Positivity of Amplitudes, Weak Gravity Conjecture, and Modified Gravity

Bellazzini, Brando; Lewandowski, Matthew; Serra, Javi

doi:10.1103/physrevlett.123.251103

Cited by 161 publications

(219 citation statements)

References 38 publications

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“…Thus, not all the solutions of the Einstein-Maxwell theory can be embedded in the Heterotic Superstring effective action because unequal electric and magnetic charges always generate a non-trivial scalar field. quantum black hole physics is currently attracting much attention [19,34,35,31,36,37,32,20,33,38]. A recurrent assumption in these explorations is that no additional degrees of freedom are activated at higher orders.…”

Section: Discussionmentioning

confidence: 99%

α′ corrections of Reissner-Nordström black holes

Cano

Chimento

Linares

et al. 2020

J. High Energ. Phys.

109

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We study the first-order in α corrections to non-extremal 4-dimensional dyonic Reissner-Nordström (RN) black holes with equal electric and magnetic charges in the context of Heterotic Superstring effective field theory (HST) compactified on a T 6 . The particular embedding of the dyonic RN black hole in HST considered here is not supersymmetric in the extremal limit. We show that, at first order in α , consistency with the equations of motion of the HST demands additional scalar and vector fields become active, and we provide explicit expressions for all of them. We determine analytically the position of the event horizon of the black hole, as well as the corrections to the extremality bound, to the temperature and to the entropy, checking that they are related by the first law of black-hole thermodynamics, so that ∂S/∂M = 1/T. We discuss the implications of our results in the context of the Weak Gravity Conjecture, clarifying that entropy corrections for fixed mass and charge at extremality do not necessarily imply corrections to the extremal chargeto-mass ratio. a pabloantonio.cano[at]kuleuven.be

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Section: Discussionmentioning

confidence: 99%

α′ corrections of Reissner-Nordström black holes

Cano

Chimento

Linares

et al. 2020

J. High Energ. Phys.

109

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“…For example S-matrix positivity arguments have been applied to quartic curvature interactions in [26]. Recent works have applied these ideas more specifically to the weak gravity conjecture, which focusses on the EFT for gravity and a U (1) gauge field [27][28][29]. In what follows we shall see that positivity bounds will provide very useful guidance on corrections to propagation speeds.…”

Section: Contentsmentioning

confidence: 99%

Speed of gravity

Rham

Tolley

2020

Phys. Rev. D

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Within the standard effective field theory of General Relativity, we show that the speed of gravitational waves deviates, ever so slightly, from luminality on cosmological and other spontaneously Lorentz-breaking backgrounds. This effect results from loop contributions from massive fields of any spin, including Standard Model fields, or from tree level effects from massive higher spins s ≥ 2. We show that for the choice of interaction signs implied by S-matrix and spectral density positivity bounds suggested by analyticity and causality, the speed of gravitational waves is in general superluminal at low-energies on NEC preserving backgrounds, meaning gravitational waves travel faster than allowed by the metric to which photons and Standard Model fields are minimally coupled. We show that departure of the speed from unity increases in the IR and argue that the speed inevitably returns to luminal at high energies as required by Lorentz invariance. Performing a special tuning of the EFT so that renormalization sensitive curvature-squared terms are set to zero, we find that finite loop corrections from Standard Model fields still lead to an epoch dependent modification of the speed of gravitational waves which is determined by the precise field content of the lightest particles with masses larger than the Hubble parameter today. Depending on interpretation, such considerations could potentially have far-reaching implications on light scalar models, such as axionic or fuzzy cold dark matter. arXiv:1909.00881v2 [hep-th] 8 Sep 2019 B Tensor Modes on FLRW from Dimension-6 Operators 46 C Resumming Green's Function Secular Behaviour 49 Effective Field Theory for Gravity at Low-energyWe shall have in mind two different scenarios:• Tree level corrections to the EFT, whereby tree level effects of massive particles potentially generate higher curvature interactions• Loop level corrections to the EFT coming from integrating out standard matter (e.g. Standard Model fields) of any spin, including s ≤ 1.

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“…The dynamics of the new degree of freedom is parametrized in a general way, based on exact and approximate symmetries which provide well defined powercounting rules for the derivative and field expansions within the effective Lagrangian. The regime of applicability of the EFT is also imposed to be consistent with the strongest constraints coming from amplitude's positivity conditions derived up to now in this class of theories [27], which also ensures compatibility with constraints on the speed of gravitational waves [18].…”

Section: Discussionmentioning

confidence: 98%

“…It is well known that general properties of the S-matrix, unitarity, analyticity and crossing symmetry, imply positivity bounds for amplitudes at low energies, which in turn constrain the coefficients of EFT operators [26]. When these bounds are applied to theories with weakly broken galileon invariance [15], they imply that the separation between symmetry breaking and symmetry preserving operators cannot be too large while keeping the UV cutoff fixed [27] (see [28][29][30] for closely related prior work). More specifically, in the case of the Lagrangian (3) the condition becomes…”

Section: Introduction and Setupmentioning

confidence: 99%

Black hole ringdown as a probe for dark energy

2020

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Under the assumption that a dynamical scalar field is responsible for the current acceleration of the Universe, we explore the possibility of probing its physics in black hole merger processes with gravitational wave interferometers. Remaining agnostic about the microscopic physics, we use an effective field theory approach to describe the scalar dynamics. We investigate the case in which some of the higher derivative operators, that are highly suppressed on cosmological scales, instead become important on typical distances for black holes. If a coupling to the Gauss-Bonnet operator is one of them, a non-trivial background profile for the scalar field can be sourced in the surrounding of the black hole, resulting in a potentially large amount of 'hair'. In turn, this can induce sizeable modifications to the spacetime geometry or a mixing between the scalar and the gravitational perturbations. Both effects will ultimately translate into a modification of the quasi-normal mode spectrum in a way that is also sensitive to other operators besides the one sourcing the scalar background. The presence of deviations from the predictions of general relativity in the observed spectrum can therefore serve as a window onto dark energy physics.

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Positivity of Amplitudes, Weak Gravity Conjecture, and Modified Gravity

Cited by 161 publications

References 38 publications

α′ corrections of Reissner-Nordström black holes

α′ corrections of Reissner-Nordström black holes

Speed of gravity

Black hole ringdown as a probe for dark energy

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