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

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