Sadra Jazayeri

Department of Physics, Imperial College London

Cosmological Phonon Collider 

Abstract: The expansion of the universe spontaneously breaks time translation by selecting a preferred time foliation. As a consequence, very much like a superfluid at zero temperature, the low-energy description of single-field inflation can be organised in terms of the associated Goldstone mode of the broken symmetry (aka the phonon). Similar to particle colliders, if we were to scatter sound waves, the presence of additional heavy fields coupled to the medium would manifest as distinct peaks in the cross-section of the phonons. In this talk, I introduce a cosmological version of this idea, in which the imprints of additional heavy particles during inflation are encoded in the late time boundary correlators of the Goldstone boson. I discuss various phenomenological consequences of this setup for the primordial bispectrum and trispectrum.

یکشنبه  29 بهمن 1402، ساعت 17:00

Sunday 18 February 2023 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3   /

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Reza Rezaei

Department of Physics, Sharif University of Technology

Radio telescopes and the ongoing project in the Physics Department

Abstract: We will resume our seminar at the beginning of the second semester with a talk by Dr Reza Rezaei on Radio telescopes and the ongoing project in the Physics Department of Sharif University for building radio antennas.

The M.Sc. and B.Sc. Students interested in knowing more and being involved in this project, please attend the seminar.

یکشنبه 15 بهمن 1402، ساعت 17:00

Sunday 4 February 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3   /

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Hamed Manouchehri Kousha

Department of Physics, Sharif University of Technology

The Effective Field Theory of Large-Scale Structures  of a Fuzzy Dark Matter Universe

Abstract: Ultra-light scalar fields and their non-interacting class, the so-called fuzzy dark matter (FDM), are candidates for dark matter, introduced to solve the small-scale problems of the standard cold dark matter. In this talk, after reviewing FDM and its main effects, I address whether the small-scale effects of FDM, specifically the quantum pressure, could leave sizable imprints on the large-scale statistics of the matter. For this purpose, we utilized the effective field theory of large-scale structures wherein small-scale physics is integrated and represented on large scales by only a set of free parameters. These parameters can be determined by fitting to the cosmological simulations. We performed three FDM simulations with different masses and compared their sound speed with the standard cold dark matter (CDM) simulation. We found that the FDM sound speed is slightly higher than CDM’s. We conclude that the impact of the FDM is not limited to the small scales alone, and we can search for them by studying the matter on large scales. Though it is beyond the observations’ scope today, it is possible to discriminate it with upcoming observations.

یکشنبه 10 دی 1402، ساعت 17:15

Sunday 31 December 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Mohammad Hassanshahi

Department of Physics and Astronomy, University College London, UK

The use of quantum computers in machin  learning algorithms and its application in physics

استفاده از کامپیوترهای کوانتومی در الگوریتم­های یادگیری ماشین و کاربرد آن در فیزیک

 چکیده: «در این ارائه ابتدا برخی مفاهیم و روش­های یادگیری ماشین را مرور می­کنم. سپس با ذکر چند مثال نشان می­دهم که کامپیوترهای کوانتومی پتانسیل این را دارند که به بهبود این روش ها کمک کنند. الگوریتم ­هایی وجود دارند که اجرای آن­ها در کامپیوترهای کوانتومی سریع اما در کامپیوترهای غیر کوانتومی (کلاسیکی) بسیار زمانگیر است. آیا می­توان از این الگوریتم­ها در روش­های یادگیری ماشین استفاده کرد؟ در انتها به برخی چالش­ها در این الگوریتم­ها اشاره کرده و در نهایت مثال­هایی می­زنم از کاربرد این الگوریتم­ها در برخی حوزه­ های فیزیک (مثل ذرات بنیادی و نجوم)».

یکشنبه  3 دی 1402، ساعت 17:15

Sunday 24 December 2023 – 17:15 Tehran Time

Hybrid Seminar

آمفی تئاتر دانشکده فیزیک-تالار جناب   /   Physics Department – Amphitheater- Jenab Hall

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Amin Farhang

School of Astronomy, Institute for Research in Fundamental Sciences (IPM)

How heavy molecules are living in ISM?

Abstract: In the study of heavy molecular formation and evolution, we aim to understand the processes involved in the creation and development of complex molecules in various interstellar environments. The interstellar medium (ISM) is a vast and dynamic region that contains a wide range of elements and compounds, including carbon-based molecules. Through our recent research conducted as part of the VLT large survey, we have been able to investigate the interaction of unknown molecules with carbon in different environments within the ISM. By analyzing spectroscopic data obtained from the VLT, we can identify and characterize these molecules, shedding light on their properties and behavior. One particular aspect of interest is the correlation relationships between these unknown molecules. By studying the patterns and connections between different molecular species, we can gain insights into their mutual influences and the underlying mechanisms that govern their presence and distribution. Our ongoing research efforts also involve investigating the formation mechanisms of these molecules in planetary nebulae. We plan to explore the role of various environmental factors, such as temperature, pressure, and radiation, in shaping the molecular composition of the ISM. Additionally, we aim to investigate the influence of specific astrophysical events, such as gas depletion, on the formation and evolution of these complex molecules.

یکشنبه 12 آذر 1402، ساعت 17:15

Sunday 3 December 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3/   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Parisa Arabameri

Department of Physics, Shahid Beheshti University

k−Dependent Dark Matter 

Abstract: With the emersion of precise cosmology and the emergence of cosmic tensions, we are faced with the question of whether the simple model of Cold Dark Matter needs to be extended and whether doing so can alleviate the tensions and improve our understanding of the properties of dark matter. In this talk, first, I will briefly review Cold Dark Matter challenges, and Warm and Mixed Dark Matter models as solutions to some of these challenges. Then, I will introduce a new model that examines whether Dark Matter has any scale-dependent behavior. This model is one of the generalized models of dark matter with the non-zero equation of state (w) so that the behavior of this dark matter changes according to the scale of (k). In large scales (small (k)’s), the dark matter is cold (w = 0), while it becomes warm (w \neq 0) for small scales (large k’s). This behavior is modeled phenomenologically for two different cases:(I) the sound speed behaves independently of (k) as a constant parameter and (II) it changes depending on (k).

یکشنبه 5 آذر 1402، ساعت 17:15

Sunday 26 November 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3/ Physics Department – first floor – Room Physics 3   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Maryam Zeinali

Research Center for High Energy Physics, Department of Physics,

Sharif University of Technology

Luminosity at LHC  

Abstract: Luminosity, along with the center of mass energy, is the most important figure of merit of any particle collider. It quantifies the power of a machine to squeeze particles through a given space in a given time. The precision luminosity measurement is crucial as it directly affects the other physics parameters like physics process’s production cross section. In this talk the luminosity is first introduced. Then the technique used to measure this quantity is presented, which yields in determining a calibration constant; so-called \sig_{visible}, via some specific van-der-Meer (vdM) scans. Finally, the contribution from several sources of systematic uncertainties on the measurement of the luminosity is discussed.

یکشنبه  28 آبان 1402، ساعت 17:15

Sunday 19 November 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک، طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3   / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Hassan Khalvati

University of Guelph, Canada

Perimeter Institute for Theoretical Physics, Canada

Observational Features in a Beyond Kerr Spacetime

Abstract: Recently, we computed the metric of a vacuum stationary axisymmetric spacetime using Ernst formalism. The metric contains a generic non-Kerr deviation in the quadrupole moment and is accurate up to very high order in the inverse radial distance. Using such a metric, we have tried to study any potential observational feature of such a Beyond-Kerr spacetime. We have studied the deviation in the observable size of the central object by numerical ray-tracing approach and compared the deviation with the critical curve for the Kerr black hole photon sphere. We also concluded that there is a degeneracy in simulating the shape of the central object in the parameter space between spin and the deviation in quadrupole moments of the central object. In addition, we tried to study an EMRI (Extreme Mass Ratio Inspiral) system considering this modified spacetime as the background and calculated the phase difference between the gravitational radiation from this system and the Kerr background. In the end, we have shown that both of these observational features are potentially detectable by future space-based black hole detectors and gravitational wave detectors

یکشنبه  21 آبان 1402، ساعت 17:15

Sunday 12 November 2023 – 17:15 Tehran Time

Hybrid Seminar

آمفی تئاتر دانشکده فیزیک-تالار جناب / Physics Department – Amphitheater- Jenab Hall

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Mohammad Hossein Jamshidi

Department of Physics, Shahid Beheshti University

Cap anomaly in the CMB

Abstract: The standard model of cosmology has explained lots of features of the CMB accurately. This model is based on the so-called cosmological principle which states that the distributions of matter and light in the universe are homogeneous and isotropic at any epoch. Nevertheless, there are different well known anomalies in the statistical features of the CMB. Among all these, of more interest for us is directional dependencies of the CMB statistics. One of them is modeled in terms of a dipole modulation in the CMB temperature and a dipole in the amplitude of CMB fluctuations. Having a pure dipole modulation in the CMB sky seems to require fine-tuning. So there is a need to study this anomaly in more detail. In our recent study on Planck data, we have studied caps instead of hemispheres by using variance-based probes and We have found that the anomaly in the CMB temperature modulations is more severe on some particular spherical caps than that of the hemisphere.

یکشنبه  14 آبان 1402، ساعت 17:15

Sunday 5 November 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Javad Tabatabaei

Department of Physics, Sharif University of Technology

Local Limit of Nonlocal Gravity: ‌ A cosmological Investigation

Abstract: In this talk, we explore accepts of the newly developed extension of teleparallel equivalence of GR, which coincides with the local limit of the “Nonlocal Gravity” theory developed by Nonlocal Gravity theory developed by Mashhoon (see Nonlocal Gravity by Bahram Mashhoon, Oxford University Press, 2017). This formulation of gravity has been developed in close accordance with electrodynamics of mediums; both in local and nonlocal versions. This newly added ‘medium’-like effect of gravity can affect cosmology in many ways; we review these effects by studying back-ground level cosmology, linear perturbations in cosmology, gravitational wave propagation, anisotropic models of cosmology and even black-holes geometries. Our theoretical/numerical investigation reveals many interesting features of this theory, such as the denial of static dark-energy and cosmological constant. We also achieve some alleviation of the H_0 tension problem through our model.

یکشنبه 7 آبان 1402، ساعت 17:15

Sunday 29 October 2023 – 17:15 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3   /

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest