15 APR 2021
11:00 - 13:00

Schubert Derivations are distinguished instances of Higher Order (or Hasse-Schmidt) derivations on exterior algebras [8], originally introduced to phrase Schubert Calculus for Grassmannians varieties, solely in terms of Leibniz rules and integration by parts. The purpose of the talk is showing their applications to find explicit vertex operators representations of Lie algebras of endomorphisms on exterior algebras and related spaces [1, 2, 3, 4], like the infinite wedge power (as in [9] and the bosonic Fock space (a polynomial ring in infinitely many indeterminates). This is related with some pioneering work done by Date, Jimbo, kashiwara and Miwa at the beginning of the Eighties [5]. The premises are the following two elementary observations: each vector space is a representation of the Lie algebra of its own endomorphisms and the r-th exterior power of a polynomial ring in one indeterminate is isomorphic to a polynomial ring in r indeterminates.
References
[1] O. Behzad, Hasse-Schmidt Derivations and Vertex Operators on Exterior Algebras. Ph.D. Thesis, IASBS, Zanjan, 2021;
[2] O. Behzad, A. Contiero, L. Gatto, R. Vidal Martins, Polynomial ring representation of endomorphisms of exterior powers. Collectanea Math., 2021 (to appear), ArXiv:2005.01154.pdf,
[3] O. Behzad, L. Gatto, Bosonic and Fermionic Representations of Endomorphisms of Exterior Algebras, Fundamenta Math. 2021 (to appear), ArXiv:2009.00479.pdf

Join Zoom Meeting
https://zoom.us/j/9299700405?pwd=VTM5OW53dWFkbjcxQXBBalhiNWc2dz09
Meeting ID: 929 970 0405
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15 APR 2021
11:00 - 12:05

Abstract: Very recently, the LHCb collaboration @ CERN and muon g-2 collaboration @ Fermilab have announced their results on the lepton flavor universality violation (LFUV) and muon magnetic dipole moment, which deviate from the SM theory predictions by 3.1 and 4.2 standard deviations, respectively. In this talk we address these results and talk about their meanings and possible scenarios to explain the observed deviations if they are confirmed.



http://meet.google.com/iys-ixfq-gwm

14 APR 2021
16:30 - 17:30

The Eigenvalue Theorem is a basic result in computational algebraic geometry. It says that solving a zero-dimensional system of polynomial equations can be reduced to an eigenvalue problem in linear algebra. The name of Ludwig Stickelberger (1850-1936) is often attached to this theorem, yet papers that use his name never cite any of his papers. My lecture will explore the reasons for this. The answer involves a lovely trace formula in algebraic number theory and an algebra textbook published by Gunter Scheja and Uwe Storch in 1988.
To get more information about the colloquium, join to the following google group:
https://groups.google.com/g/ipm-math-colloquium

14 APR 2021
11:00 - 12:00

Abstract: We study the dynamics of electroweak phase transition in a simple extension of the Standard Model where the Higgs sector is extended by adding an $SU(2)_L$-mutiplet. By making random scans over the parameters of the model, we show that there are regions consistent with constraints from collider experiments and the requirement for a strong first-order electroweak phase transition which is needed for electroweak baryogenesis. Further, we also study the power spectrum of the gravitational waves which can be generated due to the first-order phase transitions. Observation of such gravitational waves, such as by future space-based gravitational wave detectors, could yield information that is complementary to collider and dark matter experiments.


Indico: https://indico.particles.ipm.ir/indico/event/408
https://meet.google.com/hkp-tout-qzi

14 APR 2021
16:30 - 18:00

Abstract:
Axions and Axion-like fields are popular in cosmology, both as the inflaton and as dark matter. Such fields can naturally condense into long-lived, spatially localized configurations (oscillons, axion stars etc). I will discuss conditions under which such solitons become effective antennas for electromagnetic radiation by converting axions to photons, which can lead to potential observational signatures. I will also discuss multimessenger signals: electromagnetic and gravitational wave emission from soliton collisions. Time permitting, I will digress to advertise a separate topic of CMB birefringence from a different type of soliton: string loops in ultralight-axions.
To join the seminar, please click on the following link

https://www.skyroom.online/ch/soa/weekly-seminar

Then click on the guest bottom to participate

13 APR 2021
14:00 - 15:00

Abstract:

Recent developments on black holes have shown that a unitarity-compatible Page curve can be obtained from an ensemble-averaged semi-classical approximation. In this talk, we emphasize (1) that this peculiar manifestation of unitarity is not specific to black holes, and (2) that it can emerge from a single realization of an underlying unitary theory. To make things explicit, we consider a hard sphere gas leaking slowly from a small box into a bigger box. This is a quantum chaotic system in which we expect to see the Page curve in the full unitary description, while semi-classically, eigenstates are expected to behave as though they live in Berry's ensemble. We reproduce the unitarity-compatible Page curve of this system, semi-classically. The computation has structural parallels to replica wormholes, relies crucially on ensemble averaging at each epoch, and reveals the interplay between the multiple time-scales in the problem. Working with the ensemble averaged state rather than the entanglement entropy, we can also engineer an information "paradox". Our system provides a concrete example in which the ensemble underlying the semi-classical Page curve is an ergodic proxy for a time average, and not an explicit average over many theories. The questions we address here are logically independent of the existence of horizons, so we expect that semi-classical gravity should also be viewed in a similar light.



Date: Tuesday, April 13th

2 p.m. - 3 p.m. (Tehran time)

Zoom. (click)

Meeting ID: 884 3079 2016

Passcode: 395721

12 APR 2021
11:00 - 12:00

Based on
https://arxiv.org/abs/2101.05095


Abstract: This article presents a new set of proton parton distribution functions, ATLASepWZVjet20, produced in an analysis at next-to-next-to-leading order in QCD. The new data sets considered are the measurements of W+ and W− boson and Z boson production in association with jets in pp collisions at √ s =8 TeV performed by the ATLAS experiment at the LHC with integrated luminosities of 20.2 fb−1 and 19.9 fb−1, respectively. The analysis also considers the ATLAS measurements of differential W and Z boson production at √ s =7 TeV with an integrated luminosity of 4.6 fb−1 and deep-inelastic-scattering data from e p collisions at the HERA accelerator. An improved determination of the sea-quark densities at high Bjorken x is shown, while confirming a strange-quark density similar in size to the up- and down-sea-quark densities in the range x≲0.02 found by previous ATLAS analyses.


meet.google.com/mim-xppw-ncq

7 APR 2021
11:00 - 12:00

Abstract: In the collision of heavy ions, due to the fast-moving charged particles, a strong magnetic field of the order of 10^{18-20} Gauss is expected to be generated. In the presence of such a strong magnetic field, several novel phenomena like Magnetic catalysis of chiral symmetry restoration, the chiral magnetic effect may arise. Therefore, the knowledge of the evolution of the magnetic field, its lifetime, and possible effects on the plasma is of primary interest.
In this talk, I start with a short overview of the properties of the generated magnetic field. Then I will consider the interaction of the spin of the constituent particles with the background magnetic field. This leads to a finite magnetization. Finite magnetization causes anisotropy in the pressure of the system. In this case, using the quantum kinetic theory the effect of finite magnetization on the evolution of plasma will be discussed.. Finally, I will present part of the results obtained in Phys.Rev.D 101 (2020) 7, 076022.


Indico: https://indico.particles.ipm.ir/indico/event/407

7 APR 2021
13:30 - 15:00

Abstract:
Filamentary structures are omnipresent in the cold interstellar medium. They are found both in star-forming and non-star-forming regions. It has been revealed that these filaments are the hosts of early stages of formation of stars, so their study provides key insight to understand how do stars form? In this talk, I will try to briefly discuss this new filamentary paradigm of star formation and present some of our recent works on the stability and fragmentation of filaments.
To join the seminar, please click on the following link

https://www.skyroom.online/ch/soa/weekly-seminar

Then click on the guest bottom to participate

6 APR 2021
14:00 - 15:00

Abstract:
The program will not be in the form of usual seminars (maybe without slides). This will be an announcement on the recent news with some questions and answers.

Date: Tuesday, April 6th
2 p.m. - 3 p.m. (Tehran time)

Zoom. (click)
Meeting ID: 884 3079 2016
Passcode: 395721

5 APR 2021
11:00 - 12:00

Based on
https://inspirehep.net/literature?sort=mostrecent&size=25&page=1&q=1205.5040


Abstract: These are pedagogical lecture notes on hydrodynamic fluctuations in normal relativistic fields. The lectures discuss correlation functions of conserved densities in thermal equilibrium, interactions of the hydrodynamic modes, an effective action for viscous fluids, and the breakdown of the derivative expansion in hydrodynamics.


meet.google.com/mim-xppw-ncq

16 MAR 2021
14:00 - 15:00

Abstract:

Dualities (stringy or not) have long been used in physics as a way of describing physical theories where a direct description of them seems difficult or even out of reach. In this talk, after a brief introduction to the Buscher rules of string world-sheet T-duality, I will discuss a generalization of Buscher rules to higher mixed tensor theories where the non-stringy essence of these dualities can be exemplified. Moreover, I show how a formalism based on graded geometry can help to find a universal language for such analysis. Then, I will go on to present an off-shell formulation of dualities in linearized gravity in the presence of a gravitational theta term. Such a theta-term is understood as the linearised limit of the Nieh-Yan invariant. In the end, I will give some examples where one can go beyond dualities of linearized theories.


Date: Tuesday, March 16th

2 p.m. - 3 p.m. (Tehran time)


Zoom. (click)

Meeting ID: 812 4428 3537

Passcode: 047580

15 MAR 2021
16:00 - 18:00

Avicenna on the Semantics of Ma'na


https://www.skyroom.online/ch/ipmseminars/ipm-seminars-2021

User: biweeklyseminars
Pass: biweeklyseminars

10 MAR 2021
16:00 - 17:30

Organized by: School of Cognitive Sciences
to receive the link to join online, please send email to theoretical.neurosci.ipm@gmail.com

Abstract:


Classic reinforcement learning (RL) theories cannot explain human behavior in response to changes in the environment or in the absence of external reward. Here, we design a deep sequential decision-making paradigm with sparse reward and abrupt environmental changes. To explain the behavior of human participants in these environments, we show that RL theories need to include surprise and novelty, each with a distinct role. While novelty drives exploration before the first encounter of a reward, surprise increases the rate of learning of a world-model as well as of model-free action-values. Even though the world-model is available for model-based RL, we find that human decisions are dominated by model-free action choices. The world-model is only marginally used for planning but is important to detect surprising events. Our theory predicts human action choices with high probability and allows us to dissociate surprise, novelty, and reward in EEG signals.






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