Jump to content

A Portal Special Presentation- Geometric Unity: A First Look: Difference between revisions

no edit summary
No edit summary
(15 intermediate revisions by 6 users not shown)
Line 1: Line 1:
== Description ==
{{EpisodeInfoBox
|title=Geometric Unity: A First Look
|image=[[File:The-portal-podcast-cover-art.jpg]]
|length=02:49:23
|releasedate=2 April 2020
|youtubedate=2 April 2020
|customlabel1=
|customdata1=
|customlabel2=
|customdata2=
|customlabel3=
|customdata3=
|customlabel4=
|customdata4=
|art19=[https://art19.com/shows/the-portal/episodes/1d49f5d9-c0ff-470d-bcaf-23348dad8ad4 Listen]
|download=[https://rss.art19.com/episodes/1d49f5d9-c0ff-470d-bcaf-23348dad8ad4.mp3 Download]
|youtube=[https://www.youtube.com/watch?v=Z7rd04KzLcg Watch]
|link4title=Blog Post
|link4=[https://theportal.group/a-portal-special-presentation-geometric-unity-a-first-look/ Read]
|prev=ep28
|next=ep29
}}


A Portal Special Presentation- Geometric Unity: A First Look
A Portal Special Presentation- Geometric Unity: A First Look


 
{{#widget:Art19Episode|show=the-portal|id=1d49f5d9-c0ff-470d-bcaf-23348dad8ad4|width=56%}}
<span class="button">[[ep28 | << Previous Episode]]</span> <span class="button">[https://art19.com/shows/the-portal/episodes/1d49f5d9-c0ff-470d-bcaf-23348dad8ad4 Listen to Presentation]</span> <span class="button">[https://rss.art19.com/episodes/1d49f5d9-c0ff-470d-bcaf-23348dad8ad4.mp3 Download Presentation (mp3)]</span> <span class="button">[https://www.youtube.com/watch?v=Z7rd04KzLcg Watch Presentation]</span> <span class="button">[[ep29 | Next Episode >>]]</span>
 
 
[[All Episodes]]


== Community Notes ==
== Community Notes ==
* https://docs.google.com/document/d/1gPU_bJR5wBs7MCsNGCW5Y06Jh3SzarX5OnJHyLxQfDQ/edit
* https://docs.google.com/document/d/1gPU_bJR5wBs7MCsNGCW5Y06Jh3SzarX5OnJHyLxQfDQ/edit


Line 17: Line 33:


== Transcript ==
== Transcript ==
[https://theportal.wiki/images/b/b9/Geometric-Unity-A-First-Look_-_YouTube.vtt Raw transcript file]
<small>[https://theportal.wiki/images/b/b9/Geometric-Unity-A-First-Look_-_YouTube.vtt Raw transcript file]</small>


===== Geometric Unity: A First Look =====
===== Geometric Unity: A First Look =====
Line 95: Line 111:
<p>[00:15:41] I respect Tyler a great deal and I enjoy his company, but I have to say that I am absolutely of a different opinion. My belief is that one has no rights and no ability as a scientist to fudge the data to meet social goals in this fashion. Another interesting interaction was the interaction with Professor [[Agnes Callard]] of the University of Chicago.
<p>[00:15:41] I respect Tyler a great deal and I enjoy his company, but I have to say that I am absolutely of a different opinion. My belief is that one has no rights and no ability as a scientist to fudge the data to meet social goals in this fashion. Another interesting interaction was the interaction with Professor [[Agnes Callard]] of the University of Chicago.


<p>[00:16:05] Now, when she listened to [[episode 19]] about [[Bret Weinstein]], she found that it was a very compelling episode, but strangely, even though the point of the episode was to surface Bret's long forgotten theory, because Bret had not been acknowledged as having predicted that laboratory mice would in particular have radically elongated [[telomere]]s where it was thought that all mice had long, radically elongated telomeres which has incredible potential implications for drug testing and all of the work that is done on laboratory, rodents as model organisms.
<p>[00:16:05] Now, when she listened to [[19: Bret Weinstein - The Prediction and the DISC|episode 19]] about [[Bret Weinstein]], she found that it was a very compelling episode, but strangely, even though the point of the episode was to surface Bret's long forgotten theory, because Bret had not been acknowledged as having predicted that laboratory mice would in particular have radically elongated [[Telomere|telomeres]] where it was thought that all mice had long, radically elongated telomeres which has incredible potential implications for drug testing and all of the work that is done on laboratory, rodents as model organisms.


<p>[00:16:43] This is an episode you should definitely listen to if you haven't already. But Agnes's perspective was very different than mine. Her feeling was that because we were in a situation in which the work actually surfaced, that the system worked, even if it was the case that Bret's name was erased from the history of the development.
<p>[00:16:43] This is an episode you should definitely listen to if you haven't already. But Agnes's perspective was very different than mine. Her feeling was that because we were in a situation in which the work actually surfaced, that the system worked, even if it was the case that Bret's name was erased from the history of the development.
Line 175: Line 191:
<p>[00:32:34] I also want to thank [[Isadore Singer]] for effectively saving me from not getting a PhD. By, I think, putting pressure on the Harvard department and for coming to my assistance, making sure that I got a postdoc at MIT, despite not having any publications at all.  
<p>[00:32:34] I also want to thank [[Isadore Singer]] for effectively saving me from not getting a PhD. By, I think, putting pressure on the Harvard department and for coming to my assistance, making sure that I got a postdoc at MIT, despite not having any publications at all.  


<p>[00:32:56] I'd like to think Raoul Bott, who's no longer with us. Who I should have invited to my wedding. I was very angry at him, but I didn't realize that he was saving me in a very difficult situation against the department that probably just wanted to see me gone. I'd like to thank Peter Thiel. One of my closest friends is like a brother to me for allowing me these seven years since this lecture to lick my wounds, to get strong, to have a 401(k), to buy a house. And, to begin coming back to regular society after a very difficult and strained career.  
<p>[00:32:56] I'd like to thank Raoul Bott, who's no longer with us. Who I should have invited to my wedding. I was very angry at him, but I didn't realize that he was saving me in a very difficult situation against the department that probably just wanted to see me gone. I'd like to thank Peter Thiel. One of my closest friends is like a brother to me for allowing me these seven years since this lecture to lick my wounds, to get strong, to have a 401(k), to buy a house. And, to begin coming back to regular society after a very difficult and strained career.  


<p>[00:33:21] I'd like to thank Adil Abdulali and Michael Grossberg. The two greatest, best friends from college a guy could have. I'd like to thank my grandfather, Harry Ruben, who believed in things that couldn't possibly be true and made some of them happen.
<p>[00:33:21] I'd like to thank Adil Abdulali and Michael Grossberg. The two greatest, best friends from college a guy could have. I'd like to thank my grandfather, Harry Ruben, who believed in things that couldn't possibly be true and made some of them happen.
Line 200: Line 216:
I first met Eric Weinstein when we were both post-docs at the Hebrew University just over 20 years ago, and I had the feeling then that he was working on something big, but it wasn't until two years ago that Eric met me at a bar in New York.
I first met Eric Weinstein when we were both post-docs at the Hebrew University just over 20 years ago, and I had the feeling then that he was working on something big, but it wasn't until two years ago that Eric met me at a bar in New York.


<p>[00:36:24] And we began, he began to explain the mathematics teaching working on in private for the last 20 years. As he took me through the equations he had been formulating, I began to see emerging before my eyes potential answers to many of the major problems in physics. It was an extremely exciting, daring proposal, and also mathematically so natural that it started to work it's magic on me. Over the last two years, I have had the privilege of being taken through the twists and turns of Eric's ideas. After our postdocs in Israel when I went the academic route getting my professorship here in Oxford, Eric went a more independent route working in economics, government, and finance.
<p>[00:36:24] And we began, he began to explain the mathematics he had been working on in private for the last 20 years. As he took me through the equations he had been formulating, I began to see emerging before my eyes potential answers to many of the major problems in physics. It was an extremely exciting, daring proposal, and also mathematically so natural that it started to work it's magic on me. Over the last two years, I have had the privilege of being taken through the twists and turns of Eric's ideas. After our postdocs in Israel when I went the academic route getting my professorship here in Oxford, Eric went a more independent route working in economics, government, and finance.


<p>[00:37:05] So he comes here today as something of an insider and an outsider, a difficult place from which to propose bold ideas. But having spent time seeing how powerful these ideas appear to be, I felt it that it was time that Eric shared his ideas more widely as I believe his perspective could give the scientific community a new story to explain to some of the big questions on the scientific books.
<p>[00:37:05] So he comes here today as something of an insider and an outsider, a difficult place from which to propose bold ideas. But having spent time seeing how powerful these ideas appear to be, I felt it that it was time that Eric shared his ideas more widely as I believe his perspective could give the scientific community a new story to explain to some of the big questions on the scientific books.
Line 219: Line 235:
<p>[00:39:33] So we have to, in some sense, begin to undo some of what we think we know, in order to truly reconsider, and allow me to put some of these ideas before you today.
<p>[00:39:33] So we have to, in some sense, begin to undo some of what we think we know, in order to truly reconsider, and allow me to put some of these ideas before you today.


<p>[00:39:47] Marcus asked me to begin presenting these ideas here. And hopefully this is the first opportunity, but if the ideas are not good then lighting on the aisles will lead you to safety and your exits may be behind you. But, in the event of a good flight , hopefully this will begin a conversation rather than be the end of one.
<p>[00:39:47] Marcus asked me to begin presenting these ideas here. And hopefully this is the first opportunity, but if the ideas are not good, then lighting on the aisles will lead you to safety, and your exits may be behind you. But, in the event of a good flight, hopefully this will begin a conversation rather than be the end of one.


<p>[00:40:10] I feel in some sense that I'm presenting the works of another man, a younger man. Someone who came of age right in the middle of the great string theory boom. With the anomaly cancellation in 1984. And I look at this work and I see a young person struggling with the idea, why can't I see that string theory is going to answer all of these questions over the next ten years, as we were told at the time, and making a very dangerous decision, which was, I think I'm not going to follow that particular path, and I'm going to follow another.
<p>[00:40:10] I feel in some sense that I'm presenting the works of another man, a younger man. Someone who came of age right in the middle of the great string theory boom. With the anomaly cancellation in 1984. And I look at this work and I see a young person struggling with the idea: "why can't I see that string theory is going to answer all of these questions over the next ten years?", as we were told at the time, and making a very dangerous decision, which was, "I think I'm not going to follow that particular path, and I'm going to follow another."


<p>[00:40:45] And it's not clear where this path is going to lead us, but we're going to explore it today and see as best we can. So, in some sense, I've been able to polish some of that young man's work, but I'm also struggling to reconstruct it, because as someone spending full time on that theory, he knew a lot of things that I no longer know.
<p>[00:40:45] And it's not clear where this path is going to lead us, but we're going to explore it today and see as best we can. So, in some sense, I've been able to polish some of that young man's work, but I'm also struggling to reconstruct it, because as someone spending full time on that theory, he knew a lot of things that I no longer know.
Line 239: Line 255:
<p>[00:43:12] And, of course, I'm running into the margin. Okay.
<p>[00:43:12] And, of course, I'm running into the margin. Okay.


<p>[00:43:18] So, it says that a piece of the [[Riemann curvature tensor]] or the Ricci tensor minus an even smaller piece, the scalar curvature multiplied by the metric is equal plus the cosmological constant is equal to some amount of matter and energy, the stress energy tensor. So it's intrinsically a curvature equation.  
<p>[00:43:18] So, it says that a piece of the [[Riemann curvature tensor]], or the Ricci tensor minus an even smaller piece, the scalar curvature multiplied by the metric is equal, plus the cosmological constant, is equal to some amount of matter and energy, the stress energy tensor. So it's intrinsically a curvature equation.  


<p>[00:43:47] The second fundamental insight... I'm going to begin to start drawing pictures here as well.
<p>[00:43:47] The second fundamental insight... I'm going to begin to start drawing pictures here as well.


<p>[00:43:55] So, if this is the space-time manifold, "the arena"; the second one concerns symmetry groups which cannot necessarily be deduced from any structure inside of "the arena". They are additional data that come to us out of the blue without explanation and these symmetries for a non-Abelian group, which is currently SU(3) "color" x SU(2) "weak" x U(1) "weak hypercharge", which breaks down to SU(3)xU(1), where the broken U(1) is the electromagnetic symmetry.
<p>[00:43:55] So, if this is the space-time manifold, "the arena"; the second one concerns symmetry groups which cannot necessarily be deduced from any structure inside of "the arena". They are additional data that come to us out of the blue without explanation and these symmetries from a non-Abelian group, which is currently SU(3) "color" x SU(2) "weak" x U(1) "weak hypercharge", which breaks down to SU(3)xU(1), where the broken U(1) is the electromagnetic symmetry.


<p>[00:44:54] This equation is also a curvature equation, the corresponding equation, the curvature of an auxiliary structure known as a gauge potential when differentiated in a particular way is equal, again, to the amount of stuff in the system that is not directly involved in the left-hand side of the equation. So, it has many similarities to the above equation. Both involve curvature. One involves a projection or a series of projections. The other involves a differential operator.
<p>[00:44:54] This equation is also a curvature equation. The corresponding equation, the curvature of an auxiliary structure known as a gauge potential when differentiated in a particular way is equal, again, to the amount of stuff in the system that is not directly involved in the left-hand side of the equation. So, it has many similarities to the above equation. Both involve curvature. One involves a projection or a series of projections. The other involves a differential operator.


<p>[00:45:44] The third point surrounds the matter in the system.
<p>[00:45:44] The third point surrounds the matter in the system.
Line 253: Line 269:
<p>[00:46:12] One of the great insights is that the reason for the lightness of matter in the natural mass scale of physics has to do with the fact that this $$\psi$$ really should have two components and the differential operators should map to one component on the other side of the equation, but the mass operators should map to another.
<p>[00:46:12] One of the great insights is that the reason for the lightness of matter in the natural mass scale of physics has to do with the fact that this $$\psi$$ really should have two components and the differential operators should map to one component on the other side of the equation, but the mass operators should map to another.


<p>[00:46:33] And so if one of the components is missing, if the equation is intrinsically lopsided, chiral, asymmetric, then the mass term and the differential term have difficulty interacting, which is sort of overcompensating for the mass scale of the universe so you get to a point where you actually have to define a massless equation, but then just like overshooting a putt, it's easier to knock it back by putting in a [[Higgs field]] in order to generate an "as-if" fundamental mass through the [[Yukawa couplings]].
<p>[00:46:33] And so if one of the components is missing, if the equation is intrinsically lopsided, chiral, asymmetric; then the mass term and the differential term have difficulty interacting, which is sort of overcompensating for the mass scale of the universe, so you get to a point where you actually have to define a massless equation. But then, just like overshooting a putt, it's easier to knock it back by putting in a [[Higgs field]] in order to generate an "as-if" fundamental mass through the [[Yukawa couplings]].


<p>[00:47:15] Let me, for consistency, say "matter is asymmetric", okay. "and therefore light".
<p>[00:47:15] Let me, for consistency, say "matter is asymmetric", okay. "and, therefore [also], light".


<p>[00:47:35] And then interestingly, he went on to say one more thing. He said, of course, these three central observations must be supplemented with the idea that this all [be] treated in quantum mechanical fashion or quantum field theoretic [fashion]. So it's a bit of an after-market modification, rather than his opinion at the time, [or] one of the core insights.
<p>[00:47:35] And then interestingly, he went on to say one more thing. He said, of course, these three central observations must be supplemented with the idea that this all [be] treated in quantum mechanical fashion or quantum field theoretic [fashion]. So it's a bit of an after-market modification rather than, in his opinion at the time, one of the core insights.


<p>[00:48:07] I actually think that that's in some sense about right. No. One of my differences with the [modern-day physics] community in some sense is I question whether the quantum isn't in good enough shape. We don't know whether we have a serious quantum mechanical problem or not. We know that we have a quantum mechanical problem, a quantum field theoretic problem, [but only] relative to the current formulations of these theories.
<p>[00:48:07] I actually think that that's in some sense about right. No. One of my differences with the [modern-day physics] community -- in some sense -- is I question whether the quantum isn't in good enough shape. We don't know whether we have a serious quantum mechanical problem or not. We know that we have a quantum mechanical problem, a quantum field theoretic problem, [but only] relative to the current formulations of these theories.


<p>[00:48:31] But we know that in some other cases, the quantum becomes incredibly natural, sometimes sort of almost magically natural, and we don't know whether the true theories that we will need to be generalizing, in some sense, have beautiful quantum mechanical treatments. Whereas the effective theories that we're dealing with now may not survive the quantization.
<p>[00:48:31] But we know that in some other cases, the quantum becomes incredibly natural, sometimes sort of almost magically natural, and we don't know whether the true theories that we will need to be generalizing, in some sense, have beautiful quantum mechanical treatments. Whereas the effective theories that we're dealing with now may not survive the quantization.
Line 278: Line 294:
<p>[00:51:34] In addition to all of that freedom is some means of taking away some of the redundancy that comes with that freedom, which is the action of the gauge group. Now we can allow the gauge group of symmetries to act on both sides of the equation, but the key problem is that.
<p>[00:51:34] In addition to all of that freedom is some means of taking away some of the redundancy that comes with that freedom, which is the action of the gauge group. Now we can allow the gauge group of symmetries to act on both sides of the equation, but the key problem is that.


<p>[00:52:03] If I act on connections on the right and then take the Einstein projection, this is not equal to first taking the projection and then conjugating with the gauge action. So the problem is, is that the projection is based on the fact that you have a relationship between the intrinsic geometry. If this is an ad-valued two-form, the two-form portion of this and the adjoint portion of this are both associated to the structure group of the tangent bundle.
<p>[00:52:03] If I act on connections on the right and then take the Einstein projection, this is not equal to first taking the projection and then conjugating with the gauge action. So the problem is, is that the projection is based on the fact that you have a relationship between the intrinsic geometry. If this is an ad[joint]-valued two-form, the two-form portion of this and the adjoint portion of this are both associated to the structure group of the tangent bundle.


<p>[00:52:52] But the gauge rotation is only acting on one of the two factors. Yet the projection is making use of both of them. So there is a fundamental incompatibility in the claim that Einstein's theory is a gauge theory relies more on analogy than an exact mapping between the two theories. What about the incompatibilities between the Einstein theory of general relativity and the Dirac theory of matter?
<p>[00:52:52] But the gauge rotation is only acting on one of the two factors. Yet the projection is making use of both of them. So there is a fundamental incompatibility in the claim that Einstein's theory is a gauge theory relies more on analogy than an exact mapping between the two theories. What about the incompatibilities between the Einstein theory of general relativity and the Dirac theory of matter?
Line 455: Line 471:
<p>[01:24:06] So when I was thinking about this, I used to be amazed by ships in bottles. I must confess that I never figured out what the trick was for ships in bottles, but once I saw it, I remembered thinking, that's really clever. So if you've never seen it, you have a ship, which is like a curvature tensor. And imagine that the mast is the Ricci curvature.
<p>[01:24:06] So when I was thinking about this, I used to be amazed by ships in bottles. I must confess that I never figured out what the trick was for ships in bottles, but once I saw it, I remembered thinking, that's really clever. So if you've never seen it, you have a ship, which is like a curvature tensor. And imagine that the mast is the Ricci curvature.


<p>[01:24:30] If you just try to shove it into the bottle, you're undoubtedly going to snap the mast. So, you imagine that you've transformed your gauge fields, you've kept track of where the Ricci curvature was, uou try to push it from one space, like ad-valued two-forms into another space like ad-valued one-forms, where connections live.
<p>[01:24:30] If you just try to shove it into the bottle, you're undoubtedly going to snap the mast. So, you imagine that you've transformed your gauge fields, you've kept track of where the Ricci curvature was, you try to push it from one space, like ad[joint]-valued two-forms into another space like ad[joint]-valued one-forms, where connections live.


<p>[01:24:54] That's not a good idea. Instead, what we do is the following: imagine that you're carrying around group theoretic information and what you do is you do a transformation based on the group theory. So you lower the mast. You push it through the neck, having some string attached to the mast, and then you undo the transformation on the other side.
<p>[01:24:54] That's not a good idea. Instead, what we do is the following: imagine that you're carrying around group theoretic information and what you do is you do a transformation based on the group theory. So you lower the mast. You push it through the neck, having some string attached to the mast, and then you undo the transformation on the other side.
Line 463: Line 479:
====== Unified Content ======
====== Unified Content ======


<p>[01:25:43] Let's think about unified content. We know that we want a space of connections, $$A$$ for our field theory, but we know because we have a Levi-Civita connection, that this is going to be equal on-the-nose to ad-valued one-forms $$(\Omega^{1}(Ad))$$ as a vector space. The gauge group represents an ad-valued one-forms. So, if we also have the gauge group ($$\mathcal{H}$$), but we think of that instead as a space of sigma fields.
<p>[01:25:43] Let's think about unified content. We know that we want a space of connections, $$A$$ for our field theory, but we know because we have a Levi-Civita connection, that this is going to be equal on-the-nose to ad[joint]-valued one-forms $$(\Omega^{1}(Ad))$$ as a vector space. The gauge group represents an ad[joint]-valued one-forms. So, if we also have the gauge group ($$\mathcal{H}$$), but we think of that instead as a space of sigma fields.


<p>[01:26:16] What if we take the semi-direct product ($$\ltimes$$) at a group theoretic level between the two and call this our group of interest. Well, by analogy, we've always had a problem with the Poincaré group being too intrinsically tied to rigid, flat Minkowski space. What if we wanted to do quantum field theory in some situation which was more amenable to a curved space situation?
<p>[01:26:16] What if we take the semi-direct product ($$\ltimes$$) at a group theoretic level between the two and call this our group of interest. Well, by analogy, we've always had a problem with the Poincaré group being too intrinsically tied to rigid, flat Minkowski space. What if we wanted to do quantum field theory in some situation which was more amenable to a curved space situation?


<p>[01:26:44] It's possible that we should be basing it around something more akin to the gauge group. And in this case, we're mimicking the construction where $$\Xi$$ here would be analogous to the Lorentz group fixing a point in Mankowski space. And the ad-valued one-forms would be analogous to the four momentums we take in the semi-direct product to create the inhomogeneous Lorentz group, otherwise known as the Poincaré group, or rather its double cover to allow spin.
<p>[01:26:44] It's possible that we should be basing it around something more akin to the gauge group. And in this case, we're mimicking the construction where $$\Xi$$ here would be analogous to the Lorentz group fixing a point in Mankowski space. And the ad[joint]-valued one-forms would be analogous to the four momentums we take in the semi-direct product to create the inhomogeneous Lorentz group, otherwise known as the Poincaré group, or rather its double cover to allow spin.


<p>[01:27:12] So we're going to call this the inhomogeneous gauge group, or iggy.
<p>[01:27:12] So we're going to call this the inhomogeneous gauge group, or iggy.
Line 515: Line 531:
<p>[01:37:34] So, for example, I can define a Shiab ("Ship in a bottle") operator that takes [$$\Omega^{i}$$] $$i$$-forms valued in the adjoint bundle to much higher-degree forms valued in the adjoint bundle.  
<p>[01:37:34] So, for example, I can define a Shiab ("Ship in a bottle") operator that takes [$$\Omega^{i}$$] $$i$$-forms valued in the adjoint bundle to much higher-degree forms valued in the adjoint bundle.  


<p>[01:38:00] So, for in this case, for example [where i = 2], it would take a two-form to a d-minus-three-plus-two or a d-minus-one-form. So, curvature is an ad-valued two-form. And, if I had such a Shiab operator, it would take ad-valued two-forms to ad-valued d-minus-one-forms, which is exactly the right space to be an $$\alpha$$ coming from the derivative of an action.
<p>[01:38:00] So, for in this case, for example [where i = 2], it would take a two-form to a d-minus-three-plus-two or a d-minus-one-form. So, curvature is an ad[joint]-valued two-form. And, if I had such a Shiab operator, it would take ad[joint]-valued two-forms to ad[joint]-valued d-minus-one-forms, which is exactly the right space to be an $$\alpha$$ coming from the derivative of an action.


<p>[01:38:38] This is exactly what Einstein was doing. He took the curvature, which was large, and he bent it back and he sheared off the [[Weyl curvature]] and he took that part and he pushed it back along the space of metrics to give us something which we nowadays call [[Ricci Flow]] and ability for the curvature to direct us to the next structure.
<p>[01:38:38] This is exactly what Einstein was doing. He took the curvature, which was large, and he bent it back and he sheared off the [[Weyl curvature]] and he took that part and he pushed it back along the space of metrics to give us something which we nowadays call [[Ricci Flow]] and ability for the curvature to direct us to the next structure.
Line 576: Line 592:
<p>[01:49:59] But I am also going to have a derivative operator if I just do a star operation. So, I need another derivative operator to kill it off here. So I'm going to take minus the derivative with respect to the connection, $$H^{-1}$$ $$d_{A_0}$$ $$H$$ which defines a connection one-form as well as having the same derivative coming from the Levi-Civita connection on $$U$$.
<p>[01:49:59] But I am also going to have a derivative operator if I just do a star operation. So, I need another derivative operator to kill it off here. So I'm going to take minus the derivative with respect to the connection, $$H^{-1}$$ $$d_{A_0}$$ $$H$$ which defines a connection one-form as well as having the same derivative coming from the Levi-Civita connection on $$U$$.


<p>[01:50:15] So in other words, I have two derivative operators here. I have two ad-value one-forms. The difference between them has been to be a zero-th order, and it's going to be precisely the augmented torsion. And that's the same game I'm going to repeat here.
<p>[01:50:15] So in other words, I have two derivative operators here. I have two ad[joint]-value one-forms. The difference between them has been to be a zero-th order, and it's going to be precisely the augmented torsion. And that's the same game I'm going to repeat here.


<p>[01:50:52] I'm going to do the same thing here. I'm going to define a bunch of terms. In the numerator I'm going to pick up a $$\pi$$ as well as the derivative in the denominator -- because I have no derivative here -- I'm going to pick up this $$H^{-1}$$ $$d_{A_0}$$ $$H$$.
<p>[01:50:52] I'm going to do the same thing here. I'm going to define a bunch of terms. In the numerator I'm going to pick up a $$\pi$$ as well as the derivative in the denominator -- because I have no derivative here -- I'm going to pick up this $$H^{-1}$$ $$d_{A_0}$$ $$H$$.
Line 745: Line 761:
<p>[02:28:10] Yeah. We can call this map the bi-connection, which gives us two separate connections for any point in the inhomogeneous gauge group. And we can notice that it can be viewed as a section of a bundle over the base space to come. We find an interesting embedding of the gauge group that is not the standard one in the inhomogeneous gauge group.
<p>[02:28:10] Yeah. We can call this map the bi-connection, which gives us two separate connections for any point in the inhomogeneous gauge group. And we can notice that it can be viewed as a section of a bundle over the base space to come. We find an interesting embedding of the gauge group that is not the standard one in the inhomogeneous gauge group.


<p>[02:28:42] So our summary diagram looks something like this. Take a look at the Taus of $$A_0$$. We will find a homeomorphism of the gauge group into its inhomogeneous extension that isn't simply inclusion under the first factor. And I'm realizing that I have the wrong pi production. That should just be as simple $$\pi$$, projecting down, we have a map from the inhomogeneous gauge group, via the bi-connection to A cross A connections cross connections, and that that behaves well according to the difference operator $$\delta$$ that takes the difference of two connections and gives an honest ad-valued one-form.
<p>[02:28:42] So our summary diagram looks something like this. Take a look at the Taus of $$A_0$$. We will find a homeomorphism of the gauge group into its inhomogeneous extension that isn't simply inclusion under the first factor. And I'm realizing that I have the wrong pi production. That should just be as simple $$\pi$$, projecting down, we have a map from the inhomogeneous gauge group, via the bi-connection to A cross A connections cross connections, and that that behaves well according to the difference operator $$\delta$$ that takes the difference of two connections and gives an honest ad[joint]-valued one-form.


<p>[02:29:23] The infinitesimal action of the gauge transformation of a gauge transformation, or at least an infinite testable one on a point inside of the group is given by a somewhat, almost familiar expression, which should remind us of how the first term in the gauge deformation complex for Self-Dual Yang-Mills actually gets started.
<p>[02:29:23] The infinitesimal action of the gauge transformation of a gauge transformation, or at least an infinite testable one on a point inside of the group is given by a somewhat, almost familiar expression, which should remind us of how the first term in the gauge deformation complex for Self-Dual Yang-Mills actually gets started.
Line 755: Line 771:
<p>[02:30:42] So we're dealing with, I think it's $$U^{128}$$, $$U^{2^7}$$. That is our structure group and it is fixed by the choice of $$X^4$$ not anything else. So what do we get? Well, as promised, there is a tilted homomomorphism which takes the gauge group into its inhomogeneous extension. It acts as inclusion on the first factor, but it uses the Levi-Civita connection to create a second sort of Maurer-Cartan form.
<p>[02:30:42] So we're dealing with, I think it's $$U^{128}$$, $$U^{2^7}$$. That is our structure group and it is fixed by the choice of $$X^4$$ not anything else. So what do we get? Well, as promised, there is a tilted homomomorphism which takes the gauge group into its inhomogeneous extension. It acts as inclusion on the first factor, but it uses the Levi-Civita connection to create a second sort of Maurer-Cartan form.


<p>[02:31:17] I hope I remember the terminology right. It's been a long time. The map is injective because it's injective under the first factor, but it actually gives us a nontrivial embedding of the gauge group in its inhomogeneous extension, which makes the whole theory work. We then get to Shiab operators. Now, a Shiab operator a map from the group crossed the ad-valued i forms.
<p>[02:31:17] I hope I remember the terminology right. It's been a long time. The map is injective because it's injective under the first factor, but it actually gives us a nontrivial embedding of the gauge group in its inhomogeneous extension, which makes the whole theory work. We then get to Shiab operators. Now, a Shiab operator a map from the group crossed the ad[joint]-valued i forms.


<p>[02:31:43] In this case, the particular Shiab operators we’re interested in is mapping i form is to d minus three, plus i forms. So, for example, you would map a two form to a d minus three plus i. So if d, for example, were 14, ..., and i was equal to two. Then 14 minus three is equal to 11 plus two is equal to 13. So that would be an ad-valued 14 minus one form, which is exactly the right place for something to form a current. That is the differential of a Lagrangian on the space.
<p>[02:31:43] In this case, the particular Shiab operators we’re interested in is mapping i form is to d minus three, plus i forms. So, for example, you would map a two form to a d minus three plus i. So if d, for example, were 14, ..., and i was equal to two. Then 14 minus three is equal to 11 plus two is equal to 13. So that would be an ad[joint]-valued 14 minus one form, which is exactly the right place for something to form a current. That is the differential of a Lagrangian on the space.


<p>[02:32:38] Now the augmented torsion, the torsion is a very strange object. It's introduced sort of right at the beginning of learning a differential geometry, but it really doesn't get used very much. One of the reasons it doesn't get used, gauge theory is that it's not gauge invariant. It has a gauge and variant piece to it, but then a piece that spoils the gauge invariant.
<p>[02:32:38] Now the augmented torsion, the torsion is a very strange object. It's introduced sort of right at the beginning of learning a differential geometry, but it really doesn't get used very much. One of the reasons it doesn't get used, gauge theory is that it's not gauge invariant. It has a gauge and variant piece to it, but then a piece that spoils the gauge invariant.
Line 838: Line 854:


<p>[02:48:08] And most particularly an American science, which I think is still the envy of the world. So you've been through the portal. I know it was a long slog. I hope you found it interesting and enjoyable and we'll see you again soon. Be well, everybody stay safe.
<p>[02:48:08] And most particularly an American science, which I think is still the envy of the world. So you've been through the portal. I know it was a long slog. I hope you found it interesting and enjoyable and we'll see you again soon. Be well, everybody stay safe.
[[Category:Podcast Episodes]]