Interview with Richard Price

0:00 Some sort of understanding of the need for communication that wasn't there when this type of meeting was originated 15 years ago. Well, certainly my own experience at PCBMs is that talks which weren't in my immediate area, especially saying more mathematical talks, were very difficult to follow. They were speaking a different language. it's a good place to start because it's a place where students give their first talk and if they are sensitized very early on to the need to give talks comprehensively to a wide audience that seed that's the efficient way to do it so is your approach to encourage people at the meeting talk to the advisors and the group leaders to get them to encourage their students or both? It's too late at the meeting. People are alive. I would encourage the advisor, I mean, I've already, I can't remember now in detail, I mean, I probably didn't do it this year, but in the announcement for the meeting, you have a reminder to people that our field has become very broad and the need for some going into communication is not to be forgotten. As I mentioned, I'm particularly interested in the language boundary, if there is any between, I've certainly heard many comments, but it's my impression that there is between numerical relativity and people who are solely doing analytic work. Of course, still up to this point, many of the people doing numerical relativity have experience. certainly know how to do analytic relativity as well, but do you see it as a possibility that those two fields might grow quite widely apart or that one would simply eclipse the other? They've already grown wide apart. Numerical relativity is a great thing for you to study. It would be not only good for a sociologist and historian to study,

2:30 it might be good for someone doing a thesis in management to study. It has been a failure. This is one of the reasons why I warned you that you should use a lot of discretion in using what I say. the way the Grand Challenge was set up was an example in how to do everything wrong in setting up a management structure but if you're interested in the sociology I think then what has happened is the need for people who have expertise in how to use big computer codes has led to a subclass of people who can do those things Some of those people have been physicists, have had the insights of physicists, the attitudes of physicists, and there's been a tolerance for people who don't have those skills. An example of someone who was... One thing that really annoys me is that possibly the best person in the field, Andrew Abrahams, did not get a faculty position. because he was a physicist. He was someone who could efficiently write code. He was someone who knew all of the issues about getting big codes to run. And he was a terrible loss. In any case, but he's not an example of the sociology. He's an example of the mismanagement of the field. There are some people in numerical relativity who kind of understand physics. but as I said there's a tolerance for those who don't and then there's an interesting backlash the mathematical physicists who see themselves becoming irrelevant see themselves becoming dinosaurs run into some of these, the numerical types and they resent them deeply the numerical types, at the post-doc level at least are making higher salaries than postdocs in quantum gravity, for instance. The people in numerical relativity can get jobs outside of relativity. People in quantum cosmology and quantum gravity cannot.

5:00 Instead of the people in the mathematical and trying to bridge the gap, circling the wagons. There's no place where this sickness is more virulent than at the Einstein Institute, of course, where the mathematical physicists who are left over from a previous research generation, who also have prickly personalities, they scorn numerical relativity. They scorn numerical relativity, sure that there's no way that numerical relativity is going to get anywhere, because the people doing it may know to get a computer code to run, but they know nothing about physics. In fact, this is an incredible loss of talent because synergy would be so good. We don't know why numerical relativity has made such poor progress. Part of it may be that the hardware doesn't exist, and even if there were no other problems, we still wouldn't be ready to collide black holes in a true 3D, with a true 3D code. But even if the hardware did exist, I don't think we'd be doing it. It's because we don't have the people with the physical understanding and the mathematical understanding, in general, are not contributing. A very interesting sociological problem. So you think part of the reason that the mathematical people much is actually fear of displacement, as it were, that there's the possibility of a numerical relativist. And turning back to the language barrier, is that also part of the problem, especially given, as you say, that maybe some of the numerical people are not well-versed on the physics side of relative numeric? I don't think this is much of a language barrier. The kind of encounter I see that's is functional is not a language barrier as much as a scientific, a lack of some common scientific tools. So a typical scene will be that someone from numerical relativity presents a result, and people from numerical, people from the previous generation,

7:30 and mathematical relativists, people from quantum gravity, will say, well, what are you plotting there? And the person in numerical relativity, if the person is not good, will not quite understand the justification of what is being plotted and the mathematical nuances. If the person is good and understands these things, if it's someone like Andrew Abrahams, then the person would explain what's being plotted. And the mathematical type will say, why did you do that? some plot, will have some fantasy about what he or she would like to see and it's a fantasy because there's no way in the world this can be computed. The person from mathematics will have no idea what difficulties are encountered in generating something like this and in seeing what would be viewed as a big achievement, the achievement of the year in numerical relativity is viewed as a waste of time by the mathematical people having no sensitivity that was held by the computer people. So actually, the practice, the way of doing things that the two sides have are so different that they're not in a position to actually appreciate the goals that are arising out of that experience. A lot of it is the fault of the people in mathematical relativity. Of course, there are significant exceptions to this rule, One exception is Abayashtaka, who was certainly someone who was unhappy about the amount of money going into numerical relativity, the appearance of lack of success, which was more than appearance, and the attempt to, the hypocrisy about claiming success when in fact it was failure. and um you know he was perfectly justified in being resentful but instead of doing what the Einstein the people at the Einstein Institute did he got involved with numerical relativity we have a weekly teleconference I have a weekly teleconference with the Penn State group and Abai is there and he's asking mathematical questions but he's fully sensitive to the difficulty he doesn't ask he asks for something to be computed and they say we can't compute it reason. And he says, well, how about computing this? So he is being cooperated.

10:00 So at least within the field of relativity, for the moment, at any rate, the differences aren't so great that they couldn't in principle be overcome by our willingness to actually start talking and building some common understanding. which is why I feel we're at a sensitive point, because a little bit of administrative nudging in the right direction could make a big difference a couple of years down the road. The people in experiment, the people in numerical relativity, will need their own conferences. But we have conferences which are not exclusive to such subgroups, and at those conferences it is important that they try to understand each other's problems. So would you put the people, which sort of community within Relativity would you describe the people at this conference as being part of? And somewhere in the middle, an eclectic group, just as KIPP doesn't sit quite in one camp, certainly not mathematical. There's no mathematics. You know, people have mentioned a couple of things about the BMS group in connection with angular momentum. There's no fascination with mathematics. There's a fascination with getting answers. We don't fall... We fall somewhere in between. So you might say there's no dysfunctionality in this group. This group should be able to communicate with either group. But not at the extremes. so do you think there's some sense in which groups like this which do fall in between or can be a conduit for a translation between yeah I definitely think so this will be the bulk near the center of mass if you were trying to bring simply two different groups together the natural thing would be for them to form two different groups But because there is a continuum with the sort of people we have here at the middle,

12:30 then it doesn't make sense for it to fractionate. What would these people do? Decide which camp to go into? How much do you think LIGO and the other big detector projects have influenced this process that we're speaking of? This divergent process that we're speaking of hasn't tended to accelerate it? 100%. Without this, relativity would have remained an intellectual curio and would have died out. People weren't hiring relativists. Someone I've become very close to in the past couple of years is Ted Newman, who is a mathematician of the previous generation. He hates to see... I mean, it hurts him. He's a wonderful person, but it really hurts him to see what has happened to relativity. It's not the way it was 30 years ago, 40 years ago. And I don't say anything to him, but you know, there's something wrong with a field that's the same way it was 40 years ago. This is healthy and natural and good. So, if it weren't for the new stuff, if it weren't for numerical relativity and experimental relativity and astrophysical relativity, then relativity would really, I don't think there'd be many graduate relativity courses taught, I think it would become something that was done as frequently or more frequently in math departments than in physics departments. maybe in connection with string theory people would be doing something they call general relativity but you know it wouldn't be the kind of thing that ted newman was doing either but just quickly without necessarily getting too much into specific managerial things obviously there are interesting sociological implications of these efforts have big collaborations like the grand challenge and actually the einstein institute in europe is just starting a quite a lot again a similar large collaboration with a much different focus really but connecting various groups around Europe so they're both examples of management mistakes and it's obvious and it's no secret

15:00 they're different mistakes do you think that the so do you think that that type of effort to make these big collaborations is just misguided as a general rule or Wonderful. Bernie Schuetz, I think, is very effective. Hermann Nicolai has shown no interest in really setting up a synergistic communication between the quantum gravity people and the relativistic astrophysics people. I don't know what Mark Hanoe is going to be doing, but the Einstein Institute could have been just incredible. Imagine if they had three groups that really did work together, if there really was energy flowing amongst the mathematicians, the quantum gravity people, and the relativistic astrophysics people, which includes numerical relativity. Imagine if people were going from floor to floor and region to region changing ideas, giving, acting as resources for each other, keeping each other up with what was new, it would be wonderful. But it's ridiculously far from that. I guess it is an interesting case because whatever about other issues, one obvious problem that the grand challenge had is that the different groups were at different places and the opportunity for interactions were limited in that respect. But of course, in the Einstein Institute case, it shows that you can't just bring everybody together and it's just going to happen in itself. Well, you've alluded to the lack of progress within numerical relativity. And of course, one of the reasons, as we've discussed, for the increasing focus on numerical relativity in recent years is this effort to actually produce waveforms that will be useful for data analysis in the future. That seems to have been part of the sales for the Grand Challenge, but when it became very, very clear, which was very, very early, that they weren't going to have anything like that, then they said, no, no, no, look at what we said we would do. And they signed a contract not to do anything like that.

17:30 Yes, the feeling, the aura of hypocrisy that formed around that program is just terrible. I guess there are worse managed programs or worse managerial structures than the Grand Challenge, but it's certainly got to be up there in candidacy for the top. The worst thing they did was to give money to eight universities, to eight groups at universities, each of which was pretty well funded, and each of which was getting an amount of money as part of the Grand Challenge program, which was roughly comparable to the money it was getting from other grants. The self-interest of each group was to take that money and use it to supplement what it was already doing and what would be uniquely identified with that group um and maybe to try to cooperate with the grand challenge in some sort of way that the work unique to the group and the work of grand challenge was the same but that meant that you couldn't make decisions based only on what was best for the grand challenge you had to make they were making decisions based on what was best for themselves and so cornell did things one stars texas did things another way because they were interested in developing um codes with applications beyond grand challenge the dag h code um syracuse which was really out of it was developed coming to it completely from the point of view of computer science and computer infrastructure um pittsburgh this is of course it would be really discreet with this pittsburgh was led by Jeff Winokur, who really didn't know how to run a program very well. He had a guy named Roberto Gomez who was running the program. So Gomez was an okay physicist, but just did what Jeff Winokur said. Jeff Winokur wanted to use characteristic method. I think that was great, and I certainly believed that it was valid to be exploring different ways of doing things, but not if you're trying to get a big project and you've got limited resources you can't explore every nook and cranny and go down the little byway that Jeff Winokur wanted to sniff out so he was of

20:00 no use thank God recently it turns out that the Pittsburgh group has become quite useful and is as well broader horizons and has become an important contributor but back then when Grand Challenge was really underway he didn't North Carolina well they had Andrew Abrahams doing a lot of the work they had Chuck Evans so they had two of the really hot guys two guys who understood both physics and had to get computer programs running and Chuck unfortunately was preoccupied with some other things but they they accomplished a lot especially considering the resources they had Jim York doing the so where else who am I leaving oh god then there's the Saul Tokolsky Stu Shapiro thing which you must have heard enough about Stu to realize that he's at least three studies in and of himself NCSA of course was Mostly, Stu was at Cornell at that time, so the button pushed in my head was a little bit inappropriate. NCSA was focused, was Ed Seidel. Ed Seidel had been, you know, a reasonable physicist at the postdoc level, a student of Vince Moncrief, a greatly respected mathematical physicist, and Ed became interested in computers through relativity, Ended up much more interested in computers than in the relativity itself, but a hell of a good guy, and someone who pretty much understood his own shortcomings, and allowed the people working under him, and does allow the people working under him now at the Einstein Institute, to do what seems like good physics. And while he does what seems like good, not exactly computer science, but I don't know what you would call it, setting up computer infrastructure for big computations, he was not at all, he was not respected by those who had more mathematical sophistication.

22:30 So, that's it, right? Texas, Syracuse, NCSA, North Carolina, Cornell, oh, Sam Finn. He, what the hell was he doing in that? near uh near the let's see at a point at which it was pretty clear that grand challenge was failing by the way i was brought in in some very strange way from the point of view of business school or sociology or history richard matzner asked me to attend a grand challenge meeting in north carol at north Carolina and help him decide on the allocation of remaining resources. I'm not that stupid. I knew that what he wanted was to help spread the blame when he cut some people off. But that was fine, because first of all, I had more, maybe respect might not be the right word, sympathy for Richard Matzner than other people did. I didn't think he was doing a great job, but I also didn't think he quite asked for that job. I thought that someone had to run the show. It was a totally unrunnable show, and that everyone was just saying bad things about Richard Manson. He wasn't just, you know, he wasn't that bad a guy, and so I was willing to help with this, and I also didn't think I would personally suffer from because I had a reputation for being brutal, you know, being straight and fair. And people accept a little bit of pain if they think it's being done in a fair way. So I went to that North Carolina meeting and I made recommendations to him, which he ignored. I recommended cutting certain people. I recommended not following two paths, hyperbolic NADM because of limited resources he didn't do it probably wouldn't have mattered but at that meeting Sam Finn got up and said he was willing to give back the rest of the remaining

25:00 grand challenge funds I don't think it was done rather he hired a postdoc I guess Larry Kidder who was working on grand challenge issues but he never should have been in that, it was a political thing where, you know, while Sam has a political influence because of his connection with LIGO, let's bring him in. Besides, we want this to look like a big collaboration. So there was Sam at Northwestern, and we're leaving out one place, aren't we? There were eight places? Yeah, that's right. Two places... I guess we did Penn State, Pittsburgh. Penn State, of course. Pablo was buffeted by what was going on. He was a good guy, he was a good manager, very little of the fault. There was nothing he could do. He was one of the least at fault, but he was a little bit in the periphery of the leadership well anyway the people reviewing the Grand Challenge proposal the reviewers who were against it said this was a welfare a welfare program for numerical relativists and that's exactly what it turned out to be so you've been involved in working on more working on alternative approaches to doing parts of the calculation that it was hoped that numerical relativity would do looking at two black holes as they approach close together is this something that you'd been interested in and finally do all along or were you motivated by the lack of progress serendipity first of all The basic suggestion came from Larry Smarr, and then the whole calculation took about three days. One day right after, there was a Penn State conference, I went there, I saw Larry Smarr. We had been contemporaries, so he made an off-the-cuff remark that when the black holes were close,

27:30 in other words, when you were starting with initial data that corresponded to a Misner solution with a small mu zero, you should be able to use perturbation theory. an obvious statement. I went home, the whole calculation, well, it's a little bit of a complicated statement, which really isn't complicated in principle. The basic work took less than a day, so I had the result, and I just needed, there was an arbitrary, there was a multiplicative factor that would require just generating a simple program to advance, to evolve the Schwarzschild perturbations. It was a very easy code. But I didn't really need that because I could just adjust that constant by fitting it to the data, to the supercomputer data for very low mu zero. And so, you know, I saw with less than one day of work, most of which was background reading, that curve that has become mildly famous of the close limit. Jorge Pullen had been my postdoc and just moved to Penn State. I wanted to bring him in on the project first because he had better computer skills than I, not that this was a big computer project, and secondly, to help his own career. So he came out, he visited Utah a month later, and in a day or two we wrote up, we got a code, he wrote up the code and I wrote the code. My code was better but didn't work. worked but had some high frequency noise so he got my code to work. They both worked fine at L equals 2 but at higher L there was some good noise. It had to do with whether you use a leapfrog method or something else, not important. But incredibly little effort went into that paper and of course it was a significant success. I love doing this stuff because I guess i'm not as philosophical as some other physicists um i don't really get fascinated by well sometimes by thinking about the ultimate nature of things and the meaning of this and the meaning of that i like solving little problems and knowing when i'm right you're never going to know when you're whether you're right if you're doing quantum gravity well what a wonderful

30:00 opportunity it was to mess around the periphery of the grand challenge because i could do these little things. Well, clever. Let me be a little more modest. I could do these not totally straightforward things, these approximation methods and come up with answers. And then there were 300 man years of work going into doing it with computers. And I could compare them. It was such fun. Second order perturbations weren't that easy, but they were still enormously easy compared to numerical relativity. So it was, for me, it was somewhat serendipitous. It was Larry Smarr's remark that got me started. I badly wanted to hire Andrew Abrahams at Utah because of political machinations in my department. They promised me a position that didn't come through. I almost left my department. Andrew's probably happier now on Wall Street, so it all worked out for the best, I guess. Well, I guess now there are the approaches to actually extend, as you say, these approximate methods to actually try to calculate a waveform for the whole period of the interspiral and merger of the back hole by sort of taking different approaches And in fact, considering that you discussed earlier the eclecticism of this group here, I guess this Lazarus project is actually referred to as an eclectic. I gave them that word. Manuela, it turns out it's very close to a word in Italian, eclectica. So she accepted that. I can't remember what word they had been planning on using, but it wasn't quite as appropriate as eclectic. Mm-hmm. So, do the backgrounds of the people involved reflect the eclecticism there? I mean, are they kind of different? Yeah, we're different. Well, at the AEI, at the Einstein Institute, Bruin Brugman is actually someone who's both expert with computing and has a solid background in mathematical relativity. Um, Carlos, Carlos and Manuela both have a background in, um, quantum gravity, uh, more

32:30 quantum fields on curved spacetimes than quantum gravity. Um, and, um, I got them both interested in the kind of applied mathematics, um, that I do, and they're both much happier. um let's see john baker was a student of jorge pullin the four the group of four that did the lazarus project or those four so um it isn't it isn't an example of a collaboration of people with divergent interests it's an example of people who are working uh kind of on the same thing although carlos and manuel because they drifted from one end of the field to the other themselves represent some sort of internal collaboration of people from different fields. They knew nothing about computing, and of course now they're running big computer programs, but it helps to have the infrastructure of the AEI where there's very good, excellent resources. My impression, I forgot to ask him again at this meeting, was that maybe Brugman was an example of one or two people at the AI who had moved across from the mathematical group to the macro group. He saw the light and had the ability. You know, there are some people who just, whatever skills it takes to be good at running programs, they don't have it. It's a different kind of thinking. I don't know. Maybe it's nothing but chutzpah, the willingness to take a chance of learning something new. If you asked me, though, if I had to speculate on what kind of qualities it takes to do good computing, I would say an ability with language, you know, understanding of syntax. Right. But then my colleague, Karl Kukash, is very good with language, and i know no one who's as bad with computers including my dog but i think that's just he has a closed mind he just doesn't want to learn the so although the lazarus group is based at ai with the eclectic approach i guess they're taking advantage of work that's been done in

35:00 in several different places? They haven't. It's not what they've done so far and what they'll be able to do without further resources is not completely eclectic. The eclectic approach means you start with post-Newtonian, then you do numerical relativity, then you attach on late time, that is, close-limit perturbation theory. They've only done the latter part of that. They've attached perturbation theory to numerical relativity. They've attached perturbation theory at the end of a numerical relativity run. It had been done in 1995 by Andrew Abrahams, and Abraham Shapiro-Takowski, which means Andrew. But it was with two-dimensional relativity, and so it proved nothing because, well, it didn't prove nothing. It wasn't nearly the challenge that the AEI group met because they were attaching late-time perturbation theory to a true 3D code. And the simple way of understanding the meaning of that, because sometimes we need a simple picture to keep in our minds, is that if you do the transition from the numerical code to the perturbative calculation, if you do that transition too late, your result is nonsense. Andrew was doing the 2D example, all you had to do was do the transition late enough. The code would run to completion. You didn't need the perturbation theory. Right. And what Bernd and John and Carlos and Manuela are doing, you need the perturbation, the late-time perturbation calculation. We should start drifting back. I'll experiment and try continuing to record as we walk along see how that goes what was I going to say So do you think this eclectic approach will suffice to give the sort of waveforms that LIGO will need?

37:30 I mean, is this somehow in any case not so much to be seen as a substitute for numerical relativity someday being able to do everything? Or, I mean, can it be seen as really the right way to do things to just take the... about the idea of putting perturbation theory in as the late stage of a numerical calculation, then I'll say two somewhat disconnected things about it, or two things that answer, two answers to different questions. First of all, I think they've got a good running shot at having the first answers from numerical relativity for some sort of meaningful fraction of an orbit, like a quarter of an orbit. because the limited stability of these codes means you're just absolutely out of your way. At this point, you need every trick you can think of, and you might get the numerical code to run for a quarter of an orbit before the event horizon forms, and then you better put on perturbation, you better go into the perturbation calculation, which takes no resources. So that's one answer is that they are likely to have the most astrophysically inkling. They are likely to have astrophysically inkling. So, before anyone else, I don't want it to be like that. There's a good chance that they will have it. The second answer to a very different question is, I can't believe that it will not be the case that everyone is going to use this. The Ventura is a total no-brainer. A little bit here. The interesting sociology is going to see how slow other groups are to adapt this. So, once you have formed an event, once you have formed a nearly equilibrium event horizon, your codes can crash, and your computation doesn't have to. It is just painfully obvious that at that point, where you still need to compute, you still need to get the quasi-normal ringing.

40:00 At that point, why in the world do anything other than a perturbation calculation? You're using a complex, difficult code with all of the dimensions that are in attendance to the non-linear way you're doing it to calculate something which is linearized theory. Everyone will eventually do this. So is everyone gearing up to do this? I mean, after all, Andrew Abrahams did it in 1995 with a 2D code, so it wouldn't be surprising that that really didn't quite act as the right stimulus codes to do it. I mean, you didn't need it on the 2-D codes. Carlos and Manuela have written this up. They can't get it published as a FISRAV letter, because the numerical relativity community is as conservative as farmers. Farmers don't want anything to change because they've got their emotional and financial lives invested in a certain pattern. It takes a lot of work to make any kind of change, and going to the late-time perturbation calculation is a big change for them. They're not going to do it until people laugh at them if they present any work that doesn't have it. Now, in connection with the idea of keeping meetings open, or keeping the group together, if the numerical relativity community just has little meetings in which they meet with each other and if everyone wants to keep from doing the late time renovation theory then it won't be an embarrassment to them because they'll all be committing the same sin but if they're exposed to a wider audience, this kind of thing will be an embarrassment so there is an example of why it's best to keep things open I do predict that in two or three years everyone will be using late time renovation theory Because they'll be laughed at if they don't. You understand, it's no great insight. I was speaking to Andrew about a week ago, and he's an extraordinarily funny guy, and part of his humor is sarcasm, and he said something like, calling what a great idea to use perturbation theory and i said andrew you did it in 95

42:30 and then he told me that he was being sarcastic because it isn't a great idea it's completely obvious but the implementation was not obvious and that was the great achievement of the group at the Einstein Institute it was a very it's rather difficult to understand how to take those numerical data out of them get a perturbation in fact there's a practical reason why one needs to these different sections of the community being able to talk to them, part of a broader community because you feel that numerical relativity is unlikely just on its own terms to be able to solve all with gravitational waves from binary black hole. They're still going to need to adopt these other techniques where appropriate approximation techniques, and they're going to have to understand them and know how to implement them with their own work. Absolutely. It's always bad for a community to be isolated when new ideas from the outside are important. It's interesting because I remember, since his name already came out, to Jeff Winokur, and part of what I recall him saying was that he saw numerical relativity as a way to do mathematical relativity without, you know, more successfully, you know, and without the limiting cases, but without doing approximations. But, you know, so... Well, that's completely consistent with the attitude he had early on, but it was not healthy for the grand challenge. He was interested in using characteristic methods. And good idea, but as part of the grand challenge, he should have been interested in colliding through black holes. So numerical relativity, rather than going off on its own or supplanting previous branches of relativity to be successful, So you think it'll probably have to be a more integrated part of the relativity community?

45:00 So that it's at least better connected to the... It would have to maybe be too strong. There are different ways it could go. It certainly already has played a role as part of mathematical relativity, who are actually mathematical physics in the Chapsworth work. I think there are lots of interesting things that you can tell us about the way horizons form, angular momentum, and I don't know whether that's numerical relativity, or relativity, or what. But it could go that way. Or it could, as the government partly planned, it could be a way of efficiently developing, well, it's too late for efficiency. It could be a way of developing computers, teaching people how to set up the infrastructure to solve between hyperbolic systems. that was part of the motivation for the grand challenge I guess the people who still seem to be very interested in that side of the thing are the Einstein Institute well thanks very much Richard very interesting I figured my own interests are probably Yeah, although I do find that the experience of the Grand Challenge seems to have put the idea of sociological problems in people's minds. Because when I talk to a number of the, some of the Grand Challenge people, I thought that was an example, they immediately go, oh wow, sociology. Let me tell you about the sociology. Oh, yeah. The grand challenge won't resolve the importance to research of sociological elements. So, I'm just locked up. Yeah, see you later. So I was speaking with Richard Smith at Caltech between 1 and 2 o'clock in the afternoon

47:30 of the 6th of June, 2000.