arXiv subjects

Naman Kumar

Publications and source records attributed to Naman Kumar.

At least 19 recordsLinked to original sources

arXiv2026

Entropy Obstruction to Closed Semiclassical Bounces

We prove a finite-$G\hslash$ singularity theorem for semiclassical spacetimes with compact Cauchy slices. Let a compact Cauchy slice be divided by a compact surface into regions $B$ and $C$. Suppose that $B$ is conditionally hyperentropic, $H_{\max,\mathrm{gen}}^\varepsilon(BC|C)>0$, that the future-inward null boundary from the dividing surface toward $B$ is a discrete max lightsheet, and that $C$ is robustly quantum trapped. Assuming discrete max-focusing and a regular semiclassical endpoint for a closing lightsheet, the future Cauchy development of $B$ contains an incomplete null generator. This parallels entropy singularity theorems in which hyperentropy is combined with the existence of an inward lightsheet, while robust quantum trapping supplies the additional finite-$G\hslash$ local obstruction needed here. In a closed Friedmann universe, the theorem excludes a controlled semiclassical bounce when a contracting hemisphere lies on such a lightsheet and contains more independent information than its boundary can support.

gr-qc↗

arXiv2026

Reverse Isoperimetric Conjecture as a Noether-Charge Stability Theorem

The reverse isoperimetric conjecture asserts that, at fixed thermodynamic volume, Schwarzschild--AdS black holes maximize entropy. We prove that this statement is the fixed-volume form of a boundary-completed Noether-charge stability theorem. The essential observation is that the bulk Hollands--Wald canonical energy is not the full entropy Hessian: along exact stationary black-hole families it vanishes, and the missing curvature is supplied by a constrained asymptotic charge Hessian. Combining this boundary term with bulk canonical-energy positivity gives entropy concavity on admissible fixed-volume components, while zero-energy rigidity determines the equality sector. The theorem reproduces the Einstein-gravity area-volume inequality and extends naturally to Wald entropy in higher-derivative theories. Known violations are thereby reinterpreted as failures of compactness, positivity, or rigidity rather than failures of the variational mechanism.

gr-qc↗

arXiv2026

Quantum Black Hole Chemistry from Double Holography

Extended black hole thermodynamics exposes a sharp tension in the usual holographic dictionary: at fixed boundary conformal frame, changing the AdS radius changes both the central charge and the spatial volume of the CFT, apparently locking the color and volume sectors of the first law. We show that this degeneracy is naturally removed for quantum black holes in Karch--Randall double holography. The mechanism is intrinsically semiclassical. Replacing the holographic regulator surface by a physical brane induces gravity coupled to a cutoff CFT, so classical bulk black holes become lower-dimensional quantum black holes whose geometry includes the cutoff-matter stress tensor to all orders in backreaction. This backreacting matter sector supplies a color variable distinct from the defect volume. We demonstrate the mechanism explicitly for the quantum BTZ black hole. Thus quantum backreaction resolves the same color-volume degeneracy addressed by the recent Weyl-factor proposal, but without introducing a non-standard boundary modulus. Instead, the missing thermodynamic direction is supplied by the physical cutoff-matter sector of the doubly holographic quantum black hole.

hep-th↗

arXiv2026

Massless Islands in Wedge Holography

Entanglement islands are most easily realized in doubly holographic models with massive gravitons or non-gravitating baths. In wedge holography, however, Neumann boundary conditions on both branes give a normalizable massless graviton, while the island saddle of the purely geometric Ryu--Takayanagi (RT) problem collapses to the horizon. Negative Dvali--Gabadadze--Porrati (DGP) terms can restore nontrivial islands by modifying the endpoint condition, but this branch contains a massive ghost. We propose a different semiclassical mechanism. We keep the wedge gravitational action free of DGP terms and couple the healthy Neumann wedge sector to a unitary defect CFT localized at the codimension-two corner. This sector is distinct from the standard corner CFT dual to the undeformed wedge, so its entropy enters as the ordinary matter-entropy term in the quantum extremal surface (QES) prescription without double counting the wedge RT area. If the defect theory is holographic, this entropy can be evaluated by an auxiliary RT surface. We show that when the wedge endpoint determines the defect entangling region, the auxiliary area can vary in the opposite way to the wedge area while all couplings and central charges remain positive. A local endpoint model gives an isolated stable saddle that dominates over the Hartman--Maldacena (HM) surface at late times. The QES condition then replaces the pure orthogonality condition and permits a non-horizon island saddle in a long-range, massless, ghost-free gravitational theory. Thus, the obstruction to massless islands in minimal wedge holography is not masslessness itself, but the absence of a healthy matter-entropy contribution capable of balancing the horizon-minimizing area variation.

hep-th↗

arXiv2026

Topology sums, sectorwise holography, and horizon normalcy

The ``holography of information'' (HoI) principle argues that gravity can encode information redundantly in asymptotic observables. Although HoI is ultimately a nonperturbative claim, its standard motivation uses semiclassical gravitational constraints, the boundary nature of the Hamiltonian, and vacuum-sector cyclicity. We ask what happens when the same semiclassical path-integral reasoning allows topology sums that generate baby-universe or $\alpha$-sector data. Our analysis is conditional: such sectors need not survive in every unitary completion, and the Baby Universe Hypothesis of McNamara and Vafa instead suggests $\dim\mathcal H_{\rm BU}=1$ in consistent $d>3$ quantum gravity. If $\mathcal H_{\rm BU}$ is nontrivial, as in the Marolf--Maxfield formulation and in ensemble-like examples such as JT gravity, then HoI is naturally refined to an $\alpha$-sectorwise statement, $\overline{\mathcal A_\infty^{(\alpha)}|0_\alpha\rangle}=\mathcal H_\alpha$, rather than completeness on the full topology-summed Hilbert space. In a fixed $\alpha$-sector, HoI may obstruct AMPS factorization and allow a smooth horizon; in an unconditioned topology-summed state, the sector-independent obstruction is not automatic. A Bell-pair diagnostic shows that a sector-independent smooth interior requires aligned interior reconstructions, or access to the sector label. Thus the HoI-based absence of firewalls becomes conditional on global sector data, in tension with the generally covariant expectation emphasized by Bousso that horizon normalcy should be determined by local semiclassical geometry. If the exact theory collapses $\mathcal H_{\rm BU}$ to one dimension, the obstruction discussed here is absent.

hep-th↗

arXiv2026

An Algebraic Resolution of the Firewall Paradox

The AMPS firewall argument relies on treating early radiation, late outgoing Hawking modes, and interior partner modes as approximately independent quantum subsystems. In diffeomorphism-invariant quantum gravity, however, gravitational dressing and asymptotic constraints obstruct such a tensor-product factorization of physical observables. In this essay, we sharpen this obstruction by formulating subsystem independence directly in operator-algebraic terms. Using modular theory, half-sided modular inclusions along null directions, and the sector-wise maximality of the dressed radiation algebra at future null infinity, we show that -- within a fixed asymptotic charge sector -- the algebra associated with the interior Hawking partner cannot form an independent commuting subalgebra, but must be contained as a (non-commuting) subalgebra of the radiation algebra itself. The subsystem-independence assumption underlying the AMPS paradox therefore fails, and the entanglement-monogamy step never becomes applicable. As a result, unitary black hole evaporation and semiclassical horizon smoothness are compatible in asymptotically flat quantum gravity, without invoking entanglement islands, replica wormholes, or modifications of semiclassical horizon physics.

hep-th↗

arXiv2026

Entropy bound and the non-universality of entanglement islands

The island prescription reproduces the Page curve and avoids the Almheiri--Marolf--Polchinski--Sully (AMPS) monogamy conflict for suitable radiation subsystems by placing the corresponding interior partners in their entanglement wedges. This mechanism is intrinsically region-dependent. We define a common compact semiclassical support as a finite semiclassical domain that contains representatives of the interior partners of a chosen family of late Hawking modes, while each radiation subsystem need reconstruct only its own partner. We ask whether these separate mode-by-mode reconstructions can be represented within such a common support at a fixed evaporation epoch. The physical motivation is that horizon normalcy---the requirement that the horizon remain smooth for an infalling observer and that semiclassical effective field theory remain valid across it---is a local property, whereas the island condition that resolves AMPS for a given late mode depends on the radiation subsystem used for reconstruction. Using a bounded null realization of the common support together with the quantum Bousso bound, we show that no regular common compact semiclassical support can realize all of the relevant AMPS partner sectors once the support enters the hyperentropic regime. The argument is formulated entirely within the semiclassical region in which the AMPS setup is valid and does not require extending the null surface to the Planckian singularity.

hep-th↗

arXiv2026

Dynamical tidal response of regular black holes: Perturbative analysis and shell EFT interpretation

We compute the frequency-dependent quadrupolar tidal response of Bardeen, Hayward, and Fan-Wang regular black holes in the polar and axial sectors by solving the coupled gravitational-electromagnetic perturbation equations numerically. Our analysis independently recovers the static Love numbers and their scaling at small regularization, while differences can occur at finite regularization due to higher-order corrections. The ratios of metric source-response coefficients at low frequencies ($\omega$) have smooth corrections starting at $\mathcal{O}(\omega^{2})$. Furthermore, we compare the peaks in the response coefficients with the real parts of the quasinormal mode (QNM) frequencies and find that in the polar sector for Bardeen, Hayward and Fan-Wang, peaks for small values of the regularization parameter, align with the corresponding QNM frequencies within the damping width provided by the imaginary part of the respective QNM. On the other hand, in the axial sector, the Bardeen and Hayward maxima of the response coefficients are not aligned with the real part of the QNM, whereas all the Fan-Wang peaks are. Moreover, we perform a shell EFT calculation using a scalar field as a simpler probe. The shell EFT construction expresses the response in terms of renormalised Wilson coefficients and helps isolate the scheme-dependent finite terms from the scheme-independent part. We also show that it yields the same source-response ratio as the direct calculation when the source is subtracted in the same background. This agreement, obtained in the simpler probe case, further supports the broader interpretation of the dynamical tidal response as a well-defined gauge-invariant observable.

hep-th↗

arXiv2026

A Quantum Weak Cosmic Censorship and Its Proof

Recent work has highlighted the deep connection between quantum information and spacetime geometry. Bousso and Shahbazi-Moghaddam (Phys. Rev. Lett. 128, 231301 (2022)) proved that ``hyperentropic'' regions -- where entropy exceeds the area bound -- inevitably lead to singularity formation. In this work, we explore the converse implication: does the thermodynamic consistency of such singularities require them to be hidden? We answer in the affirmative, establishing a Quantum Weak Cosmic Censorship principle governed by Generalized Entropy. This provides a semiclassical mechanism for censorship which forbids naked singularities. Since Quantum Weak Cosmic Censorship is a semiclassical statement, it is more robust than the classical Weak Cosmic Censorship showing naked singularities are forbidden in nature even if quantum effects are taken into account.

hep-th↗

arXiv2026

Highest-weight truncation, graded EFT structure, and renormalization of black hole Love numbers

The static tidal Love numbers of four-dimensional black holes vanish identically, unlike their nontrivial dynamical response at finite frequency. Recent work has provided three complementary descriptions of this phenomenon: an emergent $\mathrm{SL}(2,\mathbb{R})$ organization of static near-zone perturbations, a graded logarithmic and multi-zeta structure in Shell Effective Field Theory (Shell EFT), and an on-shell matching framework based on gravitational Raman scattering with renormalization group (RG) running. We show that these features arise from a common near-zone truncation mechanism. For a massless scalar field, horizon regularity selects a unique static solution forming a highest-weight-type representation, truncating the hypergeometric solution to a finite polynomial and eliminating the independent decaying branch at large radius. This excludes a static Wilson coefficient in the effective theory. We demonstrate that the same truncation operates in the static Regge-Wheeler and Zerilli equations for four-dimensional Schwarzschild black holes. Analytic continuation of the horizon-regular solution to small frequency via the Coulomb-hypergeometric or Mano-Suzuki-Takasugi formalisms preserves this truncation as an anchoring condition for the renormalized angular momentum parameter. The resulting low-frequency expansion is controlled by Gamma and hypergeometric functions, generating a graded algebra of logarithms and odd Riemann zeta values. Within this structure no invariant of negative weight exists in the static sector, so the vanishing of the static Love number follows as a structural consequence. This explains the ``zero-sum'' rule of Shell EFT and why the self-induced RG flow in gravitational Raman scattering cannot generate a static invariant.

hep-th↗

arXiv2025

Marginal IR running of Gravity as a Natural Explanation for Dark Matter

We propose that the infrared (IR) running of Newton's coupling provides a simple and universal explanation for large-distance modifications of gravity relevant to dark matter phenomenology. Within the effective field theory (EFT) framework, we model $G(k)$ as a scale-dependent coupling governed by an anomalous dimension $\eta$. We show that the marginal case $\eta = 1$ is singled out by renormalization group (RG) and dimensional arguments, leading to a logarithmic potential and a $1/r$ force law at large distances, while smoothly recovering Newtonian gravity at short scales. The logarithmic correction is universal and regulator independent, indicating that the $1/r$ force arises as the robust IR imprint of quantum-field-theoretic scaling. This provides a principled alternative to particle dark matter, suggesting that galactic rotation curves and related anomalies may be understood as manifestations of the IR running of Newton's constant.

gr-qc↗

arXiv2025

Extended black hole thermodynamics in a DGP braneworld

We develop extended black-hole thermodynamics on a Dvali--Gabadadze--Porrati (DGP) brane by promoting the brane tension $\sigma$ to a thermodynamic variable within the extended Iyer--Wald framework. The brane tension acts as a localized vacuum energy with pressure $P_\sigma \equiv -\sigma$, yielding a new work term $V_\sigma\,\mathrm{d}P_\sigma$ in the first law and the corresponding Smarr relation. For static, spherically symmetric black holes we show that the conjugate volume equals the geometric volume $V_\sigma=\tfrac{4\pi}{3}r_h^3$; for stationary, axisymmetric solutions it admits a covariant, slice-independent definition and evaluates to $V_\sigma=\tfrac{4\pi}{3}\!\left(r_+^3+a^2 r_+\right)$. Working on the ghost-free normal branch, the brane is asymptotically flat with a single horizon, so the construction avoids de Sitter obstructions. Along a flat-brane path, asymptotic flatness is preserved by co-varying the bulk cosmological constant, and induced-gravity effects are suppressed by $r_h/r_c$. These results establish a consistent flat-braneworld realization of black-hole chemistry in which brane tension provides the physically motivated pressure variable.

gr-qc↗

arXiv2025

A proof of the reverse isoperimetric inequality using a geometric-analytic approach

We present a proof of the reverse isoperimetric inequality - a central conjecture in extended black hole thermodynamics - for black holes in Einstein gravity with $D \geq 4$, employing a two-pronged geometric-analytic method. Our analysis shows that the reversal of the usual isoperimetric inequality originates from the structure of curved backgrounds governed by Einstein's equations, thereby underscoring the fundamental role of gravity in the reverse isoperimetric property of AdS black hole horizons.

gr-qc↗

arXiv2025

Love beyond Einstein: Metric reconstruction and Love number in quadratic gravity using WEFT

We study tidal Love numbers of static black holes in four-dimensional quadratic theory of gravity, extending the result of GR. We use worldline effective field theory (WEFT) methods to compute metric perturbations from one-point functions, treating the higher-derivative terms perturbatively. We show that insertions of scalar fields on the worldline induce non-zero tidal tails, and the corresponding Love number displays no RG running. The same conclusion holds for the insertions of tensor fields. Furthermore, for scalar dipole perturbations, we derive a Yukawa-deformed Frobenius solution and match the asymptotic behavior to fix the UV charge, finding agreement with EFT predictions of Wilson coefficients. Our work demonstrates that quadratic higher-curvature corrections induce non-zero but scale-independent tidal responses, offering a robust EFT framework to test deviations from GR in gravitational wave observations.

hep-th↗

arXiv2025

Non-linear equation of motion for higher curvature semiclassical gravity

We derive the non-linear semiclassical equation of motion for a general diffeomorphism-invariant theory of gravity by leveraging the thermodynamic properties of closed causal horizons. Our work employs two complementary approaches. The first approach utilizes perturbative quantum gravity applied to a Rindler horizon. The result is then mapped to a stretched light cone, which can be understood as a union of Rindler planes. Here, we adopt the semiclassical physical process formulation, encapsulated by $\langle Q\rangle = T \delta S_{gen}$ where the heat-flux $\langle Q\rangle$ is related to the expectation value of stress-energy tensor $T_{ab}$ and $S_{gen}$ is the generalized entropy. The second approach introduces a "higher curvature" Raychaudhuri equation, where the vanishing of the quantum expansion $\Theta$ pointwise as required by restricted quantum focusing establishes an equilibrium condition, $\delta S_{\text{gen}} = 0$, at the null boundary of a causal diamond. While previous studies have only derived the linearized semiclassical equation of motion for higher curvature gravity, our work resolves this limitation by providing a fully non-linear formulation without invoking holography.

gr-qc↗

arXiv2024

CrowdSurfer: Sampling Optimization Augmented with Vector-Quantized Variational AutoEncoder for Dense Crowd Navigation

Navigation amongst densely packed crowds remains a challenge for mobile robots. The complexity increases further if the environment layout changes, making the prior computed global plan infeasible. In this paper, we show that it is possible to dramatically enhance crowd navigation by just improving the local planner. Our approach combines generative modelling with inference time optimization to generate sophisticated long-horizon local plans at interactive rates. More specifically, we train a Vector Quantized Variational AutoEncoder to learn a prior over the expert trajectory distribution conditioned on the perception input. At run-time, this is used as an initialization for a sampling-based optimizer for further refinement. Our approach does not require any sophisticated prediction of dynamic obstacles and yet provides state-of-the-art performance. In particular, we compare against the recent DRL-VO approach and show a 40% improvement in success rate and a 6% improvement in travel time.

cs.RO↗

arXiv2024

A Statistical Derivation of Bekenstein-Hawking Entropy for Schwarzschild Black Holes

A microscopic derivation of the Bekenstein-Hawking entropy for the Schwarzschild black hole was presented earlier by using a non-trivial phase space. It was argued that the Schwarzschild black hole behaves like a 1D quantum mechanical system. In this paper, we show that if we assume the phase space to obey the holographic principle and take the microscopic particles inside the quantum gravitational system to be ideal bosonic gas, we can derive the Bekenstein-Hawking entropy. The assumption of the phase space to follow the holographic principle such that the Schwarzschild black hole behaves as a 2D system is very much in the spirit of our understanding of black holes than their behavior as a 1D system. However, the argument suggests that the black hole be treated as a system with the equation of state $P=\rho$.

gr-qc↗

arXiv2024

On the Accelerated Expansion of the Universe

If we look from a quantum perspective, the most natural way in which the universe can be created is in entangled pairs whose time flow is oppositely related. This suggests the idea of the creation of a universe-antiuniverse pair. Assuming the validity of this hypothesis, in this paper, we show that the universe expands in an accelerated manner. The same reasoning holds for the anti-universe as well. This idea does not require any form of dark energy as used in the standard cosmological model of ${\Lambda}$CDM or in the modified theories of gravity.

gr-qc↗