arXiv subjects

Miguel A. Vazquez-Mozo

Publications and source records attributed to Miguel A. Vazquez-Mozo.

At least 19 recordsLinked to original sources

arXiv2026

Chiral Transport in Metric-Affine Geometries

Anomalous transport in equilibrium fermionic fluids chirally coupled to background Weyl-type nonmetricity is studied. A formal descent analysis is carried out in which the dependence of the anomaly polynomial on the nonmetricity tensor is encoded in a Weyl invariant four-form. The constitutive relation of the axial-vector current is evaluated from the equilibrium partition function obtained using transgression techniques, showing the existence of nonmetricity-mediated chiral separation effects driven by the fluid's vorticity and the Weyl magnetic field. A second nonminimal coupling of fermionic matter to metric-affine geometries proposed in the literature is also discussed.

hep-th↗

arXiv2025

High Temperature Massless Scalar Partition Function on General Stationary Backgrounds

The high temperature equilibrium partition function of a massless real scalar field nonminimally coupled to the scalar curvature is computed at second order in the derivative expansion on a generic stationary background. Using covariant perturbation theory, the expression of the thermal partition function at second order in powers of curvatures is also obtained, including its nonlocal contributions. For conformal coupling, the Weyl anomaly at fourth order in derivatives and second order in curvatures is evaluated using both expansions and the results found to be consistent.

hep-th↗

arXiv2024

Torsional Constitutive Relations at Finite Temperature

The general form of the linear torsional constitutive relations at finite temperature of the chiral current, energy-momentum tensor, and spin energy potential are computed for a chiral fermion fluid minimally coupled to geometric torsion and with nonzero chiral chemical potential. The corresponding transport coefficients are explicitly calculated in terms of the energy and number densities evaluated at vanishing torsion. A microscopic calculation of these constitutive relations in some particular backgrounds is also presented, confirming the general structure found.

hep-th↗

arXiv2024

Anomalies and the Green-Schwarz Mechanism

Anomalies are a very powerful tool in constraining theories beyond the standard model. We give a pedagogical overview of some topics illustrating the important role played by spacetime anomalies in string theory. After discussing the general problem of anomaly cancellation in quantum field theory, the focus is set on the cancellation of anomalies in type-I string theory through the Green-Schwarz mechanism. The notion of anomaly inflow is also reviewed, as well as its application to the evaluation of D-brane anomalous couplings. Finally, we briefly comment on recent developments concerning the reformulation of anomalies in the language of category theory.

hep-th↗

arXiv2024

Anomalous Strangeness Transport

Nondissipative transport of strangeness is studied in a chiral hadronic plasma with three flavors. In the phase in which chiral symmetry is preserved, strangeness transport is found to be driven by both an external magnetic field and fluid vorticity. As for the constitutive relations of the baryon and electromagnetic currents, they exhibit vortical terms proportional to the strangeness chemical potential. In the superfluid phase, transverse nondissipative diffusion of the baryon, electromagnetic, and strangeness charges is found, which survives in the limit of vanishing chiral imbalance and mixes in a fashion similar to standard dissipative diffusion in quark-gluon plasma.

hep-th↗

arXiv2023

Lectures on Field Theory and the Standard Model: A Symmetry-Oriented Approach

The standard model of particle physics represents the cornerstone of our understanding of the microscopic world. In these lectures we review its contents and structure, with a particular emphasis on the central role played by symmetries and their realization. This is not intended to be an exhaustive review but a discussion of selected topics that we find interesting, with the specific aim of clarifying some subtle points and potential misunderstandings. A number of more technical topics are discussed in separated boxes interspersed throughout the text.

hep-th↗

arXiv2022

On Nieh-Yan Transport

We study nondissipative transport induced by the Nieh-Yan anomaly. After computing the torsional terms in the equilibrium partition function using transgression, we find the constitutive relations for the covariant axial-vector, heat, stress, and spin currents. A number of new transport effects are found, driven by background torsion and the spin chemical potential. Torsional constitutive relations in two-dimensional systems are also analyzed.

hep-th↗

arXiv2021

Chiral Torsional Effects in Anomalous Fluids in Thermal Equilibrium

Using the similarity between spacetime torsion and axial gauge couplings, we study torsional contributions to the equilibrium partition function in a stationary background. In the case of a charged fluid minimally coupled to torsion, we spot the existence of linear torsional magnetic and vortical effects, while the axial-vector current and the spin energy potential do not receive corrections in the torsion at linear order. The covariant energy-momentum tensor, on the other hand, does contain terms linear in the torsion tensor. The case of a two-flavor hadronic superfluid is also analyzed, and the torsional contributions to the constitutive relations computed. Our results show the existence of a torsional electric chiral effect mediated by the charged pions.

hep-th↗

arXiv2021

Constitutive relations of a chiral hadronic fluid

We study the role of non-abelian anomalies in relativistic fluids. To this end, we compute the local functional that solves the anomaly equations, and obtain analytical expressions for the covariant currents and the Bardeen-Zumino terms. We particularize these results to a background with two flavors, and consider the cases of unbroken and broken chiral symmetry. Finally, we provide explicit results for the constitutive relations of chiral nuclear matter interacting with external electromagnetic fields and in presence of chiral imbalance. We emphasize the non-dissipative nature of the chiral electric effect.

hep-th↗

arXiv2019

Anomalous Currents and Constitutive Relations of a Chiral Hadronic Superfluid

The anomalous currents of two-flavor chiral nuclear matter in the presence of chiral imbalance are computed, using recently developed methods exploiting generalized transgression, which facilitates the evaluation of both the equilibrium partition function and the covariant currents. The constitutive relations for both the broken and unbroken phase of the theory are studied and the out-of-equilibrium nondissipative transport coefficients determined. In the superfluid phase, the vector covariant currents exhibit nondissipative chiral electric, magnetic, and vortical effects, the latter governed by chiral imbalance.

hep-th↗

arXiv2018

Non-Abelian Anomalous (Super)Fluids in Thermal Equilibrium from Differential Geometry

We apply differential geometry methods to the computation of the anomaly-induced hydrodynamic equilibrium partition function. Implementing the imaginary-time prescription on the Chern-Simons effective action on a stationary background, we obtain general closed expressions for both the invariant and anomalous part of the partition function. This is applied to the Wess-Zumino-Witten action for Goldstone modes, giving the equilibrium partition function of superfluids. In all cases, we also study the anomaly-induced gauge currents and energy-momentum tensor, providing explicit expressions for them.

hep-th↗

arXiv2017

Projectivity of Planar Zeros in Field and String Theory Amplitudes

We study the projective properties of planar zeros of tree-level scattering amplitudes in various theories. Whereas for pure scalar field theories we find that the planar zeros of the five-point amplitude do not enjoy projective invariance, coupling scalars to gauge fields gives rise to tree-level amplitudes whose planar zeros are determined by homogeneous polynomials in the stereographic coordinates labelling the direction of flight of the outgoing particles. In the case of pure gauge theories, this projective structure is generically destroyed if string corrections are taken into account. Scattering amplitudes of two scalars with graviton emission vanish exactly in the planar limit, whereas planar graviton amplitudes are zero for helicity violating configurations. These results are corrected by string effects, computed using the single-valued projection, which render the planar amplitude nonzero. Finally, we discuss how the structure of planar zeros can be derived from the soft limit behavior of the scattering amplitudes.

hep-th↗

arXiv2017

Galileon Radiation from a Spherical Collapsing Shell

Galileon radiation in the collapse of a thin spherical shell of matter is analyzed. In the framework of a cubic Galileon theory, we compute the field profile produced at large distances by a short collapse, finding that the radiated field has two peaks traveling ahead of light fronts. The total energy radiated during the collapse follows a power law scaling with the shell's physical width and results from two competing effects: a Vainshtein suppression of the emission and an enhancement due to the thinness of the shell.

hep-th↗

arXiv2016

Planar Zeros in Gauge Theories and Gravity

Planar zeros are studied in the context of the five-point scattering amplitude for gauge bosons and gravitons. In the case of gauge theories, it is found that planar zeros are determined by an algebraic curve in the projective plane spanned by the three stereographic coordinates labelling the direction of the outgoing momenta. This curve depends on the values of six independent color structures. Considering the gauge group SU(N) with N=2,3,5 and fixed color indices, the class of curves obtained gets broader by increasing the rank of the group. For the five-graviton scattering, on the other hand, we show that the amplitude vanishes whenever the process is planar, without imposing further kinematic conditions. A rationale for this result is provided using color-kinematics duality.

hep-th↗

arXiv2015

Constraints on hidden photons from current and future observations of CMB spectral distortions

A variety of beyond the standard model scenarios contain very light hidden sector U(1) gauge bosons undergoing kinetic mixing with the photon. The resulting oscillation between ordinary and hidden photons leads to spectral distortions of the cosmic microwave background. We update the bounds on the mixing parameter $χ_0$ and the mass of the hidden photon $m_{γ'}$ for future experiments measuring CMB spectral distortions, such as PIXIE and PRISM/COrE. For $10^{-14}\;{\rm eV}\lesssim m_{γ'}\lesssim 10^{-13}\;{\rm eV}$, we find the kinetic mixing angle $χ_0$ has to be less than $10^{-8}$ at 95\% CL. These bounds are more than an order of magnitude stronger than those derived from the COBE/FIRAS data.

astro-ph.CO↗

arXiv2015

The Double Copy Structure of Soft Gravitons

The subleading corrections to factorization theorems for soft bremsstrahlung in nonabelian gauge theories and gravity are investigated in the case of a five point amplitude with four scalars. Building on recent results, we write the action of the angular momentum operators on scattering amplitudes as derivatives with respect to the Mandelstam invariants to uncover a double copy structure in the contribution of the soft graviton to the amplitude, both in the leading term and the first correction. Using our approach, we study Gribov's theorem as extended to nonabelian gauge theories and gravity by Lipatov, and find that subleading corrections can be obtained from those to Low's theorem by dropping the terms with derivatives with respect to the center-of-mass energy, which are suppressed at high energies. In this case, the emitted gravitons are not necessarily soft.

hep-th↗

arXiv2013

Color-Kinematics Duality in Multi-Regge Kinematics and Dimensional Reduction

In this note we study the applicability of the color-kinematics duality to the scattering of two distinguishable scalar matter particles with gluon emission in QCD, or graviton emission in Einstein gravity. Previous analysis suggested that direct use of the Bern-Carrasco-Johansson double-copy prescription to matter amplitudes does not reproduce the gravitational amplitude in multi-Regge kinematics. This situation, however, can be avoided by extensions to the gauge theory, while maintaning the same Regge limit. Here we present two examples of these extensions: the introduction of a scalar contact interaction and the relaxation of the distinguishability of the scalars. In both cases new diagrams allow for a full reconstruction of the correct Regge limit on the gravitational side. Both modifications correspond to theories obtained by dimensional reduction from higher-dimensional gauge theories.

hep-th↗

arXiv2013

Color-kinematics duality and dimensional reduction for graviton emission in Regge limit

In this talk we review the work in [1,2,3] where we have studied the applicability of the color-kinematics duality to the scattering of two distinguishable scalar matter particles with one gluon emission in QCD, or one graviton emission in Einstein gravity. We have shown that the duality works well in the Regge limit under two different extensions of the gauge theory: the introduction of a new scalar contact interaction and the relaxation of the distinguishability of the scalars. Both modifications correspond to theories obtained by dimensional reduction from higher-dimensional pure gauge theories.

hep-th↗