scholarly journals Manifestly gauge invariant theory of the nonlinear cosmological perturbations in the leading order of the gradient expansion

2011 ◽  
Vol 84 (2) ◽  
Author(s):  
Takashi Hamazaki
Keyword(s):  
Invariant Theory ◽  
Leading Order ◽  
Cosmological Perturbations ◽  
Gradient Expansion ◽  
Gauge Invariant

THE NAMBU-JONA-LASINIO MODEL AND GAUGE THEORIES IN 2+1 DIMENSIONS

1991 ◽  
Vol 06 (04) ◽  
pp. 667-694 ◽  
Author(s):  
K.M. COSTA
Keyword(s):  
Gauge Theory ◽  
Invariant Theory ◽  
Gauge Theories ◽  
Leading Order ◽  
Coupling Constant ◽  
Gauge Invariant ◽  
Strongly Coupled ◽  
Njl Model ◽  
Weakly Coupled ◽  
Bare Coupling Constant

The weakly coupled globally invariant Nambu-Jona-Lasino (NJL) model in 2+1 dimensions is shown to be equivalent to a strongly coupled gauge theory. This equivalence is demonstrated for the renormalized theories in the 1/N expansion utilizing an unconventional, cutoff-dependent bare coupling constant to take the limit of weak or strong bare couplings. The weakly coupled Abelian NJL model is renormalized to order 1/N and compared to a renormalized strongly coupled QED3. Next, the U(2) globally invariant NJL model is studied in the broken phase and renormalized to leading order. The resulting U(1)×U(1) gauge-invariant theory is shown to be equivalent to a spontaneously broken U(2) gauge theory analyzed in the 1/N expansion.

The Standard Theory

2017 ◽  
Author(s):  
John Iliopoulos
Keyword(s):  
Gauge Theory ◽  
Invariant Theory ◽  
Standard Theory ◽  
Strong Interactions ◽  
Gauge Invariant ◽  
Electromagnetic Interactions ◽  
Protons And Neutrons ◽  
Free Particles ◽  
Theoretical Predictions ◽  
Theory And Experiment

All ingredients of the previous chapters are combined in order to build a gauge invariant theory of the interactions among the elementary particles. We start with a unified model of the weak and the electromagnetic interactions. The gauge symmetry is spontaneously broken through the BEH mechanism and we identify the resulting BEH boson. Then we describe the theory known as quantum chromodynamics (QCD), a gauge theory of the strong interactions. We present the property of confinement which explains why the quarks and the gluons cannot be extracted out of the protons and neutrons to form free particles. The last section contains a comparison of the theoretical predictions based on this theory with the experimental results. The agreement between theory and experiment is spectacular.

scholarly journals Mixed NNLO QCD×electroweak corrections of $$ \mathcal{O} $$(Nfαsα) to single-W/Z production at the LHC

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Stefan Dittmaier ◽  
Timo Schmidt ◽  
Jan Schwarz
Keyword(s):  
Z Bosons ◽  
Leading Order ◽  
Current Standard ◽  
Gauge Invariant ◽  
Mass Distributions ◽  
Self Energy ◽  
Electroweak Gauge Boson ◽  
First Results ◽  
Invariant Part ◽  
The Impact

Abstract First results on the radiative corrections of order $$ \mathcal{O} $$ O (Nfαsα) are presented for the off-shell production of W or Z bosons at the LHC, where Nf is the number of fermion flavours. These corrections comprise all diagrams at $$ \mathcal{O} $$ O (αsα) with closed fermion loops, form a gauge-invariant part of the next-to-next-to-leading-order corrections of mixed QCD×electroweak type, and are the ones that concern the issue of mass renormalization of the W and Z resonances. The occurring irreducible two-loop diagrams, which involve only self-energy insertions, are calculated with current standard techniques, and explicit analytical results on the electroweak gauge-boson self-energies at $$ \mathcal{O} $$ O (αsα) are given. Moreover, the generalization of the complex-mass scheme for a gauge-invariant treatment of the W/Z resonances is described for the order $$ \mathcal{O} $$ O (αsα). While the corrections, which are implemented in the Monte Carlo program Rady, are negligible for observables that are dominated by resonant W/Z bosons, they affect invariant-mass distributions at the level of up to 2% for invariant masses of ≳ 500 GeV and are, thus, phenomenologically relevant. The impact on transverse-momentum distributions is similar, taking into account that leading-order predictions to those distributions underestimate the spectrum.

TREE DIAGRAMS IN WITTEN’S SUPERSTRING FIELD THEORY

1989 ◽  
Vol 04 (21) ◽  
pp. 2063-2071
Author(s):  
GEORGE SIOPSIS
Keyword(s):  
Field Theory ◽  
Scattering Amplitudes ◽  
Invariant Theory ◽  
Higher Order ◽  
Contact Term ◽  
Tree Level ◽  
Gauge Invariant

It is shown that the contact term discovered by Wendt is sufficient to ensure finiteness of all tree-level scattering amplitudes in Witten’s field theory of open superstrings. Its inclusion in the action also leads to a gauge-invariant theory. Thus, no additional higher-order counterterms in the action are needed.

scholarly journals Breaking the cosmological background degeneracy by two-fluid perturbations in f(R) gravity

2015 ◽  
Vol 24 (07) ◽  
pp. 1550053 ◽  
Author(s):  
Amare Abebe
Keyword(s):  
General Relativity ◽  
Exact Solutions ◽  
Structure Formation ◽  
Background Level ◽  
Cosmological Perturbations ◽  
Gauge Invariant ◽  
First Order ◽  
Cosmological Background ◽  
Theories Of Gravity ◽  
Two Fluid

One of the exact solutions of f(R) theories of gravity in the presence of different forms of matter exactly mimics the ΛCDM solution of general relativity (GR) at the background level. In this work we study the evolution of scalar cosmological perturbations in the covariant and gauge-invariant formalism and show that although the background in such a model is indistinguishable from the standard ΛCDM cosmology, this degeneracy is broken at the level of first-order perturbations. This is done by predicting different rates of structure formation in ΛCDM and the f(R) model both in the complete and quasi-static regimes.

scholarly journals Renormalization of a distorted gauge-invariant theory

1977 ◽  
Vol 15 (6) ◽  
pp. 1668-1674 ◽  
Author(s):  
J. P. Hsu ◽  
J. A. Underwood
Keyword(s):  
Invariant Theory ◽  
Gauge Invariant

To Restore the Broken Symmetry in the Nonconfining Schwinger Model

1997 ◽  
Vol 12 (31) ◽  
pp. 5625-5637 ◽  
Author(s):  
Anisur Rahaman
Keyword(s):  
Phase Space ◽  
Gauge Symmetry ◽  
Effective Action ◽  
Invariant Theory ◽  
Broken Symmetry ◽  
Quantum Mechanical ◽  
Gauge Invariant ◽  
Schwinger Model ◽  
Proper Extension

A new generalization of the vector Schwinger model is considered where gauge symmetry is broken at the quantum mechanical level. By proper extension of the phase space this broken symmetry has been restored in two different ways. One of these two leads to a BRST-invariant effective action. An equivalent gauge-invariant theory is reformulated even in the usual phase space also.

Sectional Curvature and Chaos in Dynamical Problems: Toward the Invariant Measure of Chaos in Hamiltonian Systems

1993 ◽  
Vol 46 (7) ◽  
pp. 427-437 ◽  
Author(s):  
Marek Szydłowski ◽  
Adam Krawiec
Keyword(s):  
General Relativity ◽  
Invariant Measure ◽  
Coordinate System ◽  
Sectional Curvature ◽  
Hamiltonian Systems ◽  
Invariant Theory ◽  
Space Time ◽  
Gauge Invariant ◽  
Time Coordinate ◽  
Physical Description

Chaotic phenomena in general relativity are investigated. In relativistic astrophysical problems no space-time coordinate system is privileged in any way as far as the physical description of phenomena is concerned. Effects which depend on the choice of the particular coordinate system should be treated as an artifact of the incorrect methods. To avoid such difficulties the gauge invariant theory of chaos is proposed.

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