arXiv subjects

Panos Betzios

Publications and source records attributed to Panos Betzios.

18 recordsLinked to original sources

arXiv2026

Factorizations of 3d Interval Partition Functions

We show that interval partition functions (transition amplitudes) of three- dimensional $\mathcal{N} = 2$ theories admit factorizations into sums of products of hemisphere partition functions with Wilson loop insertions glued by suitable factors. We prove the factorization explicitly for supersymmetric quantum electrodynamics and Chern-Simons- Yang-Mills theories. In the former case, we show that the gluing factors can be naturally interpreted in terms of $S^2 \times S^1$ partition functions. In the latter case, we prove that hemisphere partition functions are affine characters and determine the gluing factors explicitly in special cases.

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arXiv2026

A Menagerie of Wormholes and Cosmologies in the Gravitational Path Integral

We analyse a variety of Euclidean saddles in the gravitational path integral, with asymptotic AdS boundary conditions, in a class of Einstein-Scalar-Maxwell models. These include single boundary solutions, usual and wineglass wormholes, as well as more exotic (quasi)-oscillatory saddles. Our construction shows how an unbound number of oscillations gets tamed, when flat directions of the potential get lifted. We find several interesting phase transitions between these solutions. The Euclidean wormhole backgrounds can be analytically continued to Lorentzian FLRW universes. Some of them contain an early period of inflation. We delineate the conditions under which they can be the dominant saddles in the gravitational path integral and use them to estimate ratios of probabilities for different cosmological outcomes.

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arXiv2026

Before the Bang: Wormholes at the Dawn of the Universe

This essay discusses recent progress on Euclidean wormholes as candidate contributions to the Universe's initial quantum state. The comparison with the Hartle-Hawking no-boundary proposal highlights both a conceptual affinity and genuine advance: wormholes retain the relevance of Euclidean-saddles as encoders of properties of cosmological wavefunctions, while they broaden the class of regular saddles that are physically relevant for inflating universes and are capable of resolving issues that plague the no-boundary proposal. The principal achievement of the wormhole program is to enlarge the semiclassical initial-condition land-scape in a way that is physically rich, conforms with Holographic expectations and as such becomes increasingly relevant for early-universe model building, within UV complete theories of quantum gravity.

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arXiv2026

Bubbling wormholes and matrix models

The thermofield double state entangles two copies of a CFT via a sum over energy eigenstates and is dual to the two-sided eternal black hole. We explore an analogous construction using sums over gauge group representations of half-BPS Wilson loops in multiple copies of $U(N)$ $\mathcal{N}=4$ super Yang-Mills. These sums act as delta function-like operators that correlate the eigenvalues of the corresponding half-BPS matrix models. We suggest that the holographic duals are ''bubbling wormhole'' geometries: multi-covers of AdS$_5$ $\times S^5$ whose conformal boundary consists of multiple four-spheres intersecting on a common circle. We analyze the matrix model free energy, discuss its bulk interpretation, and study probe loops in these backgrounds.

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arXiv2025

A microscopic Normal Matrix Model for $(A)dS_2$

We describe the duality between the gravitating $c=1$ (compact) Sine-Gordon model and a normal matrix model. From a two-dimensional quantum gravity perspective and due to the periodic nature of the potential, this model admits both anti-de Sitter and de-Sitter saddles, similarly to simpler models of Sine-Dilaton gravity, as well as more complicated interpolating "wineglass wormhole" geometries. From a string theory perspective the Euclidean de-Sitter (genus zero) saddles are related to the presence of a classical entropic contribution associated to the target space geometry. The gravitating Sine-Gordon model corresponds to a well defined CFT by construction and the eigenvalues of the dual normal matrix model are supported in a compact region of the complex plane. The duality with the normal matrix model is operationally defined even for a finite, but sufficiently large matrix size $N$, depending on the precise observable to be determined. We define and study a "microscopic" version of the large-N limit that allows us to recover non-perturbative results for all physical observables.

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arXiv2025

Near-extremal quantum cross-section for charged fields and superradiance

We study the scattering and absorption properties of charged scalar fields on a near-extremal Reissner-Nordström black hole background. We show that in this low-temperature regime the near-horizon throat experiences large quantum fluctuations, whose leading contribution is described by the one dimensional Schwarzian effective action, while the soft $U(1)$ gauge modes can only contribute to subleading order. We investigate the role of the leading quantum effects both inside and outside the superradiant regime. These effects result in an enhanced reflection coefficient within the superradiant regime, while causing a suppression in the non-superradiant regime. On the other hand, the absorption cross-section increases in both regimes. Additional physical features appear as kinks in the reflection coefficient and absorption cross-section plots, corresponding to the shutdown of absorption in the superradiant regime and of stimulated emission in the non-superradiant regime.

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arXiv2025

Magnetic Anti-de Sitter Wormholes as seeds for Higgs Inflation

We show how certain types of magnetic asymptotically Anti-de Sitter Euclidean wormholes can catalyze the onset of inflation. These wormholes can be embedded as saddle point solutions of General Relativity coupled to the Standard Model, the inflaton being identified with the Higgs particle. Our scenario is based on the assumption that the quantum effective potential for the Higgs turns negative at a certain high energy window, in line with current measured values for the Higgs and Top quark masses. Within our proposal, we can estimate various parameters and physical quantities of interest, in consistency with current observational bounds.

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arXiv2024

An inflationary cosmology from anti-de Sitter wormholes

We propose a new type of wavefunction for the universe computed from the Euclidean path integral, with asymptotically $AdS$ boundary conditions. In the semiclassical limit, it describes a Euclidean (half)-wormhole geometry, exhibiting a local maximum of the scale factor at the surface of reflection symmetry, giving rise to an expanding universe upon analytic continuation to Lorentzian signature. We find that these Euclidean wormholes set natural initial conditions for inflation and that the semi-classical Wheeler-DeWitt wavefunction can favor a long lasting inflationary epoch, resolving a well known issue of the no-boundary proposal. Due to the asymptotic $AdS$ conditions in the Euclidean past they raise the possibility of describing the physics of inflating cosmologies and their perturbations within the context of holography.

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arXiv2024

Wilson Loops and Wormholes

We analyse the properties of Wilson loop observables for holographic gauge theories, when the dual bulk geometries have a single and/or multiple boundaries (Euclidean spacetime wormholes). Such observables lead to a generalisation and refinement of the characterisation in arXiv:2202.01372 based on the compressibility of cycles and the pinching limit of higher genus Riemann surfaces, since they carry information about the dynamics and phase structure of the dual gauge theory of an arbitrary dimensionality. Finally, we describe how backreacting correlated observables such as Wilson loops can lead to wormhole saddles in the dual gravitational path integral, by taking advantage of a representation theoretic entanglement structure proposed in arXiv:2110.14655 and arXiv:2204.01764 .

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arXiv2023

Black hole - wormhole transitions in two dimensional string theory

We study charged black hole and wormhole solutions of Type 0A/IIA string theory in two dimensions. There is a competition between Euclidean wormholes and near extremal black holes in the thermodynamic ensemble. In a certain regime of phase space, the former can disassociate into the latter. Since such solutions are of string scale near the wormhole throat that takes an $AdS_2$ form, there is a need for an exact worldsheet description. We discuss relevant WZW coset models which we we argue will shed light on this problem. Finally, we present appropriate versions of the Type 0A/IIA matrix quantum mechanics models that are expected to describe these geometries.

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arXiv2023

Emergent gravity from hidden sectors and TT deformations

We investigate emergent gravity extending the paradigm of the AdS/CFT correspondence. The emergent graviton is associated to the (dynamical) expectation value of the energy-momentum tensor. We derive the general effective description of such dynamics, and apply it to the case where a hidden theory generates gravity that is coupled to the Standard Model. In the linearized description, generically, such gravity is massive with the presence of an extra scalar degree of freedom. The propagators of both the spin-two and spin-zero modes are positive and well defined. The associated emergent gravitational theory is a bi-gravity theory, as is (secretly) the case in holography. The background metric on which the QFTs are defined, plays the role of dark energy and the emergent theory has always as a solution the original background metric. In the case where the hidden theory is holographic, the overall description yields a higher-dimensional bulk theory coupled to a brane. The effective graviton on the brane has four-dimensional characteristics both in the UV and IR and is always massive.

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arXiv2022

Microstates of a $2d$ Black Hole in string theory

We analyse models of Matrix Quantum Mechanics in the double scaling limit that contain non-singlet states. The finite temperature partition function of such systems contains non-trivial winding modes (vortices) and is expressed in terms of a group theoretic sum over representations. We then focus in the case when the first winding mode is dominant (model of Kazakov-Kostov-Kutasov). In the limit of large representations (continuous Young diagrams), and depending on the values of the parameters of the model such as the compactification radius and the string coupling, the dual geometric background corresponds to that of a long string (winding mode) condensate or a $2d$ (non-supersymmetric) Black Hole. In the matrix model we can tune these parameters and explore various phases and regimes. Our construction allows us to identify the origin of the microstates of these backgrounds, arising from non trivial representations, and paves the way for computing various observables on them.

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arXiv2022

Baby Universes born from the Void

We propose a novel construction of a third quantised baby universe Hilbert space $\mathcal{H}_{BU}$ for the quantum gravity path integral. In contrast to the original description of $α$-parameters, both the bulk and boundary microscopic parameters are fixed in our proposal. Wormholes and baby universes appear due to refined observables, of the boundary dual quantum field theories, that crucially involve the space of representations of the gauge group. Irreducible representations, on which the path integral factorises, give rise to field theoretic superselection sectors and replace the $α$ states.

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arXiv2022

Interacting systems and wormholes

We consider a class of tripartite systems for which two $d$-dimensional QFTs are cross-coupled via a third $d+1$-dimensional "messenger" QFT. We analyse in detail the example of a pair of one-dimensional matrix quantum mechanics, coupled via a two-dimensional theory of the BF-type and compute its partition function and simple correlators. This construction is extendible in higher dimensions, using a Chern-Simons "messenger" theory. In all such examples, the exact partition function acquires a form, speculated to correspond to systems dual to Euclidean wormholes and the cross correlators are sufficiently soft and consistent with analogous gravitational calculations. Another variant of the tripartite system is studied, where the messenger theory is described by a non-self-interacting (matrix)-field, reaching similar conclusions. While the Euclidean theories we consider are perfectly consistent, the two possible analytic continuations into Lorentzian signature (messenger vs. boundary QFT directions) of the tripartite models, reveal physical features and "pathologies" resembling those of the expected Lorentzian gravitational backgrounds.

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arXiv2021

Black Hole S-matrix for a scalar field

We describe a unitary scattering process, as observed from spatial infinity, of massless scalar particles on an asymptotically flat Schwarzschild black hole background. In order to do so, we split the problem in two different regimes governing the dynamics of the scattering process. The first describes the evolution of the modes in the region away from the horizon and can be analysed in terms of the effective Regge-Wheeler potential. In the near horizon region, where the Regge-Wheeler potential becomes insignificant, the WKB geometric optics approximation of Hawking's is replaced by the near-horizon gravitational scattering matrix that captures non-perturbative soft graviton exchanges near the horizon. We perform an appropriate matching for the scattering solutions of these two dynamical problems and compute the resulting Bogoliubov relations, that combines both dynamics. This allows us to formulate an S-matrix for the scattering process that is manifestly unitary. We discuss the analogue of the (quasi)-normal modes in this setup and the emergence of gravitational echoes that follow an original burst of radiation as the excited black hole relaxes to equilibrium.

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arXiv2021

Black holes, quantum chaos, and the Riemann hypothesis

Quantum gravity is expected to gauge all global symmetries of effective theories, in the ultraviolet. Inspired by this expectation, we explore the consequences of gauging CPT as a quantum boundary condition in phase space. We find that it provides for a natural semiclassical regularisation and discretisation of the continuous spectrum of a quantum Hamiltonian related to the Dilation operator. We observe that the said spectrum is in correspondence with the zeros of the Riemann zeta and Dirichlet beta functions. Following ideas of Berry and Keating, this may help the pursuit of the Riemann hypothesis. It strengthens the proposal that this quantum Hamiltonian captures the near horizon dynamics of the scattering matrix of the Schwarzschild black hole, given the rich chaotic spectrum upon discretisation. It also explains why the spectrum appears to be erratic despite the unitarity of the scattering matrix.

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arXiv2020

FZZT branes and non-singlets of Matrix Quantum Mechanics

We explore the non-singlet sector of matrix quantum mechanics dual to $c=1$ Liouville theory. The non-singlets are obtained by adding $N_{f}\times N$ bi-fundamental fields in the gauged matrix quantum mechanics model as well as a one dimensional Chern-Simons term. The present model is associated with a spin-Calogero model in the presence of external magnetic field. In chiral variables, the low energy excitations-currents satisfy an ${SU(2N_{f})}_{\tilde{k}}$ Kǎc-Moody algebra at large $N$. We analyse the canonical partition function as well as two and four point correlation functions, discuss a Gross-Witten-Wadia phase transition at large $N, N_f$ and study different limits of the parameters that allow us to recover the matrix model of Kazakov-Kostov-Kutasov conjectured to describe a two dimensional black hole. The grand canonical partition function is a $τ$- function obeying discrete soliton equations. We finally conjecture a possible dynamical picture for the formation of a black hole in terms of condensation of long-strings in the strongly coupled region of the Liouville direction.

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arXiv2019

Euclidean Wormholes and Holography

Asymptotically AdS wormhole solutions are considered in the context of holography. Correlation functions of local operators on distinct boundaries are studied. It is found that such correlators are finite at short distances. Correlation functions of non-local operators (Wilson loops) on distinct boundaries are also studied, with similar conclusions. Deformations of the theory with multi-trace operators on distinct boundaries are considered and studied. As a consequence of these results, the dual theory is expected to factorize in the UV, and the two sectors to be coupled by a soft non-local interaction. A simple field theory model with such behavior is presented.

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