CHEP

Special Lecture: Priyadarshi Paul, ICTS
2024-10-04 11:00 - 13:00 UTC
Title : The Hilbert space and holography of information in de Sitter quantum gravity
Abstract : In the 1st lecture, I will discuss the solutions we obtained for the Wheeler-DeWitt equation with positive cosmological constant for a closed universe in the large-volume limit. We argue that this space of solutions provides a complete basis for the Hilbert space of quantum gravity in an asymptotically de Sitter spacetime. Our solutions take the form of a universal phase factor multiplied by distinct diffeomorphism invariant functionals, with simple Weyl transformation properties, that obey the same Ward identities as a CFT partition function. The Euclidean vacuum corresponds to a specific choice of such a functional but other choices are equally valid. Each functional can be thought of as specifying a “theory” and, in this sense, the space of solutions is like “theory space”. We describe another basis for the Hilbert space where all states are represented as excitations of the vacuum that have a specific constrained structure. This gives the finite G_N generalization of the basis proposed by Higuchi in terms of group averaging, which we recover in the nongravitational limit.
In the 2nd lecture, I will talk about the natural norm on the space of solutions to the Wheeler-DeWitt equation in an asymptotically de Sitter spacetime. We propose that the norm is obtained by integrating the squared wavefunctional over field configurations and dividing by the volume of the diff-and-Weyl group. We impose appropriate gauge conditions to fix the diff-and-Weyl redundancy and obtain a finite expression for the norm using the Faddeev-Popov procedure. This leads to a ghost action that has zero modes corresponding to a residual conformal subgroup of the diff-and-Weyl group. By keeping track of these zero modes, we show that Higuchi’s norm for group-averaged states emerges from our prescription in the nongravitational limit. We apply our formalism to cosmological correlators and propose that they should be understood as gauge-fixed observables. We identify the symmetries of these observables. In a nongravitational theory, it is necessary to specify such correlators everywhere on a Cauchy slice to identify a state in the Hilbert space. In a theory of quantum gravity, we demonstrate a version of the principle of holography of information: cosmological correlators in an arbitrarily small region suffice to completely specify the state.
References : (1) arxiv : 2303.16315
(2) arxiv : 2303.16316

Special Lecture : Priyadarshi Paul, ICTS
2024-10-01 11:00 - 13:00
Title : The Hilbert space and holography of information in de Sitter quantum gravity
Abstract : In the 1st lecture, I will discuss the solutions we obtained for the Wheeler-DeWitt equation with positive cosmological constant for a closed universe in the large-volume limit. We argue that this space of solutions provides a complete basis for the Hilbert space of quantum gravity in an asymptotically de Sitter spacetime. Our solutions take the form of a universal phase factor multiplied by distinct diffeomorphism invariant functionals, with simple Weyl transformation properties, that obey the same Ward identities as a CFT partition function. The Euclidean vacuum corresponds to a specific choice of such a functional but other choices are equally valid. Each functional can be thought of as specifying a “theory” and, in this sense, the space of solutions is like “theory space”. We describe another basis for the Hilbert space where all states are represented as excitations of the vacuum that have a specific constrained structure. This gives the finite G_N generalization of the basis proposed by Higuchi in terms of group averaging, which we recover in the nongravitational limit.
In the 2nd lecture, I will talk about the natural norm on the space of solutions to the Wheeler-DeWitt equation in an asymptotically de Sitter spacetime. We propose that the norm is obtained by integrating the squared wavefunctional over field configurations and dividing by the volume of the diff-and-Weyl group. We impose appropriate gauge conditions to fix the diff-and-Weyl redundancy and obtain a finite expression for the norm using the Faddeev-Popov procedure. This leads to a ghost action that has zero modes corresponding to a residual conformal subgroup of the diff-and-Weyl group. By keeping track of these zero modes, we show that Higuchi’s norm for group-averaged states emerges from our prescription in the nongravitational limit. We apply our formalism to cosmological correlators and propose that they should be understood as gauge-fixed observables. We identify the symmetries of these observables. In a nongravitational theory, it is necessary to specify such correlators everywhere on a Cauchy slice to identify a state in the Hilbert space. In a theory of quantum gravity, we demonstrate a version of the principle of holography of information: cosmological correlators in an arbitrarily small region suffice to completely specify the state.
Reference:
References : (1) arxiv : 2303.16315
(2) arxiv : 2303.16316

SEMINAR - Shouvik Roy Choudhury
2024-09-23 14:30 - 16:00
Speaker: Shouvik Roy
Title: Cosmology in an extended parameter space: new constraints on dark energy and neutrino masses with DESI BAO
Abstract: We update constraints on cosmological parameters in a 12-parameter model, which extends the standard 6-parameter ΛCDM to include dynamical dark energy and massive neutrinos, along with other new parameters. We use the latest Planck PR4 (2020) likelihoods, DESI DR1 BAO, and the latest uncalibrated type Ia Supernovae (SNe) datasets. In this talk, I will discuss the implications for dynamical dark energy in such an extended model, and at the same time, provide robust bounds on neutrino masses which will be useful for the astro- and particle physics communities. I will also discuss the current status of the weak lensing tension and the Hubble tension in this extended cosmology.

SEMINAR - Dibya Chakraborty
2024-09-10 14:30 - 16:00
Speaker: Dibya Chakraborty, IIT-M.
Title: Inflationary Models in Perturbative LVS
Abstract: Contrary to the usual Large Volume Scenario (LVS), in the perturbative LVS case, the overall volume modulus is dynamically stabilized to an exponentially large value only via perturbative corrections. In the first part of my talk, I will present the global embedding of a single field inflationary model in the framework of perturbative LVS using an orientifold of a K3-fibred CY3. The robustness of the single field inflationary model, where the overall volume drives the accelerated expansion, is checked against possible sub-leading corrections such as winding-type string loop corrections and the higher derivative F^4-corrections. Having a complete global construction facilitates writing the scalar potential as a function of all the sub-leading corrections. In the second half of my talk, I will focus on the global embedding of the fibre inflation in perturbative LVS. In the vanilla fibre inflationary model, the inflaton field range is largely constrained by the conditions arising from K'”ahler cone which creates a challenge towards realizing the cosmological observables while consistently respecting the underlying supergravity approximations. I will show how the global embedding again is proven to be useful to naturally alleviate this issue by embedding fibre inflation in perturbative LVS.

SEMINAR - Prof. Nirmalya Kajuri
2024-09-04 14:30 - 16:00
Speaker: Nirmalya Kajuri, IIT Mandi
Title: HKLL in deSitter
Abstract: In this talk, I will present recent work on construction of boundary representations of de Sitter fields. I will start by introducing the HKLL construction of boundary representations in AdS. Then, we will review previous work on construction of boundary representations on de Sitter and finally present our results.

Colloquium
2024-08-30 16:00 - 18:00

Event 3
2024-07-25 08:00 - 17:00 | LH4
Description: Event description goes here
Speaker: Prolay Mal (NISER, Bhubaneswar)
Venue: LH4

Pheno-Coffee Talk
2024-07-22 16:00 - 17:00 | LH-3, India
Description: Physics at the HL-LHC and beyond
Speaker: Prolay Mal (NISER, Bhubaneswar)
Venue: LH3

Event 4
2024-07-18 10:00 - 13:00 | LH-3, India
Physics at the HL-LHC and beyond

Speaker: Prolay Mal (NISER, Bhubaneswar)

Venue: LH-3
Time: 2:30pm

Event 2
2024-07-16 08:00 - 17:00 | Physical Sciences Auditorium
Description: Event details or description goes here
Speaker: Prolay Mal (NISER, Bhubaneswar)
Venue: LH5

Test event for July
2024-07-11 08:00 - 17:00 | Auditorium
Description: Event description goes here. Lorem Ipsum is simply dummy text of the printing and typesetting industry.
Speaker: Prolay Mal (NISER, Bhubaneswar)
Venue: Auditorium
