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Journal articleCable A, Rajantie A, 2021,
Free scalar correlators in de Sitter space via the stochastic approach beyond the slowroll approximation
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, ISSN: 15502368The stochastic approach to calculating scalar correlation functions in de Sitter spacetime is extended beyond the overdamped “slowroll” approximation. We show that with the correct noise term, it reproduces the exact asymptotic longdistance behavior of field correlators in free field theory, thereby demonstrating the viability of the technique. However, we also show that the naïve way of calculating the noise term by introducing a cutoff at the horizon does not give the correct answer unless the cutoff is chosen specifically to give the required result. We discuss the implications of this for interacting theories.

Journal articleGonzalez MC, de Rham C, Tolley AJ, 2021,
Scattering amplitudes for binary systems beyond GR
, The Journal of High Energy Physics, Vol: 87, Pages: 136, ISSN: 10298479Amplitude methods have proven to be a promising technique to perform PostMinkowskian calculations used as inputs to construct gravitational waveforms. In this paper, we show how these methods can be extended beyond the standard calculations in General Relativity with a minimal coupling to matter. As proof of principle, we consider spinless particles conformally coupled to a gravitational helicity0 mode. We clarify the subtleties in the matching procedure that lead to the potential for conformally coupled matter. We show that in the probe particle limit, we can reproduce well known results for the field profile. With the scattering amplitudes at hand, we compute the conservative potential and scattering angle for the binary system. We find that the result is a non trivial expansion that involves not only the coupling strengths, but also a non trivial dependence on the energy/momentum of the scattered particles.

Journal articleFerrero P, Gauntlett JP, Martelli D, et al., 2021,
M5branes wrapped on a spindle
, The Journal of High Energy Physics, Vol: 2021, Pages: 121, ISSN: 10298479We construct supersymmetric AdS5 × Σ solutions of D = 7 gauged supergravity, where Σ is a twodimensional orbifold known as a spindle. These uplift on S4 to solutions of D = 11 supergravity which have orbifold singularites. We argue that the solutions are dual to d = 4, N = 1 SCFTs that arise from N M5branes wrapped on a spindle, embedded as a holomorphic curve inside a CalabiYau threefold. In contrast to the usual topological twist solutions, the superconformal Rsymmetry mixes with the isometry of the spindle in the IR, and we verify this via a field theory calculation, as well as reproducing the gravity formula for the central charge.

Conference paperJones H, Kulishov M, 2021,
Solitons in a PTsymmetric gratingassisted codirectional coupler
, ISSN: 17426588We explore a codirectional coupling arrangement between two waveguides mediated by a PTsymmetric sinusoidal grating characterized by an indexmodulation parameter κ and a gain/loss parameter g. We show that the device supports solitonlike solutions for both the PTconserving regime g < κ and the PTbroken regime g > κ. In the first case the coupler exhibits a gap in wavenumber k, and the solitons can be regarded as an extension of a previous solution found for pure index modulation. In the second case the coupler exhibits a gap in frequency ω and the solutions are entirely new.

Journal articleCamargoMolina JE, Enberg R, Lofgren J, 2021,
A new perspective on the electroweak phase transition in the Standard Model Effective Field Theory
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 10298479 
Journal articleCassani D, Gauntlett JP, Martelli D, et al., 2021,
Thermodynamics of accelerating and supersymmetric AdS(4) black holes
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 123, ISSN: 15502368We study the thermodynamics of AdS4 black hole solutions of EinsteinMaxwell theory that are accelerating, rotating, and carry electric and magnetic charges. We focus on the class for which the black hole horizon is a spindle and can be uplifted on regular SasakiEinstein spaces to give solutions of D=11 supergravity that are free from conical singularities. We use holography to calculate the Euclidean onshell action and to define a set of conserved charges which give rise to a first law. We identify a complex locus of supersymmetric and nonextremal solutions, defined through an analytic continuation of the parameters, upon which we obtain a simple expression for the onshell action. A Legendre transform of this action combined with a reality constraint then leads to the BekensteinHawking entropy for the class of supersymmetric and extremal black holes.

Journal articleBeccaria 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: 142, ISSN: 10298479As a continuation of the study (in arXiv:2102.07696 and arXiv:2104.12625) of strongcoupling expansion of nonplanar corrections in N = 2 4d superconformal models we consider two special theories with gauge groups SU(N) and Sp(2N). They contain Nindependent numbers of hypermultiplets in rank 2 antisymmetric and fundamental representations and are planarequivalent to the corresponding N = 4 SYM theories. These N = 2 theories can be realised on a system of N D3branes with a finite number of D7branes and O7plane; 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 12BPS 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 nonplanar 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 articleKarnesis N, Babak S, Pieroni M, et al., 2021,
Characterization of the stochastic signal originating from compact binary populations as measured by LISA
, PHYSICAL REVIEW D, Vol: 104, ISSN: 24700010 Author Web Link
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 Citations: 32

Journal articleMomeni A, Rumbutis J, Tolley AJ, 2021,
KaluzaKlein from colourkinematics duality for massive fields
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 10298479 Author Web Link
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 Citations: 13

Journal articleTennyson D, Waldram D, 2021,
Exceptional complex structures and the hypermultiplet moduli of 5d Minkowski compactifications of Mtheory
, The Journal of High Energy Physics, Vol: 201, Pages: 164, ISSN: 10298479We 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 Mtheory or type IIB supergravity in six or five dimensions, and as such characterises, in part, the geometry of generic supersymmetric compactifications to fivedimensional 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 Mtheory of the form ℝ4,1 × M, where the SU*(6) moduli correspond to the hypermultiplet moduli in the lowerdimensional theory. Such geometries are of class zero or one. The former are equivalent to a choice of (nonmetriccompatible) conventional SL(3, ℂ) structure and strikingly have the same space of hypermultiplet moduli as the fluxless CalabiYau case.

Journal articleGomis J, Joung E, Kleinschmidt A, et al., 2021,
Colourful Poincare symmetry, gravity and particle actions
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 10298479 
Journal articleFerrero P, Gauntlett JP, Ipina JMP, et al., 2021,
Accelerating black holes and spinning spindles
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 137, ISSN: 15502368We 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 EinsteinMaxwell 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 SasakiEinstein sevenmanifold, 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 twodimensional 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 articleBourget A, Dancer A, Grimminger JF, et al., 2021,
Orthosymplectic implosions
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 10298479 Author Web Link
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 Citations: 7

Journal articlede Rham C, Melville S, Noller J, 2021,
Positivity bounds on dark energy: when matter matters
, Journal of Cosmology and Astroparticle Physics, Vol: 2021, Pages: 125, ISSN: 14757516Positivity bounds — constraints on any lowenergy effective field theory imposed by the fundamental axioms of unitarity, causality and locality in the UV — have recently been used to constrain scalartensor 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 articlePage J, Magueijo J, 2021,
Linking the BaumHawkingColeman mechanism with unimodular gravity and Vilenkin's probability flux
, Journal of Cosmology and Astroparticle Physics, Vol: 2021, Pages: 114, ISSN: 14757516We 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 fourform field strength F = dA to the cosmological constant via a dynamical field λ(x), a novel BaumHawkingColeman 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 3form is closely related to the ChernSimons 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 articleAllanach BC, CamargoMolina JE, Davighi J, 2021,
Global fits of third family hypercharge models to neutral current Banomalies and electroweak precision observables
, EUROPEAN PHYSICAL JOURNAL C, Vol: 81, ISSN: 14346044 Author Web Link
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 Citations: 11

Journal articleGoodhew H, Jazayeri S, Lee MHG, et al., 2021,
Cutting cosmological correlators
, Journal of Cosmology and Astroparticle Physics, Vol: 2021, ISSN: 14757516The 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 singlecut rules that generalize the Cosmological Optical Theorem and relate a certain discontinuity of any treelevel npoint function to that of lowerpoint functions. Our rules are closely related to, but distinct from the recently derived Cosmological Cutting Rules. They follow from the choice of the BunchDavies vacuum and a simple property of the (bulktobulk) 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 BunchDavies vacuum, including de Sitter, slowroll inflation, powerlaw cosmologies and even resonant oscillations in axion monodromy. We verify the singlecut rules in a number of nontrivial examples, including four massless scalars exchanging a massive scalar, as relevant for cosmological collider physics, four gravitons exchanging a graviton, and a scalar fivepoint function.

Journal articleAlday F, Argyres P, Lemos M, et al., 2021,
The Pollica perspective on the (super)conformal world
, JOURNAL OF PHYSICS AMATHEMATICAL AND THEORETICAL, Vol: 54, ISSN: 17518113 Author Web Link
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 Citations: 1

Journal articleYao Q, Evans T, Chen B, et al., 2021,
Higherorder temporal network effects through triplet evolution
, Scientific Reports, Vol: 11, Pages: 117, ISSN: 20452322We study the evolution of networks through ‘triplets’ — threenode graphlets. We develop a method to compute a transitionmatrix to describe the evolution of triplets in temporal networks. To identify the importance of higherorder interactions inthe evolution of networks, we compare both artificial and realworld 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 nonpairwise interactions exist for various realworld systems in space and time, such as our data sets. Furthermore,this also reveals that different patterns of higherorder interaction are involved in different realworld 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 higherorder 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 nonlocal interactions, give the best overall performance. Theresults also confirm the concept that the higherorder interaction patterns, i.e., triplet dynamics, can help us understandand predict the evolution of different realworld systems.

Journal articleGould O, Ho DLJ, Rajantie A, 2021,
Schwinger pair production of magnetic monopoles: momentum distribution for heavyion collisions
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, ISSN: 15502368Magnetic 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 heavyion collisions. We use thecomplex worldline instanton method to calculate the momentum distribution of magnetic monopolesproduced in heavyion collisions, in an approximation that includes the effect of the magnetic field to allorders but neglects monopole selfinteractions. The result saturates the preparation timeenergy uncertaintyprinciple, and yields a necessary ingredient for experimental monopole searches in heavyion collisions.

Journal articleArav I, Gauntlett JP, Roberts MM, et al., 2021,
Marginal deformations and RG flows for type IIB Sfolds
, The Journal of High Energy Physics, Vol: 2021, Pages: 141, ISSN: 10298479We construct a continuous one parameter family of AdS4 × S1 × S5 Sfold 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 Sfold 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 Sfold solutions, dual to d = 3 SCFTs. We construct additional flows between the AdS5 dual of the LeighStrassler SCFT and an N = 2 Sfold as well as RG flows between various Sfolds.

Journal articleKaram A, Markkanen T, Marzola L, et al., 2021,
Higgslike spectator field as the origin of structure
, European Physical Journal C: Particles and Fields, Vol: 81, ISSN: 11241861We 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 nonrenormalisable interactions. The scenario gives rise to local nonGaussianity 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 righthanded neutrinos. For the Standard Model running we find, however, that the scenario analysed does not seem to produce the observed perturbation.

Journal articleBeccaria M, Dunne G, Tseytlin AA, 2021,
BPS Wilson loop in N=2 superconformal SU(N) "orientifold" gauge theory and weakstrong coupling interpolation
, The Journal of High Energy Physics, Vol: 2021, Pages: 130, ISSN: 10298479We 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 rank2 symmetric and antisymmetric representations. This theory admits a regular large N expansion, is planarequivalent 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 nonplanar 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 highprecision resummation and extrapolation of the weakcoupling expansion using conformal mapping improved Padé analysis.

Journal articleGolat 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: 14, ISSN: 03702693Signals from millisecond pulsars travel to us on geodesics along the lineofsight that are affected by the space–time metric. The exact pathgeometry and redshifting along the geodesics determine the observed TimeofArrival (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 linesofsight. This suggests geodesic noise is relevant for estimates of PTA sensitivity and may limit future efforts for detection of gravitational waves by PTAs.

Journal articleMagueijo J, 2021,
Cosmological time and the constants of nature
, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 820, Pages: 14, ISSN: 03702693We 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 ChernSimons 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 articleMagueijo J, 2021,
Real ChernSimons wave function
, Physical Review D, Vol: 104, Pages: 110, ISSN: 24700010We examine the status of the ChernSimons (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 selfdual 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) EinsteinCartan action, forgoing the addition of the usual Holst (or NiehYan) term with an imaginary coefficient. It is then found that the constraints are solved by a modification of the ChernSimons state which is a pure phase (in the Lorentzian theory, we stress), the phase containing only the fully gaugeinvariant imaginary part of the ChernSimons 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 ChernSimons 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 ChernSimons integral. The trick only works for the quasiEuler theory with a critical coupling previously identified in the literature. It does not apply to the quasiPontryagin theory.

Journal articleChester SM, 2021,
Anomalous dimensions of monopole operators in scalar QED3 with ChernSimons 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 ChernSimons 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:inlineformula><jats:alternatives><jats:texmath>$$ \mathrm{\ell}<O\left(\sqrt{N}\right) $$</jats:texmath><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ℓ</mml:mi> <mml:mo><</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:inlineformula> and associated flavor representations are expected to have the same scaling dimension to subleading order in 1/<jats:italic>N</jats:italic>. We use the stateoperator correspondence to calculate the scaling dimension to subleading 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 subleading order for monopoles with

Journal articleHo DLJ, Rajantie A, 2021,
Instanton solution for Schwinger production of 't HooftPolyakov monopoles
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 19, ISSN: 15502368We present the results of an explicit numerical computation of a novel instanton in GeorgiGlashow 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 AmbjørnOlesen critical field strength.

Journal articleAlberte L, de Rham C, Jaitly S, et al., 2021,
QED positivity bounds
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 126, ISSN: 15502368We 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 tchannel 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 EulerHeisenberg 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 articleXie Y, Zhang J, Silva HO, et 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: 17, ISSN: 00319007The 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.
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