Search results for "Effective Field Theory"
showing 10 items of 212 documents
Derivation of spontaneously broken gauge symmetry from the consistency of effective field theory I: Massive vector bosons coupled to a scalar field
2018
We revisit the problem of deriving local gauge invariance with spontaneous symmetry breaking in the context of an effective field theory. Previous derivations were based on the condition of tree-order unitarity. However, the modern point of view considers the Standard Model as the leading order approximation to an effective field theory. As tree-order unitarity is in any case violated by higher-order terms in an effective field theory, it is instructive to investigate a formalism which can be also applied to analyze higher-order interactions. In the current work we consider an effective field theory of massive vector bosons interacting with a massive scalar field. We impose the conditions o…
DsixTools 2.0: The Effective Field Theory Toolkit
2021
$\tt DsixTools$ is a Mathematica package for the handling of the Standard Model Effective Field Theory (SMEFT) and the Low-energy Effective Field Theory (LEFT) with operators up to dimension six, both at the algebraic and numerical level. $\tt DsixTools$ contains a visually accessible and operationally convenient repository of all operators and parameters of the SMEFT and the LEFT. This repository also provides information concerning symmetry categories and number of degrees of freedom, and routines that allow to implement this information on global expressions (such as decay amplitudes and cross-sections). $\tt DsixTools$ also performs weak basis transformations, and implements the full on…
Factorization at Subleading Power, Sudakov Resummation and Endpoint Divergences in Soft-Collinear Effective Theory
2020
Starting from the first renormalized factorization theorem for a process described at subleading power in soft-collinear effective theory, we discuss the resummation of Sudakov logarithms for such processes in renormalization-group improved perturbation theory. Endpoint divergences in convolution integrals, which arise generically beyond leading power, are regularized and removed by systematically rearranging the factorization formula. We study in detail the example of the $b$-quark induced $h\to\gamma\gamma$ decay of the Higgs boson, for which we resum large logarithms of the ratio $M_h/m_b$ at next-to-leading logarithmic order. We also briefly discuss the related $gg\to h$ amplitude.
Born-Infeld Gravity: Constraints from Light-by-Light Scattering and an Effective Field Theory Perspective
2021
By using a novel technique that establishes a correspondence between general relativity and metric-affine theories based on the Ricci tensor, we are able to set stringent constraints on the free parameter of Born-Infeld gravity from the ones recently obtained for Born-Infeld electrodynamics by using light-by-light scattering data from ATLAS. We also discuss how these gravity theories plus matter fit within an effective field theory framework.
Structure of infrared singularities of gauge-theory amplitudes at three and four loops
2012
The infrared divergences of massless n-parton scattering amplitudes can be derived from the anomalous dimension of n-jet operators in soft-collinear effective theory. Up to three-loop order, the latter has been shown to have a very simple structure: it contains pairwise color-dipole interactions among the external partons, governed by the cusp anomalous dimension and a logarithm of the kinematic invariants s_{ij}, plus a possible three-loop correlation involving four particles, which is described by a yet unknown function of conformal cross ratios of kinematic invariants. This function is constrained by two-particle collinear limits and by the known behavior of amplitudes in the high-energy…
Multigluonic scattering amplitudes of heavy quarks
2005
We consider heavy quark and antiquark off-shell spinorial currents with emission of an arbitrary number of gluons of positive helicity. From this results we calculate the corresponding on-shell scattering amplitude and the quark-antiquark vector current. Then, we show that in the heavy top quark effective theory the holomorfic component of the Higgs $\to q \bar{q} + n$-gluon amplitude vanish for helicity conserving configurations.
Generalized Slow Roll in the Unified Effective Field Theory of Inflation
2017
We provide a compact and unified treatment of power spectrum observables for the effective field theory (EFT) of inflation with the complete set of operators that lead to second-order equations of motion in metric perturbations in both space and time derivatives, including Horndeski and GLPV theories. We relate the EFT operators in ADM form to the four additional free functions of time in the scalar and tensor equations. Using the generalized slow roll formalism, we show that each power spectrum can be described by an integral over a single source that is a function of its respective sound horizon. With this correspondence, existing model independent constraints on the source function can b…
Consistent QFT description of non-standard neutrino interactions
2019
Neutrino oscillations are precision probes of new physics beyond the Standard Model. Apart from neutrino masses and mixings, they are also sensitive to possible deviations of low-energy interactions between quarks and leptons from the Standard Model predictions. In this paper we develop a systematic description of such non-standard interactions (NSI) in oscillation experiments within the quantum field theory framework. We calculate the event rate and oscillation probability in the presence of general NSI, starting from the effective field theory (EFT) in which new physics modifies the flavor or Lorentz structure of charged-current interactions between leptons and quarks. We also provide the…
Critical reflections on asymptotically safe gravity
2020
Asymptotic safety is a theoretical proposal for the ultraviolet completion of quantum field theories, in particular for quantum gravity. Significant progress on this program has led to a first characterization of the Reuter fixed point. Further advancement in our understanding of the nature of quantum spacetime requires addressing a number of open questions and challenges. Here, we aim at providing a critical reflection on the state of the art in the asymptotic safety program, specifying and elaborating on open questions of both technical and conceptual nature. We also point out systematic pathways, in various stages of practical implementation, towards answering them. Finally, we also take…
Sterile Neutrinos, Black Hole Vacuum and Holographic Principle
2021
We construct an effective field theory (EFT) model that describes matter field interactions with Schwarzschild mini-black-holes (SBH's), treated as a scalar field, $B_0(x)$. Fermion interactions with SBH's require a random complex spurion field, $\theta_{ij}$, which we interpret as the EFT description of "holographic information," which is correlated with the SBH as a composite system. We consider Hawking's virtual black hole vacuum (VBH) as a Higgs phase, $\langle B_0 \rangle =V$. Integrating sterile neutrino loops, the field $\theta_{ij}$ is promoted to a dynamical field, necessarily developing a tachyonic instability and acquiring a VEV of order the Planck scale. For $N$ sterile neutrino…