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  • Journal article
    Dowker F, Sorkin RD, 2023,

    An intrinsic causality principle in histories-based quantum theory: a proposal

    , Journal of Physics A: Mathematical and Theoretical, Vol: 56, ISSN: 1751-8113

    Relativistic causality (RC) is the principle that no cause can act outside its future light cone, but any attempt to formulate this principle more precisely will depend on the foundational framework that one adopts for quantum theory. Adopting a histories-based (or 'path integral') framework, we relate RC to a condition we term 'Persistence of Zero' (PoZ), according to which an event E of measure zero remains forbidden if one forms its conjunction with any other event associated to a spacetime region that is later than or spacelike to that of E. We also relate PoZ to the Bell inequalities by showing that, in combination with a second, more technical condition it leads to the quantal counterpart of Fine's patching theorem in much the same way as Bell's condition of local causality leads to Fine's original theorem. We then argue that RC per se has very little to say on the matter of which correlations can occur in nature and which cannot. From the point of view we arrive at, histories-based quantum theories are nonlocal in spacetime, and fully in compliance with RC.
  • Conference paper
    Gheorghiade P, Price H, Rivers R, 2023,

    The importance of geography to the networked Late Bronze Age Aegean

    , Socio-Environmental Dynamics over tha last 15,000 years: The Creation of Landscapes VI, ISSN: 2590-1222
  • Journal article
    Tseytlin AA, 2023,

    Comments on a 4-derivative scalar theory in 4 dimensions

    , Theoretical and Mathematical Physics, Vol: 217, Pages: 1969-1986, ISSN: 0040-5779

    We review and elaborate on some aspects of the classically scale-invariant renormalizable 4-derivative scalartheory L = φ ∂4φ + g(∂φ)4. Similar models appear, e.g., in the context of conformal supergravity or inthe description of the crystalline phase of membranes. Considering this theory in Minkowski signature, wesuggest how to define Poincar´e-invariant scattering amplitudes by assuming that only massless oscillating(nongrowing) modes appear as external states. In such shift-symmetric interacting theory, there are no IRdivergences despite the presence of 1/q4 internal propagators. We discuss how nonunitarity of this theorymanifests itself at the level of the one-loop massless scattering amplitude.
  • Journal article
    Tseytlin AA, 2023,

    Quantum supermembranes and AdS/CFT duality

    , Journal of Experimental and Theoretical Physics, Vol: 137, Pages: 846-863, ISSN: 1063-7761

    We review and extend some recent work on testing AdS/CFT correspondence between U(N)k × U(N)–k Chern-Simons-matter 3d gauge theory and M-theory in AdS4 × S7/Zk background. We demonstrate that 1-loop term in the quantum M2 brane partition function expanded near a classical solution correctly matches localization predictions on the gauge theory side in the case of BPS Wilson loop expectation value and instanton corrections to free energy.
  • Journal article
    Jazayeri S, Renaux-Petel S, Werth D, 2023,

    Shapes of the cosmological low-speed collider

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

    Massive particles produced during inflation leave specific signatures in soft limits of correlation functions of primordial fluctuations. When the Goldstone boson of broken time translations acquires a reduced speed of sound, implying that de Sitter boosts are strongly broken, we introduce a novel discovery channel to detect new physics during inflation, called the cosmological low-speed collider signal. This signal is characterised by a distinctive resonance lying in mildly-soft kinematic configurations of cosmological correlators, indicating the presence of a heavy particle, whose position enables to reconstruct its mass. We show that this resonance can be understood in terms of a non-local single-field effective field theory, in which the heavy field becomes effectively non-dynamical. This theory accurately describes the full dynamics of the Goldstone boson and captures all multi-field physical effects distinct from the non-perturbative particle production leading to the conventional cosmological collider signal. As such, this theory provides a systematic and tractable way to study the imprint of massive fields on cosmological correlators. We conduct a thorough study of the low-speed collider phenomenology in the scalar bispectrum, showing that large non-Gaussianities with new shapes can be generated, in particular beyond weak mixing. We also provide a low-speed collider template for future cosmological surveys.
  • Journal article
    Jazayeri S, Renaux-Petel S, 2023,

    Cosmological bootstrap in slow motion

    , The Journal of High Energy Physics, Vol: 2022, ISSN: 1029-8479

    Speed matters. How the masses and spins of new particles active during inflation can be read off from the statistical properties of primordial density fluctuations is well understood. However, not when the propagation speeds of the new degrees of freedom and of the curvature perturbation differ, which is the generic situation in the effective field theory of inflationary fluctuations. Here we use bootstrap techniques to find exact analytical solutions for primordial 2-,3- and 4-point correlators in this context. We focus on the imprints of a heavy relativistic scalar coupled to the curvature perturbation that propagates with a reduced speed of sound cs, hence strongly breaking de Sitter boosts. We show that akin to the de Sitter invariant setup, primordial correlation functions can be deduced by acting with suitable weight-shifting operators on the four-point function of a conformally coupled field induced by the exchange of the massive scalar. However, this procedure requires the analytical continuation of this seed correlator beyond the physical domain implied by momentum conservation. We bootstrap this seed correlator in the extended domain from first principles, starting from the boundary equation that it satisfies due to locality. We further impose unitarity, reflected in cosmological cutting rules, and analyticity, by demanding regularity in the collinear limit of the four-point configuration, in order to find the unique solution. Equipped with this, we unveil that heavy particles that are lighter than H/cs leave smoking gun imprints in the bispectrum in the form of resonances in the squeezed limit, a phenomenon that we call the low speed collider. We characterise the overall shape of the signal as well as its unusual logarithmic mass dependence, both vividly distinct from previously identified signatures of heavy fields. Eventually, we demonstrate that these features can be understood in a simplified picture in which the heavy field is integrated out, albeit
  • Journal article
    Gheorghiade P, Vasiliauskaite V, Diachenko A, Price H, Evans T, Rivers Ret al., 2023,

    Entropology: an information-theoretic approach to understanding archaeological data

    , Journal of Archaeological Method and Theory, Vol: 30, Pages: 1109-1141, ISSN: 1072-5369

    The main objective of this paper is to develop quantitative measures for describing the diversity, homogeneity, and similarity of archaeological data. It presents new approaches to characterize the relationship between archaeological assemblages by utilizing entropy and its related attributes, primarily diversity, and by drawing inspiration from ecology. Our starting premise is that diachronic changes in our data provide a distorted reflection of social processes and that spatial differences in data indicate cultural distancing. To investigate this premise, we adopt a parsimonious approach for comparing assemblage profiles employing and comparing a range of (Hill) diversities, which enable us to exploit different aspects of the data. The modelling is tested on two seemingly large datasets: a Late Bronze Age Cretan dataset with circa 13,700 entries (compiled by PG); and a 4th millennium Western Tripolye dataset with circa 25,000 entries (compiled by AD). The contrast between the strongly geographically and culturally heterogeneous Bronze Age Crete and the strongly homogeneous Western Tripolye culture in the Southern Bug and Dnieper interfluve show the successes and limitations of our approach. Despite the seemingly large size of our datasets, these data highlight limitations that confine their utility to non-semantic analysis. This requires us to consider different ways of treating and aggregating assemblages, either as censuses or samples, contingent upon the degree of representativeness of the data. While our premise, that changes in data reflect societal changes, is supported, it is not definitively confirmed. Consequently, this paper also exemplifies the limitations of large archaeological datasets for such analyses.
  • Journal article
    Diachenko A, Rivers RJ, Sobkowiak-Tabaka I, 2023,

    Convergent evolution of prehistoric technologies: the entropy and diversity of limited solutions

    , Journal of Archaeological Method and Theory, Vol: 30, Pages: 1168-1199, ISSN: 1072-5369

    Linking the likelihood of convergent evolution to the technologies’ complexity, this paper identifies the scales of technological diffusion and convergence, i.e., the evolving of structures that are similar, but not related to a common “ancestor.” Our study provides quantitative measures for understanding complexity and connectivity in technologies. The utility of our approach is exemplified through the case study of Cucuteni-Tripolye pottery kilns in Chalcolithic Southeastern Europe. The analysis shows that technological evolution has to be scaled to the “technologically important” (in quantitative terms) component parts, whose introduction shapes a ground for extinction and self-evolvement caused by the cascade effects along technological design structure. Similar technological solutions to the technological design structure engender the spread of similar devices in various locations. Surprisingly, such a broad distribution may be the result of relatively low internal diversity, rather than arising from higher efficiency. This gives some reasons for the underestimation of convergence as a mechanism for evolution of technology in current prehistoric archaeology.
  • Book
    , 2023,

    Encyclopedia of Cosmology, The, Set 2: Frontiers in Cosmology (in 3 Volumes)

    , ISBN: 9789811289699

    Together, these volumes will be a comprehensive review of the most important current topics in cosmology, discussing the important concepts and current status in each field, covering both theory and observation.These three volumes are ...
  • Book chapter
    Rivers R, Paliou E, Evans T, 2023,

    Gravity and Maximum Entropy Models

    , The Oxford Handbook of Archaeological Network Research, Editors: Brughmans, Mills, Munson, Peeples, Publisher: Oxford University Press, Pages: 186-199, ISBN: 9780198854265

    Gravity models are a class of quantitative models that can be used for describing the spatial characteristics of social interactions, providing a realization of Tobler’s “law” of geography that “near things are more related than distant things.” In archaeology, they are particularly suited for describing historic and prehistoric “exchange” and “settlement formation.” Although, quantitatively, they were originally little more than mimicry of Newtonian gravitation, they arise naturally in some forms of economic modeling and as the “most likely” outcomes (MaxEnt) from limited knowledge. We discuss several of their key applications to archaeological data.
  • Journal article
    Magueijo J, 2023,

    Evolving laws and cosmological energy

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 108, ISSN: 1550-2368

    We couple the issue of evolution in the laws of physics with that of violations of energy conservation. Avoiding a time dependence in terms of coordinate time, we define evolution as a function of time variables canonically dual to “constants” (such as Λ, the Planck mass, or the gravitational coupling), mimicking a procedure associated with one formulation of unimodular gravity. We then introduce variability via a dependence of other fundamental “constants” on these clocks. Although this is not needed, sharper results are obtained if this procedure violates local Lorentz invariance, which we define in the spirit of Horava-Lifshitz theories (modifying a 3+1 split action, so that a Lorentz invariant 4D reassembly is no longer possible). We find that variability in the “laws of physics” generically leads to violations of energy conservation if either a matter parameter varies as a function of a gravitational clock, or a gravity parameter depends on a matter clock, with the other combinations sterile. In general the matter components associated with the varying parameter or the clock absorb or give off the violated energy. We illustrate this with a variety of clocks (ticking unimodular time, Ricci time, etc.) and parameters (mainly the gravitational and matter speed of light, but also Λ). We can accommodate in this construction (and improve on) several early varying speed of light models, allowing for variability effects related to the spatial curvature and Λ to cause creation of radiation and a hot big bang.
  • Journal article
    Benetti Genolini P, Gauntlett JP, Sparks J, 2023,

    Localizing wrapped M5-branes and gravitational blocks

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

    We consider d ¼ 2, N ¼ ð0; 2Þ SCFTs that can arise from M5-branes wrapping four-dimensional,complex, toric manifolds and orbifolds. We use equivariant localization to compute the off-shell centralcharge of the dual supergravity solutions, obtaining a result that can be written as a sum of gravitationalblocks and precisely agrees with a field theory computation using anomaly polynomials and cextremization.
  • Journal article
    Sirks EL, Massey R, Gill AS, Anderson J, Benton SJ, Brown AM, Clark P, English J, Everett SW, Fraisse AA, Franco H, Hartley JW, Harvey D, Holder B, Hunter A, Huff EM, Hynous A, Jauzac M, Jones WC, Joyce N, Kennedy D, Lagattuta D, Leung JSY, Li L, Lishman S, Luu TVT, McCleary JE, Nagy JM, Netterfield CB, Paracha E, Purcaru R, Redmond SF, Rhodes JD, Robertson A, Romualdez LJ, Roth S, Salter R, Schmoll J, Shaaban MM, Smith R, Smith R, Tam SI, Vassilakis GNet al., 2023,

    Data Downloaded via Parachute from a NASA Super-Pressure Balloon

    , Aerospace, Vol: 10

    In April 2023, the superBIT telescope was lifted to the Earth’s stratosphere by a helium-filled super-pressure balloon to acquire astronomical imaging from above (99.5% of) the Earth’s atmosphere. It was launched from New Zealand and then, for 40 days, circumnavigated the globe five times at a latitude 40 to 50 degrees south. Attached to the telescope were four “drs” (Data Recovery System) capsules containing 5 TB solid state data storage, plus a gnss receiver, Iridium transmitter, and parachute. Data from the telescope were copied to these, and two were dropped over Argentina. They drifted 61 km horizontally while they descended 32 km, but we predicted their descent vectors within 2.4 km: in this location, the discrepancy appears irreducible below ∼2 km because of high speed, gusty winds and local topography. The capsules then reported their own locations within a few metres. We recovered the capsules and successfully retrieved all of superBIT’s data despite the telescope itself being later destroyed on landing.
  • Journal article
    de Rham C, Kozuszek J, Tolley AJ, Wiseman Tet al., 2023,

    Dynamical formulation of ghost-free massive gravity

    , PHYSICAL REVIEW D, Vol: 108, ISSN: 2470-0010
  • Journal article
    Toomey MW, Koushiappas SM, Alexandre B, Magueijo Jet al., 2023,

    Quantum gravity signatures in the late Universe

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

    We calculate deviations in cosmological observables as a function of parameters in a class of connection-based models of quantum gravity. In this theory nontrivial modifications to the background cosmology can occur due to a distortion of the wave function of the Universe at the transition from matter to dark energy domination (which acts as a “reflection” in connection space). We are able to exclude some regions of parameter space and show with projected constraints that future experiments like DESI will be able to further constrain these models. An interesting feature of this theory is that there exists a region of parameter space that could naturally alleviate the S8 tension.
  • Journal article
    Beccaria M, Giombi S, Tseytlin AA, 2023,

    Instanton contributions to the ABJM free energy from quantum M2 branes

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Boido A, Gauntlett JP, Martelli D, Sparks Jet al., 2023,

    Gravitational blocks, spindles and GK geometry

    , Communications in Mathematical Physics, Vol: 403, Pages: 917-1003, ISSN: 0010-3616

    We derive a gravitational block formula for the supersymmetric action for ageneral class of supersymmetric AdS solutions, described by GK geometry. Extremalpoints of this action describe supersymmetric AdS3 solutions of type IIB supergravity,sourced by D3-branes, and supersymmetric AdS2 solutions of D = 11 supergravity,sourced by M2-branes. In both cases, the branes are also wrapped over a two-dimensionalorbifold known as a spindle, or a two-sphere. We develop various geometric methodsfor computing the gravitational block contributions, allowing us to recover previouslyknown results for various explicit supergravity solutions, and to significantly generalizethese results to other compactifications. For the AdS3 solutions we give a general proofthat our off-shell supersymmetric action agrees with an appropriate off-shell c-functionin the dual field theory, establishing a very general exact result in holography. Forthe AdS2 solutions our gravitational block formula allows us to obtain the entropy forsupersymmetric, magnetically charged and accelerating black holes in AdS4.
  • Journal article
    Genolini PB, Gauntlett JP, Sparks J, 2023,

    Equivariant localization in supergravity

    , Physical Review Letters, Vol: 131, ISSN: 0031-9007

    We show that supersymmetric supergravity solutions with an R-symmetry Killing vector are equipped with a set of equivariantly closed forms. Various physical observables may be expressed as integrals of these forms, and then evaluated using the Berline-Vergne-Atiyah-Bott fixed point theorem. We illustrate with a variety of holographic examples, including on-shell actions, black hole entropies, central charges, and scaling dimensions of operators. The resulting expressions depend only on topological data and the R-symmetry vector, and hence may be evaluated without solving the supergravity equations.
  • 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
    McCleary JE, Everett SW, Shaaban MM, Gill AS, Vassilakis GN, Huff EM, Massey RJ, Benton SJ, Brown AM, Clark P, Holder B, Fraisse AA, Jauzac M, Jones WC, Lagattuta D, Leung JSY, Li L, Thuy TV, Nagy JM, Netterfield CB, Paracha E, Redmond SF, Rhodes JD, Schmoll J, Sirks E, Tam SIet al., 2023,

    Lensing in the Blue. II. Estimating the Sensitivity of Stratospheric Balloons to Weak Gravitational Lensing

    , Astronomical Journal, Vol: 166, ISSN: 0004-6256

    The Superpressure Balloon-borne Imaging Telescope (SuperBIT) is a diffraction-limited, wide-field, 0.5 m, near-infrared to near-ultraviolet observatory designed to exploit the stratosphere’s space-like conditions. SuperBIT’s 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, we have developed a weak-lensing measurement pipeline with modern algorithms for PSF characterization, shape measurement, and shear calibration. We validate our pipeline and forecast SuperBIT survey properties with simulated galaxy cluster observations in SuperBIT’s near-UV and blue bandpasses. We predict imaging depth, galaxy number (source) density, and redshift distribution for observations in SuperBIT’s three bluest filters; the effect of lensing sample selections is also considered. We find that, in three hours of on-sky integration, SuperBIT can attain a depth of b = 26 mag and a total source density exceeding 40 galaxies per square arcminute. Even with the application of lensing-analysis catalog selections, we find b-band source densities between 25 and 30 galaxies per square arcminute with a median redshift of z = 1.1. Our analysis confirms SuperBIT’s capability for weak gravitational lensing measurements in the blue.
  • 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
    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
    Evnin O, Mkrtchyan K, 2023,

    Three approaches to chiral form interactions

    , DIFFERENTIAL GEOMETRY AND ITS APPLICATIONS, Vol: 89, ISSN: 0926-2245
  • Journal article
    Babak S, Caprini C, Figueroa DG, Karnesis N, Marcoccia P, Nardini G, Pieroni M, Ricciardone A, Sesanah A, Torradol Jet al., 2023,

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

    , JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516

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