20 OCT 2020
14:00 - 15:00

Abstract:

In this talk, we will study a particular deformation of the Jackiw-Teitelboim gravity recently considered by Witten and others. We will compute the partition function of this model as well as its higher order correlators to all orders in genus expansion in the low temperature limit for small perturbations. In this limit, the results match with those obtained from the Airy limit of a Hermitian random matrix ensemble. Using this result, we will also study the free energy of the model. One observes that although the annealed free energy has pathological behaviors, under certain assumptions, the quenched free energy evaluated by replica trick exhibits the desired properties at low temperatures.


Date: Tuesday, 20 October - ۲۹ مهر

2 p.m. - 3 p.m.


Skyroom Link: https://www.skyroom.online/ch/schoolofphysics/hepco-group




Skype link for emergency

SkypeLink: https://join.skype.com/cm7iyEUWJVCf

19 OCT 2020
11:00 - 12:00

Abstract: Flow measurements and model studies over the last 20 years have revolutionized our understanding of the dynamics of the heavy-ion collisions and properties of the QCD matter created at RHIC and the LHC. This talk will describe the current mainstream paradigm coming out of these efforts, identify the challenges in achieving precision description of the dynamics and properties of the QCD matter, and discuss crucial opportunities for further improvement.


https://www.skyroom.online/ch/ipm-particles/journal-club-ep

14 OCT 2020
11:00 - 12:00

Abstract: The doubly charmed Ξ++cc(ccu) state is the only listed baryon in PDG, which was discovered in the experiment. The LHCb collaboration gets closer to discovering the second doubly charmed baryon Ξ+cc(ccd), hence the investigation of the doubly charmed/bottom baryons from many aspects is of great importance that may help us not only get valuable knowledge on the nature of the newly discovered states, but also in the search for other members of the doubly heavy baryons predicted by the quark model. In this context, we investigate the strong coupling constants among the Ξ+(+)cc baryons and π0(±) mesons by means of light cone QCD sum rule. Using the general forms of the interpolating currents of the Ξ+(+)cc baryons and the distribution amplitudes (DAs) of the π meson, we extract the values of the coupling constants gΞccΞccπ. We extend our analyses to calculate the strong coupling constants among the b-partner baryons with π mesons, as well, and extract the values of the strong couplings gΞbbΞbbπ. It is observed that the values of the couplings under study in bottom channels are about 4 times greater than those of the charmed channels. The results of this study may help experimental groups in the analyses of the data related to the strong coupling constants among the hadronic multiplets.


https://arxiv.org/pdf/2003.12723.pdf


https://www.skyroom.online/ch/ipm-particles/school-of-particles-and-accelerators-weekly-meeting


Indico: https://indico.particles.ipm.ir/indico/event/385

14 OCT 2020
11:00 - 12:00

Accelerating crystal structure prediction by machine-learning interatomic potentials with active learning

Abstract:

We propose a methodology for crystal structure prediction that is based on the evolutionary algorithm USPEX and the machine-learning interatomic potentials actively learning on-the-fly. Our methodology allows for an automated construction of an interatomic interaction model from scratch, replacing the expensive density functional theory (DFT) and giving a speedup of several orders of magnitude. Predicted low-energy structures are then tested on DFT, ensuring that our machine-learning model does not introduce any prediction error. We tested our methodology on prediction of crystal structures of carbon, high-pressure phases of sodium, and boron allotropes, including those that have more than 100 atoms in the primitive cell. All the the main allotropes have been reproduced, and a hitherto unknown 54-atom structure of boron has been predicted with very modest computational effort.

14 OCT 2020
13:30 - 15:00

I review the status of the concordance (standard) LCDM model of cosmology in light of current observations discussing about the apparent tensions in estimation of the key cosmological parameters. I will also briefly discuss the future of the field at the era of the next generation of astronomical/cosmological surveys.

14 OCT 2020
14:00 - 15:00

Abstract:

We investigate the effect of high-frequency laser pulses on a 2D honeycomb lattice described by the extended Kane-Mele-Hubbard model at half-filling and in the strongly correlated regime, i.e., an antiferromagnetic spin-orbit Mott insulator. Based on a generalized Floquet formalism, we demonstrate that by changing the amplitude and frequency of laser pulses, one can tune the strengths and signs of the Heisenberg exchange and Dzyaloshinskii-Moriya spin interactions. Our results pave the way for ultrafast optical spin manipulation and quantum magnonics in recently discovered two-dimensional magnetic materials.


Date: Wednesday, October 14, 2020

Time: 14:00-15:00

To join the webinar, please follow this link:
https://www.skyroom.online/ch/schoolofphysics/condensed-matter-and-statistical-physics
and log in as guest.

Organized by: Condensed Matter and Statistical Physics Group, School of Physics (IPM)

Queries about this event should be addressed to Dr. A. Faridi at azadeh.faridi@ipm.ir

14 OCT 2020
16:30 - 18:30

Among the many approaches to combining logic and probability, an important one has been to assign probabilities to formulas of a classical logic, instantiated from some fixed domain, in a manner that respects logical structure. A natural additional condition is to require that the distribution satisfy the symmetry property known as exchangeability. In the first part of this talk I will trace some of the history and context of this line of investigation, viewing exchangeability from a logical perspective. In the second part I will report on the current status of a joint programme of Ackerman, Freer and myself on countable exchangeable structures, which continues this line of investigation.
Please send an email to r.zoghi@gmail.com to join this webinar.

13 OCT 2020
14:00 - 15:00

Abstract:

It has been observed that for black holes in a certain family of Horndeski gravity theories Wald's entropy formula does not lead to the correct first law for black hole thermodynamics. For this family of Horndeski theories speeds of propagation of gravitons and photons are in general different and gravitons move on an effective metric different than the one seen by photons. We show that the temperature of the black hole should be modified from surface gravity over 2π to include the effects of this effective metric. The modified temperature, with the entropy unambiguously computed by the solution phase space method, yields the correct first law. Our results have far reaching implications for the Hawking radiation and species problem, going beyond the Horndeski theories.

https://arxiv.org/abs/2005.12985


Date: Tuesday, 13 October

2 p.m. - 3 p.m.


Skyroom Link: https://www.skyroom.online/ch/schoolofphysics/hepco-group




Skype link for emergency

SkypeLink: https://join.skype.com/cm7iyEUWJVCf

13 OCT 2020
19:30 - 21:30

Abstract: We study the gluon fusion and the closely related gluon splitting process, that represent channels induced by the presence of a magnetic field in semi central HIC's, for photon production. The aim is to compute the photon yield and elliptic flow coefficient. The calculation accounts for the high gluon occupation number at early times when the field strength is significant. We compare this excess to the difference between PHENIX data and recent hydrodynamic calculations for the photon transverse momentum distribution and elliptic flow coefficient v_2. The time evolution of the field strength and reaction volume is computed using UrQMD. We show that with reasonable values for the saturation scale, the calculation helps to better describe the experimental results obtained at RHIC energies for the lowest part of the transverse photon momentum at different centralities.


https://us02web.zoom.us/meeting/register/tZYuceypqzgtG9TOUMOEERTsNTaLKVFFToie

12 OCT 2020
15:00 - 17:00

IPM SCS Free Webinars

Abstract:


John Searle believes that there is a gap between the intentional states of the mind that underlie our decisions and the actual decisions and actions that are taken. He sees this gap as a precondition for freedom of will and rationality. Allameh Tabatabai also believes that desires and awareness and other mental matters do not lead to the realization of action, but the realization of action requires a cognitive mechanism. The question is, from the point of view of these two philosophers, what is the factor that leads to the causal adequacy of action and the realization of the will? Also, which answer seems acceptable in terms of the power of explanation and the strength of theoretical components? John Searle considers independent reasons from desire (derived from social obligations) and Allameh Tabatabai as validity (establishing a relation of obligation between oneself and action according to the rule of validity with the creation of the relation must) as the factor of realization of will and action. John Searle raises the gap in his more comprehensive theoretical scheme of rationality and free will, whose theoretical components are in conflict with one another, and reasons independent of desire do not solve the problem of causal determinism. On the other hand, Allameh Tabatabai's view is theoretically superior to John Searle's view in terms of theoretical strength and its conformity with some bodily cognitive views, such as Barslow's theory of perceptual symbols.