scholarly journals Cosmological implications of spectator and dynamical fields during inflation

2020 ◽  
Author(s):  
◽  
Jonathan Holland
Keyword(s):  
Vector Field ◽  
String Theory ◽  
Gauge Field ◽  
Gauge Fields ◽  
Next Generation ◽  
Single Field ◽  
Inflationary Models

Some possible cosmological implications of the inclusion of spectator gauge fields in the inflationary action are considered. In this context, a spec-tator field is a field that is not directly responsible for inflation but can affect cosmological observables. Spectator gauge fields can lead to novel and distinguishable features in inflationary models (as compared to single-field inflation) that may be detectable. A model of anisotropic inflation is considered where universal anisotropy is maintained through a vector field that is coupled to both the inflaton and its derivative. The derivative cou-pling reduces the anisotropy induced when compared to the non-derivative case, reducing tension with observations. SU(N) gauge fields appear natu-rally in the actions of string inflation models. The inclusion of an SU(N) gauge field coupled both to scalars and pseudo-scalars (axions) is considered in two models of string inflation whose inflatons are K¨ahler moduli: K¨ahler moduli inflation and fibre inflation. It is shown that the coupling between the axion and the gauge field can lead to a large (chiral) enhancement of the tensor spectrum of these two models. In the case of K¨ahler moduli inflation, a model that generically predicts an unobservable value for the tensor-to-scalar ratio (r  10−3), this enhancement is capable of boost-ing the tensor-to-scalar ratio to values that will be potentially observable at next generation detectors. However, the parameters required to achieve this goal may present a challenge for its successful realisation in string theory. In the case of fibre inflation, a model that generically predicts an observable value for the tensor-to-scalar ratio, it is shown that this enhancement can render the tensor spectrum of fibre inflation almost entirely chiral, giving it a distinguishable feature that may be detectable.

scholarly journals Nilpotent symmetries as a mechanism for Grand Unification

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Lars Andersson ◽  
András László ◽  
Błażej Ruba
Keyword(s):  
Gauge Field ◽  
Scalar Product ◽  
Local Symmetry ◽  
Matter Field ◽  
Gauge Fields ◽  
Spacetime Symmetries ◽  
Invariant Scalar ◽  
Spacetime Manifold ◽  
Local Symmetries ◽  
Dilatation Group

Abstract In the classic Coleman-Mandula no-go theorem which prohibits the unification of internal and spacetime symmetries, the assumption of the existence of a positive definite invariant scalar product on the Lie algebra of the internal group is essential. If one instead allows the scalar product to be positive semi-definite, this opens new possibilities for unification of gauge and spacetime symmetries. It follows from theorems on the structure of Lie algebras, that in the case of unified symmetries, the degenerate directions of the positive semi-definite invariant scalar product have to correspond to local symmetries with nilpotent generators. In this paper we construct a workable minimal toy model making use of this mechanism: it admits unified local symmetries having a compact (U(1)) component, a Lorentz (SL(2, ℂ)) component, and a nilpotent component gluing these together. The construction is such that the full unified symmetry group acts locally and faithfully on the matter field sector, whereas the gauge fields which would correspond to the nilpotent generators can be transformed out from the theory, leaving gauge fields only with compact charges. It is shown that already the ordinary Dirac equation admits an extremely simple prototype example for the above gauge field elimination mechanism: it has a local symmetry with corresponding eliminable gauge field, related to the dilatation group. The outlined symmetry unification mechanism can be used to by-pass the Coleman-Mandula and related no-go theorems in a way that is fundamentally different from supersymmetry. In particular, the mechanism avoids invocation of super-coordinates or extra dimensions for the underlying spacetime manifold.

scholarly journals Gauge inflation by kinetic coupled gravity

2014 ◽  
Vol 29 (30) ◽  
pp. 1450161 ◽  
Author(s):  
F. Darabi ◽  
A. Parsiya
Keyword(s):  
Field Theory ◽  
Gauge Field ◽  
Gauge Field Theory ◽  
Einstein Tensor ◽  
Abelian Gauge ◽  
Metric Tensor ◽  
New Class ◽  
Slow Roll ◽  
Set Up ◽  
Inflationary Models

Recently, a new class of inflationary models, so-called gauge-flation or non-Abelian gauge field inflation has been introduced where the slow-roll inflation is driven by a non-Abelian gauge field A with the field strength F. This class of models are based on a gauge field theory having F2 and F4 terms with a non-Abelian gauge group minimally coupled to gravity. Here, we present a new class of such inflationary models based on a gauge field theory having only F2 term with non-Abelian gauge fields non-minimally coupled to gravity. The non-minimal coupling is set up by introducing the Einstein tensor besides the metric tensor within the F2 term, which is called kinetic coupled gravity. A perturbation analysis is performed to confront the inflation under consideration with Planck and BICEP2 results

BRST QUANTIZATION OF GAUGE THEORIES ON THE HYPERSPHERE

1991 ◽  
Vol 06 (24) ◽  
pp. 2201-2203 ◽  
Author(s):  
D. G. C. McKEON
Keyword(s):  
Vector Field ◽  
Gauge Field ◽  
Gauge Theories ◽  
Brst Quantization ◽  
Radial Component ◽  
Effective Lagrangian ◽  
Abelian Case ◽  
Gauge Fixing

Drummond and Shore have shown that the most convenient gauge fixing term for gauge theories on a hypersphere is not a perfect square. We show how BRST quantization can be used to generate this gauge fixing term. This involves the introduction of two ghost fields, ci and [Formula: see text], the second of which is an anticommuting vector field. In the Abelian case, only the radial component of [Formula: see text] enters the effective Lagrangian; this is true in the non-Abelian case only if the gauge field is tangential to the hypersphere.

scholarly journals Emergent fields from hidden sectors

2021 ◽  
Vol 2105 (1) ◽  
pp. 012002
Author(s):  
Pascal Anastasopoulos
Keyword(s):  
String Theory ◽  
Particle Physics ◽  
Field Theories ◽  
Gauge Fields ◽  
Quantum Field Theories ◽  
Quantum Field

Abstract The present research proceeding aims at investigating/exploring/sharpening the phenomenological consequences of string theory and holography in particle physics and cosmology. We rely on and elaborate on the recently proposed framework whereby four-dimensional quantum field theories describe all interactions in Nature, and gravity is an emergent and not a fundamental force. New gauge fields, axions, and fermions, which can play the role of right-handed neutrinos, can also emerge in this framework. Preprint: UWThPh 2021-8

scholarly journals Vertex Corrections in Gauge Theories for Two-dimensional Condensed Matter Systems

1998 ◽  
Vol 12 (16n17) ◽  
pp. 1673-1692 ◽  
Author(s):  
Peter Kopietz
Keyword(s):  
Gauge Field ◽  
Condensed Matter ◽  
Finite Energy ◽  
Energy Scale ◽  
Gauge Fields ◽  
Logarithmic Correction ◽  
Two Dimensional ◽  
Numerical Constant ◽  
Self Energy ◽  
Vertex Corrections

We calculate the self-energy of two-dimensional fermions that are coupled to transverse gauge fields, taking two-loop corrections into account. Given a bare gauge field propagator that diverges for small momentum transfers q as 1/qη, 1<η≤ 2, the fermionic self-energy without vertex corrections vanishes for small frequencies ω as Σ(ω)∝ ωγ with γ=2/(1+η)<1. We show that inclusion of the leading radiative correction to the fermion-gauge field vertex leads to Σ(ω)∝ωγ [1-aη ln (ω0/ω)], where aη is a positive numerical constant and ω0 is some finite energy scale. The negative logarithmic correction is consistent with the scenario that higher order vertex corrections push the exponent γ to larger values.

scholarly journals Synthesis and observation of non-Abelian gauge fields in real space

Science ◽  
2019 ◽  
Vol 365 (6457) ◽  
pp. 1021-1025 ◽  
Author(s):  
Yi Yang ◽  
Chao Peng ◽  
Di Zhu ◽  
Hrvoje Buljan ◽  
John D. Joannopoulos ◽  
...  
Keyword(s):  
Gauge Field ◽  
Building Blocks ◽  
Real Space ◽  
Gauge Fields ◽  
Final States ◽  
Abelian Gauge ◽  
Classical Waves ◽  
Break Time ◽  
Bohm Effect ◽  
Aharonov Bohm

Particles placed inside an Abelian (commutative) gauge field can acquire different phases when traveling along the same path in opposite directions, as is evident from the Aharonov-Bohm effect. Such behaviors can get significantly enriched for a non-Abelian gauge field, where even the ordering of different paths cannot be switched. So far, real-space realizations of gauge fields have been limited to Abelian ones. We report an experimental synthesis of non-Abelian gauge fields in real space and the observation of the non-Abelian Aharonov-Bohm effect with classical waves and classical fluxes. On the basis of optical mode degeneracy, we break time-reversal symmetry in different manners, via temporal modulation and the Faraday effect, to synthesize tunable non-Abelian gauge fields. The Sagnac interference of two final states, obtained by reversely ordered path integrals, demonstrates the noncommutativity of the gauge fields. Our work introduces real-space building blocks for non-Abelian gauge fields, relevant for classical and quantum exotic topological phenomena.

Inflationary cosmology: First 30+ years

2015 ◽  
Vol 24 (11) ◽  
pp. 1530025 ◽  
Author(s):  
Katsuhiko Sato ◽  
Jun'ichi Yokoyama
Keyword(s):  
Inflationary Cosmology ◽  
Observational Constraints ◽  
Inflation Model ◽  
Common Framework ◽  
Single Field ◽  
The Many ◽  
Historical Developments ◽  
Inflationary Models

Starting with an account of historical developments in Japan and Russia, we review inflationary cosmology and its basic predictions in a pedagogical manner. We also introduce the generalized G-inflation model, in terms of which all the known single-field inflation models may be described. This formalism allows us to analyze and compare the many inflationary models that have been proposed simultaneously and within a common framework. Finally, current observational constraints on inflation are reviewed, with particular emphasis on the sensitivity of the inferred constraints to the choice of datasets used.

scholarly journals BICEP2 constrains composite inflation

2014 ◽  
Vol 23 (08) ◽  
pp. 1450070 ◽  
Author(s):  
Phongpichit Channuie
Keyword(s):  
Spectral Index ◽  
Cosmological Parameters ◽  
Inflationary Model ◽  
Composite State ◽  
Planck Data ◽  
Strongly Coupled ◽  
Yang Mills ◽  
Composite Models ◽  
Single Field ◽  
Inflationary Models

In light of BICEP2, we re-examine single field inflationary models in which the inflation is a composite state stemming from various four-dimensional strongly coupled theories. We study in the Einstein frame a set of cosmological parameters, the primordial spectral index ns and tensor-to-scalar ratio r, predicted by such models. We confront the predicted results with the joint Planck data, and with the recent BICEP2 data. We constrain the number of e-foldings for composite models of inflation in order to obtain a successful inflation. We find that the minimal composite inflationary model is fully consistent with the Planck data. However it is in tension with the recent BICEP2 data. The observables predicted by the glueball inflationary model can be consistent with both Planck and BICEP2 contours if a suitable number of e-foldings are chosen. Surprisingly, the super Yang–Mills inflationary prediction is significantly consistent with the Planck and BICEP2 observations.

scholarly journals ON HIGHER-SPIN GENERALIZATIONS OF STRING THEORY

1994 ◽  
Vol 09 (09) ◽  
pp. 1527-1543 ◽  
Author(s):  
H. LU ◽  
C. N. POPE ◽  
X. J. WANG
Keyword(s):  
String Theory ◽  
Gauge Field ◽  
Virasoro Algebra ◽  
Two Dimensional ◽  
Minimal Models ◽  
World Sheet ◽  
The World ◽  
Higher Spin ◽  
String Theories

We construct BRST operators for certain higher-spin extensions of the Virasoro algebra, in which there is a spin-s gauge field on the world sheet, as well as the spin-2 gauge field corrresponding to the two-dimensional metric. We use these BRST operators to study the physical states of the associated string theories, and show how they are related to certain minimal models.

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