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J. Lopez-Sarrion

Publications and source records attributed to J. Lopez-Sarrion.

14 recordsLinked to original sources

Spontaneous Symmetry Breaking and the Cosmological Constant

An approach that allows studying the relationship between the neutralization of the cosmological constant and instantons for cosmology coupled to antisymmetric fields is proposed. Using suitable variables, the Lagrangian leading to the FRW equations can be written analogously to a Ginzburg-Landau theory and we show how spontaneous symmetry breaking appears. The approach leads to three possible solutions, if we denote $Λ_1$ and $Λ_2$ as the cosmological constants that come from gravity ($Λ_1$) and antisymmetric fields ($Λ_2$), then the solutions, a) $ |Λ_2|>|Λ_1|$ is consistent with a very small but non-zero $Λ_1$, b) $|Λ_2|<|Λ_1|$, then $Λ_1$ is observationally ruled out and, c) $|Λ_2|=|Λ_1|$ is a solution with finite action and instantons restoring the symmetry $φ\to -φ$. The third solution is also consistent with neutralization of the cosmological constant in four dimensions.

hep-th

Kinetic and Magnetic Mixing with Antisymmetric Gauge Fields

A general procedure to describe the coupling $U_A (1) \times U_B (1)$ between antisymmetric gauge fields is proposed. For vector gauge theories the inclusion of magnetic mixing in the hidden sector induces millicharges -- in principle -- observable. We extend the analysis to antisymmetric fields and the extension to higher order monopoles is discussed. A modification of the model discussed in \cite{Ibarra} with massless antisymmetric fields as dark matter is also considered and the total cross section ratio are found and discussed.

hep-th

Fine-tuning problems in quantum field theory and Lorentz invariance: A scalar-fermion model with a physical momentum cutoff

We study the consistency of having Lorentz invariance as a low energy approximation within the quantum field theory framework. A model with a scalar and a fermion field is used to show how a Lorentz invariance violating high momentum scale, a physical cutoff rendering the quantum field theory finite, can be made compatible with a suppression of Lorentz invariance violations at low momenta. The fine tuning required to get this suppression and to have a light scalar particle in the spectrum is determined at one loop.

hep-th

Magnetic-Dipole Spin Effects in Noncommutative Quantum Mechanics

A general three-dimensional noncommutative quantum mechanical system mixing spatial and spin degrees of freedom is proposed. The analogous of the harmonic oscillator in this description contains a magnetic dipole interaction and the ground state is explicitly computed and we show that it is infinitely degenerated and implying a spontaneous symmetry breaking. The model can be straightforwardly extended to many particles and the main above properties are retained. Possible applications to the Bose-Einstein condensation with dipole-dipole interactions are briefly discussed.

hep-th

SU(2) Kinetic Mixing Terms and Spontaneous Symmetry Breaking

The non-abelian generalization of the Holdom model --{\it i.e.} a theory with two gauge fields coupled to the kinetic mixing term $g {tr}(F_{μν} (A) F_{μν} (B))$-- is considered. Contrarily to the abelian case, the group structure $G\times G$ is explicitly broken to $G$. For SU(2) this fact implies that the residual gauge symmetry as well as the Lorentz symmetry is spontaneusly broken. We show that this mechanism provides of masses for the involved particles. Also, the model presents instanton solutions with a redefined coupling constant.

hep-th

Axions and "Light Shining Through a Wall": A Detailed Theoretical Analysis

We give a detailed study of axion-photon and photon-axion conversion amplitudes, which enter the analysis of ``light shining through a wall'' experiments. Several different calculational methods are employed and compared, and in all cases we retain a nonzero axion mass. To leading order, we find that when the photon frequency $ω$ is very close to the axion mass $m$, there is a threshold cusp which significantly enhances the photon to axion conversion amplitude, by a factor $ω/\sqrt{ω^2-m^2}$ relative to the corresponding axion to photon conversion process. When $m=0$, the enhancement factor reduces to unity and the results of previous calculations are recovered. Our calculations include an exact wave matching analysis, which shows how unitarity is maintained near threshold at $ω=m$, and a discussion of the case when the magnetic field extends into the ``wall'' region.

hep-ph

Vortices in U(1) Noncommutative Gauge Fields

Charged vortex solutions for noncommutative Maxwell-Higgs model in 3+1 dimensions are found. We show that the stability of these vortex solutions is spoiled out for some, large enough, noncommutativity parameter. A non topological charge, however, is induced by noncommutative effects.

hep-th

String solutions in Chern-Simons-Higgs model coupled to an axion

We study a d=2+1 dimensional Chern-Simons gauge theory coupled to a Higgs scalar and an axion field, finding the form of the potential that allows the existence of selfdual equations and the corresponding Bogomolny bound for the energy of static configurations. We show that the same conditions allow for the N=2 supersymmetric extension of the model, reobtaining the BPS equations from the supersymmetry requirement. Explicit electrically charged vortex-like solutions to these equations are presented.

hep-th

Vortices, Infrared effects and Lorentz Invariance Violation

The Yang-Mills theory with noncommutative fields is constructed following Hamiltonian and lagrangean methods. This modification of the standard Yang-Mills theory shed light on the confinement mechanism viewed as a Lorentz invariance violation (LIV) effect. The modified Yang-Mills theory contain in addition to the standard contribution, the term $θ^με_{μνρλ} (A^νF^{ρλ} + {2/3} A_νA_ρA_λ)$ where $θ_μ$ is a given space-like constant vector with canonical dimension of energy. The $A_μ$ field rescaling and the choice $θ_μ=(0,0,0,θ)$, one can show that the modified Yang-Mills theory in 3+1 dimensions can be made equivalent to a Yang-Mills-Chern-Simons theory in 2+1 dimensions if one consider only heavy fermionic excitations. Thus, the Yang-Mills-Chern-Simons theory in 2+1 dimensions is a codified way of ${QCD}$ that include only heavy quarks. The classical solutions of the modified Yang-Mills theory for the SU(2) gauge group are confining ones.

hep-th

Gauge Field Theory in the Infrared Regime

We propose that the low energy behavior of a pure gauge theory can be studied by simply assuming violation of Lorentz invariance which is implemented through a deformation of the canonical Poisson brackets of the theory depending on an infrared scale. The resulting theory is equivalent to a pure gauge theory with a Chern-Simons like term. It is shown that at low energies this theory can be identified with three dimensional QCD where the mass of the fermion is related to the infrared scale.

hep-th

An Adiabatic Approximation to the Path Integral for Relativistic Fermionic Fields

A new approach to the path integral over fermionic fields, based on the extension of a reformulation of the adiabatic approximation to some quantum mechanical systems, is presented. A novel non-analytic contribution to the efective fermionic action for a fermion field coupled to a non-Abelian vector field is identified. The possible interpretation of this contribution as a violation of the decoupling theorem in Quantum Field Theory (QFT) is discussed. The generalization of the approach to the case of finite temperature and density suggests the possibility to apply it to the understanding of non-perturbative properties in QFT and their dependence on temperature and density.

hep-ph

U(1) Noncommutative Gauge Fields and Magnetogenesis

The connection between the Lorentz invariance violation in the lagrangean context and the quantum theory of noncommutative fields is established for the U(1) gauge field. The modified Maxwell equations coincide with other derivations obtained using different procedures. These modified equations are interpreted as describing macroscopic ones in a polarized and magnetized medium. A tiny magnetic field (seed) emerges as particular static solution that gradually increases once the modified Maxwell equations are solved as a self-consistent equations system.

hep-th

Central Charges and Effective Action at Finite Temperature and Density

The current algebra for gauge theories like QCD at finite temperature and density is studied. We start considering, the massless Thirring model at finite temperature and density, finding an explicit expression for the current algebra. The central charge only depends on the coupling constant and there are not new effects due to temperature and density. From this calculation, we argue how to compute the central charge for $QCD_4$ and we argue why the central charge in four dimensions could be modified by finite temperature and density.

hep-th