Papers

Due to the importance of studying quantum-gravity-induced corrections to Einstein's theory of gravity, it is of interest to consider non-extensive entropies whose potential applications include identifying such corrections. In this Letter, we investigate possible corrections to a universal relation associated with the extremality bound of the mass of a black hole by employing entropies defined as functions of the Bekenstein-Hawking entropy.

We study the role of momentum fractionation in the development of chaos on smooth 3-charge supergravity solutions of D1-D5 theory, specifically momentum-fractionated superstrata. We probe the chaos through the dynamics of null geodesics and waves. On fractionated backgrounds, both geodesics and waves show uniformly strong chaos (large chaotic sea and near-perfect agreement with the Berry random wave hypothesis). In contrast, geodesics and waves on single-mode (non-fractionated) superstrata are closer to separability (although still chaotic). We discuss a possibility that such dichotomy can be related to the expectation that monotone BPS states are less chaotic than fortuitous ones. Finally, we explain why our chaos probes are meaningful for microstate geometries even though they become trivial in the black hole limit.

Area metrics arise as effective description at intermediate scales in a number of approaches to quantum gravity, including string theory, holography and loop quantum gravity. Recently, it has been shown that area metric actions can be derived from the modified Plebanski framework on the linearized level. Surprisingly these actions avoid extra poles in the propagator for the effective length dynamics, and hence constitute interesting deformations of linearized Einstein gravity. To be able to study whether this property persist for the full theory, we construct here non-linear area metric dynamics from modified Plebanski actions. We provide the geometric tools for area metrics that do not rely on perturbation theory and allow a systematic construction and study of general non-linear area metric actions: an algorithm that extracts a length metric from an area metric and a connection on two-forms that is uniquely determined by the area metric, together with its curvature and curvature invariants. We derive area metric actions from modified Plebanski actions in first and second order versions. We also find that area metric actions can be reformulated as Poincare gauge theories. We determine the effective length metric action, which on a flat background describes a graviton and a massive spin-two field with parity-violating couplings set by the Barbero–Immirzi parameter. Additionally we discuss cosmological backgrounds and the role of the matter coupling, which together open the way to cosmological applications.

Levitated dielectric sensors are often treated as perturbative probes of a pre-existing optical field. We show that this picture fails for a novel sensor geometry: a dielectric plate whose transverse extent captures the full optical mode. Even an optically thin sensor with modest refractive index can heavily restructure the intracavity fields, effectively partitioning a cavity into two subcavities with substantial cross-coupling and producing new optical resonances and trapping sites with properties which deviate from the standard intuition. Conventional perturbative expressions for the cavity frequency shift and optomechanical coupling depart from the exact solution at thicknesses as small as $\sim\lambda/(10n)$. Furthermore, cavity locking decreases the coupling and increases the trap stiffness by orders of magnitude, and the coupled subcavity structure permits appreciable optical cooling at zero detuning, a distinct behavior unique to this nonperturbative regime. These effects, sharing a common origin, establish a distinct regime of cavity optomechanics in which the sensor is no longer merely a probe of the cavity field, but an element that helps define it.

A characteristic feature of topological field theories is the absence of local propagating degrees of freedom. In four-dimensional BF theory with cosmological term, we make this feature manifest by exactly reducing the finite non-Abelian shift symmetry. We do so by identifying a higher dressing field, a 1-form compensating the shift, allowing to build from first principles the composite shift-invariant field $\boldsymbol{B}=B-\lambda^{-1}F$. In terms of this dressed field, the dynamics becomes algebraic and sets $\boldsymbol{B}=0$, directly exposing the absence of local propagating degrees of freedom. This provides the first explicit instance of the higher-form Dressing Field Method.

This paper explores topological phase transitions in the momentum space of the $\kappa$-deformed $\phi^4$ lattice model within the mean-field approximation. We show that the double-well structure of the momentum space gives rise to degenerate momentum states at high energies and that this change is marked by a phase transition. We investigate this transition using both numerical and analytical methods, with the analytical approach based primarily on singularity theory. Our numerical analysis shows that the energy at which the topological phase transition occurs is related to the noncommutative parameter by the simple power law $E \sim 1/\alpha^{4}$. By mapping the constant-energy-level surface to the $A_{3}$ singularity, we obtain the same result analytically. We also present results unique to noncommutative systems, showing that the fraction of particles in degenerate momentum states has a nonzero commutative limit. As a nonperturbative effect, this result provides a testable prediction for the existence of noncommutative spacetime.

We investigate finite time vacuum energy relaxation in conformally coupled scalar-tensor cosmology distinguishing the suppression accumulated along a physical trajectory from its asymptotic rate. For a canonical scalar with an exponential potential and constant conformal coupling, the autonomous system exhibits a stability exchange between scalar dominated and vacuum kinetic scaling solutions. In the power-law metric $f(R)=f_0R^n$ realization with $n>2$, the stable scalar dominated branch has a sustained relaxation rate below $0.579$ decades per Einstein frame e-fold. We additionally derive a finite time upper bound that accounts for depletion of the vacuum relative to the scalar potential. For the specified reference initial state $\Omega_{\Lambda,i}=0.99$ and $\Omega_{{\rm kin},i}=10^{-4}$, the bound excludes $60$ decades of suppression within $60$ e-folds throughout the $n>2$ family: $D_\Lambda(60)<47.7$. Numerical trajectories illustrate why this bound is conservative and why the transient contribution cannot be inferred from the final attractor alone. For the reference $f(R)\propto R^{2.14}$ solution, $D_\Lambda(60)\simeq7.53$ decades including a transient excess of about $3.27$ decades relative to uniform evolution at the asymptotic rate. The relaxed quantity is the dimensionless vacuum to gravitational scale hierarchy, its evolution also entails variation of the conformal frame Planck mass. The bounds are conditional on the homogeneous model and specified initial state, not a demonstration of complete cosmological viability.

This thesis investigates the application of techniques developed in supersymmetric gauge theories to physical problems in Quantum Field Theory and Gravity, focusing on the Seiberg-Witten (SW) curve and its quantum version. After reviewing the essential concepts of Supersymmetry and the derivation of the SW curve, we explore its applications in both fields. In Quantum Field Theory, we investigate the emergence of Argyres-Douglas theories in the moduli space of supersymmetric models, focusing on extremal correlators. We analyze a conformal model to compute their instanton corrections, finding agreement with predictions from Effective Field Theory, and discuss the implications for analogous observables in Argyres-Douglas theories. In Gravity, we exploit the quantum SW curve and its relation to differential equations describing physical systems. We establish the linear stability of Topological Stars, arising in the fuzzball proposal, under massive charged scalar perturbations. We also investigate charge superradiance in configurations with a horizon and derive a novel hypergeometric representation of the confluent Heun function, relevant to gravitational-wave propagation in the Schwarzschild background. This result yields a new resummed expression for waveform tail contributions, in excellent agreement with numerical data. Finally, beyond the SW formalism, we develop a Machine Learning algorithm based on Hamiltonian Neural Networks to reproduce the geodesics of a neutral particle in a fuzzball geometry. For critical trajectories, our method outperforms standard numerical integrators in both efficiency and accuracy.

Fast radio bursts (FRBs) probe free-electron columns along cosmological sightlines through their dispersion measures (DMs), whereas baryon acoustic oscillations (BAO) constrain cosmic expansion geometry through acoustic distance ratios. In this work, we leverage their distinct physical sensitivities to simultaneously determine the Hubble constant ($H_0$) and cosmic baryon density ($\Omega_{\rm b}$) without external cosmic microwave background (CMB) or Big Bang nucleosynthesis (BBN) priors. Combining 120 localized FRBs and DESI DR2 BAO, we obtain $H_0=71.4^{+2.2}_{-2.5}\ {\rm km\ s^{-1}\ Mpc^{-1}}$ and $\Omega_{\rm b}=0.0503^{+0.0025}_{-0.0021}$ in $\Lambda$CDM, corresponding to precisions of $3.3\%$ and $4.6\%$, respectively. The inferred $H_0$ is statistically consistent with both SH0ES and CMB, and $\Omega_{\rm b}$ agrees with the joint constraint from BBN and CMB. Adopting IllustrisTNG-based DM distributions and fixing the diffuse-gas baryon fraction tightens the constraint to $H_0=68.8\pm1.0\ {\rm km\ s^{-1}\ Mpc^{-1}}$, but lowers the central value toward the CMB-inferred value, identifying extragalactic DM modeling as the dominant systematic uncertainty. These results establish FRB-BAO complementarity as a new avenue for simultaneously constraining $H_0$ and $\Omega_{\rm b}$.

In this paper, we study phase transitions and scalar quasinormal modes(QNMs) of magnetically charged Euler–Heisenberg-dilaton AdS black holes in the extended phase space. We classify the horizon structures for all three signs of the EH coupling and derive the extended first law when the pressure and coupling are varied. For negative coupling, the physical branch exhibits a Van der Waals-like small/large black-hole transition. Using the improved asymptotic iteration method, we find two separated QNM trajectories below the critical pressure, whereas they merge into one continuous curve at the critical point. The GHS limit and the positive couplings considered here do not produce a finite-radius critical point.

We formulate the finite-time response problem for a radially accelerated Unruh–DeWitt detector coupled to a real massless scalar field outside a static, spherically symmetric, horizonless compact star. The stellar exterior is described by the Schwarzschild geometry, while unresolved field–surface interactions are represented by a local Robin condition at the stellar radius. After reducing the Klein–Gordon equation to a half-line Schrödinger problem, we identify a sufficiently stable branch of the Robin family from positivity of the radial operator, construct delta-normalized continuum modes, and define the static ground state with respect to Schwarzschild time. We derive a mode-amplitude representation of the smoothly switched detector response that avoids a direct numerical treatment of the coincidence singularity of the Wightman distribution. We obtain a radially aligned trajectory of constant signed proper acceleration in terms of the rapidity measured by static observers. The resulting formulation separates the effects of compactness, surface condition, closest approach, detector gap, and interaction duration. We also state the flat-space, Dirichlet, static-detector, low-frequency, large-distance, and long-interaction limits required to validate a numerical implementation. The framework provides a controlled extension of detector studies with static reflective compact objects to finite-time moving probes.

We study the entanglement structure of gravitons in quasicrystalline inflation. Both parity-even and parity-odd interactions generate graviton pairs with nonzero total momentum. For opposite-helicity pairs with identical momenta, the parity-even contribution can be nonzero, whereas the parity-odd contribution vanishes. The transition from inflation to radiation domination produces additional conventional two-mode squeezing. We derive the resulting normal and anomalous covariances. The initially nonzero reciprocal blocks of the full field-momentum covariance remain nonzero under homogeneous evolution, although individual components can vanish. We show that this homogeneous, helicity-preserving evolution acts unitarily within each helicity sector and therefore preserves the entanglement between the complete right- and left-helicity sectors. Nevertheless, it can eliminate entanglement in the reduced state of a co-propagating pair. We illustrate this distinction using a solvable four-mode model.

We propose a geometric realization of spacetime non-commutativity where the spacetime manifold remains smooth while the commutation relation between tangent and separation vectors of geodesic congruences is generalized via Frobenius' theorem. This non-commutative kinematic deformation leads to a modified Raychaudhuri equation with a shifted expansion scalar $\tilde \theta=\theta+\theta^{\rm NC}$. We introduce a timelike and null-like Non-Commutative Energy Condition (NCEC) under which focusing and geodesic incompleteness can, in some regimes, persist even when the standard strong energy condition is violated. Using this, we generalize the key focusing lemmas, conjugate-point propositions, and singularity theorems for both timelike geodesics orthogonal to a Cauchy surface and null geodesics orthogonal to a trapped surface. Applied to a FLRW spacetime, we argue that $\theta^{\rm NC}$ modifies both the Friedmann acceleration equation and the continuity equations. The non-commutative corrections separate into a universal modification of the dilution of the standard cosmological fluids and another contribution to the dark energy sector that is non-linear in energy density. Crucially, this provides a purely geometric origin for the evolution of dark energy, without introducing exotic dark energy fields or modifying Einstein's field equations.

Dark matter environments can modify binary black hole mergers and imprint their gravitational-wave signals. We perform numerical-relativity simulations of nonspinning binary black holes immersed in complex scalar-field clouds, considering mass ratios $q=1,2,3,$ and $4$ and varying both the dimensionless scalar-field mass $\hat m_{\Phi}=m_{\Phi}M_0$ and initial amplitude $\Pi_0$, which controls the density. Our initial data keep the scalar energy-density profile and binary geometry unchanged when varying $\hat m_{\Phi}$ at fixed $\Pi_0$, allowing the dynamical effect of the field mass to be isolated. We find that the scalar environment generally accelerates the merger and significantly modifies the gravitational-wave signal. For unequal-mass binaries, differential scalar-field accretion changes the horizon-mass ratio during inspiral, weakly at low density but substantially at high density, thereby increasing the binary asymmetry before merger. Dense scalar environments suppress the energy and angular momentum carried by gravitational waves. Lighter scalar fields propagate more efficiently to large radii, whereas heavier fields remain more localized and show stronger inward energy transport. Scalar angular-momentum transport is more complex, showing nonmonotonic behavior and even direction reversal near the binary. For unequal-mass systems, gravitational and scalar radiation both carry net linear momentum, and their relative orientation determines whether the recoil is enhanced or suppressed. The largest kick is $2063.6~{\rm km,s^{-1}}$ for $q=2$, $\hat m_{\Phi}=0$, and $\Pi_0=0.0100$, compared with $137.8~{\rm km,s^{-1}}$ in vacuum. These results show that the scalar-field mass and density jointly control the binary asymmetry, dynamics, radiative channels, and momentum balance.

We study electrically charged black branes in four-dimensional Einstein-Maxwell-scalar theory with Maxwell coupling $Z(\phi)=e^{3\phi/\sqrt7}$, whose potential has an AdS$_4$ fixed point only in the infrared. For nonzero hair parameter $\alpha$ the scalar grows logarithmically at large radius and the geometry is not asymptotically AdS, so the holographic dictionary is a working assumption. With the scale-invariant multi-trace boundary condition of the neutral branes, giving conformal thermodynamics, we work to second order in the charge, obtaining the Maxwell field and susceptibility in closed form, plus the thermodynamics, condensate, incoherent conductivity and cumulant ratio $T^2\chi_4/\chi_2=6c(\alpha)<0$ for all $\alpha$ considered. Independent perturbative computations and first-law closed forms agree within $4\times10^{-6}$; nonlinear solutions reproduce second-order results to $1.2\times10^{-5}$ and $c$ to $6\times10^{-4}$. They are locally thermodynamically stable where constructed, and the pressure is analytic in $(\mu_Q/T)^2$ near zero density. No regular extremal horizon exists at finite scalar value, and $\rho/s<\sqrt{21}/(2\pi)$ exactly. The extremal limit is an AdS$_2\times\mathbb R^2$ throat where the scalar grows as $\ln\ln(1/u)$ in the AdS$_2$ radial coordinate $u$; the bound is saturated there, and extremal values are approached as powers of $1/\ln(\mu_Q/T)$. With a Dirichlet condition on the scalar source, the same solutions describe a non-conformal theory with scale $\Lambda$, whose charged branes exist only below $T_{\max}(\mu_Q)$, which falls from $0.194\Lambda$ at zero density to zero at $\mu_Q=0.506\Lambda$. This boundary is a diffusive instability where the charge susceptibility diverges at nonzero density, and the bulk viscosity violates Buchel's bound at all densities. Quasinormal modes with the normalizable large-radius condition reproduce its hydrodynamics.

The energy densities of the quantised scalar and electromagnetic fields need not be positive, but their averages along timelike worldlines are constrained by Quantum Energy Inequalities (QEIs) that hold in flat and curved spacetimes for arbitrary Hadamard quantum field states. However the general QEI bound is not easy to compute in closed form. Here, we compute closed form expressions for the massless scalar and electromagnetic fields along stationary worldlines in Minkowski spacetime. These worldlines are solutions to the four-dimensional Frenet-Serret equations with constant curvature invariants and include inertial, uniformly linearly accelerated, and uniformly rotating worldlines as special cases. The QEI bound depends on a choice of tetrad along the worldline, and we compute it for any tetrad with constant angular velocity relative to the Frenet-Serret tetrad. Optimising over the angular velocity, we show that the tightest electromagnetic QEI bound occurs when the tetrad is invariant under Fermi-Walker tetrads. Surprisingly, the Fermi-Walker tetrad does not produce the tightest QEI bound for massless scalar fields, and we investigate the optimal bound both analytically and numerically. Our results and methodology significantly improve on those in [CJ Fewster & J Thompson, Class. Quantum Grav. 40 (2023) 175008], in which only Frenet-Serret tetrads were considered for massless scalar fields.

Self-force effects are essential for accurately describing the motion of small bodies in curved spacetime. The effective-source approach privides a promising route to higher-order self-force calculations. In this paper, we construct analytic electromagnetic effective source for geodesic motion in Schwarzschild spacetime. An angular completion and a tetrad decomposition express the vector-harmonic puncture modes as finite sums of scalar modes. We derive the coupling coefficients for both parity sectors and obtain the effective sources from the Maxwell mode equations. The point-particle delta contribution cancels, and representative eccentric-orbit results show finite mode sources near the particle. These expressions provide the source terms for future $1+1$-dimensional residual-field calculations.

We investigate the gravitational waves generated by first-order phase transitions (PTs) in an expanding Universe. Using a scalar field-fluid coupled model, we perform three-dimensional lattice numerical simulations of slow first-order PTs with strong strength. We observe that the contribution from sound waves to the gravitational wave (GW) signal significantly dominates over that from bubble collisions. The sound wave spectra exhibit two peaks located at the mean bubble separation and the sound-shell width. Rotational modes are generated in the fluid during the bubble collisions, and their magnitude grows with the PT strength. The lifetime of the sound wave source increases with decreasing $\alpha$: for weaker transitions the source can persist for longer than a Hubble time, while for stronger transitions it decays within a Hubble time. When the walls propagate as deflagrations, the GW spectral shape changes drastically, with steeper ultraviolet tails and a shorter-lived sound wave source. We also observe that the magnitude of the normalized GWs is roughly an order of magnitude smaller than obtained in the Minkowski spacetime simulations.

We consider the stability of light rings in four-dimensional circular stationary axisymmetric spacetimes. Using a Hamiltonian formalism for null geodesics and the Killing symmetries of the spacetime, we show that the transverse Hessian of the geodesic potential, which controls the light ring's stability, reduces there to a pure curvature expression. Its eigenvalues are $\mu_{\pm} = \Phi_{0 0} \pm \lvert \Psi_{0} \rvert$, where $\Phi_{0 0}$ is a Ricci scalar and $\Psi_{0}$ a Weyl scalar of a complex null tetrad adapted to the light ring. Through the Sachs optical equations, these quantities are responsible for focussing and shear of a null geodesic congruence. Stability requires both eigenvalues to be positive, so a light ring is stable if and only if $\Phi_{0 0} > \lvert \Psi_{0} \rvert$ there. Assuming the Einstein field equations with generic stress–energy tensor $T_{a b}$, we recast this as $4 \pi T_{a b} p^{a} p^{b} > \lvert \Psi_{0} \rvert$, where $p^{a}$ is the light ring's tangent vector: for stability, the focussing by matter must dominate the local tidal shear. The trace of the Hessian alone provides an inexpensive test of stability, requiring no knowledge of the Weyl curvature, since a light ring at which the strict null energy condition is violated cannot be stable. Applying the test to specific matter models, we recover known results for vacuum and electrovacuum, with and without a cosmological constant. We also demonstrate that stable light rings are forbidden for a minimally coupled real scalar field with any self-interaction potential, since such a field must be invariant under both isometries. We show that a complex scalar field escapes this obstruction whenever it carries harmonic dependence on the Killing coordinates.

We derive the secular Hamiltonian of a hierarchical triple from the 1PN ADM three-body Hamiltonian by a two-stage Lie-Hori-Deprit transformation carried out entirely in canonical variables, and use it to settle the relativistic cross terms left open in Paper I. A bookkeeping rule enumerates all contributions to each order in the 1PN parameter $\delta$ and the hierarchy parameter $\varepsilon$. The 1PN monopole interaction reduces to a renormalization of the inner mass by its binding energy, and the order $\delta\varepsilon^{3/2}$, at which Lim and Rodriguez (LR) found a libration term, is empty. The electric and magnetic 1PN $\times$ quadrupole cross terms agree exactly with the effective-field-theory result of Kuntz, Serra, and Trincherini; for the magnetic term this is the first independent derivation. We give the next-to-leading order 1PN $\times$ quadrupole term in closed form; it depends on the outer argument of pericenter $\omega_2$. At quadrupole-squared order we obtain the complete secular Hamiltonian, which generates the secular equations of Will and of Conway and Will; its $2\omega_2$ harmonic is a gauge term, removable even on the commensurability between the ZLK period and the nodal precession, by a generator given in closed form via Tremaine's fictitious time. The EIH and ADM descriptions coincide at 1PN order; the formulations differ only in the definition of the elements, for which we give the osculating-contact map. In secular integrations of LR's triples, the eccentricity enhancement with the octupole is controlled by the $\omega_2$-dependent part of the next-to-leading order term and is two to three times that of Paper I, while LR's accelerated mergers remain absent.

Characteristic modes provide important information about the intrinsic properties and dynamical response of gravitational systems. In this work, we investigate characteristic modes of thick branes with a non-minimally coupled bulk scalar field. Two representative thick brane solutions are considered, corresponding to a single-kink scalar configuration and a deformed kink configuration with internal structure, respectively. By analyzing the tensor perturbation equations, we first examine the localization of the graviton zero mode in the two brane models. For both brane models, the graviton zero mode is localized on the brane. No pronounced resonant Kaluza–Klein (KK) modes are found for the single-kink brane at $\xi=1/7$. For the deformed brane, we investigate the resonant KK modes at $\xi=0.99$, finding that increasing the deformation parameter $k$ leads to more resonant modes and a longer-lived first resonance. We then calculate the quasinormal modes (QNMs) of both brane models independently in the frequency and time domains. The quasinormal frequencies (QNFs) obtained by the independent methods agree well for the low overtones. The masses and decay rates of the resonant KK modes agree closely with the real parts and the magnitudes of the imaginary parts of the corresponding QNFs, respectively.

We present a suite of 50 unpublished research-level theoretical physics problems with verifiable answers. Without AI assistance, a typical problem in our collection could be solved by a world expert in about a day or less but would take considerably longer for experts in adjacent specialties. We test the ability of off-the-shelf AI agents to tackle these problems autonomously, without human hints. When given access to tools available in a realistic setting, including the ability to search the literature and write scripts for numerical and symbolic work, the best-performing agent, GPT-6-Astra harnessed in Codex, obtains the final answers with a near-perfect accuracy of 98% at an average cost under USD 3 per problem. On average, agents show only small changes in accuracy when denied web search and access to background research papers, suggesting significant memorization of the literature. These results suggest that state-of-the-art agents can accurately perform concrete calculations required across theoretical physics research. We comment on the broader implications of these findings and discuss possible explanations for the current lack of agent-led breakthroughs in theoretical physics despite their outstanding problem-solving abilities.

We investigate non-stationary wormhole geometries in General Relativity embedded in evolving cosmological backgrounds. We employ a Simpson-Visser-like regularization of the temporal coordinate of the $(n+1)$-dimensional FLRW metric, together with a homogeneous Cuscuton field, to construct cosmological backgrounds in which the scale factor remains finite and non-zero at the would-be initial singularity. We then consider two specific dynamical wormhole geometries: the four-dimensional defect wormhole and the topologically charged Perry-Mann type wormhole. We show that the former can be supported by a canonical scalar field with vanishing potential, while the latter requires a mimetic matter sector to support its spatial structure, with the Cuscuton governing the cosmological evolution in both cases. We subsequently generalize the analysis to a separable non-stationary spacetime and derive a scaling condition that strongly constrains the admissible matter sources. In particular, for minimally coupled scalar and nonlinear electrodynamics fields, this condition removes the functional freedom available in static reconstruction schemes. We show that, within this framework, regular, asymptotically flat wormhole geometries cannot be obtained while simultaneously satisfying the required smoothness and reflection symmetry conditions. Our results illustrate both the possibility of constructing specific non-stationary wormholes in regular cosmological backgrounds and the restrictions that arise when attempting to generalize such constructions to arbitrary spatial geometries.

Recent baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument (DESI 2024) reveal a preference for dynamical dark energy with an equation of state parameter crossing the phantom divide ($w < -1$) at low redshifts. We investigate whether this phantom crossing can be realized within scale-invariant scalar-tensor theories featuring non-minimal derivative coupling (NMDC) between the scalar field and the Einstein tensor. Employing the effective field theory of dark energy formalism, we systematically derive the ghost-free and gradient stability conditions, and examine their compatibility with the swampland conjectures from quantum gravity. We establish three rigorous no-go theorems demonstrating that: (i)~phantom crossing necessitates $\xi_{\text{eff}} < 0$, directly violating the no-ghost stability requirement $\xi_{\text{eff}} > 0$; (ii)~the swampland de Sitter and distance conjectures independently obstruct phantom crossing; and (iii)~these theoretical obstructions are mutually reinforcing. Our results show that scale-invariant NMDC models cannot account for the DESI preference for $w < -1$, providing robust theoretical guidance for dark energy model building beyond this class.

In de Sitter static patch holography, coupling bulk quantum fields to an observer's dynamical clock yields a type II$_1$ von Neumann algebra $\mathcal{M}_+$ of gauge-invariant observables. However, the unique tracial state on this algebra fails to reproduce semiclassical bulk correlation functions. We resolve this issue by introducing a family of heavy-clock states, representing an observer reference frame with heavy inertia. We prove that in the heavy-clock limit, $n$-point correlation functions of gauge-invariant dressed observables reproduce the bulk quantum field correlation functions on de Sitter spacetime. Furthermore, we investigate a generalized observer Hamiltonian $\widehat{H}_{\rm obs}=|\widehat{\pi}|$ that incorporates both forward-running ($\pi\geq 0$) and backward-running ($\pi <0$) clocks. The resulting von Neumann algebra $\mathcal{M}$ of gauge-invariant observables remains a type~II$_1$ factor and is isomorphic to $\mathcal{M}_+\otimes M_2(\mathbb{C})$, where $M_2(\mathbb{C})$ is the algebra of $2\times2$ complex matrices transforming between the two clock orientations. Time-reversal symmetry is implemented in this setting as an anti-unitary operator that exchanges the two clock orientations, yielding a type~II$_1$ von Neumann algebra $\mathcal{F}$ of gauge-invariant, time-reversal-invariant observables. We generalize the heavy-clock state construction to both $\mathcal{M}$ and $\mathcal{F}$, showing that $n$-point correlation functions calculated in heavy-clock states match the corresponding semiclassical bulk correlation functions. Finally, by coupling Einstein gravity to the Brown–Kuchař dust field, we derive the observer Hamiltonian $\widehat{H}_{\rm obs}=|\widehat{\pi}|$ from a perturbative reduction along the observer's worldline in the $G \to 0$ limit. This provides a field-theoretic foundation for the observer model developed in this work.

Unless the tensor to scalar ratio is small enough, the non-adiabatic mode associated with the ultralight bosons may be dangerously comparable with the adiabatic spectrum of curvature inhomogeneities. We point out here that this statement depends on the timeline of the post-inflationary expansion rate. Provided the decelerated evolution is slower than radiation for a sufficiently long period, the relative weight of the non-adiabatic and adiabatic components does not conflict with the direct constraints coming from the large-scale observations. Conversely the presence of ultralight bosons excludes the presence of long stages expanding faster than radiation. The synthesis of the light nuclei and the spectrum of the relic gravitons at high frequencies set the relevant constraints on the duration of the decelerated stages, on the delayed dominance of radiation and on the mass range of the ultralight scalars.

We determine a universal sector of the spectrum of light operators in four-dimensional $\mathcal{N}=1$ class $\mathcal{S}$ superconformal field theories arising from M5-branes wrapped on a compact hyperbolic Riemann surface $\Sigma_2$. We work at large $N$, analysing Kaluza–Klein fluctuations about the dual Bah–Beem–Bobev–Wecht anti-de Sitter backgrounds for general values of the twist parameter $z$. To obtain these spectra, we specialise recently derived mass operators to modes that are constant on $\Sigma_2$ by imposing a suitable $z$-dependent generalised $G$-structure. We then organise the resulting eigenstates into long and protected $\mathcal{N}=1$ supermultiplets with definite flavour quantum numbers. As $z$ varies, rich patterns emerge in the spectrum, including both isolated multiplets and infinite towers of multiplets, which we characterise analytically.

The $q$-deformed Weil-Petersson volumes of Do and Norbury are the top-degree parts of Okuyama's discrete volumes, which are defined by topological recursion on the spectral curve of the double-scaled SYK (DSSYK) model. We show that the same q-deformed volumes can be obtained from a double-scaled matrix model whose disk density is found by zooming in on the soft edges of the DSSYK density. Applying the same procedure to the hard edge of $\mathcal{N}=1$ DSSYK, we obtain candidate $q$-deformed $\mathcal{N}=1$ super Weil-Petersson volumes. They are polynomials of fixed degree, and they reduce to the $\mathcal{N}=1$ super Weil-Petersson volumes in a scaled $q\to1$ limit. These candidate volumes differ from the $\mathcal{N}=1$ volumes of Do and Norbury in (arXiv:2510.12431) up to what we call "irrelevant" contributions which exactly vanish in the scaled $q\to 1$ limit. Together, these results demonstrate how q-deformed volumes can be naturally associated to the spectral edges of various DSSYK models and provides an intuitive way to construct them in supersymmetric contexts.

Contemporary large-scale structure analyses center around the galaxy power spectrum, modeled with one-loop perturbation theory. This description naturally breaks down at large wavenumbers, prohibiting the extraction of cosmological information from small-scale clustering. In this work, we present a complete model for the redshift-space galaxy power spectrum up to two-loop order, derived in the framework of the Effective Field Theory of Large Scale Structure. This accounts for a wide variety of effects, including fifth-order galaxy bias, redshift-space distortions, small-scale non-linearities, spatial non-locality, long-wavelength bulk flows, coordinate distortions, and stochasticity, involving a total of 49 free coefficients. Our model additionally encodes all deterministic contributions to the one-loop bispectrum and trispectrum (as well as the tree-level quadspectrum and pentaspectrum), which depend on many of the same parameters. We implement the model numerically, using the vegas algorithm to precompute the loop integrals; this allows the full likelihood to be evaluated in milliseconds. The approach is validated using power spectra measured from high-resolution simulations, considering both dark matter and realistic galaxy samples. The extension to two-loop order greatly increases the range of scales over which the power spectrum can be modeled, with $k_{\rm max}$ rising from $0.2h\,\mathrm{Mpc}^{-1}$ to $0.34h\,\mathrm{Mpc}^{-1}$ for a luminous red galaxy sample at $z=0.5$. Much of the additional information is absorbed by the numerous fifth-order biases and counterterms; for this reason, constraints on $\sigma_8$ are not significantly enhanced by the inclusion of two-loop terms. Future work will assess the full implications of the two-loop model for cosmological parameter inference, both alone and in combination with higher-order statistics.

We construct an exact stationary axisymmetric vacuum configuration in metric affine Kalb-Ramond gravity with zero cosmological constant. Independent variation of the metric, connection, and antisymmetric field yields the complete field equations and the algebraic relation between the physical and auxiliary geometries. A Kerr auxiliary metric and a closed corotating vacuum two form of fixed positive norm determine the physical metric. The tensor kernel contains the horizon generator, and the metrics, independent connection, and vacuum field share a smooth extension across the nonextremal physical Killing horizon and the rotation axes at finite radius for unequal deformation factors. We obtain an explicit sufficient domain for a causal exterior and an asymptotically locally flat end at fixed nonpolar angles. The physical Hamiltonian yields the timelike and null equations, equatorial effective potentials, circular orbit properties, radial stability, and perihelion advance. Numerical photon evolution determines the critical curve on an orthonormal observer screen. Its size, shape, and centroid depend on $\epsilon=\xi_2b^2/[2(1+\xi_1b^2)]$ at fixed normalized mass scale and spin, with Kerr recovered at $\epsilon=0$. Geometric observations probe this combination and retain an exact degeneracy between the curvature couplings. A static equatorial comparison with Mercury gives a conditional sensitivity of $2.30\times10^{-11}$ for $|2\epsilon|$ under the stated angular convention and mass setting.