Nonlinear, noniterative treatment of EFT-motivated gravity

Cayuso, Ramiro; Lehner, Luis

doi:10.1103/physrevd.102.084008

Cited by 54 publications

(42 citation statements)

References 40 publications

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“…(14)] and ( 17) of the complex scalar φ and needs to be computed from Eqs. (45).] The initial data for the metric variables, obtained after solving the constraint equations, is also in agreement.…”

Section: A Eft Evolution and Tricomi-type Breakdownmentioning

confidence: 52%

“…The "fixing the equations" approach [43] (see also Refs. [44,45]) provides a prescription to control the high frequency behavior of an EFT, which may be the cause of ill-posedness of the Cauchy problem. In the following, we will apply this prescription to k-essence.…”

Section: B Fixing the Equationsmentioning

confidence: 99%

“…[43] (see also Refs. [44,45]), partly inspired by dissipative hydrodynamics, and was successfully applied to gravitational collapse in k-essence by Refs. [30,31] (where it was shown to reproduce the results obtained in a gauge where breakdowns of the Cauchy problem are avoided).…”

Section: Introductionmentioning

confidence: 99%

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UV completions, fixing the equations and nonlinearities in $k$-essence

Lara,

Bezares,

Barausse

2021

Preprint

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Scalar-tensor theories with first-derivative self interactions, known as k-essence, may provide interesting phenomenology on cosmological scales. On smaller scales, however, initial value evolutions (which are crucial for predicting the behavior of astrophysical systems, such as binaries of compact objects) may run into instabilities related to the Cauchy problem becoming potentially ill-posed. Moreover, on local scales the dynamics may enter in the nonlinear regime, which may lie beyond the range of validity of the infrared theory. Completions of k-essence in the ultraviolet, when they are known to exist, mitigate these problems, as they both render Cauchy evolutions well-posed at all times, and allow for checking the relation between nonlinearities and the low energy theory's range of validity. Here, we explore these issues explicitly by considering an ultraviolet completion to k-essence and performing vacuum 1+1 dynamical evolutions within it. The results are compared to those obtained with the low-energy theory, and with the low-energy theory suitably deformed with a phenomenological "fixing the equations" approach. We confirm that the ultraviolet completion does not incur in any breakdown of the Cauchy problem's well-posedness, and we find that evolutions agree with the results of the low-energy theory, when the system is within the regime of validity of the latter. However, we also find that the nonlinear behavior of k-essence lies (for the most part) outside this regime.

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Section: A Eft Evolution and Tricomi-type Breakdownmentioning

confidence: 52%

Section: B Fixing the Equationsmentioning

confidence: 99%

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UV completions, fixing the equations and nonlinearities in $k$-essence

Lara,

Bezares,

Barausse

2021

Preprint

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“…This is useful both when these smaller scales are understood and when they are not. Although EFT methods have a long history, their use is even now still being developed for black hole applications [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]; a development that has been slowed both by the relative novelty of EFT applications to gravity in general [10,[28][29][30][31][32] and by some of the novel aspects of black hole physics in particular, since these differ from more garden-variety applications of EFT techniques.…”

Section: Introductionmentioning

confidence: 99%

“…One issue -though not the only one [25][26][27] -that complicates developing EFT methods for black-hole behaviour is their open and thermal nature, since the entanglement and decoherence that such physics can involve is not captured by traditional Wilsonian EFT tools. Such differences have led some to ask whether an effective description of extra-horizon physics might involve unusual features (such as nonlocality) or otherwise evade the arguments that usually preclude these phenomena from arising in a Wilsonian context [33][34][35][36][37][38][39][40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Influence through mixing: hotspots as benchmarks for basic black-hole behaviour

Kaplanek

Burgess

Holman³

2021

J. High Energ. Phys.

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Effective theories are being developed for fields outside black holes, often with an unusual open-system feel due to the influence of large number of degrees of freedom that lie out of reach beyond the horizon. What is often difficult when interpreting such theories is the absence of comparisons to simpler systems that share these features. We propose here such a simple model, involving a single external scalar field that mixes in a limited region of space with a ‘hotspot’ containing a large number of hot internal degrees of freedom. Since the model is at heart gaussian it can be solved explicitly, and we do so for the mode functions and correlation functions for the external field once the hotspot fields are traced out. We compare with calculations that work perturbatively in the mixing parameter, and by doing so can precisely identify its domain of validity. We also show how renormalization-group EFT methods can allow some perturbative contributions to be resummed beyond leading order, verifying the result using the exact expression.

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Qubit heating near a hotspot

Kaplanek

Burgess

Holman³

2021

J. High Energ. Phys.

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Effective theories describing black hole exteriors contain many open-system features due to the large number of gapless degrees of freedom that lie beyond reach across the horizon. A simple solvable Caldeira-Leggett type model of a quantum field interacting within a small area with many unmeasured thermal degrees of freedom was recently proposed in ref. [23] to provide a toy model of this kind of dynamics against which more complete black hole calculations might be compared. We here compute the response of a simple Unruh-DeWitt detector (or qubit) interacting with a massless quantum field ϕ coupled to such a hotspot. Our treatment differs from traditional treatments of Unruh-DeWitt detectors by using Open-EFT tools to reliably calculate the qubit’s late-time behaviour. We use these tools to determine the efficiency with which the qubit thermalizes as a function of its proximity to the hotspot. We identify a Markovian regime in which thermalization does occur, though only for qubits closer to the hotspot than a characteristic distance scale set by the ϕ-hotspot coupling. We compute the thermalization time, and find that it varies inversely with the ϕ-qubit coupling strength in the standard way.

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Nonlinear, noniterative treatment of EFT-motivated gravity

Cited by 54 publications

References 40 publications

UV completions, fixing the equations and nonlinearities in $k$-essence

UV completions, fixing the equations and nonlinearities in $k$-essence

Influence through mixing: hotspots as benchmarks for basic black-hole behaviour

Qubit heating near a hotspot

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