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

Eoin Ó Colgáin

Atlantic Technological University, AshLane, Sligo, Ireland

Is H₀ a constant in ΛCDM? 

Abstract: In physics, and science more generally, dynamical models specified by fitting parameters may only be valid in certain epochs. In short, any dynamical model with evolving or time dependent fitting parameters is no longer valid. I will apply this reasoning to the Lambda-CDM model and comment on whether the cosmological or fitting parameters evolve or not. The backdrop for this talk is H0 and S8 tensions where H0 is apparently smaller and S8 is apparently larger in the early Universe compared to the late Universe.

یکشنبه 30 مهر 1402، ساعت 17:15

Sunday 22 October 2023 – 17:15 Tehran Time

Hybrid Seminar

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

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

گزینه ورود به صورت مهمان – Enter as a Guest

Hossein Mos’hafi

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

Cosmology: In the Realm of Data and Computation

 Abstract: With the increase of theoretical models in cosmology and their variety, in the current era, the importance of analyzing physical models using observational data and numerical computation with precision tools is more needed than before. In this talk, I will review some methods of data analysis and numerical cosmology with a glimpse of some current problems in cosmology.

یکشنبه 16 مهر 1402، ساعت 17:00

Sunday 8 October 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

سمینار مشترک گروه  ذرات ، کیهان شناسی  و  مرکز پژوهشی فیزیک انرژی ­های بالا

Ali Ashtari Esfahani

Department of Physics, Sharif University of Technology

Neutrino Mass in the Crosshairs 

Abstract: The absolute scale of the neutrino mass plays a critical role in physics at every scale, from the subatomic to the cosmological. Measurements of the tritium endpoint spectrum have provided the most precise direct limit on the neutrino mass scale. In this talk, we present advances by Project 8 to the Cyclotron Radiation Emission Spectroscopy (CRES) technique culminating in the first frequency-based neutrino mass limit. With only a cm^3-scale physical detection volume, a limit of  m_\beta< 155  eV/c^2 (152 eV/c^2  ) is extracted from the background-free measurement of the continuous tritium beta spectrum in a Bayesian (frequentist) analysis. Using 83mKr calibration data, a resolution of 1.66 \pm 0.19 eV (FWHM) is measured, the detector response model is validated, and the efficiency is characterized over the multi-keV tritium analysis window. These measurements establish the potential of CRES for a high-sensitivity next-generation direct neutrino mass experiment featuring low background and high resolution.

یکشنبه 9 مهر 1402، ساعت 17:00

Sunday 1 October 2023 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 1 / Physics Department – first floor – Room Physics 1

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

گزینه ورود به صورت مهمان – Enter as a Guest

Elahe Khalouei

Research Center for Gravitational-Wave Universe (GWUniverse), Seoul National University

Observing Strategy for Electromagnetic Follow-up of Gravitational-Wave Events 

Abstract:  GW170817 is the first and only successful detection of a gravitational wave event followed by observations of the electromagnetic counterpart. This observation opens a new era in multimessenger observation. There are some challenges for electromagnetic observation. In this talk, we will discuss these challenges. Then, we will propose optimal observing strategies for gravitational follow-up observation with optical telescopes to have a successful observation in current and future observing runs of the Advanced LIGO, Advanced Virgo, and KAGRA.

یکشنبه 22 مرداد 1402، ساعت 10:00

Sunday 13 August 2023 – 10:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه 5 – اتاق 512  /  Physics Department – fifth floor – Room 512

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

گزینه ورود به صورت مهمان – Enter as a Guest

Arman Shafieloo

Korea Astronomy and Space Science Institute, (KASI), South Korea; University of Science and Technology, South Korea

Status of the Concordance Model of Cosmology

Abstract:  I review the status of the standard model of cosmology in light of recent observations discussing the current tensions and some different alternatives including some early and late universe solutions to the problem. I will also briefly discuss the near-future of the field at the era of the next generation of astronomical/cosmological surveys.

سه شنبه 27 تیر 1402، ساعت 10:00

Tuesday 18 July 2023 – 10:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه 4 – تالار پرتوی Physics Department – fourth floor – Partovi Hall/

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

گزینه ورود به صورت مهمان – Enter as a Guest

Seminar 1: Dipole Cosmology: The Dipole ΛCDM Model

Vahid Forghanipour

Department of Physics, Sharif University of Technology

Seminar 2: Investigating the halo distribution inside cosmic voids in excursion set theory and the dependence of void galaxies on large-scale environment

Zeynab Ashuri

Department of Physics, Sharif University of Technology

Abstract 1: Is our universe actually homogenous and isotropic on large scales? New observation in last two decades cast some shadow of doubts on standard model of cosmology and FLRW paradigm. In this Seminar we discuss and review the recently published article, “Towards A Realistic Dipole Cosmology: The Dipole ΛCDM Model”, by Ehsan Ebrahimian and M. M. Sheikh-Jabbari. the dipole cosmological principle is the idea that the Universe is a maximally Copernican cosmology, compatible with a cosmic flow. It serves as the most symmetric paradigm that generalizes the FLRW ansatz. In this article they assess the possibility of model building within the dipole cosmology paradigm, and discuss the dynamics of expansion rate, anisotropic shear and tilt, in various examples. A key observation is that the cosmic flow (tilt) can grow even while the anisotropy (shear) dies down. Remarkably, this can happen even in an era of late time acceleration.

Abstract 2: Investigating the formation and evolution of large-scale structures, as one of the main observables in cosmology, is of particular importance. Excursion Set Theory is one of the methods of investigating the statistics of halos and web structures of the universe.

In the standard approach, in this theory, we consider the Sharp-K window function to smooth the matter density perturbation field, which causes the paths to proceed a Markovian random walk. As a result, the statistics of the first up-crossing of the critical barrier and the statistics of the halos can be obtained analytically. Similar procedures can be followed to find Halos which reside inside cosmic voids. The aim of this talk will be to review the distribution of structures inside voids, and to analyze the environmental dependence of galaxy luminosity inside the void halos, in the framework of the Excursion Set theory.

یکشنبه 25 تیر 1402، ساعت 9:30

Sunday 16 July 2023 – 9:30 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه 5 – اتاق 512Physics Department – fifth floor – Room 512/

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

گزینه ورود به صورت مهمان – Enter as a Guest