Papers

Swampland principles, combined with the smallness of dark energy $\Lambda$, lead to the dark dimension scenario, with one extra dimension of micron size. We review this scenario and its predictions: KK graviton dark matter (or the KK tower of the quintessence field into which the gravitons convert), neutrino masses tied to $\Lambda^{1/4}$ via a bulk $B-L$ gauge symmetry, QCD axion decay constant $f_a\sim \Lambda^{1/12}\sim 10^9-10^{10}$ GeV at the 5d Planck scale $M_5$, connecting electroweak hierarchy to $\Lambda^{1/6}$, and a relation between the GUT and weak scales with $M_5$ as the geometric mean. The dark dimension also provides a concrete realization of an evolving dark sector: the evolution of its diameter correlates the variation of dark energy with that of the dark matter mass, fitting the recent DESI DR2 (+CMB+supernovae) data while avoiding the phantom crossing that the $w_0w_a$CDM parametrization would suggest—the apparent phantom behavior instead arises from the evolving dark matter mass. The fits suggest that the dark energy field sits in the interior of moduli space, near an unstable critical point. Motivated by this, we review recent progress on non-supersymmetric string vacua: isolated critical points protected by duality symmetries, in non-geometric flux compactifications and in Scherk–Schwarz compactifications of M-theory, and an emerging duality web for non-supersymmetric strings. This note is based on two talks given by the author at String Phenomenology 2026 (Paris) and Strings 2026 (Shanghai).

We study the refined de Sitter conjecture (RdSC), the Trans-Planckian Censorship Conjecture (TCC) and the species scale $\Lambda_s$ in the multifield flux potential of type IIB string theory compactified on one-parameter Calabi–Yau threefolds. The scalar potential depends on the axio-dilaton and on the single complex-structure modulus, and is no-scale along the Kähler directions. Restricting to $h^{2,1}=1$ allows us to work with the exact periods obtained from the Picard–Fuchs equations rather than with their large-complex-structure expansion, and therefore to probe the conifold region. For the mirror quintic, $(h^{2,1},h^{1,1})=(1,101)$, we scan 200 flux configurations and find unstable extrema in $96\%$ of the cases, with $c'=0.18$. Once the Kähler runaway is taken into account, the no-scale structure fixes the logarithmic slope of the potential at every critical point to the universal value $\sqrt6$, so that the first RdSC condition is satisfied throughout. Statistically, the complex structure is the heavier sector and the axio-dilaton dominates the unstable directions. For the TCC we obtain analytic results valid for the whole class of one-parameter models: the slope approaches the universal value $2$ at large complex structure, diverges at the conifold, and equals exactly $\sqrt2$ in the axio-dilaton directions, where the leading potential takes a single $SL(2)$-covariant form, as the multifield evolutions confirm numerically. The TCC further translates into a lower bound on the compactification volume, $v>v_0\sim e^{N}$, controlled by the number of e-folds. Finally, the field displacements along our trajectories are compatible with the species-scale field-range bound, and restoring the volume dependence of $\Lambda_s$ shows that $V\lesssim3\Lambda_s^2$ is implied by the TCC volume bound, which is thus the genuine constraint on these models.

We study the pseudospectrum of the Kerr black hole for gravitational perturbations with spin weight $s=2$, the case of greatest interest in gravitational-wave astronomy. In the hyperboloidal framework with two-dimensional Chebyshev collocation, we formulate the quasinormal mode problem as a non-self-adjoint eigenvalue problem. For $s\neq0$ the fields $\Psi^{(s)}$ and $\Psi^{(-s)}$ are independent, so the conserved current method yields no single-field energy norm. We overcome this with the Teukolsky–Starobinsky identities, which relate $\Psi^{(-2)}$ to a fourth-order operator on $\Psi^{(2)}$ and yield an $H^2$ energy norm after symmetrization. With the $H^1$ norm known for $s=0$, this suggests the pattern $H^{|s|}$, verified for $s=0$ and $s=2$. All results use an $\omega$-independent two-field hierarchy. We find that the pseudospectrum tightens by $1.1$ to $3.5$ decades at each step of $L^2\to H^1\to H^2$, yet stays large in every norm. The $s=+2$ and $s=-2$ operators are isospectral but not isopseudospectral: at twelve of fourteen probes the $\psi_0$ resolvent exceeds the $\psi_4$ one by $0.19$ to $0.82$ decades in the $H^2$ norm, while at the two probes furthest along the QNM line the ordering reverses by $0.18$ to $0.19$ decades. The gravitational pseudospectrum exceeds the scalar one by $0.5$ to $5.2$ decades in the window minimum and by $5.9$ decades in $L^2$ at $\omega M=0.47-0.17\,i$, while along the damping direction the $s=2$ resolvent is non-monotonic and the $s=0$ resolvent smooth. QNM spectral instability is therefore a universal feature of Kerr, and is stronger for gravitational perturbations.

After re-examining a classic article by Hugh Everett, I will discuss the entropy of de Sitter space from the standpoint of an observer living in the space. This provides a nice example of the importance – for certain questions – of taking seriously the fact that in cosmology any observer is really part of the universe that is being observed. (This article has appeared in a special issue of International Journal of Modern Physics A in honor of Gerard 't Hooft.

The SU$(N)$ matrix-model potential $V=-\tfrac{g^2}{4}\sum_{I,J}Tr[X_I,X_J]^2$, the interaction of the BFSS/BMN family, whose thermal large-$N$ states are dual to black holes, is diagonal in the coordinate basis and is compiled in the literature as a phase polynomial with $O(d^2N^4Q^4)$ rotations per Trotter step. That cost is close to optimal for its gate class: we show that for a generic Trotter step the Walsh support $m_{\min}$ lower-bounds both the rotation count and the two-qubit count of every circuit over $\{CNOT,CZ,CPhase,R_{ZZ},SWAP,X,R_z\}$, ancillas included, and we build a parity network attaining $1.01$–$1.10\,m_{\min}$. Improvement therefore requires a gate outside that class, and the exact factorisation of $V$ into a sum of squared commutator entries supplies one in each era. For NISQ, Hadamard: each squared entry is added into a Fourier register and squared there, $\Theta(d^2N^3Q^3)$ two-qubit gates. For fault tolerance, $T$: reversible arithmetic with one phase-gradient injection per squared entry, $\Theta(d^2N^3Q^2)$ T gates and no arbitrary-angle rotation. Both are built and verified. With a native $R_{ZZ}$ the NISQ circuit uses fewer two-qubit gates than every parity network from $Q=6$ at SU(2) and $Q=2$ at SU(5); the oracle beats a precision-matched Hamming-weight-phasing incumbent at every point built except the smallest, by up to $11.9\times$ in T count and, at equal width, $25.5\times$ in surface-code spacetime. An ablation with the same arithmetic but no factorisation costs up to $21\times$ more and loses to that incumbent at $15$ of $17$ points, so the factorisation, not the arithmetic, produces the win. Both constructions survive the supersymmetric deformation to mini-BMN with fermions, and complete Trotter evolutions on a statevector simulator reproduce the exact product formula to $2\times10^{-12}$.

In this work we study the Bell-CHSH inequality in the vacuum of the free massive Majorana field in $1+1$ dimensions, taking as the dichotomic observables of the two parties even bilinears of smeared fields localized in the right and in the left Rindler wedges. The test functions are generated from seeds in the modular-frequency variable through the Tomita-Takesaki operator of the right wedge and, on the side of the left wedge, through its adjoint multiplied by $i$, which accounts for twisted duality. For seeds supported at positive modular frequency the one-particle overlaps between the two parties do not depend on the modular weights, and we obtain the Bell parameter in closed form. When the seeds are phase rotations of a single compact bump, the bilinears generate a copy of the Pauli algebra in each wedge, and we compute exactly the correlation matrix of the vacuum restricted to the two copies. The optimal settings violate the classical bound up to spectral widths more than twice as large as those reached with planar settings. We also show that the Tsirelson bound is never attained in the wedge vacuum for any choice of dichotomic observables, and that approaching it forces the modular spectral weight of the Bell vectors to concentrate at the spectral point $\lambda=1$ of the modular operator. This establishes in a precise way how the even sector of the free Majorana field realizes the Summers-Werner mechanism.

Two physical consequences of the recent topological classification of 2d Fermi seas for free particles based on flat orbifolds $\mathbb{R}^2/\Gamma$ of discrete symmetry $\Gamma$, are explored. The first is a study of the spatial density behavior inside the mesoscopic window enclosed by the Fermi and (infinite) thermal lengths. It is shown that the single-particle density matrix exhibits a sharp directional anisotropy, encoding a real space diffraction pattern, i.e., a Fraunhofer-like diagram of the Fermi sea, that reveals the point-group symmetries of the background lattice $\Gamma$ in the form of anisotropic Friedel oscillations. As examples, the special cases of the $p4m$ and $p6m$ crystallographic flat orbifolds are treated in some detail. The second physical consequence is the establishment of an explicit geometric correspondence between momentum-space packing and electrical transport. A mean-field expression for the longitudinal electrical conductivity $\sigma_{xx}$ as a function of the isoperimetric parameter $\cal{I}$ of the occupied orbifold domain by utilizing geometric measure theory is presented, satisfiying the scaling law $ \sigma_{xx} \propto 1/\sqrt{\cal{I}}$. The topological transport formula naturally incorporates the vanishing conductivity ($\sigma_{xx} \to 0$) of the previously described “geometric insulators,” promoting the isoperimetric parameter as an efficient descriptor for topological and geometric phases in conductors.

We study the invertible one-form global symmetry of a (2+1)-dimensional topological quantum field theory (TQFT). A universal description of this symmetry “peels off” all the Abelian anyons from the rest of the TQFT. This allows us to study this symmetry and some of its consequences, independently of the details of the rest of the system. We then describe these Abelian anyons using $\mathrm{U}(1)$ gauge fields with Chern-Simons terms and couple them to a scalar field, thus constructing a particular non-topological theory. This new theory, our transition field theory, exhibits a phase transition from the original TQFT to another phase. The latter is either gapless or another TQFT. This discussion generalizes and extends our earlier work (arXiv:2603.00245). In particular, we give a more detailed description of the global symmetries and their fates in the various phases.

Black-hole (BH) quasinormal modes encode the properties of merger remnants and provide powerful tests of strong-field gravity. The BH spectroscopy has predominantly treated them as independent linear oscillations. Nonlinear ringdown can additionally reveal how these modes interact and which intermediate states mediate their interactions. Inspired by cosmological collider physics, we introduce quasinormal-mode collider spectroscopy (QCS), a framework for organizing and predicting nonlinear BH responses. We establish two structural results. First, at an isolated, nondegenerate intermediate pole, a cubic strain residue factorizes into an excitation amplitude and a quadratic conversion coefficient. This factorization imposes rank constraints across output channels and choices of second-order initial data, providing consistency tests of the intermediate-mode description. Second, the intermediate pole residue can be reconstructed from its horizon and infinity radiation. With the first-order field and third-order data held fixed, this reconstruction extends to the full cubic waveform difference generated by changing the second-order initial data. QCS thus connects lower-order radiation to higher-order observables and provides a framework for probing the interaction structure of nonlinear ringdown.

The Wen-Zee term is a mixed gauge-curvature coupling in the topological Chern-Simons description of a quantum Hall fluid, encoding the electric charge bound to spatial curvature. We investigate a Lorentz-covariant generalisation of this coupling, expanding its scope to black-hole spacetimes and determine its contribution to horizon entropy. Such a coupling arises naturally in three-dimensional Chern-Simons gravity based on the Maxwell algebra. We show that its Wald entropy contribution is a horizon boost charge, given by a loop integral of the additional gauge field projected along the tangent to the bifurcation circle. This contribution can be nonzero even when the mixed term vanishes on shell. We show that the integral admits an Abelian holonomy interpretation when the projection direction is covariantly constant. We evaluate the charge on a flat cosmological solution and, using smooth horizon fields and a specified thermal ensemble, on an AdS-Lorentz black hole. These results connect the geometric response familiar from quantum Hall physics to gravitational horizon thermodynamics.

The quest for a quantum theory of gravity remains a central challenge in modern physics, driven by the goal of unifying general relativity and quantum mechanics. Direct experimental access to quantum gravitational effects is notoriously difficult due to the inaccessibility of the Planck scale. Recent proposals, however, suggest that gravitationally induced quantum entanglement between two massive particles, realized through advanced quantum interferometric techniques, could provide empirical evidence for the quantum nature of gravity. We demonstrate that the geometrical configuration of an interferometer plays a decisive role in entanglement generation. Our analysis reveals that geometric optimization can substantially enhance the gravitationally induced phase shift, thereby improving the prospects for experimental detection of gravity-mediated entanglement. Moreover, we show that standard approximations employed in prior proposals may severely limit predictive accuracy and compromise experimental feasibility.

We formulate the gravitational field on maximally symmetric spacetimes as a gauge theory, and investigate higher-form symmetries of the linearized gravitational field via a series expansion in Newton's gravitational constant. To treat gravity as a gauge theory, the MacDowell-Mansouri formulation based on Cartan geometry is utilized. We show the existence of a 1-form symmetry in linearized gravity on Minkowski spacetime. Furthermore, for other maximally symmetric spacetimes (de Sitter and anti-de Sitter spacetimes) with a small cosmological constant, we demonstrate the existence of an approximate 1-form symmetry in the corresponding linearized gravity, detailing its explicit dependence on the cosmological constant.

The decay of out-of-time-ordered correlators (OTOCs) to a small residual value signals the scrambling of quantum information. This behavior is generic: it occurs in both chaotic and interacting integrable many-body systems, and therefore cannot by itself distinguish between them. In this paper we analytically study the late-time saturation value of a closely related observable, operator purity, and show that its scaling with system size robustly distinguishes chaotic from integrable systems. Our approach is based on the Mazur bound, which provides concrete scaling estimates and makes explicit why the locality of integrable charges matters. We support our findings with numerical simulations of one-dimensional spin chains.

We study anomaly constraints in six-dimensional $N=(1,0)$ supergravity with gauged $Sp(1)_R$ symmetry, one tensor multiplet, $n_V$ vector multiplets and $n_H$ hypermultiplets. Imposing cancellation of local gravitational, gauge and mixed anomalies, together with the embedding of the anomaly coefficients in a unimodular rank-two string charge lattice, the number of vector multiplets is sharply constrained: the only allowed positive values are $n_V=12$ and $n_V=96$. For a neutral abelian factor, or drone, the anomaly equations force the corresponding row and column of the abelian gauge-kinetic matrix to vanish. Such a factor therefore cannot be retained as an ordinary propagating vector multiplet. For $n_V=96$, within the class of semisimple non-$R$ gauge algebras containing no $A_1$ or $A_2$ factor, the exhaustive spectra-assembly calculation yields no drone-free spectrum. For $n_V=12$, the semisimple non-$R$ branch is necessarily $A_1^3$. In the doublet/adjoint truncation described in the text, we find $4{,}337{,}331$ consistent models, classified by $102$ anomaly-vector classes. We also consider the reductive branch $A_2\times U(1)\times Sp(1)_R$. For $A_2$ representations in $\{\mathbf 1,\mathbf 3,\overline{\mathbf 3}, \mathbf 6,\overline{\mathbf 6},\mathbf 8\}$ and primitive $U(1)$ charge assignments with $|q|\le 2$, we find $178{,}538$ solutions, classified by $21$ sets of anomaly vectors.

We investigate line defect Coulomb and Higgs indices in 3d $\mathcal{N}\ge 4$ supersymmetric gauge theories. The normalized line defect indices defined by ratios of the decorated defect indices to the ordinary indices yield well-defined integer values, the line defect Witten indices in the unit R-charge fugacity limit. We propose general formulae for these Witten indices in both Coulomb and Higgs limits for the theories without Chern-Simons terms, and we show that both count the states invariant under the residual gauge group left unbroken at a generic point of the branch, which we read off from the vacuum equations. Furthermore, we find powerful algebraic recursion relations for Wilson line defect Coulomb indices in the 3d SCFTs describing M2-branes, including ADHM-type theories and ABJ(M) theories. These relations imply that higher rank line defect indices are recursively determined by lower rank data across $U(N)$, $USp(2N)$, $SO(2N)$ and $SO(2N+1)$ ADHM-type theories and ABJ(M) theories.

Despite its remarkable empirical success and predictive power, quantum theory is riddled with mysteries. One such conceptual puzzle is the measurement problem: why do quantum systems in superposition collapse to a single-valued outcome upon being measured? The scenario of Wigner's friend illustrates this tension, with recent extensions deriving strong no-go results for the nature of reality. Another fundamental puzzle arises at the interface of quantum theory and general relativity—the black hole information paradox. This thesis further explores these two foundational paradoxes. Part I of this thesis focuses on extensions of the Wigner's friend scenario. We introduce several novel extended Wigner's friend arguments, and establish connections with notions of nonclassicality, i.e. the study of quantum phenomena that evade classical explanation. Key results are a refined version of the Frauchiger–Renner paradox, new extended Wigner's friend scenarios based on contextuality, and an argument against the absoluteness of free choices based on the Pusey–Barrett–Rudolph theorem. The latter result complements the Local Friendliness no-go theorem, which challenged the absoluteness of experimentally obtained measurement outcomes. In Part II of this thesis, we turn to black hole puzzles and the interplay of quantum theory and gravity. We present a paradox that unifies extended Wigner's friend arguments with black hole puzzles, strengthening the cloning and firewall paradoxes. After discussing subtleties in these paradoxes, we next present an analysis combining elements of quantum theory with gravity, analyzing the detector response near a superposed black hole using elements of quantum reference frames.

We conjecture an exact formula for the effective central charge, ceff, of a family of three- dimensional superconformal field theories related to Chern-Simons theory on a three-manifold by the 3d-3d correspondence. The formula determines ceff , which governs the growth of a protected sector of states in the conformal theory, in terms of the dimension of a particular space of modular forms. We confirm our approach by checking against known results computed through resurgent continuation.

Entanglement entropy plays a central role in holography. The quantum extremal surface (QES) formula is the standard tool in settings where both dynamics and bulk quantum corrections are important, such as in black hole evaporation. We derive and explore QES-equivalent prescriptions — quantum covariant bit threads — that formulate holographic entanglement entropy in terms of minimal or maximal bulk flows rather than extremal surfaces. Like classical covariant bit threads, our prescriptions come in two types: (typically) spacelike V-flows, and timelike U-flows. To account for bulk quantum corrections, the flow lines can start and end at points in the bulk, with the distribution of endpoints controlled by bulk entanglement entropies. In our bit thread language, the QES is a quantum bottleneck to the flow, with some threads passing through it (accounting for the area term in the generalized entropy) and others jumping across it (accounting for the entropy term). Our prescriptions provide a complementary perspective to the QES formula and offer new insights on important phenomena such as black hole evaporation, islands, and baby universes.

Krylov subspace methods provide an efficient tool for modeling any quantum initial value problem as a one dimensional chain. A time ordered path formulation, in which the dynamical generator successively splits probability between paths, yields a speed limit within such dynamical subspaces. For power law growing Lanczos coefficients $b_n \sim n^\delta$ we find super ballistic lightcones, with an exponentially spreading lightcone for maximal growth $\delta = 1$. Causality in the Krylov chain constrains the Lanczos coefficients to grow at most linearly. We illustrate the validity of the above in the $SL(2, R)$ and Heisenberg Weyl algebras, and in a many body skew field Ising model. Moreover, we extend the above bound to the family of $Q$ complexities. Lastly, mapping to a spin chain gives a Lieb Robinson bound analogue and opens the problem to standard condensed matter methods.

We study correlation functions of topologically twisted $\mathcal N=2$ supersymmetric QCD with gauge group $\mathrm{SU}(N)$ on a compact four-manifold $X$. We derive the Coulomb branch integral for all $N$, including new couplings to background fluxes for the flavor symmetry. For $X$ of simple type with $b_2^+>1$, the correlators become sums over a finite number of strong-coupling singularities on the Coulomb branch, and can be expressed using a number of Coulomb branch couplings. The sum contains the $\mathcal N=1$ vacua, which become the supersymmetric vacua when the $\mathcal N=2$ theory is broken to $\mathcal N=1$ by an adjoint mass deformation, and whose contribution we attribute to the instanton branch. We focus on asymptotically free $\mathrm{SU}(N)$ QCD with $N_f<2N$ equal mass hypermultiplets, and conjecture that its instanton contribution to topological correlators agrees with the generating function of virtual Segre numbers of rank $N$, which are intersection numbers on the moduli space of semistable sheaves on an algebraic surface. We present a precise dictionary for all $N$ between universal series for Segre numbers and Coulomb branch couplings at the $\mathcal N=1$ vacua. The calculation of these couplings requires new higher-rank techniques, involving Siegel modular forms, an exact $\mathbb Z_N$ symmetry, charge conjugation symmetry, factorisation of the Seiberg–Witten curve, and the blowup formula. For pure $\mathrm{SU}(N)$, our result agrees with earlier work by Mariño and Moore, and the twisted correlators give the $\mathrm{SU}(N)$ Donaldson invariants of $X$. For $\mathrm{SU}(3)$ QCD, we determine closed-form expressions for all 13 Coulomb branch couplings for each $N_f=1,\dots, 5$, and find precise agreement with results of Göttsche and Kool for virtual rank 3 Segre numbers.

We present a method for constructing time-dependent integrable chiral quantum field theories on a finite spatial interval from the scattering and reflection data of an autonomous integrable model. Each particle carries a spectral label that is constant along its free trajectory. Requiring a right–left scattering event at a fixed time to be independent of its position forces the map from characteristic coordinates to spectral labels to be affine, with the same slope for both chiralities. As a result, all bulk scattering events at a given time sample one common spectral argument, and the two boundary reflections sample the corresponding endpoint arguments. The bulk and boundary drives are not independent time-dependent deformations: their time dependence is fixed by the same affine spectral coordinate. Successive reflections at the two endpoints translate the spectral label by a finite amount. Following a particle through a complete round trip then produces a difference transport whose consistency gives the boundary quantum Knizhnik–Zamolodchikov equations. The Yang–Baxter and reflection equations ensure local compatibility, while BqKZ flatness ensures compatibility of complete round trips. We then reconstruct the local Hamiltonian by inverting the one- and two-particle matching problems. The bulk matrix fixes the contact interaction, while the reflection matrix fixes the corresponding boundary coupling. The same autonomous factorized data determine the boundary qKZ transport problem and the local driven Hamiltonian. Once the boundary qKZ system is solved, its characteristic pullback gives the corresponding time-dependent many-body wavefunction. We illustrate the construction with rational $SU(N)$ models and an $O(3)$-invariant model with dynamical boundary impurities, obtaining driven Kondo interactions whose couplings are fixed by the same affine spectral coordinate.

We develop a higher-geometric framework for magnetic higher-form symmetries of pre-quantum field theories. The magnetic (topological) charges of a sigma-model with stacky target are encoded by the shape of the target, equivalently of its stack of fields, which is op-dual to the flat automorphism group controlling electric symmetries. Magnetic symmetry backgrounds are obtained by dualizing these charges against a chosen moduli stack of topological field theories, generalizing Pontryagin duality, and act on the theory by stacking. Cohesive modalities allow for targets with non-finite and non-discrete data. When the dualizing stack is a grouplike $E_\infty$-object, we prove a fibration theorem expressing the magnetic symmetries of an electrically gauged theory in terms of those of the ungauged theory and of the gauge group, computed by a homotopy-fixed-point spectral sequence with an explicit first page. For moduli stacks of higher $U(1)$-gerbes with connection, encoding bulk topological local Lagrangians, we prove a factorization theorem: the magnetic symmetry backgrounds of any connected target split, non-canonically, into Pontryagin duals of its integral homology groups, and are necessarily flat, as a consequence of dualizing discrete charges against a target with connections. We illustrate both theorems with pure $\mathrm{Pin}^\pm(2)$ gauge theory: $O(2)$ carries invertible magnetic $\mathbb{Z}_2$ symmetries in form degrees $d-3$, $d-4$ and $d-5$ that are absent for $\mathrm{Pin}^-(2)$, the first two distinguished by a single differential of the spectral sequence. Gauging and physical applications are developed in upcoming work.

We construct large families of mixed-state topological orders in (3+1)D, including intrinsically mixed-state topological orders. We realize these theories by relating the data parameterizing braided fusion 2-categories to the strong higher-form symmetries and their anomalies that characterize mixed-state topological order. We focus here on bosonic theories, which include theories which admit an emergent fermion in the spectrum of line operators. Our general framework is exemplified on the lattice, where we present concrete models and identify how the data of braided fusion 2-categories are physically encoded. We then formalize this data and show that every braided fusion 2-category arises from a general construction (decoherence followed by strong and weak gauging) as the category of topological operators of a (3+1)D mixed state, with intrinsically mixed-state topological orders distinguished by the presence of strong higher-form symmetries whose anomalies cannot be realized in any (3+1)D gapped ground state. Notably, we show that (3+1)D admits a new mechanism with no (2+1)D counterpart: intrinsically mixed-state order whose topological operators braid non-degenerately, but which carries a gravitational anomaly.

Relativistic heavy quarks equilibrate even when their microscopic drag and momentum diffusion violate the Einstein relation. We investigate how equilibration proceeds as a function of the coupling and compared to simplified Fokker-Planck models. To do this, we present a detailed calculation of the momentum-transfer kernel in weakly coupled non-Abelian plasmas through strict $\mathcal{O}(g^4)$, and study the resulting dynamics at leading order in the inverse heavy-quark mass. Beyond leading logarithm, its non-Gaussian structure plays a crucial role in equilibration. We examine closely the analytic structure of the evolution kernel, determine the large-order asymptotics of the momentum-transfer cumulants, and show how the kernel's bounded analytic domain fixes asymmetric exponential tails at the level of the momentum transfer probability. Strongly coupled $\mathcal{N}=4$ SYM also features an approximately Gaussian core and exponential tails, but differs in the nature of the kernel's singularities and the velocity dependence of the transport coefficients and tail exponents. These differences have distinct dynamical consequences: for the parameters studied, the persistence of the relativistic population in steeply falling spectra is largely explained by drag alone at very weak coupling, whereas fluctuation-induced survivor bias produces a large relative enhancement at strong coupling. Nevertheless, the shared qualitative structure between weak and strong coupling points the way towards a practical phenomenological description of heavy quarks anchored in first-principles field theory.

We study complex saddle points of the worldline path integral for massive charged particles in two-dimensional maximally symmetric backgrounds threaded by homogeneous electric fields. Within the worldline formalism, we show that the semiclassical saddles generically require complexifying both the target spacetime and the proper-time parameter. The resulting solutions comprise two slices of a single complex family, distinguished by the direction of proper-time evolution. The one evolving in imaginary proper time carries an action that typically controls the exponential suppression of non-perturbative effects, while that evolving in real proper time may encode additional complex phases responsible for quantum interference between saddles. Treating this family as a whole, we give a prescription for constructing and classifying all topologically inequivalent instanton sectors, and we find that the worldline action depends only on their topological data, namely winding numbers around the compact directions and certain isolated punctures. Moreover, in Anti-de Sitter spacetime, the qualitative structure of the solutions is governed by the dimensionless ratio $R |eE|/m$ ($R$ being the curvature radius), which distinguishes sub-extremal, extremal, and super-extremal regimes. By contrast, no analogous distinction occurs in de Sitter—where the instantons are insensitive to this ratio—or in Minkowski spacetime, which lacks a curvature scale altogether. We also recast the action as a sum over residues of the relevant (non-conserved) conjugate momentum, making transparent which analytic data control each contribution. Finally, we discuss the subtleties that arise when solutions built in various local patches are lifted to global (Anti-)de Sitter space. These impose further necessary conditions on which saddles can in principle contribute to the one-loop path integral.

We demonstrate that Maxwell electrodynamics interacting with a planar Chern-Simons interface does not have plane wave solutions localized on the interface. We re-examine the derivation of such waves presented by N. Kaloper in [Phys.Rev.D114(2026)L051903] and show that at an intermediate step certain terms were missed in an equation therein. Taking these terms into account changes the final conclusion of [Phys.Rev.D114(2026)L051903]. We also show that the method used in [arXiv:2606.12513 [hep-th]] to reproduce the same result is not consistent.

We construct and analyze a mirror family for the generalized complete intersection Calabi-Yau threefold $X_+=[\mathbb{P}^1\,|\,3\ {-1};\ \mathbb{P}^4\,|\,2\ 3]$, with $(h^{1,1},h^{2,1})=(2,46)$. An auxiliary-variable presentation turns the negative-degree section into a variation of toric GIT. Crossing one wall flops 16 disjoint $(-1,-1)$-curves and yields a Calabi-Yau threefold $X_-$, a nef complete intersection in a toric $\mathbb{Q}$-Fano eightfold, which carries a genus-one fibration of index 4. Because this ambient space is not Gorenstein, the Batyrev-Borisov construction does not apply. We use the Hori-Vafa equations only to select a 2-parameter Laurent family, and construct a smooth projective crepant compactification $Y$ of the Laurent model with $(h^{1,1},h^{2,1})=(46,2)$; for very general parameters the Mordell-Weil group is $\mathbb{Z}/4\mathbb{Z}$. The periods of $Y$ satisfy a rank-6 Picard-Fuchs system with two maximally unipotent boundary points, whose indicial algebras are isomorphic to the rational even cohomology rings of $X_-$ and $X_+$. The resulting genus-zero predictions agree with independent counts of 176 vertical lines and 100 vertical conics on the genus-one fibration $X_-\to\mathbb{P}^2$.

In this paper we discuss the quasinormal modes and the tidal responses of a four-dimensional asymptotically flat Reissner-Nördstrom black hole near extremality and investigate the nontrivial near-horizon quantum corrections of these observables. The near-horizon dynamics of near extremal black holes are generally governed by an effective Schwarzian action coupled to boundary gauge modes. We use this description and couple this effective theory with a massless scalar field outside. Using this setup we compute $2 \to 2$ scattering process of a black hole and a scalar particle. The poles of the scattering amplitude at complex frequencies give us the quasinormal mode spectrum and we recover the predicted zero damped modes near extremality at leading order. Next we evaluate the static Love numbers from the elastic limit of the scattering amplitude. We show that the static Love numbers are non-zero in contrast to the classical expectations. Very close to extremality, the behaviour is analytic, but as the near-extremal energy becomes sufficiently large, we find logarithmic dependence on the energy. This cannot be removed by the choice of renormalisation scheme. Thus near-horizon quantum effects non-trivially change the tidal response of near-extremal black holes.

We examine Higgsino dark matter (DM) as a potential explanation of the $248~\mathrm{keV}$ nuclear-recoil event of interest reported by the LUX-ZEPLIN (LZ) experiment, taking into account IceCube constraints on DM annihilation in the Sun. In the nearly pure Higgsino limit, two neutral Majorana states separated by a small mass splitting $\delta$ are connected by an off-diagonal coupling to the $Z$ boson, providing a natural realization of inelastic DM. Using a likelihood analysis, we identify 90% confidence regions compatible with the LZ event and consistent with the null results of IceCube searches, both with and without including a constraint from the absence of events in the LZ high-energy sideband. In our LZ analysis, we consider the DM distribution in the Standard Halo Model alone as well as possible enhancements of the high-speed tail induced by the Large Magellanic Cloud (LMC). We present four variants of bounds from IceCube on Higgsino dark matter, depending on various assumptions on cooling channels in the Sun, motivated by severe theoretical uncertainties about Higgsino-nucleon elastic scattering (unimportant for direct detection but crucial for IceCube bounds). Whereas the thermal Higgsino with a mass of $1.1~\mathrm{TeV}$ remains only marginally compatible with both the LZ event and the IceCube limits when the LMC-induced high-speed tail is included and both elastic cooling in the Sun and the LZ high-energy sideband constraint are neglected, higher mass Higgsinos are excellent candidates for the LZ event in light of IceCube constraints. Depending on the halo distribution, cooling interactions, and whether the LZ high-energy sideband is included, the compatible regions in the Higgsino parameter space $(m_\chi,\delta)$ extend from masses of $\sim2~\mathrm{TeV}$ to hundreds of TeV or higher, with mass splittings ranging approximately from $350$ to $525~\mathrm{keV}$.

The configuration matrices of generalized complete intersection Calabi-Yau (gCICY) threefolds contain negative entries, so their defining line bundles are not nef and the Batyrev-Borisov construction does not apply directly. We study gCICY threefolds in $\mathbb{P}^1\times B$ with a $[3,-1]$ block, that is, cut out by sections of $O(3)\boxtimes L$ and $O(-1)\boxtimes(L+R)$, where $B$ is a smooth projective fourfold and $2L+R=-K_B$. Auxiliary variables turn the generalized section into a relative variation of GIT, whose opposite phase is the zero locus of a rank-3 bundle on $\mathbb{P}^2\times B$; for general data the two phases are isomorphic or related by $\int_B c_1(L)^4$ disjoint Atiyah flops. Over products of projective spaces there are exactly 18 Calabi-Yau threefold configurations with a $[3,-1]$ block. All of them except the non-Gorenstein case studied in the companion paper have Gorenstein toric nef phases. Thus, for every other configuration in this classification, mirror symmetry is reduced after variation of GIT to ordinary Batyrev-Borisov duality, which gives the mirror Hodge numbers of the generalized phase itself. We analyze four examples with a $[3,-1]$ block and one outside this class in detail. For each we construct an explicit mirror and compute its fundamental period and low-order Picard-Fuchs system; the indicial algebras at the maximally unipotent boundary points are isomorphic to the rational even cohomology rings of the A-model phases.