Seminars



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Tue Jan 31, 2023 (1401/11/11)

       

Jan 31
1401/11/11

14:00
 

Horizon Strings as 3d Black Hole Microstates

Abstract:We construct microstates of 3d black holes in the Hilbert space of tensionless null strings with non-zero winding along the bifurcation horizon. Counting these string states we recover the Bekenstein-Hawking entropy and its semiclassical logarithmic corrections.
Lecturer(s): Mohammad Mehdi Sheikh-Jabbari 
From : IPM, School of Physics
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Jan 24, 2023 (1401/11/4)

       

Jan 24
1401/11/4

14:00
 

On the Merger Rate of Primordial Black Holes in Cosmic Voids

Abstract:Cosmic voids are known as underdense substructures of the cosmic web that cover a large volume of the Universe. It is known that cosmic voids contain a small number of dark matter halos. Regarding this, the existence of primordial black holes (PBHs) in these secluded regions of the Universe is not unlikely. In this talk, I intend to speak about our recent analysis on the merger rate of PBHsin cosmic voids and their contribution to gravitational wave events resulting from black hole mergers recorded by the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO)-Advanced Virgo (aVirgo) detectors.
Lecturer(s): Saeed Fakhry
From : K.N. Toosi University of Technology
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Jan 17, 2023 (1401/10/27)

       

Jan 17
1401/10/27

14:00
 

Temporal vs Spatial Conservation and Memory Effect in Electrodynamics

Abstract:We consider the standard Maxwell's theory in 1+3 dimensions in the presence of a timelike boundary. In this context, we show that (generalized) Ampere-Maxwell's law appears as a Noether charge associated with the Maxwell U(1) gauge symmetry which satisfies a spatial conservation equation. Furthermore, we also introduce the notion of spatial memory field and its corresponding memory effect. Finally, similar to the temporal case through the lens of Strominger's triangle proposal, we show how spatial memory and conservation are related.
Lecturer(s): Mohammad Hasan Vahidinia
From : Institute for Advanced Studies in Basic Sciences (IASBS)
Research Group: HEPCO Group Weekly Seminar
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Tue Jan 10, 2023 (1401/10/20)

       

Jan 10
1401/10/20

14:00
 

On the detection statistics in a double-double-slit experiment

Abstract:Double-slit experiment has always been one of the central experiments in quantum mechanics. Yet, if there is an experiment more mysterious, it is a double-double-slit experiment with entangled particle pairs. In this experiment, the two most important properties of quantum theory, i.e. superposition and entanglement, combine and lead to a non-local interference pattern. The full analysis of this experiment can be even more complex because of the third quantum effect, i.e. the collapse of the wave function when the first particle is detected in the middle of the experiment at random times. This, in principle, can change the detection statistics of the remaining particle. The analysis however is not completely straightforward in standard formalism. One of the reasons is that in the orthodox quantum mechanics we do not have a clear and agreed prediction of detection times distribution. This problem is actually very old, but it is still open. The mathematical origin of this problem is that the time is a parameter in the standard formalism, not a self-adjoint operator, hence, there is no unique and unambiguous way to compute the temporal probability distribution of detection events. Therefore, it is even not clear how one can determine the state of the system at a given time from initial two particle state; because the state and its equation of motion change at an undetermined time. In this talk, we investigate this experiment via Bohmian mechanics which can circumvent this problem and leads to a clear prediction in this situation.
Lecturer(s): Mohammad Javad Kazemi
From : Sharif University of Technology
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Jan 03, 2023 (1401/10/13)

       

Jan 03
1401/10/13

14:00
 

Constraints from the duration of supernova neutrino burst on resonant light gauge boson production by neutrinos

Abstract:We discuss the resonant production of low-mass vector mediators from neutrino antineutrino interactions in the core of proto-neutron stars, and determine how they may affect the neutrino energy distribution and their diffusion time in the first seconds after the supernova explosion. Taking into account the radial dependence of the density, energy, and temperature inside the proto-neutron star, we determine the neutrino-antineutrino interaction rate in the star interior in two well-motivated new physics scenarios that feature a low-mass vector mediator, namely $U(1)_{Bâ??L}$ and $U(1)_{ L_\mu â??L_\tau}$ . First, we determine the values of the coupling above which the neutrino self-interaction dominates over the standard neutrino nucleon scattering. We argue that, although in this regime a redistribution of the neutrino energies might take place, this only affects a small part of the neutrino population and cannot be constrained with the SN 1987A data. Thus, contrary to previous claims, the region of the parameter space where this model explains the discrepancy in the muon anomalous magnetic moment is not ruled out. We then focus on small gauge couplings, for which the decay length of the new gauge boson is comparable to (or larger than) the size of protoneutron star. We show that in this regime, the duration of the neutrino burst can be significantly reduced, and values of the coupling as small as O($10^{â??9}$) can be probed, ruling out new areas of the parameter space. These results are relevant for any other model that features new MeV-scale mediators that couple to the neutrino sector.
Lecturer(s): Yasaman Farzan
From : School of Physics, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Oct 04, 2022 (1401/7/12)

       

Oct 04
1401/7/12

14:00
 

The effect of the interaction of dark matter and dark energy in galactic physics and the ISW effect

Abstract:Since most of the matter (energy) of the universe consists of dark matter and dark energy, it is not unlikely that there is even a weak interaction between the dark elements. In this presentation, we draw on the results of two previously performed simulations of cluster-sized haloes with self-interacting dark matter and present previous work on the density profile of galaxy clusters. describe completely. This density profile helps to find a velocity dispersion profile and the relation between cluster mass and density center. We consider two uses of galaxy clusters with these relations: the mass velocity dispersion and temperature relation. We also discuss the effect of this interaction on the profile of the mass function in the galactic halo and the ISW effect.
Lecturer(s): Javad Taghizadeh Firouzjaee
From : K.N. Toosi University of Technology
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Sep 20, 2022 (1401/6/29)

       

Sep 20
1401/6/29

14:00
 

Boundary Conditions of Warped AdS_3 in GMG

Abstract:In this talk, in the framework of general massive gravity, I am looking at the asymptotic symmetry, the solution space, and the global charges using the ACDS boundary conditions in the quadratic ensemble. We also show that the boundary counting of the degeneracy of states correctly reproduces the bulk thermodynamic entropy for WBTZ black holes.
Lecturer(s): Seyed Naseh Sajadi
From : School of Physics, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Apr 06, 2022 (1401/1/17)

       

Apr 06
1401/1/17

18:00
 

Uncovering Energetic Processes in the Interstellar/Intergalactic Medium with the Square Kilometre Array

Abstract:Investigating the physics and energetic of the medium where galactic structures, on various scales, are formed is the most fundamental step to understand the formation and evolution of galaxies. Modern galaxy evolution models suggest gas accretion from the intergalactic medium (IGM) or from cosmic filaments as a mechanism to maintain star formation and active galactic nucleus (AGN). Through gas heating and/or gas removal, these models also propose supernova feedback and AGN feedback as mechanisms to quench massive star formation. Observational studies, however, have not reached to a conclusive result showing that feedback can, in some cases, trigger star formation, leaving the issue as an open challenge. It seems that some basic concepts about the formation of structures in the interstellar medium (ISM) and the IGM are missed: What are physical parameters/agents governing the structure formation on various scales? How does the ISM/IGM energy balance change over cosmic time? The advent of the square kilometre array (SKA) and its instrumental capabilities tracing the most energetic ISM components has opened a new window shedding light on the issue. The SKA's sensitive radio continuum observations will trace high-energy particles and magnetic fields not only in star forming regions and AGNs, but also in more quiescent regions in molecular clouds and diffuse IGM, enabling us to study the role of magnetic fields/cosmic rays in structure formation. Sensitive radio continuum observations on large scales may also bring constrains on the entity of dark matter mapped by the Hubble Space Telescope (HST) and Dark Energy Camera (DECam).
Lecturer(s): Fatemeh Tabatabaei
From : IPM, School of Astronomy
Research Group: Physics Colloquium
More Info. : Link

Tue Mar 15, 2022 (1400/12/24)

       

Mar 15
1400/12/24

14:00
 

Amazing Neutrino Particles
Lecturer(s): Yasaman Farzan
From : School of Physics
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Mar 08, 2022 (1400/12/17)

       

Mar 08
1400/12/17

14:00
 

Stochastic Effects in inflationary cosmology

Abstract:In this talk, I will speak about the stochastic effects in inflationary cosmology. To this end firstly I will review the stochastic formalism and discuss the properties of the Wiener process in general. In the second part, I will review how the stochastic effects can emerge in inflationary cosmology and why studying these effects in the early universe cosmology is important. Finally, the applications of these effects in different models are discussed. In particular, I will speak about the stochastic effects in axion inflation and the formation of primordial black holes.
Lecturer(s): Amin Nassiri Raad
From : School of Astronomy, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

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