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## "Modification of the radiation definition in odd dimensions"

## Mikhail Khlopunov, ITMP

**October 28, 2020 (Wednesday)**

Abstract: In this seminar, I will discuss modification of the radiation definition for the case of odd-dimensional space-time. The standard definition of the wave zone fails in odd dimensions, due to the violation of the Huygens principle: the signal from an instantaneous flash of current reaches an observer after an interval of time required for propagation of the signal at the speed of light, but then the tail is observed endlessly; while in even-dimensional spaces an instant signal ends instantly at the observation point. The reason is that the retarded Green’s functions of the wave equation in odd dimensions has support localised not only on the light cone, but also inside it. I will discuss the covariant retarded quantities technique and Rohrlich-Teitelboim definition of the wave zone. Using this definition, the scalar radiation from a point-like charge, moving along the circular trajectory in three and five-dimensional space-times, will be computed. The obtained results will be verified by the calculations of the spectral distributions of the radiated energy, which are indifferent to the dimensionality of the space-time. Also, the contributions of the tails to the radiation will be discussed.

If you want to join the seminar please register here before 14:00, October 28.

Presentation

If you would like to subscribe to newsletters about ITMP seminars, please, contact seminar@itmp.msu.ru

## "On double elliptic integrable system: characteristic determinant and Manakov triple"

## Dr. Andrei Zotov, Steklov Mathematical Institute RAS

**October 21, 2020 (Wednesday)**

Abstract: We discuss double elliptic integrable systems, where the dependence on the momenta of particles is elliptic. These models generalize the relativistic Ruijsenaars integrable systems, which contain trigonometric (exponential) dependence on momenta. A brief review on underlying dualities and interrelations between integrable systems will be given. We explain how to construct a kind of determinant representation for the known conservation laws. Finally, we will see that in the classical case the double elliptic models are naturally described by the Manakov L-A-B triple instead of the Lax pair.

If you want to join the seminar please register here before 14:00, October 21.

Presentation

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## "Production of massive particles from the decay of a free massless field"

## Dr. Ariel Arza, ITMP

**October 07, 2020 (Wednesday)**

Abstract: In this talk we will show, in a simple toy model (H=g\phi\chi^2), how Bose enhancement allows the decay of a massless field into massive particles. It happens due to a parametric resonance caused by a big energy density of the decaying field. I will show the instability conditions as well as the energy density threshold for the decay to occur. I will also compute the equivalent of the spontaneous decay rate.

ITMP seminar will be held on Wednesday, October 07 at 18:00. The seminar will be arranged via Zoom.

If you want to join the seminar please register here before 14:00, October 07.

## "Hamiltonian structures of the spin Ruijsenaars-Schneider models"

## Prof. Gleb Arutyunov, University of Hamburg

**September 30, 2020 (Wednesday)**

Abstract: TBA

ITMP seminar will be held on Wednesday, September 30 at 18:00. The seminar will be arranged via Zoom.

If you want to join the seminar please register here before 14:00, September 30.

## "Constrained modified gravities: generalized unimodular gravity and beyond"

## Nikita Kolganov, ITMP

**September 23, 2020 (Wednesday)**

Abstract: In my talk, I will give you a brief introduction into modified gravity theories, and then I will proceed to particular modified gravity models, which I'm interested in. Most of the modified gravities are equivalent to the General Relativity, equipped with some additional degrees of freedom. In our case these d.o.f. are obtained by the explicit breaking of general covariance by an algebraic constraint on metric coefficients. I'm going to discuss the covariantization issue of such theories, its duality to well-known k-essence and self-gravitating media models, and applications to inflationary cosmology.

ITMP seminar will be held on Wednesday, September 23 at 18:00. The seminar will be arranged via Zoom.

If you want to join the seminar please register here before 14:00, September 23.

## "Schwarzschild black hole thermodynamic entropy on a nice slice"

## Dr. Jose Alejandro Rosabal, Asia Pacific Center for Theoretical Physics, Pohang

**July 22, 2020 (Wednesday)**

Abstract: In this seminar I will present the calculation of the thermodynamic entropy of a Schwarzschild black hole on a nice slice. This can be seen as a warm up to address the calculation of the Von Neumann entropy for two intervals, that includes a portion of the interior of the black hole, and the Page curve. In the end I will comment on the relation between this work and some recent proposal.

ITMP seminar will be held on Wednesday, July 22 at 14:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 11:00, July 22.

## "Gauge/gravity duality and the phenomenology of hadrons"

## Dr. Frederic Brunner, Vienna University of Technology (TU Wien)

**July 8, 2020 (Wednesday)**

Abstract: I will give a pedagogical introduction to aspects of hadronic physics at low energy, and show how the methodology of gauge/gravity duality may be applied to certain problems arising in this context. As a concrete example, I will talk about the search for glueballs, bound states of gluons predicted by lattice gauge theory. These states have not been identified unambiguously among the hadrons we observe in collider experiments, in part due to the lack of theoretical predictions of their decay rates. I will show how gauge/gravity duality can be used to calculate glueball decay rates, and discuss potential implications.

ITMP seminar will be held on Wednesday, July 8 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, July 8.

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## "Current Algebra and Generalised Geometry"

## Dr. David Osten, Ludwig Maximilian University/Max-Planck-Institute for Physics, Munich

**June 24, 2020 (Wednesday)**

Abstract: The first part of the talk will be a review of T-duality and generalised geometry in string theory. Generalised geometry is a generalisation of Riemannian geometry that captures certain 'non-geometric' backgrounds which are nevertheless well-defined in string theory. A convenient characterisation of such backgrounds is given in terms of the so-called generalised fluxes. In the second part of the talk I want to discuss the meaning of these generalised fluxes in the worldsheet theory. There, they describe a deformation of the canonical Poisson structure -- namely the current algebra. Besides applications to magnetic backgrounds and integrable sigma models which motivated this work, the virtue of the deformed current algebra lies in the fact that it gives clear-cut routes to non-commutative and non-associative interpretations of the generalised flux backgrounds, to generalisations of T-duality and to generalisations to M-theory.

ITMP seminar will be held on Wednesday, June 24 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, June 23.

## “Introduction to the TT̄ deformation”

## Dr. Riccardo Conti, Turin University

**June 10, 2020 (Wednesday)**

Abstract: In this talk I will give a pedagogical introduction to a special irrelevant deformation of 2-dimensional Quantum Field Theories, the so-called TT̄ deformation, which has recently attracted the attention of the theoretical physics community due to the interesting links with string theory and the AdS/CFT correspondence. I will review some basic aspects of this deformation and describe the principal features of the deformed models both at classical and quantum level. Finally, I will briefly comment on other similar irrelevant deformations and present a series of interesting open questions that still wait for answers.

ITMP seminar will be held on Wednesday, June 10 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, June 10.

## "Efficient Rules for All Conformal Blocks: A Dream Come True"

## Dr. Valentina Prilepina, Laval University

**May 27, 2020 (Wednesday)**

Abstract: In this talk, I will lay out a set of efficient rules for computing d-dimensional global conformal blocks in arbitrary Lorentz representations in the context of the embedding space operator product expansion (OPE) formalism. With these rules in place, the general procedure for determining all possible conformal blocks is reduced to (1) identifying the relevant group theoretic quantities and (2) applying the conformal rules to obtain the blocks. The rules represent a systematic prescription for computing the blocks in a convenient mixed OPE-three-point- function basis as well as a set of rotation matrices, which are necessary to translate these blocks to the pure three-point function basis relevant for the conformal bootstrap. I will start by tracing their origin by describing some of the essential ingredients present in the formalism that naturally give rise to these rules. I will then map out the derivation of the rules, first outlining the general algorithm for the rotation matrices and then proceeding to the conformal blocks. Along the way, l will introduce a convenient diagrammatic notation (somewhat reminiscent of Feynman diagrams), which serves to encode parts of the computation in a compact form. Finally, I will treat several interesting examples to demonstrate the application of these rules in practice.

ITMP seminar will be held on Wednesday, May 27 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, May 27.

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## "The echo method for axion dark matter detection"

## Dr. Ariel Arza, ITMP

**May 13, 2020 (Wednesday)**

Abstract: The echo method is a new idea for axion dark matter search. It relies on the stimulated decay of cold axions into two photons when a powerful beam of microwave radiation is shot to the space. From the axion decay, a feeble but detectable amount of electromagnetic radiation is received nearby the location where the outgoing beam was released. In this talk I will describe the essentials of this idea as well as the challenges for the future.

ITMP seminar will be held on Wednesday, May 13 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, May 13.

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## "Polyvector deformations in supergravity and the string/M-theory dynamics"

## Dr. Ilya Bakhmatov, ITMP

**April 29, 2020 (Wednesday)**

Abstract: Integrability preserving Yang-Baxter deformations of the string sigma-model have a simple supergravity description. We will review how introducing an extra bi-vector field to account for the r-matrix, one recovers the YB deformations after the simple open/closed string map. Things can be made clearer by using the formalism of double field theory, a T-duality covariant description of supergravity defined on an extended spacetime. We will discuss generalisations to the tri-vector deformations of d=11 supergravity and potential consequences for the fundamental membrane dynamics.

ITMP seminar will be held on Wednesday, April 29 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, April 29.

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## "Review on higher-spin theories"

## Dr. Dmitry Ponomarev, ITMP

**April 15, 2020 (Wednesday)**

Abstract: I will start by explaining what is meant by higher-spin theories. Then I will illustrate why making higher-spin fields interact is not easy. I will then review the standard no-go theorems for higher-spin interactions. Next, I will discuss different approaches to circumvent these no-go’s and review the most successful attempts. Finally, I will discuss some potentially promising directions for future research.

ITMP seminar will be held on Wednesday, April 15 at 18:00. Given the situation the seminar will be arranged via Zoom.

If you want to join the seminar please register here before 15:00, April 15.

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## "Some aspects of massive gravity and Horndeski theory"

## prof. Mikhail S. Volkov (Université de Tours, France)

**March 26, 2020 (Thursday)**

Abstract: In the first part of the talk I plan to give a very brief introduction to the ghost-free massive gravity theory and then briefly describe the recent work on the theory of massive gravitons in arbitrary spacetimes. In the second part, I would like to present some new results obtained in the context of the Horndeski theory, in particular concerning the Palatini analysis of this theory.

ITMP seminar will be held on Thursday, March 26 at 16:00. Given the situation the seminar will be arranged via Skype.

If you want to join the seminar please register here before 14:00, March 26.

## "Asymptotic symmetries of electromagnetism and gravity"

prof. Marc Henneaux (Free University of Brussels)

**October 09, 2019 (Wednesday)**

Marc Henneaux - is a famous theoretical physicist, professor at the Free University of Brussels, International Solvay Institutes for Physics and Chemistry Director, professor at the Collège de France. He was rewarded with a number of prestigious awards including Francqui Prize, Humboldt Research Award and The Bogoliubov Prize (JINR).

Annotation: The asymptotic symmetries of gravity and electromagnetism are remarkably rich. The talk will explain the asymptotic structure of gravity and electromagnetism in the asymptotically flat case by making central use of the Hamiltonian formalism. In particular, how the relevant infinite-dimensional asymptotic symmetry groups emerge at spatial infinity, and the extension to higher spacetime dimensions, will be discussed.

Researchers, graduate students and postgraduates, who are specialized in theoretical physics, may get interested in this report. The working language is English.

The starting time is 18:00.

Address: Lomonosov Building MSU, office G-716.