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  • Journal article
    de Rham C, Giblin JT, Tolley AJ, 2024,

    Scalar radiation with a quartic Galileon

    , PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010
  • Journal article
    Mentasti G, Contaldi CR, 2024,

    Observing gravitational waves with solar system astrometry

    , Journal of Cosmology and Astroparticle Physics, Vol: 2024, ISSN: 1475-7516

    The subtle influence of gravitational waves on the apparent positioning of celestial bodies offers novel observational windows [1,2,3,4]. We calculate the expected astrometric signal induced by an isotropic Stochastic Gravitational Wave Background (SGWB) in the short distance limit. Our focus is on the resultant proper motion of Solar System objects, a signal on the same time scales addressed by Pulsar Timing Arrays (PTA). We derive the corresponding astrometric deflection patterns, finding that they manifest as distinctive dipole and quadrupole correlations or, in some cases, may not be present. Our analysis encompasses both Einsteinian and non-Einsteinian polarisations. We estimate the upper limits for the amplitude of SGWBs that could be obtained by tracking the proper motions of large numbers of solar system objects such as asteroids. We find that for SGWBs with negative spectral indices, such as that generated by Super Massive Black Hole Binaries (SMBHB), the constraints from these observations could rival those from PTAs. With the Gaia satellite and the Vera C. Rubin Observatory poised to track an extensive sample of asteroids — ranging from Script O(105) to Script O(106), we highlight the significant future potential for similar surveys to contribute to our understanding of the SGWB.
  • Journal article
    Colas T, de Rham C, Kaplanek G, 2024,

    Decoherence out of fire: purity loss in expanding and contracting universes

    , JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516
  • Journal article
    Lehners J-L, Stelle KS, 2024,

    Higher-order gravity, finite action, and a safe beginning for the universe

    , European Physical Journal Plus, Vol: 139, ISSN: 2190-5444

    General relativity allows for inhomogeneous and anisotropic universes with finite action. By contrast, in quadratic gravity such solutions obtain infinite action and are thus eliminated. What remains are homogeneous and isotropic solutions undergoing accelerated expansion, thereby automatically inducing an early inflationary phase. In this manner, semi-classical consistency may explain some of the basic, coarse-grained features of the early universe. This includes suitable initial conditions for the second law of thermodynamics, in the spirit of the Weyl curvature hypothesis. We note that quadratic gravity is a renormalisable theory and may admit an asymptotically safe regime at high energies, rendering the theory trustworthy to high energies. We also comment on theories containing curvature terms up to infinite derivative order, and on the contrast with no-boundary initial conditions.
  • Journal article
    Genolini PB, Gauntlett JP, Jiao Y, Luescher A, Sparks Jet al., 2024,

    Localization and attraction

    , The Journal of High Energy Physics, Vol: 2024, ISSN: 1029-8479

    We use equivariant localization to construct of-shell entropy functions for supersymmetric black holes in N = 2, D = 4 gauged supergravity coupled to matter. This allowsone to compute the black hole entropy without solving the supergravity equations of motionand provides a novel generalization of the attractor mechanism. We consider magneticallycharged black holes in AdS4 which have an AdS2 × M2 near horizon geometry, where M2 isa sphere or a spindle, and we also obtain entropy functions for ungauged supergravity as asimple corollary. We derive analogous results for black strings and rings in D = 5 supergravitywhich have an AdS3 × M2 near horizon geometry, and in this setting we derive an of-shellexpression for the central charge of the dual N = (0, 2), d = 2 SCFT.
  • Journal article
    Ghoderao PS, Rajantie A, 2024,

    Curvature perturbations from preheating with scale dependence

    , JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516
  • Journal article
    Figueroa DG, Pieroni M, Ricciardone A, Simakachorn Pet al., 2024,

    Cosmological Background Interpretation of Pulsar Timing Array Data

    , PHYSICAL REVIEW LETTERS, Vol: 132, ISSN: 0031-9007
  • Journal article
    Carrillo González M, 2024,

    Bounds on EFT’s in an expanding universe

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368

    We find bounds on the Wilson coefficients of effective field theories (EFTs) living in a universe undergoing expansion by requiring that its modes do not propagate further than a minimally coupled photon by a resolvable amount. To do so, we compute the spatial shift suffered by the EFT modes at a fixed time slice within the WKB approximation and the regime of validity of the EFT. We analyze the bounds arising on shift-symmetric scalars and curved space generalizations of Galileons.
  • Journal article
    Hull CM, 2024,

    Covariant action for self-dual <i>p</i>-form gauge fields in general spacetimes

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Isichei R, Magueijo J, 2024,

    Unimodular proca theory: breaking the U(1) gauge symmetry of unimodular gravity via a mass term

    , European Physical Journal C: Particles and Fields, Vol: 84, ISSN: 1124-1861

    We study the Hamiltonian structure ofunimodular-like theories, where the cosmological constant(or other supposed constants of nature) are demoted fromfixed parameters to classical constants of motion. No newlocal degrees of freedom are present as a result of a U(1)gauge invariance of the theory. Hamiltonian analysis of theaction reveals that the only possible gauge fixing that canbe enforced is setting the spatial components of the fourvolume time vector T i ≈ 0. As a consequence of this, thegauge-fixed unimodular path integral is equivalent to the minisuperspace unimodular path integral. However, should webreak the U(1) gauge invariance, two things happen: a massless propagating degree of freedom appears, and the (gaugeinvariant) zero-mode receives modified dynamics. The implications are investigated, with the phenomenology dependingcrucially on the target “constant”.
  • Journal article
    Beccaria M, Tseytlin AA, 2024,

    Large N expansion of superconformal index of k=1 ABJM theory and semiclassical M5 brane partition function

    , NUCLEAR PHYSICS B, Vol: 1001, ISSN: 0550-3213
  • Journal article
    Karapetyan M, Manvelyan R, Mkrtchyan K, 2024,

    On correlation functions of higher-spin currents in arbitrary dimensions <i>d</i> > 3

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Skrzypek T, Tseytlin AA, 2024,

    On AdS/CFT duality in the twisted sector of string theory on <i>AdS</i><sub>5</sub> x <i>S</i><SUP>5</SUP><i>/</i>Z<sub>2</sub> orbifold background

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Hulik O, Malek E, Valach F, Waldram Det al., 2024,

    Y-algebroids and <i>E</i><sub>7(7)</sub> x R<SUP>+</SUP>-generalised geometry

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Evnin O, Joung E, Mkrtchyan K, 2024,

    Democratic Lagrangians from topological bulk

    , PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010
  • Journal article
    Cable A, Rajantie A, 2024,

    Stochastic parameters for scalar fields in de Sitter spacetime

    , PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010
  • Journal article
    Magueijo J, 2024,

    Black holes and foliation-dependent physics

    , Physical Review D, Vol: 109, ISSN: 2470-0010

    In theories where physics depends on a global foliation of space-time, a black hole’s horizon is surrounded by an “eternity skin”: a pile-up of spacelike leaves that in the far-out region cover all times from the start of collapse to future eternity. Any future foliation-dependent change in the laws of physics would be enacted in this region and affect the last stages of collapse toward black hole formation. We show how in some cases the black hole never forms but, rather, bounces into an explosive event. There is also a nonlocal transfer of energy between the asymptotic Universe and the formed black hole precursor, so that the back hole (if formed) or the exploding star (otherwise) will have a different mass from what was initially thrown in. These last matters are generic to nonlocal theories and can be traced to the breakdown of the local Hamiltonian constraint.
  • Journal article
    Genolini PB, Gauntlett JP, Sparks J, 2024,

    Equivariant localization for AdS/CFT

    , The Journal of High Energy Physics, Vol: 2024, ISSN: 1029-8479

    We explain how equivariant localization may be applied to AdS/CFT to compute various BPS observables in gravity, such as central charges and conformal dimensions of chiral primary operators, without solving the supergravity equations. The key ingredient is that supersymmetric AdS solutions with an R-symmetry are equipped with a set of equivariantly closed forms. These may in turn be used to impose flux quantization and compute observables for supergravity solutions, using only topological information and the Berline-Vergne-Atiyah-Bott fixed point formula. We illustrate the formalism by considering AdS5 × M6 and AdS3 × M8 solutions of D = 11 supergravity. As well as recovering results for many classes of well-known supergravity solutions, without using any knowledge of their explicit form, we also compute central charges for which explicit supergravity solutions have not been constructed.
  • Journal article
    Alexandre B, Gielen S, Magueijo J, 2024,

    Overall signature of the metric and the cosmological constant

    , Journal of Cosmology and Astroparticle Physics, Vol: 2024, ISSN: 1475-7516

    We consider a little known aspect of signature change, where the overall sign of the metric is allowed to change, with physical implications. We show how, in different formulations of general relativity, this type of classical signature change across boundaries with a degenerate metric can be made consistent with a change in sign (and value) of the cosmological constant Λ. In particular, the separate "mostly plus" and "mostly minus" signature sectors of Lorentzian gravity are most naturally associated with different signs of Λ. We show how this general phenomenon allows for classical solutions where the open dS patch can arise from a portion of AdS space time. These can be interpreted as classical "imaginary space" extensions of the usual Lorentzian theory, with a2 < 0.
  • Journal article
    Roberts MM, Wiseman T, 2024,

    Analog gravity and continuum effective theory of the graphene tight-binding lattice model

    , PHYSICAL REVIEW B, Vol: 109, ISSN: 2469-9950
  • Journal article
    Ho M, Price HCW, Evans TS, O'Sullivan Eet al., 2024,

    Dynamics of technology emergence in innovation networks

    , Scientific Reports, Vol: 14, ISSN: 2045-2322

    To create the next innovative product, participants in science need to understand which existing technologies can be combined, what new science must be discovered, and what new technologies must be invented. Knowledge of these often arrives by means of expert consensus or popularity metrics, masking key information on how intellectual efforts accumulate into technological progress. To address this shortcoming, we first present a method to establish a mathematical link between technological evolution and complex networks: a path of events that narrates innovation bottlenecks. Next, we quantify the position and proximity of documents to these innovation paths. The result is an innovation network that more exhaustively captures deterministic knowledge flows with respect to a marketed innovative product. Our dataset, containing over three million biomedical citations, demonstrates the possibility of quantifying the accumulation, speed, and division of labour in innovation over a sixty-year time horizon. The significance of this study includes the (i) use of a purpose-generated dataset showing causal paths from research to development to product; (ii) analysis of the innovation process as a directed acyclic graph; (iii) comparison between calendar time and network time; (iv) ordering of science funders along technology lifecycles; (v) quantification of innovative activities' importance to an innovative outcome; and (vi) integration of publication, patent, clinical trial, regulatory data to study innovation holistically.
  • Journal article
    Bassani PM, Magueijo J, 2024,

    Unimodular-like times, evolution and Brans–Dicke gravity

    , International Journal of Modern Physics D: Gravitation, Astrophysics and Cosmology, Vol: 33, ISSN: 0218-2718

    In unimodular-like theories, the constants of nature are demoted from pre-given parameters to phase space variables. Their canonical duals provide physical time variables. We investigate how this interacts with an alternative approach to varying constants, where they are replaced by dynamical scalar fields. Specifically, we investigate the Brans–Dicke theory of gravity and its interaction with clocks dual to the cosmological constant, the Planck mass, etc. We crucially distinguish between the different role of Newton’s G in this process, leading to the possibility of local Lorentz invariance violation. A large number of possible theories emerge, for example where the Brans–Dicke coupling, ω, depends on unimodular-like times (in a generalization of scalar-tensor theories), or even become the dual variable to unimodular-like clocks ticking variations in other demoted constants, such as the cosmological constant. We scan the space of possible theories and select those most interesting regarding the joint variations of the Brans–Dicke ω and other parameters, (such as the cosmological constant); and also regarding their energy conservation violation properties. This ground work is meant to provide the formalism for further developments, namely regarding cosmology, black holes and the cosmological constant problem.
  • Book
    de Rham C, 2024,

    The Beauty of Falling: A Life in Pursuit of Gravity

    Claudia de Rham has been playing with gravity her entire life. As a diver, experimenting with her body's buoyancy in the Indian Ocean. As a pilot, soaring over Canadian waterfalls on dark mornings before beginning her daily scientific research. As an astronaut candidate, dreaming of the experience of flying free from Earth's pull. And as a physicist, discovering new sides to gravity's irresistible personality by exploring the limits of Einstein's general theory of relativity. In The Beauty of Falling, de Rham shares captivating stories about her quest to gain intimacy with gravity, to understand both its feeling and fundamental nature. Her life's pursuit led her from a twist of fate that snatched away her dream of becoming an astronaut to an exhilarating breakthrough at the very frontiers of gravitational physics. While many of us presume to know gravity quite well, the brightest scientists in history have yet to fully answer the simple question: what exactly is gravity? De Rham reveals how great minds-from Newton and Einstein to Stephen Hawking, Andrea Ghez, and Roger Penrose-led her to the edge of knowledge about this fundamental force. She found hints of a hidden side to gravity at the particle level where Einstein's theory breaks down, leading her to develop a new theory of "massive gravity." De Rham shares how her life's path turned from a precipitous fall to an exquisite flight toward the discovery of something entirely new about our surprising, gravity-driven universe.
  • Conference paper
    Redmond SF, Benton SJ, Damaren CJ, Everett SW, Fraisse AA, Gill AS, Hartley JW, Harvey D, Holder B, Huff EM, Jauzac M, Jones WC, Lagattuta D, Leung JSY, Li L, Luu TVT, Massey R, McCleary JE, Nagy JM, Netterfield CB, Paracha E, Rhodes JD, Robertson A, Romualdez LJ, Schmoll J, Shaaban MM, Sirks EL, Vassilakis GN, Vitorelli AZet al., 2024,

    To the stratosphere and beyond! Super-pressure balloon flight overview for the Super-pressure Balloon-borne Imaging Telescope (SuperBIT)

    , ISSN: 0277-786X

    The Super-pressure Balloon-borne Imaging Telescope (SuperBIT) was a diffraction limited 0.5 m optical-to-near-UV telescope that was designed to study dark matter via cluster weak lensing. SuperBIT launched from Wanaka, New Zealand via NASA's super-pressure balloon (SPB) technology on April 16, 2023 and remained in the stratosphere for 40 days. During the flight, SuperBIT obtained multi-band images for 30 science targets; data analysis to produce shear measurements for each target is ongoing. SuperBIT's pointing system comprised three nested frames that stablized the entire telescope within 0.34 arcseconds rms, plus a back-end tip-tilt mirror that achieved focal plane image stability of 0.055 arcseconds rms during 300 second exposures. The power system reached full charge every day and never dropped below 30% at night. All components remained within their temperature limits, and actively controlled components remained within a standard deviation of ∼0.1 K of their set point. In this paper we provide an overview of the flight trajectory behaviour and flight operations. The first two days of the flight were used for payload characterization and telescope alignment after which all night time was dedicated to science observations. Target scheduling was performed by an on-board “Autopilot” system which tracked available targets and prioritized completing targets over starting new targets. SuperBIT was the first balloon telescope to fly a Starlink dish to enable high-bandwidth communications with the payload. Prior to flight termination, two Data Retrieval System modules were deployed to provide a redundant data recovery method.
  • Conference paper
    Voyer P, Benton SJ, Damaren CJ, Everett SW, Fraisse AA, Gill AS, Hartley JW, Harvey D, Henderson M, Holder B, Huff EM, Jauzac M, Jones WC, Lagattuta D, Leung JSY, Li L, Luu TVT, Massey R, McCleary JE, Nagy JM, Netterfield CB, Paracha E, Redmond SF, Rhodes JD, Robertson A, Romualdez LJ, Schmoll J, Shaaban MM, Sirks EL, Vassilakis GN, Vitorelli AZet al., 2024,

    From SuperBIT to GigaBIT: Informing next-generation balloon-borne telescope design with Fine Guidance System flight data

    , ISSN: 0277-786X

    The Super-pressure Balloon-borne Imaging Telescope (SuperBIT) is a near-diffraction-limited 0.5 m telescope that launched via NASA's super-pressure balloon technology on April 16, 2023. SuperBIT achieved precise pointing control through the use of three nested frames in conjunction with an optical Fine Guidance System (FGS), resulting in an average image stability of 0.055” over 300-second exposures. The SuperBIT FGS includes a tip-tilt fast-steering mirror that corrects for jitter on a pair of focal plane star cameras. In this paper, we leverage the empirical data from SuperBIT's successful 45-night stratospheric mission to inform the FGS design for the next-generation balloon-borne telescope. The Gigapixel Balloon-borne Imaging Telescope (GigaBIT) is designed to be a 1.35m wide-field, high resolution imaging telescope, with specifications to extend the scale and capabilities beyond those of its predecessor SuperBIT. A description and analysis of the SuperBIT FGS will be presented along with methodologies for extrapolating this data to enhance GigaBIT's FGS design and fine pointing control algorithm. We employ a systems engineering approach to outline and formalize the design constraints and specifications for GigaBIT's FGS. GigaBIT, building on the SuperBIT legacy, is set to enhance high-resolution astronomical imaging, marking a significant advancement in the field of balloon-borne telescopes.
  • Journal article
    Beccaria M, Giombi S, Tseytlin AA, 2024,

    (2,0) theory on S5 x S1 and quantum M2 branes

    , NUCLEAR PHYSICS B, Vol: 998, ISSN: 0550-3213
  • Conference paper
    Shaw EC, Ade PAR, Akers S, Amiri M, Austermann J, Beall J, Becker DT, Benton SJ, Bergman AS, Bock JJ, Bond JR, Bryan SA, Chiang HC, Contaldi CR, Domagalski RS, Dore O, Duff SM, Duivenvoorden AJ, Ericksen HK, Farhang M, Filippini JP, Fissel LM, Fraisse AA, Freese K, Galloway M, Gambrel AE, Gandilo NN, Ganga K, Gibbs SM, Gourapura S, Grigorian A, Gualtieri R, Gudmundsson JE, Halpern M, Hartley J, Hasselfield M, Hilton G, Holmes W, Hristov VV, Huang Z, Hubmayr J, Irwin KD, Jones WC, Kahn A, Kermish ZD, King C, Kuo CL, Lennox AR, Leung JS-Y, Li S, Luu T, Mason P, May J, Megerian K, Moncelsi L, Morford TA, Nagy JM, Nie R, Netterfield CB, Nolta M, Osherson B, Padilla IL, Rahlin AS, Redmond S, Reintsema C, Romualdez LJ, Ruhl JE, Runyan MC, Shariff JA, Shiu C, Soler JD, Song X, Tartakovsky S, Thommesen H, Trangsrud A, Tucker C, Tucker RS, Turner AD, Ullom JN, van der List JF, Van Lanen J, Vissers MR, Weber AC, Wen S, Wehus IK, Wiebe D, Young EYet al., 2024,

    In-Flight Performance of SPIDER's 280 GHz Receivers

    , Conference on Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
  • Journal article
    Butterfield J, Dowker F, 2024,

    Recovering general relativity from a Planck scale discrete theory of quantum gravity

    , Philosophy of Physics, Vol: 2, ISSN: 2753-5908

    An argument is presented that if a theory of quantum gravity is physically discrete at the Planck scale and the theory recovers General Relativity as an approximation, then, at the current stage of our knowledge, causal sets must arise within the theory, even if they are not its basis.We lay out this argument in two claims. Roughly speaking, the first claim is that causal sets can recover continuum Lorentzian manifolds; and the second claim is that no other proposal for a set of discrete data that conforms to our sense of “fundamental discreteness at the Planck scale” is known to be able to recover continuum Lorentzian manifolds. To support this second claim, we show, in particular, that an apparent alternative discrete data set to causal sets, viz., a certain sort of combinatorial Lorentzian simplicial complex, cannot recover General Relativistic spacetimes in the appropriately unique way; for it cannot discriminate between Minkowski spacetime and a spacetime with a certain sort of gravitational wave burst.
  • Journal article
    Jazayeri S, Renaux-Petel S, Tong X, Werth D, Zhu Yet al., 2023,

    Parity violation from emergent nonlocality during inflation

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

    Parity violation in the early Universe holds great promise for uncovering new physics. In particular, the primordial scalar four-point correlation function is allowed to develop a parity-violating component when massive spinning particles coupled to a helical chemical potential are present during inflation. In this paper, we explore the rich physics of such a parity-violating trispectrum in the presence of a reduced speed of sound for the Goldstone boson of broken time translations. We show that this signal can be significantly large while remaining under perturbative control, offering promising observational prospects for future cosmological surveys. In the limit of a reduced sound speed, the dynamics admits an effective nonlocal description organized as a time-derivative expansion. This reveals that parity violation arises due to emergent nonlocality in the single-field effective theory. At leading order, this effective theory yields a compact trispectrum template, written in terms of elementary functions. We then conduct a comprehensive analysis of the kinematic dependence of this parity-violating trispectrum and reveal new features. In addition to the low-speed collider resonance, we find a new class of signals lying in the internal soft-limit of the correlator. This signal is characterized by an oscillatory pattern periodic in the momentum ratio, with a frequency determined by the speed of sound and the chemical potential, making it drastically distinct from the conventional cosmological collider signal.
  • Journal article
    Mentasti G, Contaldi CR, Peloso M, 2023,

    Intrinsic limits on the detection of the anisotropies of the stochastic gravitational wave background

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

    For any given network of detectors, and for any given integration time, even in the idealized limit of negligible instrumental noise, the intrinsic time variation of the isotropic component of the stochastic gravitational wave background (SGWB) induces a limit on how accurately the anisotropies in the SGWB can be measured. We show here how this sample limit can be calculated and apply this to three separate configurations of ground-based detectors placed at existing and planned sites. Our results show that in the idealized, best-case scenario, individual multipoles of the anisotropies at ℓ≤8 can only be measured to ∼10^{-5}-10^{-4} level over five years of observation as a fraction of the isotropic component. As the sensitivity improves as the square root of the observation time, this poses a very serious challenge for measuring the anisotropies of SGWB of cosmological origin, even in the case of idealized detectors with arbitrarily low instrumental noise.

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