arXiv subjects

Savdeep Sethi

Publications and source records attributed to Savdeep Sethi.

At least 19 recordsLinked to original sources

arXiv2026

Supersymmetry and Nonreciprocity

Nonreciprocal theories are used to model a broad array of non-equilibrium phenomena found in nature ranging from biological systems like networks of neurons to the behavior of overflowing water fountains. This includes systems broadly classified as active matter systems. We show that the stochastic theories which describe nonreciprocal interactions can be mapped into quantum field theories described by a supersymmetric action with a single supercharge. The theories are generically non-Hermitian. This generalizes the past work of Parisi and Sourlas on reciprocal theories, which model systems with interactions derived from potentials.

hep-th↗

arXiv2025

The On-shell Gravity Action and Linear Dilaton Holography

Computing the Euclidean spacetime action on-shell provides a useful way of both testing holographic proposals and determining the string theory sphere partition function. We consider families of three-dimensional linear dilaton spacetimes for which there are holographic proposals that share features of a $T\overline{T}$-deformed CFT. We extend the holographic renormalization program beyond AdS to this class of geometries by identifying the boundary terms needed for a well-defined variational principle and a finite on-shell action. We show that the spacetime energy or mass determined from the on-shell action matches the $T\overline{T}$-deformed two-dimensional CFT energy. This provides more evidence for the role of the $T\overline{T}$ deformation in this holographic correspondence.

hep-th↗

arXiv2025

Holography with Null Boundaries

One of the key issues in holography is going beyond $\mathrm{AdS}$ and defining quantum gravity in spacetimes with a null boundary. Recent examples of this type involve linear dilaton asymptotics and are related to the $T \overline{T}$ deformation. We present a holographic correspondence derived from string theory, which is an example of a kind of celestial holography. The holographic definition is a spacetime non-commutative open string theory supported on D1-D5 branes together with fundamental strings. The gravity solutions interpolate between $\mathrm{AdS}_3$ metrics and six-dimensional metrics. Radiation can escape to null infinity, which makes both the encoding of quantum information in the boundary and the dynamics of black holes quite different from $\mathrm{AdS}$ spacetimes.

hep-th↗

arXiv2024

An Exact Solution for the Kinetic Ising Model with Non-Reciprocity

A wide range of non-equilibrium phenomena in nature involve non-reciprocal interactions. To understand the novel behaviors that can emerge in such systems, finding tractable models is essential. With this goal, we introduce a non-reciprocal generalization of the kinetic Ising model in one dimension and solve it exactly. Our solution uncovers novel properties driven by non-reciprocity, such as underdamped phases, critically damped phases where a system of size $N$ is described by an $N^{th}$-order exceptional point, and wave phenomena influenced by the parity of $N$. Additionally, we examine the low-energy behavior of these systems in various limits, demonstrating that non-reciprocity leads to unique scaling behavior at zero temperature.

cond-mat.stat-mech↗

arXiv2024

Solving the Kinetic Ising Model with Non-Reciprocity

Non-reciprocal interactions are a generic feature of non-equilibrium systems. We define a non-reciprocal generalization of the kinetic Ising model in one spatial dimension. We solve the model exactly using two different approaches for infinite, semi-infinite and finite systems with either periodic or open boundary conditions. The exact solution allows us to explore a range of novel phenomena tied to non-reciprocity like non-reciprocity induced frustration and wave phenomena with interesting parity-dependence for finite systems of size $N$. We study dynamical questions like the approach to equilibrium with various boundary conditions. We find new regimes, separated by $N^{th}$-order exceptional points, which can be classified as overdamped, underdamped and critically damped phases. Despite these new regimes, long-time order is only present at zero temperature. Additionally, we explore the low-energy behavior of the system in various limits, including the ageing and spatio-temporal Porod regimes, demonstrating that non-reciprocity induces unique scaling behavior at zero temperature. Lastly, we present general results for systems where spins interact with no more than two spins, outlining the conditions under which long-time order may exist.

cond-mat.stat-mech↗

arXiv2024

Tensionless AdS$_3$/CFT$_2$ and Single Trace $T\overline{T}$

One of the few cases of AdS/CFT where both sides of the duality are under good control relates tensionless $k=1$ strings on AdS$_3$ to a two-dimensional symmetric product CFT. Building on prior observations, we propose an exact duality between string theory on a spacetime which is not asymptotically AdS and a non-conformal field theory. The bulk theory is constructed as a marginal deformation of the $k=1$ AdS$_3$ string while the spacetime dual is a single trace $T\overline{T}$-deformed symmetric orbifold theory. As evidence for the duality, we match the one-loop bulk and boundary torus partition functions. This correspondence provides a framework to both learn about quantum gravity beyond AdS and understand how to define physical observables in $T\overline{T}$-deformed field theories.

hep-th↗

arXiv2023

Non-Supersymmetric Heterotic Strings on a Circle

Motivated by a recent construction of non-supersymmetric $\text{AdS}_3$, we revisit the $O(16)\times O(16)$ heterotic string compactified on a torus. The string one-loop potential energy has interesting dependence on the classical moduli; extrema of this potential include loci where the gauge symmetry is maximally enhanced. Focusing on the case of a circle, we use lattice embeddings to find the maximal enhancement points together with their spectra of massless and tachyonic modes. We find an extended Dynkin diagram that encodes the global structure of the moduli space, as well as all symmetry enhancements and the loci where they occur. We find $107$ points of maximal enhancement with $8$ that are free of tachyons. The tachyon-free points each have positive cosmological constant. We determine the profile of the potential energy near each of these points and find that one is a maximum while three are saddle points. The remaining four live at the boundary of a tachyonic region in field space. In this way, we show that every point of maximal symmetry enhancement is unstable. We further find that the curvature of this stringy potential satisfies the de Sitter swampland conjecture. Finally, we discuss the implications for constructions of $\text{AdS}_3$.

hep-th↗

arXiv2023

Holography and Irrelevant Operators

We explore the holographic proposal involving spacetimes with linear dilaton asymptotics in three dimensions from a gravity perspective. The holographic dual shares some properties with a symmetric product conformal field theory deformed by a single-trace analogue of the $T \overline{T}$ deformation. We present solutions of ten-dimensional supergravity which interpolate from BTZ black holes in the interior to either a linear dilaton spacetime near infinity, or to flat space. This allows a precise identification of field theory parameters with gravity parameters. The solutions manifestly exhibit the square root structure that is characteristic of $T \overline{T}$-deformed conformal field theories. We compute the mass of the spacetimes using the covariant phase space formalism and find agreement with the square root formula for the case of black holes without spin. We also discuss whether closed string tachyons might play a role when the deformation parameter becomes too large and the vacuum becomes unstable.

hep-th↗

arXiv2022

Non-Supersymmetric AdS from String Theory

We construct non-supersymmetric AdS3 solutions of the O(16)xO(16) heterotic string. Most of the backgrounds have a classical worldsheet definition but are quantum string vacua in the sense that string loop corrections change the curvature of spacetime. At one-loop, the change in the cosmological constant is positive but never sufficient to uplift to de Sitter space. By computing the spectrum of spacetime scalars, we show that there are no tachyons below the BF bound. We also show that there is a solution with no spacetime NS-NS flux. This background has no classical string limit. Surprisingly, there appears to be parametric control over these constructions, which provide a framework for exploring quantum gravity and holography without supersymmetry.

hep-th↗

arXiv2022

Sequential Flows by Irrelevant Operators

We explore whether one can $T \overline{T}$ deform a collection of theories that are already $T \overline{T}$-deformed. This allows us to define classes of irrelevant deformations that know about subsystems. In some basic cases, we explore the spectrum that results from this procedure and we provide numerical evidence in favor of modular invariance. We also study the flow of the classical Lagrangian for free bosons and free fermions under successive deformations. Some of the models found by sequentially flowing are likely to have interesting holographic interpretations.

hep-th↗

arXiv2021

Gravitational Memory and Compact Extra Dimensions

We develop a general formalism for treating radiative degrees of freedom near $\mathscr{I}^{+}$ in theories with an arbitrary Ricci-flat internal space. These radiative modes are encoded in a generalized news tensor which decomposes into gravitational, electromagnetic, and scalar components. We find a preferred gauge which simplifies the asymptotic analysis of the full nonlinear Einstein equations and makes the asymptotic symmetry group transparent. This asymptotic symmetry group extends the BMS group to include angle-dependent isometries of the internal space. We apply this formalism to study memory effects, which are expected to be observed in future experiments, that arise from bursts of higher-dimensional gravitational radiation. We outline how measurements made by gravitational wave observatories might probe properties of the compact extra dimensions.

gr-qc↗

arXiv2020

Defining the $T \overline{T}$ Deformation on $\mathrm{AdS}_2$

We show that the $T \overline{T}$ deformation of two-dimensional quantum field theory on $\mathrm{AdS}_2$ is well-defined and solvable at the quantum level. Flow equations for the energy spectrum and partition function are derived in analogy with the flat space case. As a non-trivial check, we perturbatively compute the deformed energy spectrum for the case of a free scalar field. We analyze the high energy density of states of the deformed theory and find a Hagedorn growth of states.

hep-th↗

arXiv2020

A Non-Abelian Analogue of DBI from $T \overline{T}$

The Dirac action describes the physics of the Nambu-Goldstone scalars found on branes. The Born-Infeld action defines a non-linear theory of electrodynamics. The combined Dirac-Born-Infeld (DBI) action describes the leading interactions supported on a single D-brane in string theory. We define a non-abelian analogue of DBI using the $T \overline{T}$ deformation in two dimensions. The resulting quantum theory is compatible with maximal supersymmetry and such theories are quite rare.

hep-th↗

arXiv2019

$T\bar{T}$ Flows and (2,2) Supersymmetry

We construct a solvable deformation of two-dimensional theories with $(2,2)$ supersymmetry using an irrelevant operator which is a bilinear in the supercurrents. This supercurrent-squared operator is manifestly supersymmetric, and equivalent to $T\bar{T}$ after using conservation laws. As illustrative examples, we deform theories involving a single $(2,2)$ chiral superfield. We show that the deformed free theory is on-shell equivalent to the $(2,2)$ Nambu-Goto action. At the classical level, models with a superpotential exhibit more surprising behavior: the deformed theory exhibits poles in the physical potential which modify the vacuum structure. This suggests that irrelevant deformations of $T\overline{T}$ type might also affect infrared physics.

hep-th↗

arXiv2019

Non-Linear Supersymmetry and $T\bar T$-like Flows

The $T\bar{T}$ deformation of a supersymmetric two-dimensional theory preserves the original supersymmetry. Moreover, in several interesting cases the deformed theory possesses additional non-linearly realized supersymmetries. We show this for certain $\mathcal N =(2,2)$ models in two dimensions, where we observe an intriguing similarity with known $\mathcal N=1 $ models in four dimensions. This suggests that higher-dimensional models with non-linearly realized supersymmetries might also be obtained from $T\bar{T}$-like flow equations. We show that in four dimensions this is indeed the case for $\mathcal N=1 $ Born-Infeld theory, as well as for the Goldstino action for spontaneously broken $\mathcal N=1 $ supersymmetry.

hep-th↗

arXiv2019

Supersymmetry and $T \overline{T}$ Deformations

We propose a manifestly supersymmetric generalization of the solvable $T \overline{T}$ deformation of two-dimensional field theories. For theories with $(1,1)$ and $(0,1)$ supersymmetry, the deformation is defined by adding a term to the superspace Lagrangian built from a superfield containing the supercurrent. We prove that the energy levels of the resulting deformed theory are determined exactly in terms of those of the undeformed theory. This supersymmetric deformation extends to higher dimensions, where we conjecture that it might provide a higher-dimensional analogue of $T \overline{T}$, producing supersymmetric Dirac or Dirac-Born-Infeld actions in special cases.

hep-th↗

arXiv2019

Swampland Conjectures and Late-Time Cosmology

We discuss the cosmological implications of the string swampland conjectures for late-time cosmology, and test them against a wide range of state of the art cosmological observations. The refined de Sitter conjecture constrains either the minimal slope or the curvature of the scalar potential, and depends on two dimensionless constants. For constants of size one or larger, tension exists between observations, especially the Hubble constant, and the slope and curvature conjectures at a level of 4.5 sigma and 2.3 sigma, respectively. Smaller values of the constants are permitted by observations, and we determine upper bounds at varying confidence levels. We also derive and constrain the relationship between cosmological observables and the scalar field excursion during the acceleration epoch, thereby testing the distance conjecture.

hep-th↗

arXiv2018

(2,2) Geometry from Gauge Theory

Using gauge theory, we describe how to construct generalized Kahler geometries with (2,2) two-dimensional supersymmetry, which are analogues of familiar examples like projective spaces and Calabi-Yau manifolds. For special cases, T-dual descriptions can be found which are squashed Kahler spaces. We explore the vacuum structure of these gauge theories by studying the Coulomb branch, which usually encodes the quantum cohomology ring. Some models without Kahler dual descriptions possess unusual Coulomb branches. Specifically, there appear to be an infinite number of supersymmetric vacua.

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