The Meeting
Shivalik HEPCATS meetings are intended to foster discussions and collaborations among researchers in and around the Shivalik range of the Himalayas. The meetings will take place, ideally once every six months, at various institutes located in the region.
This is the 5th edition of this meeting series.
The webpages of the previous editions of the meetings are available here:
Shivalik HEPCATS Meeting - Summer 2021
Shivalik HEPCATS Meeting - Winter 2020
Shivalik HEPCATS Meeting - Summer 2020
Shivalik HEPCATS Meeting - Winter 2019
What is HEPCATS?
HEPCATS stands for High Energy Physics, Cosmology, Astrophysics, Theory and Simulations.
Venue/Time
The Winter 2021 Meeting will be hosted by IISER Mohali. It will run in a hybrid mode (at Lecture Hall 5 of IISER Mohali and over Zoom). The meeting begins at 9:50AM on December 18, 2021 (Saturday) ends at 5:30PM the same day.
Registration
You may register for the meeting by contacting one of the organizers.
Zoom Link
You may join the meeting via this Zoom link:
Shivalik HEPCATS Meeting - Winter 2021 - Zoom Link
Organizers
The organizers of the meeting are:
Dr. Jasjeet Bagla,
Dr. Harvinder Jassal,
Dr. Anosh Joseph,
Dr. Kinjalk Lochan,
Dr. Ambresh Shivaji, and
Dr. K P Yogendran.
Local Coordinators
The local coordinators of the meeting are:
Dr. Jasjeet Bagla, Dr. Minati Biswal, Mr. Navdeep Dhindsa, Dr. Harvinder Kaur Jassal, Dr. Anosh Joseph, Ms. Mandeep Kaur, Mr. Arpith Kumar, Dr. Kinjalk Lochan, Ms. Vamika Longia, Mr. Harkirat Sahota, Mr. Pramod Sharma, Mr. Akash Singh, Dr. Ambresh Shivaji, Mr. I. K. Wasimakram, and Dr. K P Yogendran.
Funding
We acknowledge funding from IISER Mohali.
Accommodation
You may book your accommodation at the IISER guesthouse on payment basis. The link to the institute guesthouse is here.
Tea/Coffee/Lunch
For those of you who are attending the meeting physically at IISER Mohali campus, tea/coffee/lunch will be provided in the foyer of the Lecture Hall Complex. Kindly maintain the protocols of social distancing while you are in the Lecture Hall Complex.
Schedule
| Time | Speaker | Affiliation | Title | Resources |
|---|---|---|---|---|
| 09:50AM - 10:00AM | Anosh Joseph | Welcome Remarks | -- | -- |
| Session 1 | Chair: Jasjeet Bagla | |||
| 10:00AM - 10:20AM | Hemant Rathi | IIT Roorkee | Holographic JT gravity with quartic couplings | --- |
| 10:25AM - 10:45AM | Swati Gavas | IISER Mohali | Probing universality of halo mass function using scale-invariant models | --- |
| 10:50AM - 11:10AM | Vamika Longia | IISER Mohali | 2D SU(2) Yang-Mills Theory using Tensor Networks | --- |
| 11:15AM - 11:45AM | Coffe/Tea Break | Location: | LHC Foyer | |
| Session 2 | Chair: Kinjalk Lochan | |||
| 11:45AM - 12:05PM | Ayan Chatterjee | Central University of Himachal Pradesh | Exact solutions in higher curvature theories | --- |
| 12:10PM - 12:30PM | Pinaki Roy | IISER Mohali | Short Waiting Time Thermonuclear X-rays Bursts in 4U 1636-536: Challenge to existing ignition models? | --- |
| 12:35PM - 12:55PM | Gopal Yadav | IIT Roorkee | Deconfinement Phase Transition from Entanglement Entropy and ${\mathscr {M}} \chi$PT Compatibility | --- |
| 01:00PM - 02:30PM | Lunch Break | Location: | LHC Foyer | |
| Session 3 | Chair: Ambresh Shivaji | |||
| 02:30PM - 02:50PM | Suraj Chopra | IISER Mohali | Quantum Rigid Body Dynamics | --- |
| 02:55PM - 03:15PM | Misba Afrin | Jamia Millia Islamia | Can the EHT probe rotating black holes in Horndeski theory? | --- |
| 03:20PM - 03:40PM | Sanjay Pant | IIT Ropar | Effect of backreaction on holographic thermal correlators: From entanglement to chaos | --- |
| 03:40PM - 04:00PM | Coffe/Tea Break | Location: | LHC Foyer | |
| Session 4 | Chair: Harvinder Jassal | |||
| 04:00PM - 04:20PM | Shafqat Ul Islam | Jamia Millia Islamia | [CANCELLED!] Investigating strong gravitational lensing effects by rotating Simpson–Visser black holes | --- |
| 04:25PM - 04:45PM | Nisha Chahal | NIT Jalandhar | Quark matter in (2+1)-flavor Polyakov quark meson model at non-zero isospin | --- |
| 04:50PM - 05:10PM | Jasjeet Bagla | IISER Mohali | Gravitational Lensing of incoherent wave packets of Gravitational Waves | --- |
| 05:15PM - 05:35PM | K. P. Yogendran | IISER Mohali | The BTZ black hole spectrum | --- |
| 05:40PM - 05:45PM | Anosh Joseph | Closing Remarks | -- | |
| 05:45PM - 06:00PM | Coffe/Tea Break | Location: | LHC Foyer | |
Abstracts of Talks
| Time/Speaker | Title/Abstract |
|---|---|
|
10:00AM - 10:20AM
Hemant Rathi (IIT Roorkee) |
Title:
Holographic JT gravity with quartic couplings
Abstract: We construct the most general theory of 2D Einstein-dilaton gravity coupled with U(1) gauge fields that contains all the 2-derivative and the 4-derivative interactions allowed by the diffeomorphism invariance. We renormalise the 2D action and obtain the vacuum solution as well as the black hole solution. The vacuum solution in the UV is dominated by Lifshitz_2 with dynamical exponent (z = 7/3) while on the other hand, the spacetime curvature diverges as we move towards the deep IR limit. We calculate the holographic stress tensor and the central charge for the boundary theory. We also compute the Wald entropy for 2D black holes and interpret its near horizon divergence in terms of the density of states. We compare the Wald entropy with the Cardy formula and obtain the eigenvalue of the Virasoro operator for our model. Finally, we explore the near horizon structure of 2D black holes and calculate the central charge corresponding to the CFT near horizon. We further show that the near horizon CFT may be recast as a 2D Liouville theory with higher derivative corrections. We study the Weyl invariance of this generalised Liouville theory and identify the Weyl anomaly associated with it. |
|
10:25AM - 10:45AM
Swati Gavas (IISER Mohali) |
Title:
Probing universality of halo mass function using scale-invariant models
Abstract: Sheth Tormen mass function is widely used to quantify the abundance of dark matter halos. It is an improvement over the Press Schechter mass function as it uses ellipsoidal collapse in place of spherical collapse. Both of these mass functions can be written in a form that is universal, i.e., independent of cosmology and power spectrum, when scaled in suitable variables. However, cosmological simulations have shown this universality is approximate. In this work, we have probed the power spectrum dependence of halo mass function through a suite of N-body simulations of eight power-law models in an Einstein-de Sitter cosmology. This choice of cosmology and power-law power spectrum ensures self-similar evolution of dark matter distribution. This allows for isolating the power spectrum dependence of mass function. In this talk, we present fits for the parameters in the Sheth-Tormen mass function and show that there is a clear non-universality in that the values of these parameters depend on the index of the power law power spectrum. A theoretical explanation requires further development of the theoretical basis of the theory of mass function. In particular, we believe that the contribution of tidal interactions across perturbations at different scales may be responsible for this departure from universality. |
|
10:50AM - 11:10AM
Vamika Longia (IISER Mohali) |
Title:
2D SU(2) Yang-Mills theory using Tensor Networks
Abstract: Two-dimensional lattice Yang-Mills theory is analytically solvable. We can exactly compute the partition function of this theory using Tensor Network methods where one can expand the partition function in terms of characters of the gauge group for a particular irreducible representation. We derive a fundamental tensor corresponding to the partition function and compute the plaquette expectation value. In practice we compare the plaquette variable with the available exact result in the complex gauge coupling plane. |
|
11:45AM - 12:05PM
Ayan Chatterjee (Central University of Himachal Pradesh) |
Title:
Exact solutions in higher curvature theories
Abstract: Exact solutions are not rare in General Relativity, but are so for higher curvature theories. However, even in 4 dimensions, it is important to search for these solutions. I shall present an effort to derive such solutions with symmetry. |
|
12:10PM - 12:30PM
Pinaki Roy (IISER Mohali) |
Title:
Short Waiting Time Thermonuclear X-rays Bursts in 4U 1636-536: Challenge to existing ignition models?
Abstract: Thermonuclear (Type I) X-ray bursts are sudden surges in X-ray emission from an accreting neutron star in a Low-Mass X-ray Binary (LMXB). They result from the unstable burning of hydrogen and helium on the surface of the neutron star. X-ray bursts have been found to recur on timescales of hours or days. Burst occurring within 45 minutes of the preceding burst is conventionally labelled as short waiting time (SWT) burst. In this talk, I will present results from the spectro-timing analysis of 4U 1636-536 observed with NuSTAR and AstroSat. In three observations of 207 ks total exposure, we identify 31 thermonuclear X-ray bursts including five doublets and a triplet. Recurrence time as short as 3.8 minutes is seen in one of the doublets. To the best of our knowledge, this is the shortest recurrence time known for this source. We will discuss the plausible origin of short-recurrence time X-ray bursts and compare our observational results with proposed models of the neutron star envelope. |
|
12:35PM - 12:55PM
Gopal Yadav (IIT Roorkee) |
Title:
Deconfinement Phase Transition from Entanglement Entropy and
${\mathscr {M}} \chi$PT Compatibility
Abstract: Construction of ${\mathscr {M}}$-theory dual of thermal QCD-like theories at intermediate coupling was missing in the literature. This was taken care of by authors from our group in arXiv:2004.07259[hep-th] by incorporating ${\cal O}(R^4)$ terms in the gravity dual that was earlier constructed in arXiv:1306.4339[hep-th] by our group. This talk is based on some portion of our two papers, (i) arXiv:2011.04660[hep-th] and (ii) arXiv:2108.05372[hep-th]. In this talk, I will describe deconfinement phase transition in thermal QCD-like theories from the perspective of entanglement entropy. By dividing one of the spatial coordinates into segment of length $l$ and its compliment. There are two Ryu-Takayanagi surfaces - connected and disconnected. Below a critical value of $l$(which is denoted by $l_{crit}$), it is the connected surface that dominates the entanglement entropy and above the critical value of $l$, it is the disconnected surface that dominates the entanglement entropy. This is interpreted as confinement-deconfinement phase transition in thermal QCD-like theories. In arXiv:2011.04660[hep-th], by matching one of the LECs of NLO $SU(3)$ $\chi$PT Lagrangian computed holographically with its phenomenological data, we found that a specific combination of integration constants appearing in ${\mathscr {M}}$-theory metric perturbation has a definite sign. I will explain how we derived aforementioned constraint in arXiv:2108.05372[hep-th]. |
|
02:30PM - 02:50PM
Suraj Chopra (IISER Mohali) |
Title:
Quantum Rigid Body Dynamics
Abstract: TBA |
|
02:55PM - 03:15PM
Misba Afrin (Jamia Millia Islamia) |
Title:
Can the EHT probe rotating black holes in Horndeski theory?
Abstract: The general belief that the Kerr metric describes the astrophysical black holes as encapsulated in the no-hair theorem remains an untested assumption. To probe the astrophysical nature of the M87* black hole, we take up rotating hairy black holes in the framework of Horndeski gravity with an additional hair parameter $h$ besides mass $M$ and spin $a$. The Event Horizon Telescope (EHT) constraints --- circularity deviation $\Delta C \leq 0.1$ and angular diameter $\theta_{d}=42 \pm 3 \mu as$ -- place upper bounds on both $a$ and negative values of $h$. Within this constrained parameter region ($a$-$h$) where the Horndeski black holes are viable candidates for the M87*, a systematic bias analysis quantifies the distinguishability of the Horndeski theory from GR over a substantial parameter region and motivates the test of the GR against the Horndeski gravity with electromagnetic observations viz., using the EHT resolution. |
|
03:20PM - 03:40PM
Sanjay Pant (IIT Ropar) |
Title:
Effect of backreaction on holographic thermal correlators: From entanglement to chaos
Abstract: We study the effect of backreaction on the entanglement structure and on the chaotic dynamics for a large N strongly coupled thermal plasma. We use the holographic conjectures proposed by Ruy, Takayanagi and Umemoto to compute the holographic entanglement entropy and holographic entanglement of purification and observe the effect of backreaction on these respective measures. We apply the shockwave analysis as a holographic tool to diagnose the effect of backreaction on chaos. Finally we confirm the realization of chaos as the spread of entanglement. |
|
04:00PM - 04:20PM
Shafqat Ul Islam (Jamia Millia Islamia) |
Title:
[CANCELLED!] Investigating strong gravitational lensing effects by rotating Simpson–Visser black holes
Abstract: We investigate strong-field gravitational lensing by rotating Simpson-Visser black hole, which has an additional parameter ($0\leq l/2M \leq1$), apart from mass ($M$) and rotation parameter ($a$). A rotating Simpson-Visser metric correspond to (i) a Schwarzschild metric for $l/2M=a/2M=0$ and $ M \neq 0 $, (ii) a Kerr metric for $l/2M=0$, $|a/2M|< 0.5$ and $ M \neq 0 $ (iii) a rotating regular black hole metric for $|a/2M|< 0.5$, $ M \neq 0 $ and $l/2M$ in the range $0 |
|
04:25PM - 04:45PM
Nisha Chahal (NIT Jalandhar) |
Title:
Quark matter in (2+1)-favor Polyakov quark meson model at non-zero isospin
Abstract: We investigate the phase structure and thermodynamics of the Polyakov loop-extended three flavored quark-meson model at different values of quark chemical potential and temperature. We explore the effect of isospin chemical potential and baryon chemical potential on phase transition from confined hadronic state to deconfined quarks. The model is extended by the inclusion of vector-interactions and isospin asymmetric matter along with Polyakov loop. Due to the induction of isospin chemical potential, the phase structure of QCD is modified and hence play a significant role in identifying the transition temperature more precisely. |
|
04:50PM - 05:10PM
Jasjeet Bagla (IISER Mohali) |
Title:
Gravitational Lensing of incoherent wave packets of Gravitational Waves
Abstract: Gravitational Waves have been detected from mergers of compact objects like neutron stars and black holes. A number of such events have been observed in the last six years. The signal from such events is coherent in that the amplitude and phase vary in a very precise manner and can be predicted given the parameters of the merging objects. Gravitational lensing of such signals has been studied and it has been shown that micro-lensing needs to be analyzed in the wave limit as the geometric optics limit is not valid. Another class of sources of gravitational waves are cataclysmic events like supernovae. Here the signal is incoherent and can be described as a noisy wavepacket. We present diagnostic tests to check for microlensing of such signals. |
|
05:15PM - 05:35PM
K. P. Yogendran (IISER Mohali) |
Title:
The BTZ black hole spectrum
Abstract: I will present a proposal for the spectrum of this Conformal field theory by displaying a modular invariant partition function. I will also try to convey its relevance for black hole physics in the context of string theory. |
Participants
| No | Name | Affiliation | |
|---|---|---|---|
| 1. | Navdeep Singh Dhindsa | IISER Mohali | |
| 2. | Gopal Yadav | IIT Roorkee | |
| 3. | Jasjeet Singh Bagla | IISER Mohali | |
| 4. | Harkirat Singh Sahota | IISER Mohali | |
| 5. | Anosh Joseph | IISER Mohali | |
| 6. | Ankit Dhanuka | IISER Mohali | |
| 7. | Kartik Joshi | IISER Mohali | |
| 8. | Nishat Fiza | IISER Mohali | |
| 9. | Swati Gavas | IISER Mohali | |
| 10. | Hemant Rathi | IIT Roorkee | |
| 11. | Minati Biswal | IISER Mohali | |
| 12. | Shagun Kaushal | IIT Ropar | |
| 13. | Kanwaljeet Singh Channey | Chandigarh University | |
| 14. | Sanatan Jaminy | IISER Mohali | |
| 15. | Harvinder Kaur Jassal | IISER Mohali | |
| 16. | Mandeep Kaur | IISER Mohali | |
| 17. | NItin Joshi | IIT Ropar | |
| 18. | Ayan Chatterjee | Central University of Himachal Pradesh | |
| 19. | Anirban Saha | Shoolini University | |
| 20. | Arpith Kumar | IISER Mohali | |
| 21. | Ambresh Shivaji | IISER Mohali | |
| 22. | Meenu | IIT Ropar | |
| 23. | Pinaki Roy | IISER Mohali | |
| 24. | Suresh C. Jaryal | Central University of Himachal Pradesh | |
| 25. | James Watt | IISER Mohali | |
| 26. | K P Yogendran | IISER Mohali | |
| 27. | Akash Singh | IISER Mohali | |
| 28. | Sanjay Pant | IIT Ropar | |
| 29. | Bharat Kumar Sirasva | IISER Mohali | |
| 30. | Nikhil Bansal | IISER Mohali | |
| 31. | Dipayan Mukherjee | IISER Mohali | |
| 32. | Gopal Yadav | IIT Roorkee | |
| 33. | Navdeep Arya | IISER Mohali | |
| 34. | Vaishali Guleria | Chandigarh University | |
| 35. | Shankhadeep Chakrabortty | IIT Ropar | |
| 36. | Kinjalk Lochan | IISER Mohali | |
| 37. | Vishal Bhardwaj | IISER Mohali | |
| 38. | Nirmalya Kajuri | IIT Mandi | |
| 39. | Vamika | IISER Mohali | |
| 40. | Pramod Sharma | IISER Mohali | |
| 41. | Arpit Maurya | IIT Ropar | |
| 42. | Ajay Sharma | IISER Mohali | |
| 43. | Abhishek Samlodia | IISER Mohali | |
| 44. | Himanshu Jain | IISER Mohali | |
| 45. | Bana Singh | IISER Mohali | |
| 46. | Nisha Chahal | NIT Jalandhar | |
| 47. | Misba Afrin | Jamia Millia Islamia | |
| 48. | Shafqat Ul Islam | Jamia Millia Islamia | |
| 49. | Sauraj Bharti | IISER Mohali | |
| 50. | Sushant Ghosh | Jamia Millia Islamia | |
| 51. | Roshan Kaundinya | IISER Mohali | |
| 52. | I. K. Wasimakram | IISER Mohali | |
| 53. | Abhinna Sundar | IISER Mohali | |
| 54. | Kala G. Pradeep | IISER Mohali | |