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  • Journal article
    Bourget A, Grimminger JF, Hanany A, Kalveks R, Sperling M, Zhong Zet al., 2023,

    A tale of N cones

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Beccaria M, Tseytlin AA, 2023,

    Comments on ABJM free energy on S3 at large N and perturbative expansions in M-theory and string theory

    , Nuclear Physics B, Vol: 994, ISSN: 0550-3213

    We compare large N expansion of the localization result for the free energy F in the 3d N = 6 superconformal U(N)k × U(N)−k Chern-Simons-matter theory to its AdS/CFT counterpart, i.e. to the perturbativeexpansion of M-theory partition function on AdS4 × S7/Zk and to the weak string coupling expansionof type IIA effective action on AdS4 × CP3. We show that the general form of the perturbative expansions of F on the two sides of the AdS/CFT duality is indeed the same. Moreover, the transcendentalityproperties of the coefficients in the large N, large k expansion of F match those in the corresponding Mtheory or string theory expansions. To shed light on the structure of the 1-loop M-theory partition functionon AdS4 × S7/Zk we use the expression for the 1-loop 4-graviton scattering amplitude in the 11d supergravity. We also use the known information about the transcendental coefficients of the leading curvatureinvariants in the low-energy effective action of type II string theory. Matching of the remaining rationalfactors in the coefficients requires a precise information about currently unknown RR field strength termsin the corresponding superinvariants.
  • Journal article
    Piazza F, Tolley AJ, 2023,

    Subadditive average distances and quantum promptness

    , CLASSICAL AND QUANTUM GRAVITY, Vol: 40, ISSN: 0264-9381
  • Journal article
    Auclair P, Bacon D, Baker T, Barreiro T, Bartolo N, Belgacem E, Bellomo N, Ben-Dayan I, Bertacca D, Besancon M, Blanco-Pillado JJ, Blas D, Boileau G, Calcagni G, Caldwell R, Caprini C, Carbone C, Chang C-F, Chen H-Y, Christensen N, Clesse S, Comelli D, Congedo G, Contaldi C, Crisostomi M, Croon D, Cui Y, Cusin G, Cutting D, Dalang C, De Luca V, Pozzo WD, Desjacques V, Dimastrogiovanni E, Dorsch GC, Ezquiaga JM, Fasiello M, Figueroa DG, Flauger R, Franciolini G, Frusciante N, Fumagalli J, García-Bellido J, Gould O, Holz D, Iacconi L, Jain RK, Jenkins AC, Jinno R, Joana C, Karnesis N, Konstandin T, Koyama K, Kozaczuk J, Kuroyanagi S, Laghi D, Lewicki M, Lombriser L, Madge E, Maggiore M, Malhotra A, Mancarella M, Mandic V, Mangiagli A, Matarrese S, Mazumdar A, Mukherjee S, Musco I, Nardini G, No JM, Papanikolaou T, Peloso M, Pieroni M, Pilo L, Raccanelli A, Renaux-Petel S, Renzini AI, Ricciardone A, Riotto A, Romano JD, Rollo R, Pol AR, Morales ER, Sakellariadou M, Saltas ID, Scalisi M, Schmitz K, Schwaller P, Sergijenko O, Servant G, Simakachorn P, Sorbo L, Sousa L, Speri L, Steer DA, Tamanini N, Tasinato G, Torrado J, Unal C, Vennin V, Vernieri D, Vernizzi F, Volonteri M, Wachter JM, Wands D, Witkowski LT, Zumalacárregui M, Annis J, Ares FR, Avelino PP, Avgoustidis A, Barausse E, Bonilla A, Bonvin C, Bosso P, Calabrese M, Çalışkan M, Cembranos JAR, Chala M, Chernoff D, Clough K, Criswell A, Das S, Silva AD, Dayal P, Domcke V, Durrer R, Easther R, Escoffier S, Ferrans S, Fryer C, Gair J, Gordon C, Hendry M, Hindmarsh M, Hooper DC, Kajfasz E, Kopp J, Koushiappas SM, Kumar U, Kunz M, Lagos M, Lilley M, Lizarraga J, Lobo FSN, Maleknejad A, Martins CJAP, Meerburg PD, Meyer R, Mimoso JP, Nesseris S, Nunes N, Oikonomou V, Orlando G, Özsoy O, Pacucci F, Palmese A, Petiteau A, Pinol L, Zwart SP, Pratten G, Prokopec T, Quenby J, Rastgoo S, Roest D, Rummukainen K, Schimd C, Secroun A, Sesana A, Sopuerta CF, Tereno I, Tolley A, Urrestilla J, Vagenas EC, van de Vis J, van de Weyget al., 2023,

    Cosmology with the Laser Interferometer Space Antenna

    , Living Reviews in Relativity, Vol: 26, ISSN: 1433-8351

    The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.
  • Journal article
    Gkountoumis G, Hull C, Stemerdink K, Vandoren Set al., 2023,

    Freely acting orbifolds of type IIB string theory on T<SUP>5</SUP>

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    De Rham C, Jaitly S, Tolley AJ, 2023,

    Constraints on Regge behavior from IR physics

    , Physical Review D, Vol: 108, ISSN: 2470-0010

    We consider positivity constraints applicable to the effective field theory (EFT) of gravity in arbitrary dimensions. By considering scattering of indefinite initial and final states, we highlight the existence of a gravitational scattering amplitude for which full crossing symmetry is manifest and utilize the recently developed crossing symmetric dispersion relations to derive compact nonlinear bounds. We show that the null constraints built into these dispersion relations lead to a finite energy sum rule for gravity which may be extended to a one-parameter family of continuous moment sum rules. These sum rules enforce a UV-IR relation which imposes constraints on both the Regge trajectory and residue. We also highlight a situation where the Regge trajectory is uniquely determined in terms of the sub-Regge scale amplitude. Generically the Regge behavior may be split into an IR sensitive part calculable within a given EFT, which mainly depends on the lightest fields in nature, and an IR independent part, which is subject to universal positivity constraints following from unitarity and analyticity.
  • Journal article
    Smith GR, Waldram D, 2023,

    M-theory moduli from exceptional complex structures

    , The Journal of High Energy Physics, Vol: 2023, ISSN: 1029-8479

    We continue the analysis of the geometry of generic Minkowski N = 1, D = 4flux compactifications in M-theory using exceptional generalised geometry, including thecalculation of the infinitesimal moduli spaces. The backgrounds can be classified into twoclasses: type-0 and type-3. For type-0, we review how the moduli arise from standard deRham cohomology classes. We also argue that, under reasonable assumptions, there areno appropriate sources to support compact flux backgrounds for this class and so the onlysolutions are in fact G2 geometries. For type-3 backgrounds, given a suitable ∂0∂¯0-lemma,we show that the moduli can be calculated from a cohomology based on an involutive subbundle of the complexified tangent space. Using a simple spectral sequence we prove quitegenerally that the presence of flux can only reduce the number of moduli compared withthe fluxless case. We then use the formalism to calculate the moduli of heterotic M-theoryand show they match those of the dual Hull-Strominger system as expected.
  • Journal article
    Dowker F, Zalel S, 2023,

    Observables for cyclic causal set cosmologies

    , Classical and Quantum Gravity, Vol: 40, ISSN: 0264-9381

    In causal set theory, cycles of cosmic expansion and collapse are modelled by causal sets with 'breaks' and 'posts' and a special role is played by cyclic dynamics in which the universe goes through perpetual cycles. We identify and characterise two algebras of observables for cyclic dynamics in which the causal set universe has infinitely many breaks. The first algebra is constructed from the cylinder sets associated with finite causal sets that have a single maximal element and offers a new framework for defining cyclic dynamics as random walks on a novel tree. The second algebra is generated by a collection of stem-sets and offers a physical interpretation of the observables in these models as statements about unlabelled stems with a single maximal element. There are analogous theorems for cyclic dynamics in which the causal set universe has infinitely many posts.
  • Journal article
    Babak S, Caprini C, Figueroa DG, Karnesis N, Marcoccia P, Nardini G, Pieroni M, Ricciardone A, Sesana A, Torrado Jet al., 2023,

    Stochastic gravitational wave background from stellar origin binary black holes in LISA

    , Journal of Cosmology and Astroparticle Physics, Vol: 2023

    We use the latest constraints on the population of stellar origin binary black holes (SOBBH) from LIGO/Virgo/KAGRA (LVK) observations, to estimate the stochastic gravitational wave background (SGWB) they generate in the frequency band of LISA. In order to account for the faint and distant binaries, which contribute the most to the SGWB, we extend the merger rate at high redshift assuming that it tracks the star formation rate. We adopt different methods to compute the SGWB signal: we perform an analytical evaluation, we use Monte Carlo sums over the SOBBH population realisations, and we account for the role of the detector by simulating LISA data and iteratively removing the resolvable signals until only the confusion noise is left. The last method allows the extraction of both the expected SGWB and the number of resolvable SOBBHs. Since the latter are few for signal-to-noise ratio thresholds larger than five, we confirm that the spectral shape of the SGWB in the LISA band agrees with the analytical prediction of a single power law. We infer the probability distribution of the SGWB amplitude from the LVK GWTC-3 posterior of the binary population model: at the reference frequency of 0.003 Hz it has an interquartile range of h2ΩGW(f = 3 × 10-3 Hz) ∈ [5.65, 11.5] × 10-13, in agreement with most previous estimates. We then perform a MC analysis to assess LISA's capability to detect and characterise this signal. Accounting for both the instrumental noise and the galactic binaries foreground, with four years of data, LISA will be able to detect the SOBBH SGWB with percent accuracy, narrowing down the uncertainty on the amplitude by one order of magnitude with respect to the range of possible amplitudes inferred from the population model. A measurement of this signal by LISA will help to break the degeneracy among some of the population parameters, and provide interesting constraints, in particular on the redshift evolution of the SOBBH merger rate.
  • Journal article
    Evnin O, Mkrtchyan K, 2023,

    Three approaches to chiral form interactions

    , DIFFERENTIAL GEOMETRY AND ITS APPLICATIONS, Vol: 89, ISSN: 0926-2245
  • Journal article
    Mentasti G, Contaldi CR, Peloso M, 2023,

    Prospects for detecting anisotropies and polarization of the stochastic gravitational wave background with ground-based detectors

    , Journal of Cosmology and Astroparticle Physics, Vol: 2023, Pages: 053-053, ISSN: 1475-7516

    We build an analytical framework to study the observability of anisotropies and a net chiral polarization of the Stochastic Gravitational Wave Background (SGWB) with a generic network of ground-based detectors. We apply this formalism to perform a Fisher forecast of the performance of a network consisting of the current interferometers (LIGO, Virgo and KAGRA) and planned third-generation ones, such as the Einstein Telescope and Cosmic Explorer. Our results yield limits on the observability of anisotropic modes, spanning across noise- and signal-dominated regimes. We find that if the isotropic component of the SGWB has an amplitude close to the current limit, third-generation interferometers with an observation time of 10 years can measure multipoles (in a spherical harmonic expansion) up to ℓ = 8 with Script O(10-3 – 10-2) accuracy relative to the isotropic component, and an Script O(10-3) amount of net polarization. For weaker signals, the accuracy worsens as roughly the inverse of the SGWB amplitude.
  • Journal article
    Alexandre B, Isichei R, Magueijo J, 2023,

    Unitary and Vilenkin's wave functions

    , Physical Review D, Vol: 108, ISSN: 2470-0010

    It is remarkably difficult to reconcile unitarity and Vilenkin’s wave function. For example, the natural conserved inner product found in quantum unimodular gravity applies to the Hartle-Hawking wave function, but fails for its Vilenkin counterpart. We diagnose this failure from different angles (Laplace transform instead of Fourier transform, non-Hermiticity of the Hamiltonian, etc.) to conclude that ultimately it stems from allowing the connection to become imaginary in a section of its contour. In turn this is the unavoidable consequence of representing the Euclidean theory as an imaginary image within a fundamentally Lorentzian theory. It is nonetheless possible to change the underlying theory and replace the connection’s foray into the imaginary axis by an actual signature change (with the connection, action and Hamiltonian remaining real). The structural obstacles to unitarity are then removed, but special care must still be taken, because the Euclidean theory a priori has boundaries, so that appropriate boundary conditions are required for unitarity. Reflecting boundary conditions would reinstate a Hartle-Hawking-like solution in the Lorentzian regime. To exclude an incoming wave in the Lorentzian domain one must allow a semi-infinite tower of spheres in the Euclidean region, wave packets traveling through successive spheres for half an eternity in unimodular time. Such a “Sisyphus” boundary condition no longer even vaguely resembles Vilenkin’s original proposal.
  • Journal article
    Chester SM, Dupuis É, Witczak-Krempa W, 2023,

    Evidence for web of dualities from monopole operators

    , Physical Review D, Vol: 108, ISSN: 2470-0010
  • Journal article
    Branchesi M, Maggiore M, Alonso D, Badger C, Banerjee B, Beirnaert F, Belgacem E, Bhagwat S, Boileau G, Borhanian S, Brown DD, Chan ML, Cusin G, Danilishin SL, Degallaix J, De Luca V, Dhani A, Dietrich T, Dupletsa U, Foffa S, Franciolini G, Freise A, Gemme G, Goncharov B, Ghosh A, Gulminelli F, Gupta I, Gupta PK, Harms J, Hazra N, Hild S, Hinderer T, Heng IS, Iacovelli F, Janquart J, Janssens K, Jenkins AC, Kalaghatgi C, Koroveshi X, Li TGF, Li Y, Loffredo E, Maggio E, Mancarella M, Mapelli M, Martinovic K, Maselli A, Meyers P, Miller AL, Mondal C, Muttoni N, Narola H, Oertel M, Oganesyan G, Pacilio C, Palomba C, Pani P, Pasqualetti A, Perego A, Perigois C, Pieroni M, Piccinni OJ, Puecher A, Puppo P, Ricciardone A, Riotto A, Ronchini S, Sakellariadou M, Samajdar A, Santoliquido F, Sathyaprakash BS, Steinlechner J, Steinlechner S, Utina A, Broeck CVD, Zhang Tet al., 2023,

    Science with the Einstein Telescope: a comparison of different designs

    , JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516
  • Journal article
    Hartwig O, Lilley M, Muratore M, Pieroni Met al., 2023,

    Stochastic gravitational wave background reconstruction for a nonequilateral and unequal-noise LISA constellation

    , Physical Review D, Vol: 107, ISSN: 2470-0010

    We explore the impact of choosing different sets of time-delay interferometry (TDI) variables for detecting and reconstructing stochastic gravitational wave background (SGWB) signals and estimating the instrumental noise in LISA. Most works in the literature build their data analysis pipelines relying on a particular set of TDI channels, the so-called AET variables, which are orthogonal under idealized conditions. By relaxing the assumption of a perfectly equilateral LISA configuration, we investigate to which degree these channels remain orthogonal and compare them to other TDI channels. We show that different sets of TDI variables are more robust under perturbations of the perfect equilateral configuration, better preserving their orthogonality and, thus, leading to a more accurate estimate of the instrumental noise. Moreover, we investigate the impact of considering the noise levels associated with each instrumental noise source to be independent of one another, generalizing the analysis from two to twelve noise parameters. We find that, in this scenario, the assumption of orthogonality is broken for all the TDI variables, leading to a misestimation of measurement error for some of the noise parameters. Remarkably, we find that for a flat power-law signal, the reconstruction of the signal parameters is nearly unaffected in these various configurations.
  • Journal article
    de Rham C, Garcia-Saenz S, Heisenberg L, Pozsgay V, Wang Xet al., 2023,

    To half-be or not to be?

    , The Journal of High Energy Physics, Vol: 2023, Pages: 1-31, ISSN: 1029-8479

    It has recently been argued that half degrees of freedom could emerge in Lorentz and parity invariant field theories, using a non-linear Proca field theory dubbed Proca-Nuevo as a specific example. We provide two proofs, using the Lagrangian and Hamiltonian pictures, that the theory possesses a pair of second class constraints, leaving D − 1 degrees of freedom in D spacetime dimensions, as befits a consistent Proca model. Our proofs are explicit and straightforward in two dimensions and we discuss how they generalize to an arbitrary number of dimensions. We also clarify why local Lorentz and parity invariant field theories cannot hold half degrees of freedom.
  • Journal article
    Beccaria M, Korchemsky GP, Tseytlin AA, 2023,

    Non-planar corrections in orbifold/orientifold <i>N</i>=2 superconformal theories from localization

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Giombi S, Tseytlin AA, 2023,

    Wilson Loops at Large N and the Quantum M2-Brane

    , PHYSICAL REVIEW LETTERS, Vol: 130, ISSN: 0031-9007
  • Journal article
    Camargo-Molina JE, Rajantie A, 2023,

    Phase transitions in de Sitter spacetimes: The stochastic formalism

    , PHYSICAL REVIEW D, Vol: 107, ISSN: 2470-0010
  • Journal article
    Dunning J, Burke T, Chan AHH, Chik HYJ, Evans T, Schroeder Jet al., 2023,

    Opposite-sex associations are linked with annual fitness, but sociality is stable over lifetime

    , Behavioral Ecology, Vol: 315, Pages: 315-324, ISSN: 1045-2249

    Animal sociality, an individual’s propensity to associate with others, has fitness consequences through mate choice, for example, directly, by increasing the pool of prospective partners, and indirectly through increased survival, and individuals benefit from both. Annually, fitness consequences are realized through increased mating success and subsequent fecundity. However, it remains unknown whether these consequences translate to lifetime fitness. Here, we quantified social associations and their link to fitness annually and over lifetime, using a multi-generational, genetic pedigree. We used social network analysis to calculate variables representing different aspects of an individual’s sociality. Sociality showed high within-individual repeatability. We found that birds with more opposite-sex associates had higher annual fitness than those with fewer, but this did not translate to lifetime fitness. Instead, for lifetime fitness, we found evidence for stabilizing selection on opposite-sex sociality, and sociality in general, suggesting that reported benefits are only short-lived in a wild population, and that selection favors an average sociality.
  • Journal article
    Mawby C, Halliwell JJ, 2023,

    Leggett-Garg violations for continuous-variable systems with Gaussian states

    , PHYSICAL REVIEW A, Vol: 107, ISSN: 2469-9926
  • Journal article
    Gledhill K, Hanany A, 2023,

    Poisson brackets for some Coulomb branches

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Camargo-Molina JE, Gonzalez MC, Rajantie A, 2023,

    Phase transitions in de Sitter spacetimes: Quantum Corrections

    , PHYSICAL REVIEW D, Vol: 107, ISSN: 2470-0010
  • Journal article
    Alexandre B, Magueijo J, 2023,

    Unimodular Hartle-Hawking wave packets and their probability interpretation

    , Physical Review D, Vol: 107, ISSN: 2470-0010

    We reexamine the Hartle-Hawking wave function from the point of view of a quantum theory whichstarts from the connection representation and allows for off-shell nonconstancy of Λ (as in unimodulartheory), with a concomitant dual relational time variable. By translating its structures to the metricrepresentation we find a nontrivial inner product rendering wave packets of Hartle-Hawking wavesnormalizable and the time evolution unitary; however, the implied probability measure differssignificantly from the naive jψj2. In contrast with the (monochromatic) Hartle-Hawking wave function,these packets form traveling waves with a probability peak describing de Sitter space, except near thebounce, where the incident and reflected waves interfere, transiently recreating the usual standing wave.Away from the bounce the packets get sharper both in metric and connection space, an apparentcontradiction with Heisenberg’s principle allowed by the fact that the metric is not Hermitian, eventhough its eigenvalues are real. Near the bounce, the evanescent wave not only penetrates into theclassically forbidden region but also extends into the a2 < 0 Euclidean domain. We work out thepropagators for this theory and relate them to the standard ones. The a ¼ 0 point (aka the “nothing”) isunremarkable, and in any case a wave function peaked therein is typically non-normalizable and/orimplies a nonsensical probability for Λ (which the Universe would preserve forever). Within this theory itmakes more sense to adopt a Gaussian state in an appropriate function of Λ, and use the probabilityassociated with the evanescent wave present near the time of the bounce as a measure of the likelihood ofcreation of a pair of time-symmetric semiclassical Universes.
  • Journal article
    Mkrtchyan K, Valach F, 2023,

    Democratic actions for type II supergravities

    , PHYSICAL REVIEW D, Vol: 107, ISSN: 2470-0010
  • Journal article
    Boido A, Gauntlett JP, Martelli D, Sparks Jet al., 2023,

    Entropy functions for accelerating black holes

    , Physical Review Letters, Vol: 130, ISSN: 0031-9007

    We introduce an entropy function for supersymmetric accelerating black holes in four-dimensional anti–de Sitter space that uplift on general Sasaki-Einstein manifolds X7 to solutions of M theory. This allows oneto compute the black hole entropy without knowing the explicit solutions. A dual holographic microstatecounting would follow from computing certain supersymmetric partition functions of Chern-Simonsmatter theories compactified on a spindle. We make a general prediction for a class of such partitionfunctions in terms of “blocks,” with each block being constructed from the partition function on a threesphere
  • Journal article
    Aharony O, Chester SM, Sheaffer T, Urbach EYet al., 2023,

    Explicit holography for vector models at finite N, volume and temperature

    , Journal of High Energy Physics, Vol: 2023

    <jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>In previous work we constructed an explicit mapping between large <jats:italic>N</jats:italic> vector models (free or critical) in <jats:italic>d</jats:italic> dimensions and a non-local high-spin gravity theory on <jats:italic>AdS</jats:italic><jats:sub><jats:italic>d</jats:italic>+1</jats:sub>, such that the gravitational theory reproduces the field theory correlation functions order by order in 1<jats:italic>/N</jats:italic>. In this paper we discuss three aspects of this mapping. First, our original mapping was not valid non-perturbatively in 1<jats:italic>/N</jats:italic>, since it did not include non- local correlations between the gravity fields which appear at finite <jats:italic>N</jats:italic>. We show that by using a bi-local <jats:italic>G</jats:italic> − Σ type formalism similar to the one used in the SYK model, we can construct an exact mapping to the bulk that is valid also at finite <jats:italic>N</jats:italic>. The theory in the bulk contains additional auxiliary fields which implement the finite <jats:italic>N</jats:italic> constraints. Second, we discuss the generalization of our mapping to the field theory on <jats:italic>S</jats:italic><jats:sup><jats:italic>d</jats:italic></jats:sup>, and in particular how the sphere free energy matches exactly between the two sides, and how the mapping can be consistently regularized. Finally, we discuss the field theory at finite temperature, and show that the low-temperature phase of the vector models can be mapped to a high-spin gravity theory on thermal AdS space.</jats:p>
  • Journal article
    Baker T, Barausse E, Chen A, de Rham C, Pieroni M, Tasinato Get al., 2023,

    Testing gravitational wave propagation with multiband detections

    , Journal of Cosmology and Astroparticle Physics, Vol: 2023, Pages: 1-21, ISSN: 1475-7516

    Effective field theories (EFT) of dark energy (DE) — built to parameterise the properties of DE in an agnostic manner — are severely constrained by measurements of the propagation speed of gravitational waves (GW). However, GW frequencies probed by ground-based interferometers lie around the typical strong coupling scale of the EFT, and it is likely that the effective description breaks down before even reaching that scale. We discuss how this leaves the possibility that an appropriate ultraviolet completion of DE scenarios, valid at scales beyond an EFT description, can avoid present constraints on the GW speed. Instead, additional constraints in the lower frequency LISA band would be harder to escape, since the energies involved are orders of magnitude lower. By implementing a method based on GW multiband detections, we show indeed that a single joint observation of a GW150914-like event by LISA and a terrestrial interferometer would allow one to constrain the speed of light and gravitons to match to within 10-15. Multiband GW observations can therefore firmly constrain scenarios based on the EFT of DE, in a robust and unambiguous way.
  • Journal article
    Gielen S, Magueijo J, 2023,

    Quantum resolution of the cosmological singularity without new physics

    , EPL, Vol: 141, ISSN: 0302-072X

    We study a quantum Hot Big Bang in the connection representation, with a matter constant of motion m whose conjugate defines time. Superpositions in m induce a unitary inner product. The wave function reveals a resolution of the singularity problem without new physics or supplementary boundary conditions. Backtracking in time, the probability peak eventually halts at a maximum curvature, its height dropping thereafter while a symmetric contracting peak rises. The Big Bang is replaced by a superposition of contracting and expanding regular Universes. We contrast these findings with the situation in the metric representation, where boundary conditions at the singularity are needed for unitary evolution.
  • Journal article
    Lehners J-L, Leung R, Stelle KS, 2023,

    How to create universes with internal flux

    , PHYSICAL REVIEW D, Vol: 107, ISSN: 2470-0010

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