scholarly journals Causality constraints in Quadratic Gravity

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
José D. Edelstein ◽  
Rajes Ghosh ◽  
Alok Laddha ◽  
Sudipta Sarkar
Keyword(s):  
Gravitational Interaction ◽  
Equations Of Motion ◽  
High Energy ◽  
Effective Field ◽  
Field Theories ◽  
Causality Violation ◽  
Higher Derivative ◽  
Quadratic Gravity ◽  
General Relativistic ◽  
The Subject

Abstract Classifying consistent effective field theories for the gravitational interaction has recently been the subject of intense research. Demanding the absence of causality violation in high energy graviton scattering processes has led to a hierarchy of constraints on higher derivative terms in the Lagrangian. Most of these constraints have relied on analysis that is performed in general relativistic backgrounds, as opposed to a generic solution to the equations of motion which are perturbed by higher curvature operators. Hence, these constraints are necessary but may not be sufficient to ensure that the theory is consistent. In this context, we explore the so-called CEMZ causality constraints on Quadratic Gravity in a space of shock wave solutions beyond GR. We show that the Shapiro time delay experienced by a graviton is polarization-independent and positive, regardless of the strength of the gravitational couplings. Our analysis shows that as far as the causality constraints are concerned, albeit inequivalent to General Relativity due to additional propagating modes, Quadratic Gravity is causal as per as the diagnostic proposed by CEMZ.

scholarly journals Effective theories with dark matter applications

2021 ◽  
Author(s):  
Subhaditya Bhattacharya ◽  
José Wudka
Keyword(s):  
Field Theory ◽  
Dark Matter ◽  
Effective Field Theory ◽  
Particle Physics ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
The Subject ◽  
Effective Theories ◽  
Detailed Nature

Standard Model (SM) of particle physics has achieved enormous success in describing the interactions among the known fundamental constituents of nature, yet it fails to describe phenomena for which there is very strong experimental evidence, such as the existence of dark matter, and which point to the existence of new physics not included in that model; beyond its existence, experimental data, however, have not provided clear indications as to the nature of that new physics. The effective field theory (EFT) approach, the subject of this review, is designed for this type of situations; it provides a consistent and unbiased framework within which to study new physics effects whose existence is expected but whose detailed nature is known very imperfectly. We will provide a description of this approach together with a discussion of some of its basic theoretical aspects. We then consider applications to high-energy phenomenology and conclude with a discussion of the application of EFT techniques to the study of dark matter physics and its possible interactions with the SM. In several of the applications we also briefly discuss specific models that are ultraviolet complete and may realize the effects described by the EFT.

scholarly journals Power counting and Wilsonian renormalization in nuclear effective field theory

2016 ◽  
Vol 25 (05) ◽  
pp. 1641007 ◽  
Author(s):  
Manuel Pavón Valderrama
Keyword(s):  
Field Theory ◽  
Effective Field Theories ◽  
Effective Field Theory ◽  
Nuclear Physics ◽  
High Energy ◽  
Effective Field ◽  
Power Counting ◽  
Low Energy ◽  
Field Theories ◽  
Nuclear Forces

Effective field theories are the most general tool for the description of low energy phenomena. They are universal and systematic: they can be formulated for any low energy systems we can think of and offer a clear guide on how to calculate predictions with reliable error estimates, a feature that is called power counting. These properties can be easily understood in Wilsonian renormalization, in which effective field theories are the low energy renormalization group evolution of a more fundamental — perhaps unknown or unsolvable — high energy theory. In nuclear physics they provide the possibility of a theoretically sound derivation of nuclear forces without having to solve quantum chromodynamics explicitly. However there is the problem of how to organize calculations within nuclear effective field theory: the traditional knowledge about power counting is perturbative but nuclear physics is not. Yet power counting can be derived in Wilsonian renormalization and there is already a fairly good understanding of how to apply these ideas to non-perturbative phenomena and in particular to nuclear physics. Here we review a few of these ideas, explain power counting in two-nucleon scattering and reactions with external probes and hint at how to extend the present analysis beyond the two-body problem.

scholarly journals 2, 84, 30, 993, 560, 15456, 11962, 261485, . . .: higher dimension operators in the SM EFT

2017 ◽  
Vol 2017 (8) ◽  
Author(s):  
Brian Henning ◽  
Xiaochuan Lu ◽  
Tom Melia ◽  
Hitoshi Murayama
Keyword(s):  
Equations Of Motion ◽  
Companion Paper ◽  
Effective Field ◽  
Conformal Group ◽  
Field Theories ◽  
Irreducible Representations ◽  
Higher Dimension ◽  
The Standard Model ◽  
Mass Dimension ◽  
Fermion Generation

Abstract In a companion paper [1], we show that operator bases for general effective field theories are controlled by the conformal algebra. Equations of motion and integration by parts identities can be systematically treated by organizing operators into irreducible representations of the conformal group. In the present work, we use this result to study the standard model effective field theory (SM EFT), determining the content and number of higher dimension operators up to dimension 12, for an arbitrary number of fermion generations. We find additional operators to those that have appeared in the literature at dimension 7 (specifically in the case of more than one fermion generation) and at dimension 8. (The title sequence is the total number of independent operators in the SM EFT with one fermion generation, including hermitian conjugates, ordered in mass dimension, starting at dimension 5.)

scholarly journals Graviballs and dark matter

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
B. Guiot ◽  
A. Borquez ◽  
A. Deur ◽  
K. Werner
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Gravitational Interaction ◽  
Equations Of Motion ◽  
High Energy ◽  
Dark Matter Candidate ◽  
Hole Formation ◽  
Time Dynamics ◽  
Energy Quantum ◽  
Relativistic Equations

Abstract We investigate the possible existence of graviballs, a system of bound gravitons, and show that two gravitons can be bound together by their gravitational interaction. This idea connects to black hole formation by a high-energy 2 → N scattering and to the gravitational geon studied by Brill and Hartle. Our calculations rely on the formalism and techniques of quantum field theory, specifically on low-energy quantum gravity. By solving numerically the relativistic equations of motion, we have access to the space-time dynamics of the (2-gravitons) graviball formation. We argue that the graviball is a viable dark matter candidate and we compute the associated gravitational lensing.

scholarly journals Multi-spin soft bootstrap and scalar-vector Galileon

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Karol Kampf ◽  
Jiří Novotný ◽  
Filip Přeučil ◽  
Jaroslav Trnka
Keyword(s):  
Effective Field Theories ◽  
Sigma Model ◽  
Bootstrap Method ◽  
Effective Field ◽  
Power Counting ◽  
Field Theories ◽  
Linear Sigma Model ◽  
Higher Derivative ◽  
Soft Limit ◽  
General Power

Abstract We use the amplitude soft bootstrap method to explore the space of effective field theories (EFT) of massless vectors and scalars. It is known that demanding vanishing soft limits fixes uniquely a special class of EFTs: non-linear sigma model, scalar Galileon and Born-Infeld theories. Based on the amplitudes analysis, we conjecture no-go theorems for higher-derivative vector theories and theories with coupled vectors and scalars. We then allow for more general soft theorems where the non-trivial part of the soft limit of the (n+1)-pt amplitude is equal to a linear combination of n-pt amplitudes. We derive the form of these soft theorems for general power-counting and spins of particles and use it as an input into the soft bootstrap method in the case of Galileon power-counting and coupled scalar-vector theories. We show that this unifies the description of existing Galileon theories and leads us to the discovery of a new exceptional theory: Special scalar-vector Galileon.

scholarly journals TOPOLOGICAL EFFECTIVE FIELD THEORIES FOR DIRAC FERMIONS FROM INDEX THEOREM

2013 ◽  
Vol 28 (01) ◽  
pp. 1350193 ◽  
Author(s):  
GIANDOMENICO PALUMBO ◽  
ROBERTO CATENACCI ◽  
ANNALISA MARZUOLI
Keyword(s):  
Effective Field Theories ◽  
Effective Action ◽  
Axial Vector ◽  
Index Theorem ◽  
High Energy ◽  
Effective Field ◽  
Field Theories ◽  
Gauge Fields ◽  
Dirac Fermions ◽  
Topological Order

Dirac fermions have a central role in high energy physics but it is well-known that they emerge also as quasiparticles in several condensed matter systems supporting topological order. We present a general method for deriving the topological effective actions of (3+1)-massless Dirac fermions living on general backgrounds and coupled with vector and axial-vector gauge fields. The first step of our strategy is standard (in the Hermitian case) and consists in connecting the determinants of Dirac operators with the corresponding analytical indices through the zeta-function regularization. Then, we introduce a suitable splitting of the heat kernel that naturally selects the purely topological part of the determinant (i.e., the topological effective action). This topological effective action is expressed in terms of gauge fields using the Atiyah–Singer index theorem which computes the analytical index in topological terms. The main new result of this paper is to provide a consistent extension of this method to the non-Hermitian case, where a well-defined determinant does not exist. Quantum systems supporting relativistic fermions can thus be topologically classified on the basis of their response to the presence of (external or emergent) gauge fields through the corresponding topological effective field theories (TEFTs).

scholarly journals Matching effective few-nucleon theories to QCD

2016 ◽  
Vol 25 (05) ◽  
pp. 1641001 ◽  
Author(s):  
J. Kirscher
Keyword(s):  
Effective Field Theories ◽  
Electromagnetic Coupling ◽  
High Energy ◽  
Effective Field ◽  
Coupling Constants ◽  
Field Theories ◽  
Current Status ◽  
Theoretical Understanding ◽  
Fundamental Parameters ◽  
Quark Masses

The emergence of complex macroscopic phenomena from a small set of parameters and microscopic concepts demonstrates the power and beauty of physical theories. A theory which relates the wealth of data and peculiarities found in nuclei to the small number of parameters and symmetries of quantum chromodynamics is by that standard of exceptional beauty. Decade-long research on computational physics and on effective field theories facilitate the assessment of the presumption that quark masses and strong and electromagnetic coupling constants suffice to parametrize the nuclear chart. By presenting the current status of that enterprise, this article touches the methodology of predicting nuclei by simulating the constituting quarks and gluons and the development of effective field theories as appropriate representations of the fundamental theory. While the nuclear spectra and electromagnetic responses analyzed computationally so far with lattice QCD are in close resemblance to those which intrigued experimentalists a century ago, they also test the theoretical understanding which was unavailable to guide the nuclear pioneers but developed since then. This understanding is shown to be deficient in terms of correlations amongst nuclear observables and their sensitivity to fundamental parameters. By reviewing the transition from one effective field theory to another, from QCD to pionful chiral theories to pionless and eventually to cluster theories, we identify some of those deficiencies and conceptual problems awaiting a solution before QCD can be identified as the high-energy theory from which the nuclear landscape emerges.

scholarly journals Horizon radiation reaction forces

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Walter D. Goldberger ◽  
Ira Z. Rothstein
Keyword(s):  
Black Hole ◽  
Equations Of Motion ◽  
Finite Size ◽  
Radiation Reaction ◽  
Effective Field ◽  
Compact Objects ◽  
Finite Size Effect ◽  
Binary Black Holes ◽  
Dissipative Effects ◽  
Reaction Forces

Abstract Using Effective Field Theory (EFT) methods, we compute the effects of horizon dissipation on the gravitational interactions of relativistic binary black hole systems. We assume that the dynamics is perturbative, i.e it admits an expansion in powers of Newton’s constant (post-Minkowskian, or PM, approximation). As applications, we compute corrections to the scattering angle in a black hole collision due to dissipative effects to leading PM order, as well as the post-Newtonian (PN) corrections to the equations of motion of binary black holes in non-relativistic orbits, which represents the leading order finite size effect in the equations of motion. The methods developed here are also applicable to the case of more general compact objects, eg. neutron stars, where the magnitude of the dissipative effects depends on non-gravitational physics (e.g, the equation of state for nuclear matter).

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