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  • Journal article
    Mitridate A, Trickle T, Zhang Z, Zurek KMet al., 2021,

    Dark matter absorption via electronic excitations

    , Journal of High Energy Physics, Vol: 2021

    We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to the target material’s optical properties. However, this is not the case for scalar dark matter, where the dominant contribution comes from a different operator than the one contributing to photon absorption, which is formally next-to-leading-order and does not suffer from in-medium screening. It is therefore imperative to have reliable first-principles numerical calculations and/or semi-analytic modeling in order to predict the detection rate. We present updated sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments.
  • Journal article
    Beccaria M, Dunne G, Tseytlin AA, 2021,

    Strong coupling expansion of free energy and BPS Wilson loop in N=2 superconformal models with fundamental hypermultiplets

    , The Journal of High Energy Physics, Vol: 2021, Pages: 1-42, ISSN: 1029-8479

    As a continuation of the study (in arXiv:2102.07696 and arXiv:2104.12625) of strong-coupling expansion of non-planar corrections in N = 2 4d superconformal models we consider two special theories with gauge groups SU(N) and Sp(2N). They contain N-independent numbers of hypermultiplets in rank 2 antisymmetric and fundamental representations and are planar-equivalent to the corresponding N = 4 SYM theories. These N = 2 theories can be realised on a system of N D3-branes with a finite number of D7-branes and O7-plane; the dual string theories should be particular orientifolds of AdS5 × S5 superstring. Starting with the localization matrix model representation for the N = 2 partition function on S4 we find exact differential relations between the 1/N terms in the corresponding free energy F and the 12-BPS Wilson loop expectation value ⟨W⟩ and also compute their large ’t Hooft coupling (λ » 1) expansions. The structure of these expansions is different from the previously studied models without fundamental hypermultiplets. In the more tractable Sp(2N) case we find an exact resummed expression for the leading strong coupling terms at each order in the 1/N expansion. We also determine the exponentially suppressed at large λ contributions to the non-planar corrections to F and ⟨W⟩ and comment on their resurgence properties. We discuss dual string theory interpretation of these strong coupling expansions.Download to read the full article text
  • Journal article
    Tennyson D, Waldram D, 2021,

    Exceptional complex structures and the hypermultiplet moduli of 5d Minkowski compactifications of M-theory

    , The Journal of High Energy Physics, Vol: 201, Pages: 1-64, ISSN: 1029-8479

    We present a detailed study of a new mathematical object in E6(6)ℝ+ generalised geometry called an ‘exceptional complex structure’ (ECS). It is the extension of a conventional complex structure to one that includes all the degrees of freedom of M-theory or type IIB supergravity in six or five dimensions, and as such characterises, in part, the geometry of generic supersymmetric compactifications to five-dimensional Minkowkski space. We define an ECS as an integrable U*(6) × ℝ+ structure and show it is equivalent to a particular form of involutive subbundle of the complexified generalised tangent bundle L1 ⊂ Eℂ. We also define a refinement, an SU*(6) structure, and show that its integrability requires in addition a vanishing moment map on the space of structures. We are able to classify all possible ECSs, showing that they are characterised by two numbers denoted ‘type’ and ‘class’. We then use the deformation theory of ECS to find the moduli of any SU*(6) structure. We relate these structures to the geometry of generic minimally supersymmetric flux backgrounds of M-theory of the form ℝ4,1 × M, where the SU*(6) moduli correspond to the hypermultiplet moduli in the lower-dimensional theory. Such geometries are of class zero or one. The former are equivalent to a choice of (non-metric-compatible) conventional SL(3, ℂ) structure and strikingly have the same space of hypermultiplet moduli as the fluxless Calabi-Yau case.
  • Journal article
    Momeni A, Rumbutis J, Tolley AJ, 2021,

    Kaluza-Klein from colour-kinematics duality for massive fields

    , Journal of High Energy Physics (JHEP), Vol: 2021, ISSN: 1126-6708

    We consider a broad class of massive four dimensional effective theories describing an infinite tower of charged massive spin 1 states, interacting with massless spin 1 and spin 0. The spectrum is chosen to be the same as that appears in the Kaluza-Klein theory reduction of 5d Yang-Mills to ensure the absence of any spurious poles in a possible double copy formulation. The effective theories are characterized by multiple different couplings between different fields which are unconstrained by symmetries and low energy criteria. Remarkably, by demanding that the scattering amplitudes preserve colour-kinematics duality for different scattering processes, required for the existence of a massive double copy, we find that our 4d Lagrangian is fixed uniquely to the Kaluza-Klein compactification of 5d Yang-Mills theory together with its known double copy consistent higher derivative operators.
  • Journal article
    Gomis J, Joung E, Kleinschmidt A, Mkrtchyan Ket al., 2021,

    Colourful Poincare symmetry, gravity and particle actions

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Ferrero P, Gauntlett JP, Ipina JMP, Martelli D, Sparks Jet al., 2021,

    Accelerating black holes and spinning spindles

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-37, ISSN: 1550-2368

    We study solutions in the Plebański–Demiański family which describe an accelerating, rotating, and dyonically charged black hole in AdS4. These are solutions of D=4 Einstein-Maxwell theory with a negative cosmological constant and hence minimal D=4 gauged supergravity. It is well known that when the acceleration is nonvanishing the D=4 black hole metrics have conical singularities. By uplifting the solutions to D=11 supergravity using a regular Sasaki-Einstein seven-manifold, SE7, we show how the free parameters can be chosen to eliminate the conical singularities. Topologically, the D=11 solutions incorporate an SE7 fibration over a two-dimensional weighted projective space, WCP1[n−,n+], also known as a spindle, which is labeled by two integers that determine the conical singularities of the D=4 metrics. We also discuss the supersymmetric and extremal limit and show that the near horizon limit gives rise to a new family of regular supersymmetric AdS2×Y9 solutions of D=11 supergravity, which generalize a known family by the addition of a rotation parameter. We calculate the entropy of these black holes and argue that it should be possible to derive this from certain N=2, d=3 quiver gauge theories compactified on a spinning spindle with the appropriate magnetic flux.
  • Journal article
    Bourget A, Dancer A, Grimminger JF, Hanany A, Kirwan F, Zhong Zet al., 2021,

    Orthosymplectic implosions

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    de Rham C, Melville S, Noller J, 2021,

    Positivity bounds on dark energy: when matter matters

    , Journal of Cosmology and Astroparticle Physics, Vol: 2021, Pages: 1-25, ISSN: 1475-7516

    Positivity bounds — constraints on any low-energy effective field theory imposed by the fundamental axioms of unitarity, causality and locality in the UV — have recently been used to constrain scalar-tensor theories of dark energy. However, the coupling to matter fields has so far played a limited role. We show that demanding positivity when including interactions with standard matter fields leads to further constraints on the dark energy parameter space. We demonstrate how implementing these bounds as theoretical priors affects cosmological parameter constraints and explicitly illustrate the impact on a specific Effective Field Theory for dark energy. We also show in this model that the existence of a standard UV completion requires that gravitational waves must travel superluminally on cosmological backgrounds.
  • Journal article
    Page J, Magueijo J, 2021,

    Linking the Baum-Hawking-Coleman mechanism with unimodular gravity and Vilenkin's probability flux

    , Journal of Cosmology and Astroparticle Physics, Vol: 2021, Pages: 1-14, ISSN: 1475-7516

    We revisit a mechanism proposed by Hawking to resolve the cosmological constant problem (and the controversy it generated) to identify possibly more palatable alternatives and explore new connections and interpretations. In particular, through the introduction of a new action coupling the four-form field strength F = dA to the cosmological constant via a dynamical field λ(x), a novel Baum-Hawking-Coleman type mechanism is presented. This mechanism can be seen as a generalisation of Unimodular Gravity. A theory with a similar coupling to "F2" is also presented, with promising results. We show how in such theories the 3-form is closely related to the Chern-Simons density, and its associated definition of time. On the interpretational front, we propose a method avoiding the standard Euclidean action prescription, which makes use of Vilenkin's probability flux.
  • Journal article
    Goodhew H, Jazayeri S, Lee MHG, Pajer Eet al., 2021,

    Cutting cosmological correlators

    , Journal of Cosmology and Astroparticle Physics, Vol: 2021, ISSN: 1475-7516

    The initial conditions of our universe appear to us in the form of a classical probability distribution that we probe with cosmological observations. In the current leading paradigm, this probability distribution arises from a quantum mechanical wavefunction of the universe. Here we ask what the imprint of quantum mechanics is on the late time observables. We show that the requirement of unitary time evolution, colloquially the conservation of probabilities, fixes the analytic structure of the wavefunction and of all the cosmological correlators it encodes. In particular, we derive in perturbation theory an infinite set of single-cut rules that generalize the Cosmological Optical Theorem and relate a certain discontinuity of any tree-level n-point function to that of lower-point functions. Our rules are closely related to, but distinct from the recently derived Cosmological Cutting Rules. They follow from the choice of the Bunch-Davies vacuum and a simple property of the (bulk-to-bulk) propagator and are astoundingly general: we prove that they are valid for fields with a linear dispersion relation and any mass, any integer spin and arbitrary local interactions with any number of derivatives. They also apply to general FLRW spacetimes admitting a Bunch-Davies vacuum, including de Sitter, slow-roll inflation, power-law cosmologies and even resonant oscillations in axion monodromy. We verify the single-cut rules in a number of non-trivial examples, including four massless scalars exchanging a massive scalar, as relevant for cosmological collider physics, four gravitons exchanging a graviton, and a scalar five-point function.
  • Journal article
    Alday F, Argyres P, Lemos M, Martone M, Rastelli L, Taronna M, Mukhi S, Cordova L, He Y, Kruczenski M, Vieira P, Pomoni E, Bourget A, Hanany A, Fazzi M, Giacomelli S, Yamazaki M, Kristjansen C, Closset C, Zhou X, Bissi A, Sleight Cet al., 2021,

    The Pollica perspective on the (super)-conformal world

    , JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 54, ISSN: 1751-8113
  • Journal article
    Gould O, Ho DL-J, Rajantie A, 2021,

    Schwinger pair production of magnetic monopoles: momentum distribution for heavy-ion collisions

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, ISSN: 1550-2368

    Magnetic monopoles may be produced by the dual Schwinger effect in strong magnetic fields. Today, thestrongest known magnetic fields in the Universe are produced fleetingly in heavy-ion collisions. We use thecomplex worldline instanton method to calculate the momentum distribution of magnetic monopolesproduced in heavy-ion collisions, in an approximation that includes the effect of the magnetic field to allorders but neglects monopole self-interactions. The result saturates the preparation time-energy uncertaintyprinciple, and yields a necessary ingredient for experimental monopole searches in heavy-ion collisions.
  • Journal article
    Yao Q, Evans T, Chen B, Christensen KIMet al., 2021,

    Higher-order temporal network effects through triplet evolution

    , Scientific Reports, Vol: 11, Pages: 1-17, ISSN: 2045-2322

    We study the evolution of networks through ‘triplets’ — three-node graphlets. We develop a method to compute a transitionmatrix to describe the evolution of triplets in temporal networks. To identify the importance of higher-order interactions inthe evolution of networks, we compare both artificial and real-world data to a model based on pairwise interactions only.The significant differences between the computed matrix and the calculated matrix from the fitted parameters demonstratethat non-pairwise interactions exist for various real-world systems in space and time, such as our data sets. Furthermore,this also reveals that different patterns of higher-order interaction are involved in different real-world situations.To test our approach, we then use these transition matrices as the basis of a link prediction algorithm. We investigate ouralgorithm’s performance on four temporal networks, comparing our approach against ten other link prediction methods.Our results show that higher-order interactions in both space and time play a crucial role in the evolution of networks as wefind our method, along with two other methods based on non-local interactions, give the best overall performance. Theresults also confirm the concept that the higher-order interaction patterns, i.e., triplet dynamics, can help us understandand predict the evolution of different real-world systems.
  • Journal article
    Arav I, Gauntlett JP, Roberts MM, Rosen Cet al., 2021,

    Marginal deformations and RG flows for type IIB S-folds

    , The Journal of High Energy Physics, Vol: 2021, Pages: 1-41, ISSN: 1029-8479

    We construct a continuous one parameter family of AdS4 × S1 × S5 S-fold solutions of type IIB string theory which have nontrivial SL(2, ℤ) monodromy in the S1 direction. The solutions span a subset of a conformal manifold that contains the known N = 4 S-fold SCFT in d = 3, and generically preserve N = 2 supersymmetry. We also construct RG flows across dimensions, from AdS5 × S5, dual to N = 4, d = 4 SYM compactified with a twisted spatial circle, to various AdS4 ×S1 ×S5 S-fold solutions, dual to d = 3 SCFTs. We construct additional flows between the AdS5 dual of the Leigh-Strassler SCFT and an N = 2 S-fold as well as RG flows between various S-folds.
  • Journal article
    Karam A, Markkanen T, Marzola L, Nurmi S, Raidal M, Rajantie Aet al., 2021,

    Higgs-like spectator field as the origin of structure

    , European Physical Journal C: Particles and Fields, Vol: 81, ISSN: 1124-1861

    We show that the observed primordial perturbations can be entirely sourced by a light spectator scalar field with a quartic potential, akin to the Higgs boson, provided that the field is sufficiently displaced from vacuum during inflation. The framework relies on the indirect modulation of reheating, which is implemented without any direct coupling between the spectator field and the inflaton and does not require non-renormalisable interactions. The scenario gives rise to local non-Gaussianity with fNL≃5 as the typical signal. As an example model where the indirect modulation mechanism is realised for the Higgs boson, we study the Standard Model extended with right-handed neutrinos. For the Standard Model running we find, however, that the scenario analysed does not seem to produce the observed perturbation.
  • Journal article
    Beccaria M, Dunne G, Tseytlin AA, 2021,

    BPS Wilson loop in N=2 superconformal SU(N) "orientifold" gauge theory and weak-strong coupling interpolation

    , The Journal of High Energy Physics, Vol: 2021, Pages: 1-30, ISSN: 1029-8479

    We consider the expectation value ⟨W⟩ of the circular BPS Wilson loop in N = 2 superconformal SU(N) gauge theory containing a vector multiplet coupled to two hypermultiplets in rank-2 symmetric and antisymmetric representations. This theory admits a regular large N expansion, is planar-equivalent to N = 4 SYM theory and is expected to be dual to a certain orbifold/orientifold projection of AdS5 × S5 superstring theory. On the string theory side ⟨W⟩ is represented by the path integral expanded near the same AdS2 minimal surface as in the maximally supersymmetric case. Following the string theory argument in [5], we suggest that as in the N = 4 SYM case and in the N = 2 SU(N) × SU(N) superconformal quiver theory discussed in [19], the coefficient of the leading non-planar 1/N2 correction in ⟨W⟩ should have the universal λ3/2 scaling at large ’t Hooft coupling. We confirm this prediction by starting with the localization matrix model representation for ⟨W⟩. We complement the analytic derivation of the λ3/2 scaling by a numerical high-precision resummation and extrapolation of the weak-coupling expansion using conformal mapping improved Padé analysis.
  • Journal article
    Golat S, Contaldi CR, 2021,

    Geodesic noise and gravitational wave observations by pulsar timing arrays

    , Physics Letters B: Nuclear Physics and Particle Physics, Vol: 818, Pages: 1-4, ISSN: 0370-2693

    Signals from millisecond pulsars travel to us on geodesics along the line-of-sight that are affected by the space–time metric. The exact path-geometry and redshifting along the geodesics determine the observed Time-of-Arrival (ToA) of the pulses. The metric is determined by the distribution of dark matter, gas, and stars in the galaxy and, in the final stages of travel, by the distribution of solar system bodies. The inhomogeneous distribution of stellar masses can have a small but significant statistical effect on the ToAs through the perturbation of geodesics. This will result in additional noise in ToA observations that may affect Pulsar Timing Array (PTA) constraints on gravitational waves at very low frequencies. We employ a simple model for the stellar distribution in our galaxy to estimate the scale of both static and dynamic sources of what we term generically “geodesic noise”. We find that geodesic noise has a standard deviation of (10) ns for typical lines-of-sight. This suggests geodesic noise is relevant for estimates of PTA sensitivity and may limit future efforts for detection of gravitational waves by PTAs.
  • Journal article
    Magueijo J, 2021,

    Cosmological time and the constants of nature

    , Physics Letters B: Nuclear Physics and Particle Physics, Vol: 820, Pages: 1-4, ISSN: 0370-2693

    We propose that cosmological time is effectively the conjugate of the constants of nature. Different definitions of time arise, with the most relevant related to the constant controlling the dynamics in each epoch. The Hamiltonian constraint then becomes a Schrodinger equation. In the connection representation, it is solved by monochromatic plane waves moving in a space generalizing the Chern-Simons functional. Normalizable superpositions exist and for factorizable coherent states we recover the classical limit and a seamless handover between potentially disparate times. There is also a rich structure of alternative states, including entangled constants, opening up the doors to new phenomenology.
  • Journal article
    Magueijo J, 2021,

    Real Chern-Simons wave function

    , Physical Review D, Vol: 104, Pages: 1-10, ISSN: 2470-0010

    We examine the status of the Chern-Simons (or Kodama) state from the point of view of a formulation of gravity that uses only real connection and metric variables and a real action. We may package the real connection variables into the complex self-dual Ashtekar connection (and will do so to make contact with previous work), but that operation is essentially cosmetic and can be undone at any step or even bypassed altogether. The action will remain the (real) Einstein-Cartan action, forgoing the addition of the usual Holst (or Nieh-Yan) term with an imaginary coefficient. It is then found that the constraints are solved by a modification of the Chern-Simons state which is a pure phase (in the Lorentzian theory, we stress), the phase containing only the fully gauge-invariant imaginary part of the Chern-Simons functional. Thus, the state for the “real theory” is nonpathological with regards to the most egregious criticisms facing its “nonreal” cousin, solving the complex theory. A straightforward modification of the real Chern-Simons state is also a solution in quasitopological theories based on the Euler invariant, for which the cosmological constant, Λ, is dynamical. In that case it is enough to shift the usual factor of Λ in the wave function to the inside of the spatial Chern-Simons integral. The trick only works for the quasi-Euler theory with a critical coupling previously identified in the literature. It does not apply to the quasi-Pontryagin theory.
  • Journal article
    Chester SM, 2021,

    Anomalous dimensions of monopole operators in scalar QED3 with Chern-Simons term

    , Journal of High Energy Physics, Vol: 2021

    <jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>We study monopole operators with the lowest possible topological charge <jats:italic>q</jats:italic> = 1/2 at the infrared fixed point of scalar electrodynamics in 2 + 1 dimension (scalar QED<jats:sub>3</jats:sub>) with <jats:italic>N</jats:italic> complex scalars and Chern-Simons coupling <jats:italic>|k|</jats:italic> = <jats:italic>N</jats:italic>. In the large <jats:italic>N</jats:italic> expansion, monopole operators in this theory with spins <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathrm{\ell}&lt;O\left(\sqrt{N}\right) $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ℓ</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mi>O</mml:mi> <mml:mfenced> <mml:msqrt> <mml:mi>N</mml:mi> </mml:msqrt> </mml:mfenced> </mml:math></jats:alternatives></jats:inline-formula> and associated flavor representations are expected to have the same scaling dimension to sub-leading order in 1/<jats:italic>N</jats:italic>. We use the state-operator correspondence to calculate the scaling dimension to sub-leading order with the result <jats:italic>N −</jats:italic> 0<jats:italic>.</jats:italic>2743 + <jats:italic>O</jats:italic>(1/<jats:italic>N</jats:italic>), which improves on existing leading order results. We also compute the <jats:italic>ℓ</jats:italic><jats:sup>2</jats:sup>/<jats:italic>N</jats:italic> term that breaks the degeneracy to sub-leading order for monopoles with
  • Journal article
    Bobev N, Gautason FF, van Muiden J, 2021,

    The holographic conformal manifold of 3d $$ \mathcal{N} $$ = 2 S-fold SCFTs

    , Journal of High Energy Physics, Vol: 2021

    <jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>We employ a non-compact gauging of four-dimensional maximal supergravity to construct a two-parameter family of AdS<jats:sub>4</jats:sub> J-fold solutions preserving <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{N} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>N</mml:mi> </mml:math></jats:alternatives></jats:inline-formula> = 2 supersymmetry. All solutions preserve <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathfrak{u} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>u</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(1) × <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathfrak{u} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>u</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(1) global symmetry and in special limits we recover the previously known <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathfrak{su} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>su</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(2) × <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathfrak{u} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>u</mml:mi> </mml:math></jats:alternat
  • Journal article
    Ho DL-J, Rajantie A, 2021,

    Instanton solution for Schwinger production of 't Hooft-Polyakov monopoles

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 1-9, ISSN: 1550-2368

    We present the results of an explicit numerical computation of a novel instanton in Georgi-Glashow SU(2) theory. The instanton is physically relevant as a mediator of Schwinger production of ’t Hooft–Polyakov magnetic monopoles from strong magnetic fields. In weak fields, the pair production rate has previously been computed using the worldline approximation, which breaks down in strong fields due to the effects of finite monopole size. Using lattice field theory we have overcome this limit, including finite monopole size effects to all orders. We demonstrate that a full consideration of the internal monopole structure results in an enhancement to the pair production rate, and confirm earlier results that monopole production becomes classical at the Ambjørn-Olesen critical field strength.
  • Journal article
    Alberte L, de Rham C, Jaitly S, Tolley AJet al., 2021,

    QED positivity bounds

    , Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 1-26, ISSN: 1550-2368

    We apply positivity bounds directly to a U(1) gauge theory with charged scalars and charged fermions, i.e., QED, minimally coupled to gravity. Assuming that the massless t-channel pole may be discarded, we show that the improved positivity bounds are violated unless new physics is introduced at the parametrically low scale Λnew∼(emMPl)1/2, consistent with similar results for scalar field theories, far lower than the scale implied by the weak gravity conjecture. This is sharply contrasted with previous treatments which focus on the application of positivity bounds to the low energy gravitational Euler-Heisenberg effective theory only. We emphasize that the low cutoff is a consequence of applying the positivity bounds under the assumption that the pole may be discarded. We conjecture an alternative resolution that a small amount of negativity, consistent with decoupling limits, is allowed and is not in conflict with standard UV completions, including weakly coupled ones.
  • Journal article
    Xie Y, Zhang J, Silva HO, de Rham C, Witek H, Yunes Net al., 2021,

    Square peg in a circular hole: choosing the right ansatz for isolated black holes in generic gravitational theories

    , Physical Review Letters, Vol: 126, Pages: 1-7, ISSN: 0031-9007

    The metric of a spacetime can be greatly simplified if the spacetime is circular. We prove that in generic effective theories of gravity, the spacetime of a stationary, axisymmetric, and asymptotically flat solution must be circular if the solution can be obtained perturbatively from a solution in the general relativity limit. This result applies to a broad class of gravitational theories that include arbitrary scalars and vectors in their light sector, so long as their nonstandard kinetic terms and nonmininal couplings to gravity are treated perturbatively.
  • Journal article
    Majidy S, Halliwell JJ, Laflamme R, 2021,

    Detecting violations of macrorealism when the original Leggett-Garg inequalities are satisfied

    , PHYSICAL REVIEW A, Vol: 103, ISSN: 2469-9926
  • Journal article
    Lee VSH, Mitridate A, Trickle T, Zurek KMet al., 2021,

    Probing small-scale power spectra with pulsar timing arrays

    , Journal of High Energy Physics, Vol: 2021

    Models of Dark Matter (DM) can leave unique imprints on the Universe’s small scale structure by boosting density perturbations on small scales. We study the capability of Pulsar Timing Arrays to search for, and constrain, subhalos from such models. The models of DM we consider are ordinary adiabatic perturbations in ΛCDM, QCD axion miniclusters, models with early matter domination, and vector DM produced during inflation. We show that ΛCDM, largely due to tidal stripping effects in the Milky Way, is out of reach for PTAs. Axion miniclusters may be within reach, although this depends crucially on whether the axion relic density is dominated by the misalignment or string contribution. Models where there is matter domination with a reheat temperature below 1 GeV may be observed with future PTAs. Lastly, vector DM produced during inflation can be detected if it is lighter than 10<sup>−16</sup> GeV. We also make publicly available a Python Monte Carlo tool for generating the PTA time delay signal from any model of DM substructure.
  • Journal article
    Tolley AJ, Wang Z-Y, Zhou S-Y, 2021,

    New positivity bounds from full crossing symmetry

    , Journal of High Energy Physics (JHEP), Vol: 2021, ISSN: 1126-6708

    Positivity bounds are powerful tools to constrain effective field theories. Utilizing the partial wave expansion in the dispersion relation and the full crossing symmetry ofthe scattering amplitude, we derive several sets of generically nonlinear positivity bounds for a generic scalar effective field theory: we refer to these as the P Q, Dsu, Dstu and D¯stu bounds. While the P Q bounds and Dsu bounds only make use of the s ↔ u dispersion relation, the Dstu and D¯stu bounds are obtained by further imposing the s ↔ t crossing symmetry. In contradistinction to the linear positivity for scalars, these inequalities can be applied to put upper and lower bounds on Wilson coefficients, and are much more con straining as shown in the lowest orders. In particular we are able to exclude theories with soft amplitude behaviour such as weakly broken Galileon theories from admitting a stan dard UV completion. We also apply these bounds to chiral perturbation theory and we find these bounds are stronger than the previous bounds in constraining its Wilson coefficients.
  • Journal article
    Cheamsawat K, Fischetti S, Wallis L, Wiseman Tet al., 2021,

    A surprising similarity between holographic CFTs and a free fermion in (2+1) dimensions

    , JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
  • Journal article
    Arav I, Cheung KCM, Gauntlett JP, Roberts MM, Rosen Cet al., 2021,

    A new family of AdS4 S-folds in type IIB string theory

    , The Journal of High Energy Physics, Vol: 2021, Pages: 1-49, ISSN: 1029-8479

    We construct infinite new classes of AdS4 × S1 × S5 solutions of type IIB string theory which have non-trivial SL(2, ℤ) monodromy along the S1 direction. The solutions are supersymmetric and holographically dual, generically, to N = 1 SCFTs in d = 3. The solutions are first constructed as AdS4 × ℝ solutions in D = 5 SO(6) gauged supergravity and then uplifted to D = 10. Unlike the known AdS4 × ℝ S-fold solutions, there is no continuous symmetry associated with the ℝ direction. The solutions all arise as limiting cases of Janus solutions of d = 4, N = 4 SYM theory which are supported both by a different value of the coupling constant on either side of the interface, as well as by fermion and boson mass deformations. As special cases, the construction recovers three known S-fold constructions, preserving N = 1, 2 and 4 supersymmetry, as well as a recently constructed N = 1 AdS4 × S1 × S5 solution (not S-folded). We also present some novel “one-sided Janus” solutions that are non-singular.
  • Journal article
    Jones H, 2021,

    Comment on 'Solvable model of bound states in the continuum (BIC) in on dimension' (Physica Scripta (2019) 94 105214)

    , Physica Scripta: an international journal for experimental and theoretical physics, Vol: 96, Pages: 1-4, ISSN: 0031-8949

    We elucidate the status of the special scattering states found in this paper and explore further the relationships between scattering states and bound states of different non-analytic segments (depending on midxmid) of the exponential potential.

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