arXiv subjects

Priyadarshi Paul

Publications and source records attributed to Priyadarshi Paul.

5 recordsLinked to original sources

arXiv2026

Mapping Tachyon effective field theory to a subsector of Klein-Gordon theory

On an unstable D-brane, the rolling of the tachyon away from the maximum of its potential is described by time-dependent solutions in string theory. Subsequent analysis leads to an understanding of physics around the tachyon vacuum in terms of an effective field theory. The classical solutions of this effective field theory in the late time limit are in one-to-one correspondence with configurations of non-rotating, non-interacting dust particles. In this work, we map this effective theory near the minimum of the potential to a consistent quantum description using collective field theory methods. The Hilbert space description we obtain in this way consists of a coherent state of particles at rest and excitations on top, i.e., a subsector of Klein-Gordon theory. This is in accordance with known results where one considers a decaying D-brane as providing a time-dependent source for closed strings, and the final closed string state produced is a coherent state. It also suggests, at the quantum level, an equivalence between the open string description and the closed string description regarding the decay of an unstable D-brane.

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arXiv2024

Interacting Fields at Spatial Infinity

We study the properties of massive fields extrapolated to the blowup of spatial infinity ($\hat{i}^0$), extending the program initiated in arXiv:2207.06406. In the free theory, we find an explicit representation of boundary two-point functions and boundary to bulk two-point functions, and also present an HKLL-type reconstruction formula for local bulk operators in terms of smeared boundary operators. We study interacting Wightman correlators and find that, generically, interacting massive fields decay slower than free fields as one approaches $\hat{i}^0$. We propose that meaningful correlators at $\hat{i}^0$ can be obtained through an LSZ-like prescription that isolates the on-shell part of bulk Wightman correlators before extrapolating them to $\hat{i}^0$. We show that a natural basis for operators at $\hat{i}^0$, defined via this prescription, is given by the average of "in" and "out" operators defined at $i^-$ and $i^+$ respectively. Therefore, correlators at $\hat{i}^0$ and cross correlators between $\hat{i}^0$, $i^-$ and $i^+$ can be represented within the class of asymptotic observables studied by Caron-Huot et al. in arXiv:2308.02125. We present several sample calculations.

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arXiv2023

The Hilbert space of de Sitter quantum gravity

We obtain solutions of 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.

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arXiv2023

Holography of information in de Sitter space

We study 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.

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arXiv2022

A monogamy paradox in empty flat space

In a recent paper, Raju showed that the essential features of the monogamy paradox for old flat space black holes could be modeled using a setup in empty AdS, leading to a violation in the monogamy of entanglement there. A physically interesting question is whether such a violation in the monogamy of entanglement can be posed in empty flat space. The answer is not immediately clear since flat space gravity has an entirely different vacuum and infrared structure than the gapped and unique AdS vacuum, which was exploited in Raju's toy model. We answer this question in the affirmative, with an explicit construction. We formulate the paradox in terms of monogamy of CHSH correlations, which we use to quantify the monogamy of entanglement. Extending Raju's analysis to empty flat space, within effective field theory, we show that the entanglement of approximately local bulk modes just outside a light cone with modes just inside the light cone as well as with modes situated far away at the past of future null infinity gives rise to an O($1$) violation in the monogamy of entanglement. This cannot be resolved by small corrections of O($\sqrt{G_N}$). The issues arising from the above-mentioned vacuum and infrared features unique to flat spacetime are dealt with by introducing a physically motivated boundary projector onto states below a given infrared cutoff, which allows us to construct suitable operators at the past of future null infinity that give rise to the violation. We argue that the resolution of the paradox is that our spatially separated observables probe the same underlying degrees of freedom, i.e., such observables act on a non-factorized Hilbert space arising from the Gauss constraint, thereby circumventing the conflict with monogamy of entanglement.

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