Showing new listings for Monday, 10 November 2025

New submissions (showing 11 of 11 entries)

We compute, for any Rényi index n, the exact difference between the mutual Rényi informations of a pair of free massless scalars and that of a Maxwell field in d=4 dimensions. Using the standard dimensional reduction method in polar coordinates, the problem is mapped to that of a single scalar field in d=2 with Dirichlet boundary conditions, which in turn can be conveniently related to the algebra of a chiral current on the full line. This latter identification, which maps algebras on an interval to two-interval algebras, yields exact results that clarify the structure of the long-distance OPE perturbative expansion of the mutual information. We find that this series has a finite radius of convergence only for integer n>1, while it becomes only asymptotical for n=1 and general non-integer values of n.

We study QCD on AdS space with scalars or fermions in the fundamental representation, extending earlier results on pure Yang-Mills theory. In the latter, the Dirichlet boundary condition is conjectured to disappear via merger and annihilation, as signaled by the lightest scalar singlet operator approaching marginality as the coupling increases. With matter, there are two candidate operators for this mechanism. We compute their one-loop anomalous dimensions via broken conformal Ward identities and Witten diagrams. In the confining phase, with Dirichlet (Neumann) boundary condition, their anomalous dimensions are negative (positive), consistent with the disappearance (persistence) of the associated boundary CFT in the flat-space limit. In the conformal window, one of these operators becomes the displacement operator of the IR CFT, as signaled by the vanishing of its one-loop anomalous dimension in the perturbative Banks-Zaks regime. Possible scenarios for the lower edge of the conformal window are discussed. Finally, we consider general boundary conditions on fermions and discuss their relation to chiral symmetry breaking in flat space.

We propose a unified framework within Type IIA string theory, based on a globally consistent intersecting D6-brane model compactified on a T^6/(mathbb{Z}_2 times mathbb{Z}_2) orientifold. The model realizes the MSSM-like spectrum providing a framework for addressing four fundamental problems: CP violation originates from both geometric phases in Yukawa couplings and non-perturbative phases induced by E2-instantons; the observed baryon asymmetry arises via instanton-mediated operators combined with moduli-driven leptogenesis; the electroweak hierarchy is stabilized through controlled SUSY breaking with a TeV-scale gravitino mass near a metastable vacuum; and a de Sitter uplift is achieved via anti-D6-branes in an STU moduli stabilization scheme. Crucially, the interplay of intersecting brane geometry, Euclidean D2-instantons, and flux-induced moduli potentials provides a coherent mechanism linking collider, flavor, and cosmological phenomena.

Within the framework of the Zakharov-Schulman approach, in close analogy with the methods of quantum field theory, the classical scattering matrix for the simplest process of interaction between hard and soft excitations in a quark-gluon plasma (QGP), is determined. The classical mathcal{S}-matrix is defined in the form of the most general integro-power series expansion in the asymptotic values as trightarrow-infty of normal bosonic variables c^{-,a}_{hspace{0.02cm}{bf k}}(t) and (c^{-,a}_{hspace{0.02cm}{bf k}}(t))^{ast}, describing the soft gluon excitations of the system, and a color charge mathcal{Q}^{-hspace{0.03cm}a}(t) of a hard particle. The first nontrivial contribution to this matrix is calculated. The quantum commutator of quantum field operators is replaced by the so-called Lie-Poisson bracket depending on the classical asymptotic variables. The developed approach is used to derive a general formula for energy loss of a fast color-charged particle during its scattering off soft bosonic excitations of QGP in the framework of the classical Hamiltonian formalism. For this purpose, the notion of an effective current of the scattering process under consideration is introduced and its relation to the classical mathcal{S}-matrix is determined. With the help of the known form of the classical scattering matrix, the desired effective current is recovered, which in turn allowed us to determine the formula for energy loss of the hard color particle. The rough estimates of energy loss at the order-of-magnitude level is provided and their comparison with the well-known results on the radiation and collision losses is performed.

In this article, we investigate the proposed duality between the island and the defect extremal surface (DES) prescriptions using the fine-grained entanglement entropy in Karch-Randall (KR) brane-world models with gravitating radiation baths. We consider the AdS_3 black string geometry and compute the entanglement entropy for radiation subsystems on an AdS_2 eternal black hole background using both the island and the DES prescriptions. We find an agreement between the two proposals for the island and the no-island phases, thus verifying the validity of the proposed duality. We further extend to a Tbar{T} deformed AdS_3 black string geometry with a cut-off and find consistent results for both phases. We finally plot and compare the Page curves for the undeformed and deformed scenarios, and discuss the modifications due to Tbar{T} deformation.

We present a non-perturbative framework for the dynamics of slow-roll inflation that consistently incorporates quantum corrections, based on an alternative functional renormalisation group (RG) approach. We derive the coupled Friedmann-RG flow equations governing the joint evolution of spacetime, the inflaton field, and its effective potential. Applying this formalism to alpha-attractor E-models, we find that the RG flow induces a dynamical destabilisation of the inflationary trajectory, leading to a premature termination of slow roll. Remarkably, the resulting predictions bring alpha-attractors into full agreement with the latest ACT data without introducing new physics beyond a consistent quantum-corrected treatment of the inflaton dynamics.

Extending the single-angular-momentum case analyzed in our previous work, we investigate the solution-generating technique based on the Breitenlohner-Maison (BM) linear system for asymptotically flat, stationary, bi-axisymmetric black hole solutions with two angular momenta in five-dimensional vacuum Einstein theory. In particular, we construct the monodromy matrix associated with the BM linear system for the doubly rotating Myers-Perry black holes and the Pomeransky-Sen'kov black rings. Conversely, by solving the corresponding Riemann-Hilbert problem using the procedure developed by Katsimpouri et al., we demonstrate that the factorization of the monodromy matrix precisely reproduces these vacuum solutions, thereby reconstructing both geometries.

The quantum induced stress tensor of 3+1-dimensional Einstein gravity, with conformally coupled matter, is studied in an effective field theory approach. In this context, Riegert's non-local effective action is sufficient to reproduce the trace anomaly in curved spacetime but in general the effective action can include additional non-local but scale invariant terms that influence the semiclassical physics without affecting the trace anomaly. Here, a truncated model, with only one additional term involving the square of the Weyl tensor, is used to find the induced stress tensor in a black hole background. With suitable physical conditions, a solution of the resulting 4th order equations leads, in a static limit, to a unique quantum state matching expected properties of the Unruh state.

Leveraging the computational framework presented in reference [JHEP 07, 062 (2024)], we evaluate the analytic scattering waveform in General Relativity to second order, G^3 M^3 /r b^2 and to all orders in velocity. This new representation of the next-to-leading order waveform is well-suited for numerical evaluation. Integrating the [modulus square of the] waveform over the angles on the celestial sphere, we also compute the power spectrum of the radiation to order G^4 numerically.

We propose a resolution to the longstanding problem of perturbative normalizability in canonical quantum gravity of the Lorentzian Chern-Simons-Kodama (CSK) state with a positive cosmological constant in four dimensions. While the CSK state is an exact solution to the Hamiltonian constraint in the self-dual formulation and semiclassically describes de Sitter spacetime, its physical viability has been questioned due to apparent nonnormalizability and CPT asymmetry. Starting from a nonperturbative holomorphic inner product derived from the reality conditions of the self-dual Ashtekar variables, we show that the linearization, in terms of gravitons, of the CSK state is perturbatively normalizable for super-Planckian cosmological constant. Furthermore, we demonstrate that a rotation in phase space, a generalization of Thiemann's complexifier, can render the full perturbative state normalizable for all Lambda by analytically continuing the non-convergent modes in phase space. This provides the first concrete realization of a CPT-breaking, yet normalizable, gravitational vacuum state rooted in a nonperturbative quantum gravity framework. Our results establish the CSK state-long thought formal-as a viable candidate for the ground state of quantum gravity in de Sitter space.

The description of low-energy (``soft") gravitons using universal theorems continues to attract attention. In this paper, we consider the emission of two soft gravitons, using a previously developed formalism that describes (next-to) soft graviton emission in terms of generalised Wilson lines (GWLs). Based on Schwinger's proper time methods, the GWL allows for a systematic accounting of graviton emission from external hard particles in the amplitude, as well as from three-graviton vertices located off the individual worldlines. By combining these effects, previously derived results for the leading double soft graviton theorem are recovered. Still, the formalism allows us to go further in deriving new universal double soft graviton terms at subleading order in the momentum expansion. We further demonstrate how gauge invariance can be utilized to account for double soft graviton emissions within the non-radiative amplitude, including the effects of non-zero initial positions of the hard particles. Our results can be packaged into an exponential dressing operator, and we comment on possible applications to the effective field theory for binary scattering processes.

Cross submissions (showing 12 of 12 entries)

The conservation of CP in QCD has been shown to follow from a careful treatment of the path integral and canonical quantization inarXiv:2001.07152andarXiv:2403.00747. Here, we refute the critique of these results put forth inarXiv:2510.18951. First, using the quantum rotor as an analogue of QCD, it is argued inarXiv:2510.18951that the topological susceptibility vanishes when using the limiting procedure ofarXiv:2001.07152. When translated to QCD, this would contradict the observed eta^prime-mass. We show that this is not the case because the susceptibility is defined from the vacuum correlator of the topological charge density, which for the rotor is just fixed by the canonical commutation relation. The latter does not depend on the disputed order of limits. Second, it is suggested inarXiv:2510.18951that CP violation in QCD can be established by considering the low-energy effective theory alone. We show that here the argument relies on assuming from the start choices of couplings that lead to CP violation but are not of the most general form allowed by spurion analysis. No valid reason is given for why allowed choices leading to CP conservation, that match the computation of ultraviolet correlators as shown inarXiv:2001.07152andarXiv:2403.00747, would be inconsistent.

We implement numerical techniques to simulate D-random feuilletages, candidates for higher-dimensional random geometries introduced in L. Lionni and J.-F. Marckert, Math. Phys. Anal. Geom. 24 (2021) 39. Using finite-size scaling techniques, our approach allows to give a numerical estimation of the Hausdorff dimension d_H of these feuilletages. The results obtained are compatible with the formal result known for the Brownian map, which corresponds to the D=2 random feuilletage. For the D=3 case, our numerical study finds a good agreement with the conjectured value d_H=8.

In this short note we analyze the inflationary dynamics in Weyl-invariant Einstein-Cartan gravity coupled to the Standard Model of particle physics. We take the axion-like particle of gravitational origin to be approximately massless in the early Universe and show how inflation with the Higgs field materializes.

We introduce the Courant algebroid lift, a new construction that takes a Courant algebroid together with a vector bundle connection and produces, when the connection is flat in the image of the anchor, a Courant algebroid. In general, this lift produces a Courant-like structure that we call a curved Courant algebroid. We start by establishing a hierarchy of Courant algebroid properties and their associated structures. In this setting, we introduce curved Courant algebroids, which we show to be related to connections with torsion and curved differential graded Lie algebras. We use this to provide a classification of exact curved Courant algebroids. We show that the Courant algebroid lift of an exact Courant algebroid yields a natural link between the Patterson-Walker metric and generalized geometry. By lifting non-exact Courant algebroids, we establish a relation of these lifts to Lie algebras, Poisson and special complex geometry. Finally, we show that Courant algebroid lifts provide a large class of examples of Courant algebroid actions.

Precision calculations in hadronic processes at high energy colliders are crucial for improving the understanding of the standard phenomena as well as for the discovery of new physics. Spinor-helicity formalism serves as one of the most efficient ways to simplify the calculations of S matrix elements. In this article, we compute the S matrix elements for the process qBar{q}rightarrow qBar{q}g mediated by photon and gluon. Ignoring the contribution of Z boson exchange, we show that the calculation of S matrix elements for this process simplifies to a great extent by using spinor-helicity formalism.

Understanding how quantum systems transition from integrable to fully chaotic behavior remains a central open problem in physics. The Sachdev--Ye--Kitaev (SYK) model provides a paradigmatic framework for studying many-body chaos and holography, yet it captures only the strongly correlated limit, leaving intermediate regimes unexplored. Here, we investigate the Yukawa--SYK (YSYK) model, where bosonic fields mediate random fermionic interactions, and demonstrate that it naturally bridges single-particle and many-body chaos. Using spectral and dynamical chaos markers, we perform a comprehensive finite-size characterization of the YSYK model. We show that the interaction strength acts as a tunable control parameter interpolating between the SYK_2 and SYK_4 limits, and introduce a framework enabling direct and quantitative comparison with these benchmark models. In the intermediate regimes, we uncover distinct dynamical regimes marked by partial ergodicity breaking, prethermalization plateaus, and incomplete scrambling. Finally, we propose a feasible optical-cavity implementation of the YSYK model using ultra-cold atoms. Our results establish the YSYK model as a unifying platform connecting single-particle and many-body chaos, paving the way for experimental observation of these phenomena.

Applications of effective field theory (EFT) and scattering amplitudes to gravitational problems have recently produced many unique results that advanced our understanding of the dynamics of compact binaries. Many of these results were made possible by comparing gravitational scattering amplitudes in EFT with exact expressions from general relativity. However, the latter expressions are not easily available as they require intricate solution techniques for the Teukolsky master equation, such as the Mano-Suzuki-Takasugi (MST) method. In this paper, we develop and present the first public package that enables computations of gravitational scattering amplitudes in black hole perturbation theory within the MST framework. Our package supports both analytic computations to a given post-Minkowskian (PM) order in the low-frequency limit and exact numerical computations for an arbitrary frequency of the perturbing field. As an application, we compute scattering phase shifts and inelasticity parameters for massless spin - 0, 1, and 2 fields resulting from scattering off a rotating Kerr black hole through the third PM order and compare these results with the exact numerical solutions.

Primordial Black Holes (PBHs) represent one of the more interesting ways to address dark matter, at the interface of both cosmology and quantum gravity. It is no surprise then that testing PBHs is a venue of active interest, with several cosmological and astrophysical probes constraining different mass ranges. In this work, we propose novel Solar System scale searches for PBHs, motivated by the unique precision and coverage of local observables. We show that asteroid to dwarf planet mass PBHs can induce measurable dipolar timing signatures in pulsar timing arrays, while planetary mass PBHs can generate detectable ADAF accretion flares through interactions with Kuiper Belt bodies. Together, these complementary approaches open a new observational frontier for probing PBHs across mass ranges that remain unconstrained by conventional cosmological methods.

The two-parameter inhomogeneous and time-dependent Pimentel solution of Brans-Dicke theory is analyzed to probe the new thermal view in which General Relativity is the zero-temperature (equilibrium) state of scalar-tensor gravity. As the parameters vary, we uncover phenomenology not found before with other exact solutions, nor contemplated thus far in the general theory. In the process, we also discuss the anomalous limit to General Relativity of the Pimentel geometry and show how the Mars solution of the Einstein equations is its Einstein frame version.

We identify curvature decay |mathrm{Riem}| sim r^{-3} as a sharp spectral threshold in linearized gravity on asymptotically flat manifolds. For faster decay, the spatial Lichnerowicz operator possesses a purely continuous spectrum sigma_{mathrm{ess}}(L) = [0,infty), corresponding to freely radiating tensor modes. At the inverse-cube rate, compactness fails and zero energy enters sigma_{mathrm{ess}}(L), yielding marginally bound, finite-energy configurations that remain spatially extended. These static modes constitute the linear precursors of gravitational memory and soft-graviton phenomena, delineating the geometric boundary between dispersive and infrared behavior. A complementary numerical study of the radial model [ L_p = -frac{d^2}{dr^2} + frac{ell(ell+1)}{r^2} + frac{C}{r^p} ] confirms the analytic scaling law, locating the same transition at p = 3. The eigenvalue trends approach the flat-space limit continuously for p > 3 and strengthen progressively for p < 3, demonstrating a smooth yet sharp spectral transition rather than a discrete confinement regime. The result parallels the critical threshold of the non-Abelian covariant Laplacian~[18], indicating a common r^{-3} scaling that governs the infrared structure of gauge and gravitational fields.

We propose a framework for applying on-shell scattering amplitude methods to emergent relativistic phases of quantum matter. Many strongly correlated systems, from Dirac and Weyl semimetals to topological-insulator surfaces, exhibit low-energy excitations that are effectively massless relativistic spinors. We show that physical observables such as nonlinear optical and Hall responses can be obtained from compact on-shell amplitudes, bypassing the complexity of Feynman diagrams. As a concrete demonstration, we derive the nonlinear Hall conductivity of a Dirac semimetal from a single parity-odd three-photon amplitude, highlighting the analytic and conceptual power of amplitude-based approaches for strongly correlated condensed-matter systems.

We present a novel robust framework for systematically constructing D-dimensional four-point higher-derivative contact amplitudes. Our modular block ("LEGO"-like) approach builds amplitudes directly from manifestly gauge-invariant kinematic blocks, color-weight factors, and scalar Mandelstam polynomials. Symmetries (Bose/Fermi) are imposed algebraically, acting as filters on combinations of compatible pieces. This framework operates entirely in D dimensions, naturally incorporating evanescent operators crucial for loop-level consistency. Scaling to arbitrary mass dimension is achieved in a highly controlled manner using permutation-invariant scalar polynomials, avoiding combinatorial explosion. A key feature is its manifest compatibility with the double-copy program, allowing the systematic generation of operator towers not only for gauge theories but also for gravity and other theories within the double-copy web.

Replacement submissions (showing 24 of 24 entries)

String geometry theory is one of the candidates of the non-perturbative formulation of string theory. In this paper, in the bosonic closed sector of string geometry theory, we completely identify the perturbative vacua, which include general string backgrounds in bosonic closed string theory. From fluctuations around these configurations, we derive the path-integrals of perturbative strings on the string backgrounds up to any order.

In field theory, one can consider a variety of states. Within the framework of factorization algebras, one typically works with the natural augmentation state langle-rangle_{rm aug}. In physics, however, other states arise naturally, such as the compactification state langle-rangle_{rm cptf} or the Schwartz state langle-rangle_{rm Sch}, defined by imposing Schwartz boundary conditions. At first sight, the relation among these three states is not obvious.This paper gives a definition of the compactification state in factorization algebras and provides a method for handling infrared divergences in the massless theory. We then prove that the three states are equivalent in both the massive and massless cases.

It is commonly believed that a unitary supersymmetric quantum field theory (QFT) involving graviton and gravitino fields on fixed 4-dimensional de Sitter spacetime (dS_{4}) cannot exist due to known challenges associated with supersymmetry (SUSY) in dS_{4}. In this paper, we contradict this expectation by presenting a new unitary supersymmetric QFT on dS_{4}: the free supersymmetric theory of the chiral graviton and chiral gravitino fields. By chiral, we mean that the corresponding field strengths are anti-self-dual, and the gauge potentials are complex, each carrying a single complex propagating degree of freedom. The global SUSY transformations are generated by the standard Dirac Killing spinors of dS_{4}. The theory overcomes the known obstacles to unitary global SUSY on dS_{4} by closing the commutator between two SUSY transformations on so(4,2) oplus u(1) rather than the de Sitter algebra so(4,1). Crucially, the so(4,2) symmetry is realised through unconventional conformal-like transformations. This free theory cannot become interacting while preserving SUSY in a way that makes the spin-2 sector the true graviton sector of General Relativity, as the three-graviton coupling cannot be u(1)-invariant. We establish the unitarity of the free supersymmetric theory in two complementary ways. First, by studying the action of the superalgebra generators on the space of physical gravitino and graviton mode solutions. Second, by quantising the fields and explicitly constructing the complex quantum supercharges Q_{A} and Q^{Adagger}, we show that the trace sum_{A} { Q_{A}, Q^{A dagger} } is positive-definite.

We investigate the q=2 SYK model with R-para-particles (R-PSYK_2), analyzing its thermodynamics and spectral form factor (SFF) using random matrix theory. The Hamiltonian is quadratic, with coupling coefficients randomly drawn from the Gaussian Unitary Ensemble (GUE). The model displays self-averaging behavior and exhibits an exponential ramp in its SFF dynamics: mathcal{K}(t) sim e^{C_0t}. The growth rate C_0 tends toward either a constant or infinity in the Nto infty limit, depending on specific statistics of the model. These results provide novel perspectives on quantum systems with unconventional statistics.

The relation between covariant fracton gauge theory and Moller-Hayashi-Shirafuji theory of gravity is investigated. The former is the gauge theory of a rank-two symmetric tensor with gauge symmetry given by the double derivative of a scalar parameter; the latter is the most general theory, whose action is quadratic in the Weitzenböck torsion. We show that the solutions of covariant fracton gauge theory describe a subsector of the space of solutions of Moller-Hayashi-Shirafuji theory, providing a new insight in the relation between covariant fractons and gravity, and elucidating the meaning of covariant fracton theory as a new type of gauge theory.

We consider a class of models in the framework of metric-affine gravity and establish their correspondence to the bosonic sector of a class of no-scale supergravity models. The excellent inflationary behavior of the gravitational models considered is carried over to the corresponding supergravity ones, thus, enriching the landscape of inflation-compatible models.

The dynamics of quantum fields become nonperturbative when their interactions are probed by a large number of particles. To explore this regime we study correlation functions which involve a large number of fields, focussing on massive scalar theories that feature arbitrary self-interactions, phi^{2p}. Treating quantum fields as operator-valued distributions, we investigate n-point correlation functions at ultra-short distances and compute moments and cumulants of fields, using a semiclassical saddle point approximation in the double scaling limit of weak coupling, lambda to 0, large quantum number, n to infty, while keeping lambda n constant. Addressing the nonperturbative regime, where lambda n gtrsim 1, requires a resummation of the effective saddle point to all orders in lambda n. We perform this resummation in zero and one dimensions, and show that the moments, corresponding to correlation functions including disconnected contributions, grow exponentially with n. This growth is significantly reduced for higher-order self-interactions, i.e. for larger p. On the other hand, we argue that the cumulants, which represent connected correlation functions, grow even more rapidly and are mostly independent of p.

In holography, flavour probe branes are used to introduce fundamental matter to the AdS/CFT correspondence. At a technical level, the probes are described by extremizing the DBI action and solving the Lagrange-Euler equations of motion. I report on applications of artificial neural networks that allow direct minimization of the regularized DBI action (interpreted as a free energy) without the need to derive and solve the equations of motion. I consider, as examples, magnetic catalysis of chiral symmetry breaking and the meson melting phase transition in the D3/D7 holographic set-up. Finally, I provide a framework which allows the simultaneous learning of the embeddings and the relevant aspects of the dual geometry based on field theory data.

We provide a concrete link between celestial amplitudes and cosmological correlators. We first construct a map from quantum field theories (QFTs) in (D+2)-dimensional Euclidean space to theories on the (D+1)-dimensional sphere, through a Weyl rescaling and a Fourier transformation. An analytic continuation extends this map to a relation between QFTs in Minkowski spacetime text{M}_{D+2} and in de Sitter spacetime text{dS}_{D+1} with the Bunch-Davies vacuum. Combining this relation with celestial holography, we show that the extrapolated operators in de Sitter space can be represented by operators on the celestial sphere S^{D}. Our framework offers a systematic route to transfer computational techniques and physical insights between celestial holography and the dS/CFT correspondence.

We study one of the simplest integrable two-dimensional quantum field theories with a boundary: N free non-compact scalars in the bulk, constrained non-linearly on the boundary to lie on an (N-1)-sphere of radius 1/sqrt{g}. The N=1 case reduces to the single-channel Kondo problem, for N=2 the model describes dissipative Coulomb charging in quantum dots, and larger N is analogous to higher-spin impurity or multi-channel scenarios. Adding a boundary magnetic field -- a linear boundary coupling to the scalars -- enriches the model's structure while preserving integrability. Lukyanov and Zamolodchikov (2004) conjectured an expansion for the boundary free energy on the infinite half-cylinder in powers of the magnetic field. Using large-N saddle-point techniques, we confirm their conjecture to next-to-leading order in 1/N. Renormalization of the subleading solution turns out to be highly instructive, and we connect it to the RG running of g studied by Giombi and Khanchandani (2020).

The dual formulations of an infinite tower of tree-level soft theorems in asymptotically flat spacetimes for scattering amplitudes in the standard energy-momentum basis and for correlators of a 2D celestial conformal field theory imply a correspondence between the celestial operator product expansion (OPE) and the higher spin charge bracket. We apply such correspondence to provide first a prescription to solve the double-soft limit ambiguity in the mixed-helicity sector of celestial OPEs. Furthermore, demanding the charge OPE/bracket correspondence to remain valid when operators are shadow transformed, we construct an algorithm to compute shadow celestial OPEs. We first test the algorithm by recovering results in the previous literature involving the celestial energy-momentum tensor; we then apply it to both gravity and Yang-Mills theory and generalize the OPE derivation to arbitrary spins.

This thesis addresses three problems arising in type II string theory compactified on a Calabi-Yau manifold. In the first one we study the hypermultiplet moduli space (HM), by working on its twistor space. Using data derived via mirror symmetry and S-duality, we compute NS5-instanton corrections to the HM metric in the one-instanton approximation.These corrections are weighted by D4-D2-D0 BPS indices, which coincide with rank 0 Donaldson-Thomas invariants and count the (signed) number of BPS black hole microstates. These invariants exhibit wall-crossing behavior and induce a Riemann-Hilbert problem. This problem can describe many setups, including the D-instanton corrected twistor space of the HM in type II string theory and is of independent mathematical interest. We consider a quantum deformation of the RH problem, induced by the refined BPS indices. Using a formulation of the problem in terms of a non-commutative Moyal star product, we provide a perturbative solution to it. From the adjoint form of this solution, we identify a generating function for coordinates on the still mysterious quantum analog of the twistor space.Finally, we study the modular properties of the D4-D2-D0 BPS indices, more precisely of their generating functions. It was previously argued, using S-duality, that the generating functions are higher depth mock modular forms. Moreover, they satisfy a modular completion equation, which fixes their shadow in terms of other (lower rank) generating functions. We start by bringing about a significant simplification to these equations and recovering subtle contributions that were overlooked. Then, we provide (a recipe for) solutions to these modular completion equations, up to all the holomorphic modular ambiguities that need to be fixed independently. For this, we use indefinite generalized theta series and Jacobi-like forms to write the solutions.

Just as linearized perturbations of time-independent configurations can be decomposed into normal modes, those of periodic systems can be decomposed into Floquet modes, which each evolve by a fixed phase over one period. We show that in the case of a (1+1)-dimensional relativistic field theory with a single scalar of mass m, all breathers, quasi-breathers and oscillons of length 1/epsilon have identical nonrelativistic Floquet modes at leading order in an epsilon/m expansion. More precisely, these Floquet modes depend only on epsilon and m, and are independent of the potential of the theory. In particular, there is a continuum of Floquet modes corresponding to each real momentum plus four discrete modes corresponding to space translations, time translations, boosts and amplitude changes. There are no discrete shape modes. We provide simple, explicit formulas for these universal leading-order, nonrelativistic Floquet modes.

We obtain generally covariant operator-valued geodesic equations on a pseudo-Riemannian manifold M as part of the construction of quantum geodesics on the algebra D(M) of differential operators. Geodesic motion arises here as an associativity condition for a certain form of first order differential calculus on this algebra in the presence of curvature. The corresponding Schrödinger picture has wave functions on spacetime and proper time evolution by the Klein-Gordon operator, with stationary modes being solutions of the Klein-Gordon equation. As an application, we describe gravatom solutions of the Klein-Gordon equations around a Schwarzschild black hole, i.e. gravitationally bound states which far from the event horizon resemble atomic states with the black hole in the role of the nucleus. The spatial eigenfunctions exhibit probability density banding as for higher orbital modes of an ordinary atom, but of a fractal nature approaching the horizon.

One of the most unconventional features of topological phases of matter is the emergence of quasiparticles with exotic statistics, such as non-Abelian anyons in two dimensional systems. Recently, a different type of exotic particle statistics that is consistently defined in any dimension, called R-parastatistics, is also shown to be possible in a special family of topological phases. However, the physical significance of emergent parastatistics still remains elusive. Here we demonstrate a distinctive physical consequence of parastatistics by proposing a challenge game that can only be won using physical systems hosting paraparticles, as passing the challenge requires the two participating players to secretly communicate in an indirect way by exploiting the nontrivial exchange statistics of the quasiparticles. The winning strategy using emergent paraparticles is robust against noise, as well as the most relevant class of eavesdropping via local measurements. This provides both an operational definition and an experimental identity test for paraparticles, alongside a potential application in secret communication.

The perturbative result for the quark-mass conversion factor between the overline{mathrm{MS}} and regularization-independent symmetric-momentum subtraction scheme (RI/SMOM) away from the chiral limit, i.e. at non-zero quark masses (RI/mSMOM), is derived up to three loops in QCD, extending the existing result by two additional orders. We further explore an illuminating possibility that in Dimensional Regularization, the original RI/(m)SMOM renormalization conditions may be interpreted merely in a weaker sense, namely as equations holding just in the 4-dimensional limit rather than exactly in d dimensions: they result in different, albeit simpler, renormalization constants but still the same finite conversion factor. This novel observation has the added benefit of reducing computational effort, particularly at high orders. Our high-order results for the conversion factor exhibit rich behaviors, and in particular a window is observed in the subtraction scale and mass where it receives less perturbative corrections than the RI/SMOM counterpart up to three loops; this finding may help to further improve the accuracy of overline{mathrm{MS}} quark-mass determinations with Lattice QCD.

We develop foundations for a relational approach to quantum field theory (RQFT) based on the operational quantum reference frames (QRFs) framework considered in a relativistic setting. Unlike other efforts in combining QFT with QRFs, we use the latter to provide novel mathematical and conceptual foundations for the former. We focus on scalar fields in Minkowski spacetime and discuss the emergence of relational local (bounded) observables and (pointwise) fields from the consideration of Poincaré-covariant (quantum) frame observables defined over the space of (classical) inertial reference frames. We recover a relational notion of Poincaré covariance, with transformations on the system directly linked to the state preparations of the QRF. We introduce and analyse various causality conditions, and construct an explicit example of a covariant scalar relational quantum field which is causal relative to operationally meaningful preparations of a relativistic QRF. The theory makes direct contact with established foundational approaches to QFT: we demonstrate that the vacuum expectation values derived within our framework reproduce many of the essential properties of Wightman functions, carry out a detailed comparison of the proposed formalism with Wightman QFT with the frame smearing functions describing the QRF's localisation uncertainty playing the role of the Wightmanian test functions, and show how the properties of algebras generated by relational local observables suitably extend the core axioms of Algebraic QFT. We finish with an extensive outlook describing a number of further research directions. This work is an early step in revisiting the mathematical foundations of QFT from a relational and operational perspective.

The Standard Model of particle physics is usually cast in symmetry-first terms. On this approach, one begins with a symmetry group and postulates matter fields as objects transforming under its representations, without requiring that the group be grounded in, or derived from, independent geometric structures. Recently, a geometry-first formulation has been proposed, in which the relevant symmetries are not fundamental. In this paper I extend this approach to two central mechanisms of the Standard Model: spontaneous symmetry breaking and the Yukawa coupling, both essential for particles to acquire mass. These reformulations offer alternative explanations cast in purely geometric terms. In particular, the quantisation of charge arises here as a purely geometric consequence of the tensorial construction of matter fields from the fundamental bundles -- a mechanism that is both more general and more transparent than the usual topological account based on the compactness of symmetry groups. More generally, I argue that a symmetry-first account in terms of principal and associated bundles admits a genuine geometry-first counterpart only under certain strict conditions.

In bouncing cosmological models, either classical or quantum, the big bang singularity is replaced by a regular bounce. A challenging question in such models is how to keep the shear under control in the contracting phase, as it is well-known that the shear grows as fast as 1/a^{6} toward the bounce, where a is the average expansion factor of the universe. A common approach is to introduce a scalar field with an ekpyrotic-like potential which becomes negative near the bounce, so the effective equation of state of the scalar field will be greater than one, whereby it dominates the shear in the bounce region. As a result, a homogeneous and isotropic universe can be produced after the bounce. In this paper, we study how the ekpyrotic mechanism affects the inflationary phase in both loop quantum cosmology (LQC) and a modified loop quantum cosmological model (mLQC-I), because in these frameworks inflation is generic without such a mechanism. After numerically studying various cases in which the potential of the inflaton consists of two parts, an inflationary potential and an ekpyrotic-like one, we find that, despite the fact that the influence is significant, by properly choosing the free parameters involved in the models, the ekpyrotic-like potential dominates in the bounce region, during which the effective equation of state is larger than one, so the shear problem is resolved. As the time continuously increases after the bounce, the inflationary potential grows and ultimately becomes dominant, resulting in an inflationary phase. This phase can last long enough to solve the cosmological problems existing in the big bang model.

We show that a family of secret communication challenge games naturally define a hierarchy of emergent quasiparticle statistics in three-dimensional (3D) topological phases. The winning strategies exploit a special class of the recently proposed R-paraparticles to allow nonlocal secret communication between the two participating players. We first give a high-level, axiomatic description of emergent R-paraparticles, and show that any physical system hosting such particles admits a winning strategy. We then analyze the games using the categorical description of topological phases (where point-like excitations in 3D are described by symmetric fusion categories), and show that only R-paraparticles can win the 3D challenge in a noise-robust way, and the winning strategy is essentially unique. This analysis associates emergent R-paraparticles to deconfined gauge theories based on an exotic class of finite groups. Thus, even though this special class of R-paraparticles are fermions or bosons under the categorical classification, their exchange statistics can still have nontrivial physical consequences in the presence of appropriate defects, and the R-paraparticle language offers a more convenient description of the winning strategies. Finally, while a subclass of non-Abelian anyons can win the game in 2D, we introduce twisted variants that exclude anyons, thereby singling out R-paraparticles in 2D as well. Our results establish the secret communication challenge as a versatile diagnostic for both identifying and classifying exotic exchange statistics in topological quantum matter.

In curved space-time, a scalar field phi is generically expected to couple to curvature, via a coupling of the form xiphi^2R. Yet in the study of Hawking emission from regular black holes (RBHs), where scalar fields are often introduced as simple probes of the geometry, and the Ricci scalar is generically non-zero, this non-minimal coupling is almost always ignored. We revisit this assumption by studying scalar Hawking emission from four representative RBHs (the Bardeen, Hayward, Simpson-Visser, and D'Ambrosio-Rovelli space-times), within two benchmark cases: the conformal case xi=1/6, and a large negative value xi=-10^4 motivated by Higgs inflation. We compute the graybody factors and emission spectra, showing that the latter can be either enhanced or suppressed, even by several orders of magnitude. A crucial role is played by the sign of the term xi fR, with f(r)=-g_{tt} in Schwarzschild-like coordinates, as it determines whether the non-minimal coupling suppresses or enhances the geometric potential barrier. For the D'Ambrosio-Rovelli case with large negative xi, the low-energy emission spectrum is enhanced by up to five orders of magnitude, since xi fR<0 throughout the space-time, leading to a deep potential well which broadens the transmissive window. The deviations we find can be particularly relevant in the case where primordial RBHs are dark matter candidates, given the impact of the non-minimal coupling on their evaporation history.

We search for gravitational-wave background signals produced by various early Universe processes in the Advanced LIGO O4a dataset, combined with the data from the earlier O1, O2, and O3 (LIGO-Virgo) runs. The absence of detectable signals enables powerful constraints on fundamental physics. We derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parameters associated with various possible processes in the early Universe: first-order phase transitions, cosmic strings, domain walls, stiff equation of state, axion inflation, second-order scalar perturbations, primordial black hole binaries, and parity violation. In our analyses, the presence of an astrophysical background produced by compact (black hole and neutron star) binary coalescences throughout the Universe is also considered. We address the implications for various cosmological and high energy physics models based on the obtained parameter constraints. We conclude that LIGO-Virgo data already yield significant constraints on numerous early Universe scenarios.

We consider detailed cosmological tests of dark energy models obtained from the general conformal transformation of the Kropina metric, representing an (alpha,beta)-type Finslerian geometry. In particular, we restrict our analysis to the osculating Barthel Kropina geometry. The Kropina metric function is defined as the ratio of the square of a Riemannian metric alpha and of the one-form beta. In this framework, we also consider the role of the conformal transformations of the metric, which allows us to introduce a family of conformal Barthel-Kropina theories in an osculating geometry. The models obtained in this way are described by second-order field equations, in the presence of an effective scalar field induced by the conformal factor. The generalized Friedmann equations of the model are obtained by adopting for the Riemannian metric alpha the Friedmann Lemaitre Robertson Walker representation. In order to close the cosmological field equations, we assume a specific relationship between the component of the one-form beta and the conformal factor. With this assumption, the cosmological evolution is determined by the initial conditions of the scalar field and a single free parameter gamma of the model. The conformal Barthel Kropina cosmological models are compared against several observational datasets, including Cosmic Chronometers, Type Ia Supernovae, and Baryon Acoustic Oscillations, using a Markov Chain Monte Carlo (MCMC) analysis, which allows the determination of gamma. A comparison with the predictions of standard LambdaCDM model is also performed. {Our results indicate that the conformal osculating Barthel Kropina model can be considered as a successful, and simple, alternative to standard cosmological models.

In this work we introduce an ansatz for continuous matrix product operators for quantum field theory. We show that (i) they admit a closed-form expression in terms of finite number of matrix-valued functions without reference to any lattice parameter; (ii) they are obtained as a suitable continuum limit of matrix product operators; (iii) they preserve the entanglement area law directly in the continuum, and in particular they map continuous matrix product states (cMPS) to another cMPS. As an application, we use this ansatz to construct several families of continuous matrix product unitaries beyond quantum cellular automata.