Interview with Yasushi Mino

0:00 So I will rush through the part about describing the experimental part of this. I think that's something that's more familiar to many of you who are involved in new ground-based gravitational wave detectors. Basically, the antenna that's proposed will have three spacecraft separated by five million kilometer arm lengths forming an interferometer. by putting each of the spacecraft in an independent orbit around the sun and picking the eccentricities and inclinations right, you can maintain the geometry so that the three spacecraft form a very nearly equilateral triangle. The triangle is in a plane tipped at 60 degrees to the ecliptic plane, and it goes around once per year around the sun. The three spacecraft rotate once per year in the plane so that the geometry changes quite a lot. And this generates a quite isotropic antenna pattern over the course of a year. This enables you to get information about the directions of the sources quite well, as well as the frequencies and other characteristics of the sources. The array is located about 50 million kilometers behind the Earth in orbit around the Sun. That's the basic geometry. This antenna was studied quite intensively in Europe, starting in 1993. and this is the LISA science study team. They're involved and present in supporting an industrial study of LISA that's going on in Europe, which will end in February. Trevor Edwards at Rutherford Appleton is the manager of the study. This group is led by Karsten Donzman from the University of Hanover and Jim Huff, and Albert Rudiger, and Bernard Schutz from the group are here. Starting about a year and a half ago in the United States, we got a Lisa Mission Definition team put together. It's led by Steril Finney from Cal Tech, and Bruce Allen from this group is also here.

2:30 There is a lot of overlap of people involved, both on the European and the U.S. side, with people who are interested also on the ground-based detectors. This is a picture Bill Faulkner from JPL put together quite recently, a little bit more graphic arts or something like that presentation. This is something with an accretion disk around it, producing gravitational waves. But the main thing is I wanted to use this to show what the individual spacecraft looked like. The spacecraft equipment inside here is not shown. This is the basic outer frame of the spacecraft. It's about two meters in diameter with the present design. This Y-shaped thing in the center is a thermal shield. and the instrument itself is basically located inside this thermal shield to improve thermal stability. On the sides of the spacecraft, there are a number of micronutrient thrusters which provide a very small amount of thrust in order to buck out mainly the solar radiation pressure on the spacecraft. and each spacecraft is controlled so that it follows a proof mass inside one of these two arms here and keeps the spacecraft centered on the proof mass so that you don't have changing separations and changing forces on the test mass. Now the basic approach is in each of the three spacecraft, there are two optical assemblies, one pointing along each arm. The two lasers inside each spacecraft are locked together, and in one of the spacecraft, the lasers are locked through a resonant cavity with a pound-fever-volved hypostabilizer. The beams that go out are used to provide a reference signal, and then the lasers in the other two spacecraft are phase-locked and then signals are sent back into the spacecraft. You then look at the beat between the transmitted laser beam and what's been out and back on that arm. So you're looking at a beat between two signals where the time delay between the two is about 60 seconds.

5:00 I'm sorry, it's 33 seconds, I think. You also exchange laser beams between the other two, which helps in terms of getting additional information the other polarization in the signal. Inside the two arms are the pair of optical assemblies. They're mounted on flexors of some kind so that during the year, as the geometry changes a little bit, you can change the angle between them by up to about a degree. But each one is kept quite rigid. Each one has an optical bench, this white thing here, with an inertial sensor that contains a test mass inside it, here in the middle, and then a telescope. In the present industrial design, it's looking like this will be a F1.3 telescope made of silicon carbide and 30 centimeters in diameter. and just to show the function of this a little bit more I have two more pictures, or three more pictures this is again the optical bench with the inertial sensor on it inside the inertial sensor there's a freely floating test mass with separations of a few millimeters for capacitor plates that are around the test mass You use the capacitor place to sense the changes in the spacecraft position with respect to the test mass. But the whole purpose is to follow the test mass and make it as inertial as possible, as free from any spurious acceleration as you can. And the telescope is rigidly mounted to this. There are stiffening rings and a support cylinder, which forms sort of a second stage of thermal isolation. And then the electronics just became preamplifiers. And just to show the optical paths and so forth, on the optical bench, there's a proof mass inside its housing here. And there are provisions for bringing in light from a laser. And I'll show this in a little bit more detail. The support cylinder and stiffening rings and so forth.

7:30 And this is the last of these pictures, shows the proof mass with the capacitor plates around it, and basically the light comes in from the laser, there is a redundant laser for lifetime considerations, the laser is run at, the diodes are run at like half of the generated power, extend the light on, and so forth. As the light comes in here to the main beam splitter, most of it is sent out to the other spacecraft. The phase lock signal then comes back through, hits the, goes through to the proof mass, bounces back, and goes through a photodetector. And a little of the original light leaks through, and this is where you generate your main signal. Some of the laser power is taken off and used to go to a reference cavity, which is used on at least one of the spacecraft. Now, that's very brief for the experimental side of this. On the sources, what's plotted here is the log of H. Now, this is not the plot you usually use in ground-based detectors where there's a square root of the frequency that's come in. This really is just the RMS value of the expected signal strength. This is because for many of the sources you expect to see in space, the signals will last the posiperiodic over quite a long period of time, like a year or more. So it does make sense to plot things in such a way that you can really plot the strength of the signals and then compare the antenna sensitivity with that. At the higher frequencies, we're limited by shock noise and a few other things like dinner and the beam pointing, mainly shock noise. There are wiggles in the response because at higher frequencies, if the lengths of the arms get comparable with the wavelength of the radiation, then when you get some orientations from which you get very poor signal generated in the interferometer, and when you average over different directions during the course of the year, you're left with little wiggles in the response. Then this curve would go flat at this point if we were just limited by the shot noise. But at lower frequencies, we run into the limitations of the disturbances on the test mass.

10:00 And even for our fairly careful work extrapolating from what's been done so far, on inertially three masses in space, this is what we think is reasonable to ask for in terms of the performance. For constant spurious acceleration as a function of frequency over this frequency interval, you get something which in H is one over F squared. So that's our antenna sensitivity we expect to get from Lisa. We may do a little better, we may not, but that's roughly what we expect to get. Now, this curve is the confusion noise limit. There are many, many compact binaries in our galaxy which give signals. There are so many below about 3 mHz, 1 or 2 mHz anyway, that in each cycle per year bin, you're likely to have more than one galactic source. So you really cannot separate them, and it appears as if it's just a noise background. And this curve, if you just plotted the RMS amplitude, it would go down something like this. However, about two or three millihertz, you start having enough of the frequency bins open where there's no binary in that bin so that you can use this information from the open bins to get information about other interesting sources like those from outside the galaxy. so that this is the corrected confusion noise level when you just allow for how much information you can get through in those windows that don't have galactic binaries in them. And it's going into down here a curve where what will be limited by the confusion noise due to all the other compact binaries in the universe so that then you have to sum over all of them further and further out and you get equal contributions from equal thickness shells all the way out to z equal to 1 or 2 or something like that. So that we just do not expect Lisa to get around this background. Now, that's still not too bad. There's actually a factor of 3 or so uncertainty in the level of that curve because most of these binaries are close white dwarf binaries,

12:30 and we don't have direct knowledge that permits us to estimate the space density of those very well. But we think it's known within at least a factor of 10. That would give a factor of 3 in terms of the level of the signal. So it could be up to three times higher than that, or it could be lower than that. Above about 3 millihertz, we will be able to observe most of the individual binaries in the galaxy. And we expect there will be roughly 3,000 binaries in the galaxy that we'll be able to resolve in terms of frequency and direction in the sky. and this shows the strength of the signal you'd expect as a function of frequency for those that happen to be at the galactic center and most of them fairly close to the galactic center five percent of them would be close enough closer to us so that they give higher than this level of signal and about five percent would be further away enough further away so we get lower than this level of signal. But we're expecting 3,000 or so with typically a signal noise of the order of 50 or 100 something like that. Now what we would do is to fit out those and solve for the parameters associated with them then subtract that from the data and that would give the data set that one can use to look for what regards the really interesting thing signals having to do with particularly massive black hole you might wonder why this curve something goes up this is because there are a lot of helium helium white dwarfs in here they run out they coalesce about this frequency so you're just looking at the more massive carbon oxygen and carbon oxygen white dwarfs at the higher frequencies and these curves are cut off where you don't expect more than about one more at higher frequency in the galaxy. Now, this lists most of the objectives for ELISA. The primary objective is really to detect and observe in detail signals from sources involving massive black holes. This is important both for the astrophysical information that it will carry, but these These also are the sources that can give information about test of relativity.

15:00 The astrophysical information is what's listed here, the kinds of information that we hope to get. And this is what we, this is, these are the things I want to talk about the remainder of the time. A secondary objective, which we're sure of, is the seeing signals from large numbers of galactic binaries. And a third objective is to put limits or detect continuous background radiation. Now, in terms of the first of those things that was listed for the astrophysical objectives, namely the learning about the origin of massive black holes, The thing that's of interest is this lowest curve, which corresponds to coalescing to two 500 solar mass black holes at a redshift of z equal one. This is from one year of observations and so forth. I should have said before, this whole curve for our sensitivity was based on one year of observation and a signal to noise of five, which is what you usually need to identify sources reliably. This shows the frequency and the amplitude expecting for this event at T equal 1. One year before coalescence, 8 tenths, 6 tenths, 4 tenths, 2 tenths, and then half a week before coalescence. So the frequency changes more and more quickly during the last year. It spends most of its time back in this part of the frequency range. clearly because it's above the level you need for a signal-to-noise of five in one year during the whole year, you clearly will be able to resolve this. In fact, you can even see this source as equal five. And if you think that you form massive black holes by successive collisions, perhaps starting from pin solar mass black holes that are produced by normal evolution of massive stars, then these are going to if these coalesce with each other they tend to sink down toward the center of the galaxy and they're likely to coalesce fairly quickly and you can build up seed massive black holes this way when they get up to a few thousand solar masses so then they're likely to grow faster by pulling in gas and kind of disrupting normal stars and that will be the way in which things evolve. The only other way, if this happens and a number of them grow to be 500 solar mass before

17:30 the end, then we would be able to see the signals due to some of these sea black holes coalescing with each other during this formation of the sea. The only other way to form the massive black hole is sudden collapse to form into the fifth but there are six solar mass black holes, which some people support. We think there's a pretty good chance, at least you would also be able to see signals from that somewhere in this sort of region, due to if you have something collapsing to form a massive black hole, you're likely to have a bar of instability, and that would radiate pretty efficiently. This just shows that for heavier pairs of masses, the frequency changes enough so that the the sensitivity of the antenna gets much better right near the end and uh vecchio and cutler have done quite a lot of work on this problem of seeing how well we really can determine the directions in the sky for the different types of sources now uh us to learn about the distributions of masses of massive black holes in normal galaxies which we really don't know much about when you get below about the million solar mass range. Sir Gertsen in recent England and Hills and I have done some estimates of expected signals from five or ten solar mass, we've taken actually seven solar mass flat holes in the region around the mass flat hole of the galactic center, spiraling in and giving you signals during the last year or so before it coalesces. And what's plotted here with the different symbols is different central masses for the central black hole, half a million, one, two, so forth. And these are for different grid shifts, equal a half, one, so forth. And this is our intensensitivity curves. And the impression that I tend to convey with this is that at least for some reasonable scenarios, one would have a couple of dozen sources that you would be able to detect Lisa. And the third of the main sources we'd be looking for is sources having to do with the formation of structure in galaxies. If there are black holes that grow by the time

20:00 you get to the 10 to the 6, 10 to the 7, 10 to the 8 or so solar mass objects, they're then going to coalesce to form the galaxies that we now see around us. If those black holes are there, and if they have time when these structures coalesce to find each other, then you could have very copious sources of gravitational radiation that would include things like 10 to the 5th solar mass pairs or 10 to the 6th solar mass and so forth coalescing. And there could be dozens of signals like this observable according to some scenarios. And these would give signals with, at least toward the end, very high signal-to-noise ratios. I want to show, I think, two more pictures here. This one shows the cumulative signal-to-noise ratio you get for some of these scenarios. Here's this 500 solar mass scenario. Here's a signal-to-noise of 5, which you need for detecting these things. But this just shows cumulative signal-to-noise. This is a week-by-week plot of how it builds up. It would be quite high. if you get up to bigger things, a lot of the signal-to-noise comes in the last week or two, and then one doesn't get as good directional information from the antenna. One gets high signal-to-noise, but somewhat limited angular detection sensitivity. But there's plenty of signal-to-noise for many of these to see them even at large distances. Now, I was... The one thing that we'd like to demonstrate beforehand is the inertial sensors for ELISA, and they have uses for other future space missions also. This is a proposed elite spacecraft, the European-led demonstration of what you can do with the inertial sensors. This would have two inertial sensors inside with laser interferometer between them that demonstrate that you really were able to get into very low levels of spurious acceleration. And then finally, I was asked to say a little bit about some discussions that are just barely starting with possible lease of follow-up on missions. This is not anything that I think one should take seriously at this point, but maybe in two or three years there'll be enough discussions, so some of this makes some sense. So far, this discussion is mainly limited to the U.S. side,

22:30 but 2020 might be the kind of timescale one is talking about, and mainly some people think it's useful to talk about this just because if there are exciting scientific possibilities, even in the indefinite future, it still sometimes is useful to be able to say what they are. But at least it has one antenna, 5 billion kilometer arm lengths, acceleration noise, I'm just using this as a reference level, 30-centimeter diameter, one moderate laser power, one micron, et cetera. For a moderately optimistic future, Lisa, one might ask for having two such antennas operating perhaps together, and maybe one of them would have half a million kilometer arm length and the other maybe 50 million kilometer arm length to emphasize different frequency regions. For the highly optimistic case, one of the scenarios is to go down to quite short NNF arm lengths in order to emphasize the high frequencies. We think we can get like 10 times improvement in the acceleration noise. The telescope diameter might be half a meter or a meter, something like that. My own feeling is 100 watts is already a lot to ask for for a long-term operation in space, to give it a one micron, but our more optimistic colleagues would like to talk about a kilowatt and half-micron wavelength, in which case you might get as much of the back of 1,000 reduction in the shot noise, for example, compressive leasing. But this is not to be taken seriously. It's only to give some idea of what you could do if you really invested heavily in trying to improve the sensitivity of the laser gravitational wave antenna in space. Thank you. Could you say what the follow-up might do for improving spochastic backgrounds? Okay. A number of groups, particularly the group in Potsdam, have been quite interested in this. And it does appear possible that you, if you really concentrate on that and follow on mission, and promoting complete antennas to it, that you should get down to roughly the 10 to the minus 15 level, either by going to high frequency where there's some uncertainties about other backgrounds, which may limit you, or by going down to a few microhertz for the frequency.

25:00 Both of those are possibilities. But if one emphasizes that, it would put strong constraints on the design, basically, of the overall mission. I should mention that if anybody is particularly interested in other things about the experimental side, particularly, there is a booklet that was the editor of it, which is available, and I have just a couple of copies of that along with me. I just want to announce that the next LISA symposium will take place next year in Potsdam, Germany, on the 11th to the 14th of June, July. Thank you, Elliot. Next speaker is Fujimoto. Canter is overview of the camera. Since tomorrow we devoted the TAMA session, so I very briefly overview the TAMA activity. As many of you have known, the Japanese collaboration constructs an intermediate field for special events. And this figure shows the collaboration. And more than 50 people from various organizations gathered to make the preparation. Very brief, talking about the common configuration, we used the Pabripero-Michelson interferometer eliminated from injection of . In detail, you can consult with other people tomorrow session.

27:30 I briefly talked about the history of TAMA. The TAMA project started in 1995, about four and a half years old. We spent about two and a half years to make the infrastructure, building panels and lighting systems. After two and a half years, in 1997, we started to install the interferometer. And so, for example, first we made a 10 meter . So we spent about two years after starting the installation of the interferometer. And now, we are ready to operate the interferometer without recycling. So, more details. For example, February this year, all of the parts of capital miners interferometer, all of them are combined together and to operate successfully to adopt the proprietary integration. After several improvements, we made the first data taking in this summer. At that time, we took the data only one night, and at that time we succeeded to work for systems for several hours. And in this September, we made the second data, and we bought the total data for about 31 hours.

30:00 At that time, we recorded the longest log operation, 7 hours and 43 minutes. So this is a very brief summary of our recent activities. so Tarnon 300 interferometer came into operation in this summer successfully but in this time this is without power recycling operation and we achieved the continuous operation of the system for 7 hours and 43 minutes And this project is firstly approved for five years, but this five year period will be finished in the next March. But we are now expecting to extend the grant. And quite recently, I heard that extension of the grant is so maybe we can continue to operate the program for more than two years. This figure shows very brief strength sensitivity obtained by Tamar and the first or the top one is recorded by the public interpreter illuminating with 700 mW. And after, for the system combined, we recently measured this system. So very close to the 10 to minus 20th in three sensitivity. And case 1 means without pariahitis. And case 1 goal is this time.

32:30 And after arriving at this hall, we will introduce the power reciting mirror to get the second. So, more details for some discussion of the panel. Please, we have a conversation tomorrow. Thank you. We have lots of time for discussion. Are there any questions? Thank you. I'd be interested to know what TAMA's plans are for analysis of the data that's been collected during the past month. So, tomorrow session you will hear about the taking with my head. I'm not here. Thank you. So we assumed that there was a coincident experiment with It's 40-litres, 40-litres, 40-litres, 40-litres and 40-litres mark. Other questions? Next speaker is Kuroda and the title is LCGT Project and RRB.

35:00 The time in the system is prolonged up to 15 minutes. Thank you. Thank you so much. It was a large-scale lightning gravitational wave telescope. So someone asked, why telescopes? And you have to explain later. It's a collaboration of ABCD. Can you use the microphone? It's ok? Yeah. Gravitational wave is a wave of space-time distortion predicted by Einstein's computer activity. It has a wave form, a solution. It is a transverse wave and it has two fingers of freedom. Also, it carries huge energy. It is hard to be detected with extremely wave interaction with matter. Corruption wave sources are a dynamic motion of astronomical objects. It is impossible to produce and it has a particular object. Corruption waves. So, sources of Corruption waves are fluorescence of a binary neutron star, supernova explosion, and pulsars. These are the main target for the present ongoing project. In future, Here, it will be possible to detect the wave from black hole fluorescence, falling mobility black holes, and the binary neutron stars, continuous waves. And the remote feature, we can detect the wave from cosmic swings, vibration of the main poles, and the background variation, and so on. But anyhow, we are focused on this very high-frequency corruption wave. In the beginning of the next century, we have three-kilometer baseline in the formulator and two of intermediate one.

37:30 The main target is the event of a coalescence of neutron binary coalescence in bird cluster. However, since the event rate is very small, it's 10 to minus 6 per year per one galaxy as measured as ours. This view graph shows the situation. This is a coverage scope of of Tama, it extends to about one megaparsec. It includes about one galaxy. And the target of Rhygian Virgo extends to 20 megaparsec. It includes about a thousand of galaxies. But you can easily see the estimated rate is 10 to minus 6. we can wait about 1,000 years on a project. So it is clear to everyone to increase the depictable sensitivity. And if we can increase the sensitivity up to 20 megaparsec, we can include about 10 to 6 galaxies. So in this case, we can expect to catch at least one event in a year. This is the reason why we plan the LCTD project. So, how to raise the sensitivity? The first possibility is to make longer the baseline length. The sensitivity is proportional to the baseline length. And second, to increase the higher frequency sensitivity, we need higher radio power. And finally, we reduce thermal noise by cooling the mirror. And this velocity project leads to attend sensitivity by more than 10 times. And this detector adopts the pricing technique with higher laser power. And this project succeeded the TAMAR and planned to be built in an underground site,

40:00 a site super-commute and neutron detector. And the operation of the system is the same as the TAMAR interferometer. It's a good public cavity with a microtronome. High thermometer, more cleaner, here. And the temperature is the same as the camera. And here is the target sensitivity. On the desk calculation, we can get this sensitivity. It's to improve the camera by more than two orders, and we improve more than one quarter, LIGO, PARS, and VARGO sensitivity. We just put the event of the fluorescent smoke, neutron barrier star, and if it occurs in Andromeda, it sits here. In VARGO, it comes here, and 200 KM is coming here. So we need to increase the sensitivity. This detector is put in the Kamiyako mine in Giff Prefecture here. It is in Tokyo, far from 250 kilometers in the west. I'm sorry you can not see clearly those sections of the site. Here is a super tunnel on the side. We utilize existing mining tunnel. It is 3 km length. If the project improves, we dig a new one. It is similar to 3 km here. The mountain covers about 1,000 m bar. This is not necessary for a detector. But it is indispensable for the neutron detector to prevent the cosmic ray noise. But it is not very important for our project. This is the root of the site. It is now digged for the 20-meter prototype interferometer for the inspection of the site. Site and the performance for data digging. And the success of TAMA and the R&D is a condition of the approval of this project.

42:30 And the success of TAMA you will find tomorrow. So I believe that TAMA is successful. And so I moved to the exploration of the planet system. Why we need to cool down the mirror? This is the main noise source of thermal. Thermal is making noise. This is a pendulum mode coming from the pendulum ocean, excited by thermal force. It has a peak around 1L and it extends in this way. If you increase the Q, the mechanical Q, inverse of the internal force, you increase the Q, it decreases the noise around the band. So if you can get a higher Q material, you cannot, you don't need to decrease it. But this is the relation. The amplitude is proportional to the temperature divided by Q. So if you increase the Q with decreasing the temperature, it can improve the noise of the amplitude. And for the mirror internal mode, it has about 50 km per ton of difference. And it extends the noise curve here. Here is a little bit of a band. If you increase the Q, also the noise decreases. So, the important thing is to increase the temperature with increasing the Q. So, here is a schematic view of the present mirror. Basically, it is suspended in this way, and it is covered with a shielding, a radiation shield, and it is put in a vacuum. And we need some anti-vibrations system like this. To make the classic mirror practical, we need to solve the problem.

45:00 The mirror dissipates the laser power here, so there is heat production. So we need to prove it done by some method. Because it is isolated thermally, the radiation cannot convey the heat because it is less than 20 Kelvin and there is a high vacuum, so we cannot expect conduction. So, we only use this fiber through the mirror. And second, there is a heat must heat roll coming from the low temperature duct. So we need some long radiation shield extended to the B2. This is not necessary if we use a whole present system, but it is very, very costly and expensive. And the third problem is that the mirror can act as a variable. The hot molecule coming onto the mirror surface and it is positive. So it contaminates the reflectivity of the mirror. So far, we solved these problems. First, we did the cooling experiment. We used sapphire crystal, 10-centimeter diameter, 6-centimeter in this. We loaded the sapphire, coarse sapphire fiber here. And we put the heater inside the center. And this is put into this vacuum chamber, and all this system is immersed in the liquid here. And we tested it, and we got the props in the reserve. Since the thermal conductivity on sapphire present temperature is very very high, so we get very reformed temperature distribution. And next, even if we can cool down the mirror, the cube degrades if not good. So we check the quality cube on the system by using this system. The sapphire is suspended by two groups of sapphire fiber and excited by this mechanism

47:30 and sensed by this transfuser in a vacuum, always heading to the camera and the forks and the laser. It's more than 10 to 8, about 10, 30. So we measured two fundamental models and the next lowest model. And this affects the thermal noise in the first place. So this result may promise us the reduction of the thermal noise. And finally, we measured the Q of the pendulum. But it is difficult to measure directly the pendulum of 1Hz. So in place of that, we measure the cube of fiber in this way. And we've got a promising result also here. And this result will be presented on Thursday morning by a student. And the final problem is the mirror contamination. Anyhow, hot gas coming from the room temperature, the dark, to the mirror. And you can easily estimate by the volume of glass, like this, from the earth. And we support the parameter like this, and then assuming oxygen. Coil, don't ask. Coil oxygen. And we have to make the layer of the surface, and it takes 50 days to form one layer of the surface in the mirror. But at present, it is hard to estimate how it affects the optical performance. So we need to do the measurement and repeat by measuring the long-term change of the committee's penis and this situation is already set and we look these up and this is presented on Friday by Mio and I see the explanation.

50:00 Anyhow, we believe the first stage of the climate test is successful. The next problem is how to determine the climate system. This will be possible to be done with the function of the large state of the kilometer. Therefore, we apply to the project in this financial year. In parallel with this effort, we proceed with several experiments to show how climate works. This is how to hide the contamination by using two pairs of public cabinets, if one is working and the other is off in room temperature. We can switch in this way to improve the running time. Here is a rough sketch of the current system. And we are now making a new trial stack like this. It's a trial stack. It's cooled down by the high conductivity material. We use a trial bomb. And basically, we don't need liquid helium, but just in case we put liquid helium here for some power failures. And this year, we plan to make a 6-meter base rain project informator. We are going to move a new campus in Toshiba, so we plan to restore this system. And here is a schedule of organization for this project. And the cover ends in the next year, and we need some extra 3 years of ecosystem sensitivity. And after that, we wanted to start this project. And this is the organization, this MCD project. Anyhow, the basic of the coastal groups are removed. Condamnation determined that you recycle, which is not a necessary problem. The present quality of sapphire, We are looking for a worldwide program. Thank you.

52:30 Thank you. Are there any questions? What is the relationship between the temperature and the food? Yes, I don't know, but it has no relation with the temperature Q. For example, for thin silicon, the Q decreases if you decrease the temperature. And how do you explain that? I think some material science people can explain, but I don't know, several ideas, but it's hard to say that. You mentioned using one at room temperature and one at cryo temperature in order to get more duty cycles. Why not use two at cryo temperature for you all to make? Why not use two detectors at cryogenic temperatures, each of which you use half a time? That was it. Yes, sorry, I just sketched it. Other questions? Can you show the view graph of the cube of the fiber? This one? Oh, fiber? Fiber, that's right. It depends on the frequency, so we need some explanation because I think it doesn't reflect I think it's affected some fixing or some other things, but it's basically higher than 26.

55:00 Can you just briefly tell us what loss you measured in the contamination experiment, what sensitivity you had to the loss? I can't read it, just tell me what you measure. We measure the finesse and cavity transmeters and cavity regretters. And up to 30 days, it was constant. And anyhow, this was made up to 60 days. And Miyake has a recent diagram. So this trend is a very slowly decreasing trend. And I think it's corresponding to the latest measure as I explained by oxygen reading. And this rapid abrupt decrease coming from water accumulation I think this has a trouble with the vacuum system with water coming from the dead. Okay. Other questions? Okay, thank you again. I have a couple of announcements. everything's switched on I'll just say quickly that it's 1.30 on the 20th of October and I'm talking with Yasushi Mino I guess I was going to ask quickly Yasushi about the work you started on in gravitational waves As a graduate student, you started working on radiation reaction. Yeah. Well, my graduate course is at Kyoto University. And in Kyoto University, I would think that general education is important, especially the first year of master course.

57:30 So the first year in master course, I studied various things, and say, field theory, and nuclear physics, and of course, astrophysics, and the relativity and some other thing. And in the second year, you know, Shibato-san, Tanaka-san, they are great in the relativity and they suggest me to attend some seminar. But that same thing is quite informal, and there we are just reading a paper by Lan Shea or something like that, mainly a post-Newtonian, but maybe that's the beginning of my research of gravitational radiation. Yeah. And, well, of course, the linear perturbation approach is something they are most interested in. And every time they are discussing about how to calculate, I mean, how to integrate the equation using some special function, but to me, it's hard to understand because I don't know well about special function at that time. but I must think that such kind of approach is interesting or not and I thought that they are always using a global conservation law but I think that everything should be decided locally that's my idea and I asked Sasaki-san about that type of approach and he said that he also thought about that kind of approach doctor-co-student. Right. And he said that approach is very difficult when I first discussed with him. But I was very interested about this idea because no one thinks about such kind of approach at that time. So I think by myself, only by myself. And yeah, I really remember that it was the end of the year. I mean, December or something like that. At that time, just now I found that we can do the calculation following that idea.

1:00:00 But the time is, I didn't have enough time because, well, you know, our academic year began from April and end at the March 30th. So I have to submit my master's thesis around January... No, no, no. Around the beginning of February. So I have to write my master's thesis. So I only have about one month for calculation and write the master's thesis. I don't have the time, but, yeah, so I try to calculate in the laboratory. Everybody go back to their home because it's New Year days, but I just stay in the institute and calculate. And did you manage to do it in the one month? Well, you know, I think you see my Japanese thesis. Yeah, I write. I'm amazed. I did it. I wondered if you got an extension on the thesis. Yeah, too many calculations. But most of the calculations are just a copy. A little bit. Very interesting. Yeah, that's the beginning of my research about gravitational waves. So the... And what... I guess what was the particular thing that convinced you problem that way? What was the central idea that you felt? Of course, the central idea is what I made by myself. But, well, maybe I'm not some, in a sense, strange person. For the first moment, Saki-san said that it's very difficult. That was a challenge. But, yeah, I like that kind of challenging problem. And on the other hand, I myself think that if I want to be some great scientist, I have to discover something which others do not find out. So I think that problem is very interesting and it should be done by myself.

1:02:30 Yeah, that's the main motivation. Of course, if I can find some other challenging problem in other topics, I'll do some other topic. So, at the moment, you're interested in data analysis? Sorry? At the moment, you said you're interested in data analysis, right? Yeah, yeah, yeah. But data analysis is something almost established. Yes, sure. A lot of people are working on that. I can hardly find the challenging problem. So I'm not so interested compared to the radiation reaction problem. So that's still the radiation reaction? Yeah, radiation reaction is still... I mean, we only have some formal prescription about the regularization, but we do not have the method of calculation. Right. So I guess I was going to ask you if you're going to push ahead to try to calculate out. Yeah, yeah. I think I am the most near to solving the problem. Yeah. That's not true to me. So what is your goal for that? Is it to calculate, say, are you interested in calculating waveforms? It's not a waveform, it's just a force. You just want to get the motion of the evolution? Right. And are you interested at all in the waveforms coming from them, or just in the evolution? Well, I think the calculation of the waveform is not a serious problem. I mean, as long as we use linear perturbation waveform, it's easy to calculate. So the next problem is the second perturbation. Oh, okay. Yeah. So you think once you have calculated the evolution of, say, a general orbit in a linear perturbation? Yeah, I think that the serious problem in the second perturbation is also a kind of singularity, how to extract a singularity coming from the divergent potential in the linear perturbation. So I think that I can use most of the similar approach in the calculation, and I must find out some way to integrate. Do you see the work that you're doing on the radiation reaction force using the linear perturbation, do you see it as in any way, or do you see it as being motivated in any

1:05:00 way by the problem of detecting gravitational waves? I mean, do you see any connections between your work and, say, detectors like TAMO or maybe detectors like LISA? Yeah, of course, as for the detection, it must be related with LISA, especially, or the next generation detector in Brandeis. Well, I myself do not so interested about that. But we are physicists, so we have to think about such kind of detection first. that it's not so important for me, honestly speaking. Sure, it's just a challenging problem. Yeah, yeah, yeah. And so where does your work stand right now? You're looking at actually working through the calculation to evolve a general orbit around a curve? Yeah, of course, general orbit. But first of all, how to establish the calculation method. Right. Yeah. So you're still developing the method? How long do you think it will take before you can, say, evolve? Yeah, and for the method of calculation, I begin to think about. And I, yeah, in fact, my doctor's thesis is mainly the topic. Main topic of my doctor's thesis is the method to calculate. Well, so, this is the third year, so I spent two years, and, well, I think this year, I hope I can make some method, but I'm not sure, because I didn't try yet to calculate, for example, in the short sheet case or something like that. And I think that the method is almost exactly me. I was just curious about the tools that you use when you're working do you make use of do you use all pen and paper or do you sometimes make use of programs like Mathematica paper? of course I published my paper but more than one year ago I mean when you're working when you're calculating

1:07:30 do you use programs like Mathematica Mathematica, no. I don't use Mathematica recently. Yeah. Yeah, but maybe from now I have to use... Well, I prefer to use Maple rather than Mathematica. Yeah, that's what I mean. And when you use Maple, do you use it... How do you use it? Do you use it... Do you do a calculation by hand and then check it with Maple? Yeah, yeah. That's the usual way? Yeah, first calculate by hand. Well, for example, in the case, calculate by hand in the Newtonian case, and in my argument, maybe I have to calculate the full order calculation, not in the Newtonian limit. So that calculation is a little bit complicated, and I have to depend fully on Maple. But I can check by my Newtonian result. So you'll do it by hand in a limited case and do the full thing with Maple. I'm curious, actually. Some people have been asking. I've been talking to some people about using packages like Maple and Mathematica. And I know that some mathematicians, I think, complain that sometimes they get it wrong. Do you ever have problems with them? have you ever come across the case of it making a mistake yeah yeah yeah so I usually I also think I also know that sometimes I make errors so I have a collaborator you know Nakano-kun he's now at Osaka University and I make the program Maple and independently he makes a program Maple I hope that The difference of the program can classify the error of the MAPLE, I hope. But at least you've never come across a case where MAPLE has disagreed with your new programming. Yeah, yeah, yeah. Okay, that's interesting. And so this will all be part still of your doctoral thesis? Sorry?

1:10:00 In my doctor's thesis, I do my calculation by hand. So it's only now that you're using it? Yeah, because in the doctor's thesis, I just calculate the Newtonian case. Because of the higher-order case, we have some disagreement in my calculation method. Okay. So you're still working? Yeah. And with your collaborator, Nagano, in Osaka, do you meet regularly with him or do you mostly work by email? Well, mostly email, but we don't have regular meetings with him. And because, well, I think that every research should be done independently. And it is just a, this collaboration is just something special because in order to check the calculation result, because this calculation is something important for the gravitational wave research, which needs some precision of the result. So I always think that it must be done independently. Okay, so for that reason it's actually good that you don't make that up. And I myself, I have a broad interest in the physics, so I sometimes do field theory or some usual astrophysics and something like that. So I don't make some regular meetings with him. Because you're working on other problems in astrophysics. And I expect him to have such kinds of style. Sure, yeah. He probably has other things as well. Yeah. It's funny that, well, I must have think that astrophysics is some, well, integrated physics because, for example, in the galaxy formation or something like that, we need some other knowledge about the physics. So that I think this is my picture about the astrophysics and I expect him to have a similar idea of physics. so do you enjoy working in astrophysics particularly because it has more it draws on more areas of physics as opposed to say relativity where it's more pure field theory relativity is something mathematical

1:12:30 yeah very much so you so you try to you try to work a lot in astrophysics too I was curious as to whether, since you've visited Potsdam and you were in Caltech recently, is there, how much communication there is between the physics community here, or the relativity community here in Japan, and between those communities in other countries? Do you have some special communication with them? Well, I mean... I don't have some special communication. Well, because of some linguistic problem and some geographic problem, it's hard to take some communication with them. Well, it's only the time I have some special idea or something like that. discuss with them. Well, another meeting is something special because I didn't mean to attend that meeting on the street. In fact, I submitted my intention to present some talk, but after that I canceled the appointment application. But there is some trouble about that keeps me to ask you to come anyway. So I said, please give me more time to stay there in order to discuss with someone in Caltech. But it was a really good chance to make friends there. Sure. And did you find that you... Did you start any collaborations while you were in Potsdam? Oh, unfortunately not. because I could not find any good idea to collaborate with them. But, of course, I believe that the connection with Bernie is a very important thing. And, well, like this time, if I have a good chance to meet with him, I want to discuss with him. In fact, in this conference, I sent him a mail that I want to discuss about my recent idea about the data analysis.

1:15:00 But unfortunately he didn't see my mail. Right, he hasn't looked at it yet. He's a very busy person. Yeah, I know that. But then you were saying that you're not so sure about the idea now anyway. Yeah, but yesterday I said to him that I want to discuss with him today or tomorrow. So your ideas about data analysis are just sort of more general ideas? You're not involved with the TAMA much? Yeah, of course, a general idea about the data analysis. I believe that it could be an alternative for the filtering. But it's just an extension of the filtering, in fact. Yeah, it's just an extension of... You know, we usually use filtering. Oh, yeah. Yeah, but mostly the filtering, by filtering, we mean the linear, linear filtering. So I just want to say the non-linear filtering method. There seems to be some modification. Well, I don't think, I'm not sure it will be an improvement or not, but it could be an improvement if it's worse results. I was curious if you noticed that there are differences in emphasis between or that maybe the people in one country are interested in different problems than the people in another country. For instance, you mentioned that at the time. Well, of course, the difference of the interest is important, but I believe that physics, especially theoretical physics, is something which makes some frontier. The idea or the method or something like that in various aspects of physics. So, I believe that the country is not so important, but what is important is that each person has its own unique idea. So, in fact, in Japanese, most of the people are now, for example, Tanaka-san is working for making the data analysis system.

1:17:30 Of course, that's an important problem, but for me, that should not be an important problem because even if I join that kind of collaboration, I think it cannot be my unique position. So I try to be a unique. So I hope that this alternative data analysis could be an idea. Right. Sure. but it's more important for each person to have their own unique way of looking at problems I haven't made it important well thanks very much that's great thanks a lot