scholarly journals Lattice studies of quantum chromodynamics-like theories with many fermionic degrees of freedom

2011 ◽  
Vol 369 (1946) ◽  
pp. 2701-2717 ◽  
Author(s):  
Thomas DeGrand
Keyword(s):  
Fixed Point ◽  
Standard Model ◽  
Quantum Chromodynamics ◽  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Gauge Coupling ◽  
Higgs Sector ◽  
Intrinsic Interest ◽  
The Standard Model

I give an elementary introduction to the study of gauge theories coupled to fermions with many degrees of freedom. Besides their intrinsic interest, these theories are candidates for non-perturbative extensions of the Higgs sector of the standard model. While related to quantum chromodynamics, these systems can exhibit very different behaviour from it: they can possess a running gauge coupling with an infrared-attractive fixed point. I briefly survey recent lattice work in this area.

scholarly journals Investigating BSM Models with Large Scale Separation

2018 ◽  
Vol 175 ◽  
pp. 08007 ◽  
Author(s):  
Anna Hasenfratz ◽  
Claudio Rebbi ◽  
Oliver Witzel
Keyword(s):  
Fixed Point ◽  
Standard Model ◽  
Large Scale ◽  
Gauge Coupling ◽  
Model Systems ◽  
Beyond The Standard Model ◽  
Heavy Flavor ◽  
Scale Separation ◽  
The Standard Model ◽  
Effective Description

Mass-split systems based on a conformal infrared fixed point provide a lowenergy effective description of beyond the standard model systems with large scale separation. We report results of exploratory investigations with four light and eight heavy flavors using staggered fermions, and up to five different values for the light flavor mass, five different heavy flavor masses, and two values of the bare gauge coupling.

scholarly journals CONSTRAINTS ON UNIFIED GAUGE THEORIES FROM NONCOMMUTATIVE GEOMETRY

1996 ◽  
Vol 11 (32n33) ◽  
pp. 2561-2572 ◽  
Author(s):  
F. LIZZI ◽  
G. MANGANO ◽  
G. MIELE ◽  
G. SPARANO
Keyword(s):  
Standard Model ◽  
Noncommutative Geometry ◽  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Gauge Groups ◽  
The Standard Model ◽  
Number Of Particles

We analyze the possibility to extend the Connes and Lott reformulation of the standard model to larger unified gauge groups. Noncommutative geometry imposes very stringent constraints on the possible theories, and remarkably, the analysis seems to suggest that no larger gauge groups are compatible with the noncommutative structure, unless one enlarges the fermionic degrees of freedom, namely the number of particles.

scholarly journals A study of how the particle spectra of SU(N) gauge theories with a fundamental Higgs emerge

2018 ◽  
Vol 175 ◽  
pp. 08002 ◽  
Author(s):  
Pascal Törek ◽  
Axel Maas ◽  
René Sondenheimer
Keyword(s):  
Standard Model ◽  
Gauge Theories ◽  
Higgs Field ◽  
Higgs Sector ◽  
Fundamental Representation ◽  
The Standard Model ◽  
Physical Spectrum ◽  
Particle Spectra ◽  
Invariant States ◽  
General Gauge

In gauge theories, the physical, experimentally observable spectrum consists only of gauge-invariant states. In the standard model the Fröhlich-Morchio-Strocchi mechanism shows that these states can be adequately mapped to the gauge-dependent elementary W, Z, Higgs, and fermions. In theories with a more general gauge group and Higgs sector, appearing in various extensions of the standard model, this has not to be the case. In this work we determine analytically the physical spectrum of SU(N > 2) gauge theories with a Higgs field in the fundamental representation. We show that discrepancies between the spectrum predicted by perturbation theory and the observable physical spectrum arise. We confirm these analytic findings with lattice simulations for N = 3.

scholarly journals Warm Dark Matter from Higher-Dimensional Gauge Theories

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 462
Author(s):  
Sinziana Paduroiu ◽  
Michael Rios ◽  
Alessio Marrani ◽  
David Chester
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Particle Physics ◽  
Degrees Of Freedom ◽  
Gauge Theories ◽  
The Other ◽  
Small Scale ◽  
Group Representations ◽  
Higher Dimensional ◽  
The Standard Model

Warm dark matter particles with masses in the keV range have been linked with the large group representations in gauge theories through a high number of species at decoupling. In this paper, we address WDM fermionic degrees of freedom from such representations. Bridging higher-dimensional particle physics theories with cosmology studies and astrophysical observations, our approach is two-folded, i.e., it includes realistic models from higher-dimensional representations and constraints from simulations tested against observations. Starting with superalgebras in exceptional periodicity theories, we discuss several symmetry reductions and we consider several representations that accommodate a high number of degrees of freedom. We isolate a model that naturally accommodates both the standard model representation and the fermionic dark matter in agreement with both large and small-scale constraints. This model considers an intersection of branes in D = 27 + 3 in a manner that provides the degrees of freedom for the standard model on one hand and 2048 fermionic degrees of freedom for dark matter, corresponding to a ∼2 keV particle mass, on the other. In this context, we discuss the theoretical implications and the observable predictions.

scholarly journals Complete leading-order standard model corrections to quantum leptogenesis

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Paul Frederik Depta ◽  
Andreas Halsch ◽  
Janine Hütig ◽  
Sebastian Mendizabal ◽  
Owe Philipsen
Keyword(s):  
Standard Model ◽  
Gauge Coupling ◽  
Thermal Bath ◽  
Leading Order ◽  
Boltzmann Equations ◽  
The Standard Model ◽  
Majorana Neutrinos ◽  
Infinite Loop ◽  
First Time ◽  
The Universe

Abstract Thermal leptogenesis, in the framework of the standard model with three additional heavy Majorana neutrinos, provides an attractive scenario to explain the observed baryon asymmetry in the universe. It is based on the out-of-equilibrium decay of Majorana neutrinos in a thermal bath of standard model particles, which in a fully quantum field theoretical formalism is obtained by solving Kadanoff-Baym equations. So far, the leading two-loop contributions from leptons and Higgs particles are included, but not yet gauge corrections. These enter at three-loop level but, in certain kinematical regimes, require a resummation to infinite loop order for a result to leading order in the gauge coupling. In this work, we apply such a resummation to the calculation of the lepton number density. The full result for the simplest “vanilla leptogenesis” scenario is by $$ \mathcal{O} $$ O (1) increased compared to that of quantum Boltzmann equations, and for the first time permits an estimate of all theoretical uncertainties. This step completes the quantum theory of leptogenesis and forms the basis for quantitative evaluations, as well as extensions to other scenarios.

scholarly journals Standard model from a supergravity model with a naturally small cosmological constant

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Shing Yan Li ◽  
Yu-Cheng Qiu ◽  
S.-H. Henry Tye
Keyword(s):  
String Theory ◽  
Standard Model ◽  
Cosmological Constant ◽  
Supersymmetry Breaking ◽  
Supersymmetric Standard Model ◽  
Degrees Of Freedom ◽  
Interaction Terms ◽  
Supersymmetric Version ◽  
The Standard Model ◽  
Linear Version

Abstract Guided by the naturalness criterion for an exponentially small cosmological constant, we present a string theory motivated 4-dimensional $$ \mathcal{N} $$ N = 1 non-linear supergravity model (or its linear version with a nilpotent superfield) with spontaneous supersymmetry breaking. The model encompasses the minimal supersymmetric standard model, the racetrack Kähler uplift, and the KKLT anti-D3-branes, and use the nilpotent superfield to project out the undesirable interaction terms as well as the unwanted degrees of freedom to end up with the standard model (not the supersymmetric version) of strong and electroweak interactions.

scholarly journals Lorentz Violation of the Photon Sector in Field Theory Models

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lingli Zhou ◽  
Bo-Qiang Ma
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Degrees Of Freedom ◽  
Lorentz Violation ◽  
Detailed Structure ◽  
Standard Model Extension ◽  
Model Extension ◽  
The Standard Model ◽  
Minimal Standard

We compare the Lorentz violation terms of the pure photon sector between two field theory models, namely, the minimal standard model extension (SME) and the standard model supplement (SMS). From the requirement of the identity of the intersection for the two models, we find that the free photon sector of the SMS can be a subset of the photon sector of the minimal SME. We not only obtain some relations between the SME parameters but also get some constraints on the SMS parameters from the SME parameters. The CPT-odd coefficients(kAF)αof the SME are predicted to be zero. There are 15 degrees of freedom in the Lorentz violation matrixΔαβof free photons of the SMS related with the same number of degrees of freedom in the tensor coefficients(kF)αβμν, which are independent from each other in the minimal SME but are interrelated in the intersection of the SMS and the minimal SME. With the related degrees of freedom, we obtain the conservative constraints(2σ)on the elements of the photon Lorentz violation matrix. The detailed structure of the photon Lorentz violation matrix suggests some applications to the Lorentz violation experiments for photons.

scholarly journals HIDING THE EXISTENCE OF A FAMILY SYMMETRY IN THE STANDARD MODEL

2005 ◽  
Vol 20 (36) ◽  
pp. 2767-2774 ◽  
Author(s):  
ERNEST MA
Keyword(s):  
Standard Model ◽  
Neutrino Mass ◽  
Mass Matrix ◽  
Higgs Sector ◽  
Higgs Doublet ◽  
Neutrino Mass Matrix ◽  
Tree Level ◽  
Family Symmetry ◽  
The Standard Model

If a family symmetry exists for the quarks and leptons, the Higgs sector is expected to be enlarged to be able to support the transformation properties of this symmetry. There are, however, three possible generic ways (at tree level) of hiding this symmetry in the context of the Standard Model with just one Higgs doublet. All three mechanisms have their natural realizations in the unification symmetry E6 and one in SO (10). An interesting example based on SO (10)×A4 for the neutrino mass matrix is discussed.

EFFECTS OF THE CHARGED HIGGS BOSON ON THE b→sl+l− DECAY

1989 ◽  
Vol 04 (20) ◽  
pp. 1945-1954 ◽  
Author(s):  
M. CIUCHINI
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Higgs Sector ◽  
Higgs Doublet ◽  
Charged Higgs Boson ◽  
The Standard Model ◽  
Charged Higgs ◽  
Free Parameters

The 2H model that resembles the Higgs sector of the minimal N=1 SUSY version of the standard model is considered and the contribution of the charged Higgs boson to the rate of the b→sl+l− transition is studied as a function of the free parameters MH, Mt and the squared two Higgs doublet v.e.v. ratio r. It is shown that this process can be suppressed by the charged Higgs boson contribution and that in general it is not very sensitive to its presence unless (SUSY-forbidden) values of r>1 are assumed.

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