arXiv subjects

Dibakar Roychowdhury

Publications and source records attributed to Dibakar Roychowdhury.

At least 37 records · Page 2Linked to original sources

arXiv2025

Time-like Entanglement Entropy: a top-down approach

We investigate the concept of time-like entanglement entropy (tEE) within the framework of holography. We introduce a robust top-down prescription for computing tEE in higher-dimensional QFTs, both conformal and confining, eliminating the ambiguities typically associated with analytic continuation from Euclidean to Lorentzian signatures. We present accurate analytic approximations for tEE and time-like separations in slab geometries. We establish a clear stability criterion for bulk embeddings and demonstrate that tEE serves as a powerful tool for computing CFT central charges, extending and strengthening previous results. Finally, we apply our framework to holographic confining backgrounds, revealing distinctive behaviours like phase transitions.

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arXiv2025

Field theory aspects of $ η$-deformed superstring background

We explore various field theory aspects of integrable $ η$-deformed geometry in type IIB supergravity by employing several holographic probes. These include the computation of holographic timelike entanglement entropy and estimation of various other field theory observables for example, the flow central charge and the quantum complexity. We also discuss the associated brane set up and compute Page charges. We further use them to calculate the coupling constant in the dual QFTs considering both small and large deformation limits.

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arXiv2025

Holographic timelike entanglement and $c$ theorem for supersymmetric QFTs in ($ 0+1 $)d

We present a holographic set up that computes timelike Entanglement Entropy (tEE) in $ (0+1) $d QFTs preserving some amount of SUSY. The first example we consider is that of $\mathcal{N}=2$ matrix models with massive deformations. These are dual to non-Abelian T-dual of $AdS_5 \times S^5$ that asymptotes to \emph{smeared} D0 branes. The second example, that we consider is of $ \mathcal{N}=4 $ superconformal quantum mechanical quivers in ($ 0+1 $)d that are dual to a class of type IIB backgrounds with an $ AdS_2 $ factor. In both of these examples, tEE reveals a remarkable similarity with holographic $ c $ function pertaining to a RG flow. We further compute the complexity in these models, which also reveals an identical behaviour indicating the fact that tEE is a measure of number of degrees of freedom for these ($ 0+1 $)d SQFTs in a RG flow from UV to deep IR.

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arXiv2025

Topology of black hole phase transition in JT gravity

We present a JT gravity setup coupled with $U(1)$ and $SU(2)$ Yang-Mills fields in two dimensions that reveals the onset of a small black hole to large black hole phase transition at finite chemical potential(s). We identify these black hole solutions as topological defects in the thermodynamic phase space and calculate the associated topological numbers following the standard procedure. We confirm the robustness of our model by estimating perturbative corrections to the bulk free energy at an arbitrary order in the Yang-Mills coupling. We also construct the Schwarzian for the boundary theory using the 2D gravitational action in the bulk and comment on the dual SYK like model where similar observations can be made.

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arXiv2025

Metallic transports from accelerating black holes

We probe four dimensional accelerating black holes with D-brane and build up the notion of metallic holography for spacetime with negative cosmological constant. We explore various thermodynamic entities associated with the boundary QFT at low temperatures and finite chemical potential. The DC conductivity in the boundary QFT is enhanced due to the effects of black hole acceleration in the bulk counterpart. We further compute resistivity in different temperature regime, which reveals a new quantum liquid phase with dynamic critical exponent $ z=3 $.

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arXiv2024

Carrollian expansion of Born-Infeld Electrodynamics

In this paper, we carry out a detailed investigation of Born-Infeld Electrodynamics in the Carrollian limit. We explore these theories by looking at expansion in a small c limit at the level of Lagrangian. Particularly, we study the symmetries and correlation functions in the presence of non-linear interactions.

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arXiv2024

Holographic zero sound for $\mathcal{N}=2$ SCFTs in 4d

We build up the notion of metallic holography for $\mathcal{N}=2$ SCFTs in four dimensions, in the presence of a finite $U(1)$ chemical potential. We compute two point correlation functions and study their properties in the regime of low frequency and low momentum. The color sector reveals gapless excitations, one of which propagates with a finite phase velocity while the other mode attenuates through scattering. The flavour sector, on the other hand, reveals spectrum that contains quasiparticle excitations which propagate with a definite phase velocity together with modes that propagate with a finite group velocity which quantum attenuates quite similar in spirit as that of Landau's zero sound modes. We also compute associated AC conductivities, which exhibit different characteristics for different (color and flavour) sectors of $\mathcal{N}=2$ SCFTs.

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arXiv2024

Factorised scattering and (non)integrability for marginally deformed $ AdS_5/CFT_4 $

We study non-SUSY CFTs that are marginal deformations of $ \mathcal{N}=2 $ SCFTs in 4d. We explore the fate of integrability and/or non-integrability in these CFTs using the techniques of factorisation of scattering amplitudes in 2d sigma models. We show possibilities for the factorisation of scattering amplitudes in the absence of flavour D6 branes which rules out non-integrability in the dual non-SUSY CFTs.

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arXiv2024

Magnons and spikes for $\mathcal{N}=2$ linear quivers and their non-Abelian T-duals

We compute the spectra associated with various semiclassical string states that propagate over $\mathcal{N}=2$ Gaiotto-Maldacena backgrounds. As an interesting special case, for the Abelian T- dual solution, we discover giant magnon and single spike configurations while imposing appropriate boundary conditions. However, for Sfetsos-Thompson backgrounds, one has to adopt a different string embedding which reveals ``modified'' dispersion relations both for magnons and spikes. These results boil down into the standard dispersion relations in the limit when the rank of the associated $SU(N_c)$ color gauge group becomes large enough. We further generalize our analysis in the presence of flavor D6 branes. Our analysis reveals a new set of dispersion relations, which shows that both magnons and spikes are ceased to exist in the presence of flavor excitations.

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arXiv2024

Non-chaotic dynamics for Yang-Baxter deformed $\text{AdS}_{4}\times \text{CP}^{3}$ superstrings

We explore a novel class of Yang-Baxter deformed AdS$_{4}$ $\times$ CP$^{3}$ backgrounds [Jour. High Ener. Phys. \textbf{01} (2021) 056] which exhibit a non-chaotic dynamics for (super)strings propagating over it. We explicitly use the \textit{Kovacic's algorithm} in order to establish non-chaotic dynamics of string $ σ$ models over these deformed backgrounds. This analysis is complemented with numerical techniques whereby we probe the classical phase space of these (semi)classical strings and calculate various chaos indicators, such as, the Poincaré sections and the Lyapunov exponents. We find compatibility between the two approaches. Nevertheless, our analysis does not ensure integrability; rather, it excludes the possibility of non-integrability for the given string embeddings.

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arXiv2024

Matrix model correlators from non-Abelian T-dual of $AdS_5 \times S^5 $

We study various perturbations and their holographic interpretation for non-Abelian T-dual of $ AdS_5 \times S^5 $ where the T-duality is applied along the $ SU(2) $ of $ AdS_5 $. This paper focuses on two types of perturbations, namely the scalar and the vector fields on NATD of $ AdS_5 \times S^5 $. For scalar perturbations, the corresponding solutions could be categorised into two classes. For one of these classes of solutions, we build up the associated holographic dictionary where the asymptotic radial mode sources scalar operators for the $ (0+1) $d matrix model. These scalar operators correspond to either a marginal or an irrelevant deformation of the dual matrix model at strong coupling. We calculate the two point correlation between these scalar operators and explore their high as well as low frequency behaviour. We also discuss the completion of these geometries by setting an upper cut-off along the holographic axis and discuss the corresponding corrections to the scalar correlators in the dual matrix model. Finally, we extend our results for vector perturbations where we obtain asymptotic solutions for a particular class of modes. These are further used to calculate the boundary charge density at finite chemical potential.

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arXiv2024

Covariant action for M5 brane in nonrelativistic M-theory

We construct the nonrelativistic covariant world-volume action for a single M5 brane of $ D=11 $ supergravity in M-theory. The corresponding non-Lorentzian (NL) background possesses a codimension three foliation and is identified as the Membrane Newton-Cartan manifold in the presence of background fluxes that are suitably expanded in $ 1/c^2 $ expansion. We also expand the associated world-volume fields in $ 1/c^2 $ expansion. The above procedure eventually results into a well defined world-volume action that is coupled to Membrane Newton-Cartan background.

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arXiv2023

Nonrelativistic expansion of Green-Schwarz strings on $ AdS_5 \times S^5 $

We perform nonrelativistic expansions of type IIB $ AdS_5 \times S^5 $ Green-Schwarz (GS) superstrings upto quadratic order in fermionic excitation. We carry out a systematic $ 1/c $ expansion both for the bosonic as well as the fermionic sector of the type IIB model and explore the LO theory in detail. We explore various global as well as local symmetries of the nonrelativistic sigma model at LO including the world-sheet supersymmetry. As a special case, we choose the flat gauge and explore the longitudinal T-duality rules for the LO theory. Finally, we comment on the NLO theory and some interesting properties of it.

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arXiv2023

Integrability and non-integrability for marginal deformations of 4d $\mathcal N = 2$ SCFTs

We study integrability and non-integrability for marginal deformations of 4d $\mathcal N =2$ SCFTs. We estimate various chaos indicators for the bulk theory which clearly shows the onset of a chaotic string dynamics in the limit of large deformations. On the other hand, for small values of the deformation parameter, the resulting dynamics exhibits a non-chaotic motion and therefore presumably an underlying integrable structure. Our analysis reveals that the $γ$-deformation in the type-IIA theory could be interpreted as an interpolation between a class of integrable $\mathcal N =2$ SCFTs and a class of non-integrable $\mathcal N =1$ SCFTs at strong coupling. We also generalise our results in the presence of the flavor branes.

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arXiv2023

Nonrelativistic expansion of type IIA NS5 brane

We carry out nonrelativistic expansion for NS5 brane based on a codimension two foliation of type IIA supergravity background. We simultaneously expand the world-volume fields in an appropriate $ 1/c^2 $ expansion together with the background fluxes. When put together, the resulting procedure yields a finite world-volume action for nonrelativistic NS5 brane that is coupled to String Newton-Cartan background.

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arXiv2023

Matrix models and non-Abelian T dual of $AdS_5 \times S^5 $

We compute Euclidean Wilson loops for BMN Plane Wave Matrix Models. The stringy counterpart of these Wilson loops corresponds to various semi-classical open string embedding that probe a class of half BPS geometries in Type IIA supergravity. These geometries fall under the general category of Lin-Lunin and Maldacena (LLM). As a special class of solutions within the LLM category, we construct Wilson operators corresponding to the non-Abelian T dual (NATD) of $ AdS_5 \times S^5 $. Our analysis shows close agreement between matrix model and string theory calculations.

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arXiv2023

Phases of Euclidean wormholes in JT gravity

We present a JT gravity set up that reveals the evidence of (Euclidean) wormhole to black hole phase transition at finite charge density and/or chemical potential. We identify the low temperature phase of the system as the charged wormhole solution. As the temperature of the system is increased, it undergoes a first order phase transition to a two black hole system at finite charge density. At the critical point ($T = T_0$) of the phase transition, both the Free energy (density) and the charge undergoes a discontinuous change. Finally, we conjectured that the field theory dual to this gravitational set up is a two-site (uncoupled) complex SYK model at a finite chemical potential.

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arXiv2023

$AdS_2$ holography and ModMax

We present a JT gravity set up in the presence of projected ModMax corrections in two dimensions. Our starting point is the Einstein's gravity in four dimensions accompanied by the ModMax Lagrangian. The 2D gravity action is obtained following a suitable dimensional reduction which contains a 2D image of the 4D ModMax Lagrangian. We carry out a perturbative analysis to find out the vacuum structure of the theory which asymptotes to $AdS_2$ in the absence of $U(1)$ gauge fields. We estimate the holographic central charge and obtain corrections perturbatively upto quadratic order in the ModMax and the $U(1)$ coupling. We also find out ModMax corrected 2D black hole solutions and discuss their extremal limits.

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