an inspiring binary, subject which I've published one paper on and it wasn't very good I think the answer is no well I think whatever they say it will be very exciting because then we will certainly know to what extent some of the models if it does confirm some kind of calculation whether they actually work and that will be tremendously important right of course the moment when they see our modes then we will be very happy

42:30 or anything like that that would be absolutely it would also be quite surprising I think it was Ian that asked me the other week he said well so we've written this just written this paper where we say well it could work like this mechanism, speculation, speculation hand waving, hand waving and there is a number coming out and isn't it beautiful and then he said to me I have to ask you sometimes you can do a theoretical piece of work get a result and it makes logical sense within your theory etc etc but then you can ask yourself well alright so my theory here says that gravitational waves are very weakly coupled to matter actually drive force a neutron star that spins you know many many hundred hertz so it revolves many hundred times per second it forces it to spin down to a fraction of that is that the way that it works? I think if you ask that question the answer has to be no because intuitively it just doesn't sound right but on the other hand it would be absolutely beautiful if it did work like that so why not? And just because it doesn't strike you as, oh, obviously. Because I don't think it does that. It's a bit counterintuitive. It doesn't have to be wrong. It's just that when you ask, well, does it really work like that? You know, are we going to be able to dig out the signal from an in-spiraling binary by using billions and billions of filters, matched filters, in a very noisy detector? it just sounds like an awesome task if you ask are we really going to be put your hand on your heart and say that we're going to be able to do it is it a dream or is it a distinct possibility and I think at the moment it's still somewhere in between and of course when they do see it that's when it changes completely that's when you know that you can do it So I think that psychologically is probably very important, no matter what you do, as long as it's in the right area.

45:00 Of course it might dispel some myths, like the myth that you need full 3D numerical relativity for LIGO. If they go away and detect something anyway, which they probably have to do, then you know, these papers just can't make those statements in papers anymore. For example, after they detect, I don't know what they will detect, but something, I don't know, oscillating cosmic strings or something. It's got nothing to do with any of the sources people normally talk about. It will be very hard to write papers like, inspiring compact binaries is one of the most promising sources for LIGO. Either it is then or it isn't, right? so I think it's going to be a very dramatic change but what I think will be very exciting if they start actually seeing things is how you know how accepted it gets I mean how easily will it be for people to accept it and is it going to be clear cut or is it going to be open to interpretations Sure. Well, given the history of the field, I suppose. Oh, given the history of the field, yes. I can certainly see that there may be a period of death and uncertainty. Well, so touching back on something, we mentioned this more earlier on. At what point do you see it possibly happening that the astrophysicists really start to pick up their ears and get interested in real estate? gravitational waves or just relativity. I think if we want to make the astrophysicists become interested in relativity or in gravitational waves, then detection has to provide more than just basically proving that our source modeling for, say, inspiring binaries is okay. Because I think you can legitimately make a claim that we more or less know that it is from the binary pulsar. I think what we would be able, need to do, is we need to be able to, say, probe inside neutron stars or inside supernovae

47:30 and provide some kind of information that is unique that they cannot possibly get in any other way but through gravitational waves. And I think that the field has the capacity of doing that with a little bit of luck. I mean, pulsations in stars, for example, certainly gives you a probe to the inside. the equation of state and many other things. And so I think if gravitational wave astronomy is to be a reality and be taken seriously, then that's what is required. If all we can do with gravitational wave detectors is log up a number of coalescing binaries per year, and maybe the odd supernova, without actually learning anything more about supernovae, people will do. It will be an enormous achievement, but it's not going to be a new branch of astronomy, if you see what I mean. Yeah. If the question had been will it take for astronomers to realize that they ought to learn relativity, I think that requires a different answer. Because I think they Seeing that now with the kilohertz QPOs in low-mass X-ray binaries, X-ray and radio signals. I mean, the numerous claims that we have huge black holes in galactic centers, etc. All these things basically point to saying that, look, if you want to understand the universe, you need to understand relativity or relativistic effects. so I think that's that's sort of a lower requirement than the other one so that's something that changes something gradually taking place I think that has changed I don't know if you thought about the following thing but ask yourself who believed in black holes who made statements like Cygnus X1

50:00 candidate 25 years ago? Well, the answer is relativists, right? Who would make that statement today? I think the answer is relativists. And in the meantime, astronomers used to say, well no that's ridiculous or well even if it's not very interesting and today astronomers, observational astronomers are the ones that they don't even talk about black hole candidates anymore nowadays Hubble Space Telescope sees a new black hole in that and that galaxy and I think that's an interesting change you know how where relativists it might be a black hole it used to be quite you know, almost a challenge now that is conservative so that's sort of the it's a very good point I've noticed that in myself but without really remarking on it just the way that you put it there because in recent years I have noticed astronomers talking about black holes and finding that I myself as you said, tend to be taking the conservative thing something to refer to it as a black hole candidate and you know I guess I've just never really gone to it the reason it's so disconcerting is that astronomers are now on the other side it's sort of like I was I thought about it a while ago and it was quite amusing and I was asked by someone from The Economist who was writing about this you know the CERN had discovered or managed to create this called gluon plasma so this guy thought we've got to write something about this but he didn't think it was very I shouldn't say that on tape but he didn't think it was very interesting it seemed so he wanted to write about the possibility of building stars out of quarks so he called me and he called some other people and then he asked one of his first questions was do you think it's fair to say that strange stars or quark stars have now replaced black holes as the sort of exotic object in people's imagination I said I don't think most people have heard of strange quark stars

52:30 and I think he was a bit disappointed when I said that and then I reflected on the same thing he wasn't particularly interested in that either but I think it is interesting the subtleties and how things change it's interesting to I mean because as a relativist we know perfectly well that we haven't seen the black hole I don't know if you looked at the I remember there was a talk a couple of years ago at one of the India conferences this guy showed these results for where they mapped, basically trying to map the motion of an accretion disc through certain oscillations etc Oh, it matches beautifully to an accretion disc. Look at this. And someone asked, yeah, but now the innermost point that you see, what is the distance from the center? And you say, oh, it's 10 to the 4 Schwarzschild radii. You know, a lot can happen in those 10 to the 4. And I just thought it was poignant because he made it very strong. at that point that was one of the best the strongest cases for a black hole the fact that they were still observing like well literally miles that's an interesting point and so I guess just continuing on the general theme I mean, what's the reaction of the sort of astrophysical community been to the discovery of this gravitational wave instability and are what's a neutral star? I mean, that's a vague question, but I mean, obviously I see the relativity end where people People are excited about it, you know, think it connects to astrophysics, possible source of gravitational waves and so on. So I was wondering whether the astrophysicists are enthusiastic, skeptical, indifferent, is it mass? I think there is a small number of astrophysicists who are encouragingly enthusiastic, or at

55:00 least positive about it. There is a large group that believe very strongly that our models are ridiculously simplified, which is true. I mean, that's absolutely true. But it's also true that we actually don't know how to, for example, I mean if you want to study a neutron star, you have to study an object with a large magnetic field, solid parts, sort of solid lattice exterior, super fluid superconducting interior, possibly with three quarks at the centre and all sorts of things have it spinning very fast and you have to do it in full relativity I'm sorry for using simplified models but actually no one has come you know, even taken the first steps towards studying those things so obviously we are looking at simplified things and extrapolating but if you come from two different directions one where you try to do like the relativists have traditionally tried to do I think detailed calculations and theoretical studies of things and you come you contrast that with the astrophysical modelling which sometimes is strong magnetic field I will just invent the dynamo effect that boosts the magnetic field I don't have to actually have a calculation that shows this, I can just put it there if you contrast those two approaches then there's going to be two traditions that could potentially clash and I think sometimes we've sort of seen that I think it's also true that When people have been... I mean, the strongest criticism, I think, have come from people that have their own agendas, where you have some other mechanism that you would like to work instead of this. And again, I think that we've actually been fairly... Certainly, we've tried to, in my work, in my collaborators' work, we've tried to

57:30 be very appreciative of the fact that other models other mechanisms might well be just as relevant or more relevant than this so my attitude is that just because we have something that we're excited about that might work, it doesn't mean that someone else's model doesn't work and in fact you know there's a big universe out there they could all be operating, why not unless you have a reason, some reason to argue that this can't work, so you can actually put some solid, put it to a solid test. Unless you have that, I don't think you should rule out anything. No, I think Ian's made this point earlier as well, and I think we have a lot to learn from the astrophysicists as far as what we should do, you know, to fit this into, available observations and data and how they think about things so that we can try to speak the same kind of language and maybe it works maybe it doesn't work at the moment I think it's premature to say either way but I mean it's clear that people are quite excited about it in fact I wish they weren't so excited about it at all I've been trying to write a review article for about three months now. It's very hard to write a review article with the intention of describing essentially everything that's been done when there are three papers coming out on the preprint server per week. And that was the stator for some time just before Christmas. And now there was a couple of weeks here that were a bit mad as well. It does make life a bit difficult for you. on the other I mean I'm not complaining for the benefit of your recording it was a bit it did make life a bit difficult it still does because I still haven't finished it and I just wish people could hold up for a couple of weeks give me a chance to get some inroads into the writing and then I can say well yeah okay I'll add a sentence about that but right now Are most of those papers written by Relativists or by Asher Husses or I think they're 50-50

1:00:00 See the Situation right now is very much We need Detailed calculations They will take Some time And effort Some of those are ongoing are working on, etc. Some other is such in trying to do it in full relativity and fast rotating stars. I don't know if anyone has actually made any progress at all on that. But of course that's what we need. So right now we're at this point where people are speculating about mechanisms and how they what effect they could have without actually knowing anything at all which is quite stimulating but could obviously be quite dangerous as well in the sense that we could be wildly optimistic or pessimistic because after all there's so many details that we don't know. So, we'll see. I can wait around and see. I'll just stop working right myself and see what happens. I don't know. So, should I actually go to this meeting? Oh, I'll forget about it. Until they come and pick me up. Can't be bothered. so I'm squeezing a couple of extra questions before they haul you away so the I'm still quite interested in this sort of culture clash when the astrophysicists do their modelling they tend to stick to Newtonian gravity exclusively do they do numerical modelling or is it just sort of as yet I mean, apart from sort of mode calculations, which is a numerical calculation, but it's not proper. It's like just an eigenvalue calculation in a way. It could be difficult, but it's not. There are no numerical models as far as how fluid pulsates and stuff like this. Very rare. Just now, I think groups are starting to work on that. That's one of the things that we will put the emphasis on at our end of the network. Trying to do that, trying to model things dynamically without several of the assumptions that one will do if you want to calculate just the mode frequencies and stuff like that.

1:02:30 Some of the simple mode characters. Because when you start looking at rotating stars, things do get a bit complicated for the standard kinds of calculations. I mean, the typical assumptions was that slow rotation, small perturbations, and several other assumptions that you put in, and then it's not always clear how these relate to each other. I mean, if this quantity is small, and that quantity is small, then is that a meaningful assumption? Does that approximation actually make sense, or are you throwing away the terms that you're trying to model. And I think the aim of going to sort of numerical evolutions, for example, or dynamical calculations for doing these things, which is a challenge, the aim of doing that is simply to be able to forget about the theoretical complexity of trying to do the standard kind of calculations I mean one has to be aware of the fact that there has not been a single calculation of modes of a relativistic star I mean in relativity of a rapidly rotating relativistic star so there are no such results and so then to say that there are no results for our modes is not very surprising There are no results, period. So there's a huge amount of work that remains to be done there. Of course, the difficulty is that it's conceptually difficult. We actually don't know how to do it. Right. Given that, say, 50% of the papers at the moment in this particular topic are from the Asheris there is something like that I was wondering if you think the relatives actually have an advantage in that if we argue that both sides

1:05:00 need to get to grips with the other side's body of knowledge and so on to really tackle the problem if the relatives being, I don't know, in some broad sense the despised minority have more of an I think we do, absolutely no doubt in my mind because if you go to the very core of this we're talking about a genuinely relativistic effect we're claiming that radiation reaction can under some circumstances drive the motion of a fluid unstable or drive certain motions in a fluid and affect the bulk properties of a rotating star that's a genuinely and in order if you want to do that proper it will not be sufficient to say well the quadrupole formula does this we actually have to look at things like back reaction issues in a detailed way and clearly if you want to do that you need to do it in relativity so I think we have a fantastic advantage because if the advantage that the astrophysicists have is that they might have a little bit better of an idea of the realistic equation of states and observations of x-ray systems and stuff like that and other kinds of physics that might operate that's easier, I believe maybe that's being a bit rude to them but I think that it's easier for us to incorporate without understanding it fully by picking it up from papers and previous models then what it is and then how it is for someone who doesn't know relativity proper or has a working expertise in relativity to actually model something that's so much at the heart of relativity like the back reaction problem which is enormously difficult so I think if you ask who is going to find the pot of gold if there is one at the centre of this then I think the relativists are the ones the honours is clearly on the relativists

1:07:30 maybe that's a better description I think the pressure is on to start working together with astrophysicists on these things. I'm just going to say collaboration. As long as they can learn to speak a common language and not insult each other in every single corner. do you suspect it would be a difficult business? Are the languages quite different? It's an interesting question because in the last century since I came here and I realised that starting up a teaching job at a point in your career when you have normally some research results that people are very interested in where you really should take it one year out and just do research, really. because at that point there were several interesting ideas that we could have followed up etc and then to start teaching and taking almost a full time job without research I said to myself well ok so I will not be able to do to follow up on all these research leads that's simply it I'm not going to be able to do that so what I'll do instead is I'll try to learn how this could fit into astrophysics because then I could do that by just reading papers in my spare time and thinking about how does this mechanism what does this mechanism do to that how does these observations affect or are there observations that could be relevant for this and stuff like that and so I've probably wasted a huge amount of time doing that it's quite entertaining and I think very good education and I think at the end of it I'm on the way towards being able to speak the language if you see what I mean and I think that is quite quite useful so I think it's not

1:10:00 but it does take some time and I think that the most difficult thing for every relativist as you said, we're a little bit of the minority that it is imperative that the astrophysicists as a community stop thinking about relativists as this lonely guy this single guy in his office doesn't really understand what's important, because that attitude is certainly still our thing. But if they were just to, I mean, and a lot of people don't have that attitude, but if the people that have that attitude were to stop doing that and just have proper communications with relativists that are working on these kinds of problems, and I'm sure Because it does seem as if, you know, they're too obvious. One of the things I looked at so far was the Wilson and Matthews controversy. And where you had a similar case where, well, you know, you had a result that people in one field had and where they were looking for reception for people in another field. And in that case, of course, the people in the other field were very skeptical. But anyway, you certainly had the thing, two factors that, well, for instance, as an example, would certainly have made it very difficult for the two sides to, for people from the two sides to collaborate about the calculations designed to find where the truth lay in that, on the one hand, they didn't speak the same language, so they found it difficult to talk to each other. And then on the other hand, as some people remarked, you know, the numerical people maybe were looked down a bit, looked down upon a dead thought, kind of pure relativity. And so I suppose those are at least two factors which, you know, have to be overcome for any successful cloud cross-food coverage. So in this instance, I suppose, the relativists are the ones we're being looked down upon.

1:12:30 I think probably because it's a smaller community and we do tend to be slow on the uptake of work on some detailed models etc simply because most relativistic calculations are not necessarily harder than doing a detailed Newtonian calculation but they are hard and sometimes they just drag on and I think there is a legitimate question one can ask which is to what extent has relativistic calculations actually been needed to understand astrophysical system right now, and I think it is changing, right, but if you look historically, then ten years ago, well, you needed relativity, special relativity and a few other things, but proper GR effects were not really that common. Now that I think that's changing rapidly, but there's still that attitude out there. I mean, statements like about R-modes that I heard someone say, well, what's going on? Someone asked what was going on in the field, and an astrophysicist said, well, the relativists are off trying to do better mode calculations, and we're trying to understand the physics, or to put the right physics in. Which I thought was a bit of a frightening answer, because if you want to do better mode calculations, that exactly means putting better physics in you know putting both better mathematics and better physics in so there's absolutely no contrast there really it's just that in his mind what the relativists were off doing was something different and I don't think it was clear to him what that was but it was something that was not what he was interested in doing and that I think I really don't think there is a huge divide it's clearly as we've agreed there are different languages that people and different ways that people present their results I think you mean they're putting a different emphasis on the meaning of them

1:15:00 because they're interested in different Absolutely, yeah. Actually, are there different outlets that people have for things? I mean, presumably, for instance, on the Los Alamos web server, I guess, when you were talking a minute ago, do the astrophysicists post on astrophysicists? Yeah. So, you have to sort of look in both of your... Yeah, definitely, but you also have to post on both. are genuinely interested in reaching both communities so in that sense I think it's very exciting it's frightening to be working on that subject right now because there's so much activity obviously anyone with a slight inferiority complex will be scared by seeing one paper a week appearing on something that often being ideas that you could have worked on or you thought well maybe I'll work on this and then say no I'll work on this other thing instead because you can then see well exactly the thing that's sitting on my desk right now might be the one next week and stuff like that it's also stimulating I think because you do need to be able to speak both languages and you do need to be able to understand both sides of the coin. And I think that's very stimulating. It's clearly very exciting in that respect. I mean, I think one is very fortunate if one is working on some problem that suddenly attracts attention, be it really important or not. I mean, this fad could be over. It just takes one paper to kill it, right? Are most of the papers now cross-posted between the two? No. Most papers are not. In fact, one could check and see that a lot of the papers that ought to have been cross-posted are not, which is surprising. But I think people might simply

1:17:30 or GRQC, so you don't need both. Well, I don't think that's true. It simply depends on what end of the spectrum you come. If you're a pure astrophysicist, you would never read GRQC. If you're a pure relativist, you would never even consider reading astral pH. So somewhere in between, that's the people that post all over the place I think and I guess another, well I suppose also they probably publish in different journals but I suppose it's probably the e-print archive that's important oh well, it's another interesting thing I didn't realise that I met an astrophysicist these problems in the 80s in Newtonian gravity and he said well I've looked into some of these papers they're really interesting and then he listed a number of papers he says yeah but that's only half the other half were in visor of D and visor of letters he said oh I don't read those and of course for us that's almost blasphemy so oh gosh so I thought that's clearly another wouldn't even consider, you know, you could publish a paper in PRL and think, well, you could be very happy with yourself thinking, oh, this is great, you know, cross-border journal and all that stuff, it's going to be read by everyone, fantastic. But not that. That's right. And conversely, I think if you publish something in astrophysics journal, you lose a lot of the relativists. So, I don't know. I didn't know what one should aim for. So I think it was Nick Sturge who said, well, we should aim for the largest community. So we go for the astrophysicists, because there's more of them. Right, sure. And then, do the two groups of people meet anywhere? Are there conferences, like, say, the Texas meeting or that, where you get a mixture? yeah I think it would be the Texas meeting

1:20:00 would be the typical one but that's so dominated by astrophysics now so there's very few relativists relatively few relativists but that would be the obvious one I think because I suppose that would be if one thinks of collaborations beginning to take place if that were to happen it would either be people who were at the same institution Or that they meet at that meeting, so I'm just curious if they have any meetings in common. Apart from special workshops and stuff like that, when you organize them, you invite people from across other fields, just because that's what you want, you're aiming at to collaborate around that. So have there been workshops? How many workshops have you been in for this? not many there's been one or two there is a big Santa Barbara session coming up this year six months which will be interesting I'm sure but that's broader that's sort of young neutron stars in general so it's very I think there's going to be a lot of relatives Hugging around. Taking the opportunity of spending some time with the only university in the world where the students show up at their surfboards. Why not go to Santa Barbara? Yeah, why not? Give me one reason why we shouldn't spend a couple of weeks at Santa Barbara. I'm sure you can't. I certainly can't. So, I guess the other question then is I guess something I don't have any notion about. But, you know, apart from LIGO detecting gravitational waves from hormonal disabilities, what observational evidence might arise from the astronomers that would have a bearing on this topic? it's um now this is a very good question um because obviously it's not natural maybe for a relativist to stop thinking about at this point in time to to drop gravitational waves and say well what else could we use but i think it's a very good one um the obvious ones would be

1:22:30 things like if an R-mode were to operate in a star, it would, it seems right now, it wouldn't necessarily heat the star up. So a star with an operating mode might ought to be hotter, significantly hotter than one without the mode. And if you could catch such a star in a clean enough environment, etc., then maybe you could see it, see the difference in X-rays, that's a little bit of a stretch but I mean that's thinking in the right direction another one would be all these different frequencies that people see from x-ray sources now, x-ray binaries if one could show for some reason or other that the mode structure is actually such that one or several of these frequencies that we see are not due to the disk but are due to modes in the star modes in the star and something else. I don't know, for example, modes in the star shaking the magnetic field and giving off some signature. It's not at all clear whether you can do that, but why not? And so I think that it's an interesting question. And I think certainly if you were to start trying to model, as some people have done now, although very basically, you try to model the effect that the presence of the magnetic field would have on fluid motions or conversion of fluid motions affecting the magnetic field, because that's obviously where you would be looking for observational bits. Otherwise, you could try to do something that's a bit harder, which is trying to figure out the initial spin periods of young neutral stars that are, say, thousands of years old. But then you have to guess at how they spin, you know, how they change their rotation. So what sorts of forensics you can do, I suppose? That's a good question. And do the astrovisors talk much about tests like that?

1:25:00 It hasn't been a whole lot, no. There's been a few papers, a few comments. is that because they're sort of already dated or because maybe they were skeptical so they're not really looking for I don't know the answer that's hard to say or maybe not even aware of it which is just as likely I mean it's not we might think in this office I might think that this is a big thing but it's not like it's not a huge affair for astrophysics I mean if it were to be true if these models are correct then absolutely it's a gigantic thing for pulsar physics a neutron star physics absolutely But that's still a very small part of astrophysics here. So in that sense, I mean, it doesn't matter how important it might be for that sub-area. There's still a lot of people that aren't thinking in those lines at all. I suppose we should leave it there. That was extremely interesting and I've managed to kill most of your afternoon. Excellent. Nice strike with the... So how were you getting down to the station? I was just going to get the bus.