arXiv subjects

Manuel Valle

Publications and source records attributed to Manuel Valle.

17 recordsLinked to original sources

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↗

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

Singular perturbation theory for the thermodynamic properties of holographic QCD

We explore the thermodynamics of a black-hole solution in improved holographic QCD with a simple dilaton potential having two parameters. By applying techniques of singular perturbation theory, we get uniform approximations for the metric and the dilaton field in the two regimes of big and small black-holes. These techniques lead to a resummation of the naive expansion at high temperatures, providing an important theoretical improvement with respect to previous results in the literature. By using this technique, it is shown how a quadratic dependence at low enough temperatures can naturally appear in the free energy. A comparison with lattice data of gluodynamics is performed. It is provided as well an estimate of the value of the gluon condensate at zero temperature which turns out to be in quite good agreement with the accepted values in the literature from phenomenological studies of QCD.

hep-th↗

arXiv2016

Anomalous transport in second order hydrodynamics

We study the non-dissipative transport effects appearing at second order in the hydrodynamic expansion for a non-interacting gas of chiral fermions by using the partition function formalism. We discuss some features of the corresponding constitutive relations, derive the explicit expressions for the conductivities and compare with existing results in the literature.

hep-th↗

arXiv2015

Torsional response of relativistic fermions in $2+1$ dimensions

We consider the equilibrium partition function of an ideal gas of Dirac fermions minimally coupled to torsion in $2+1$ dimensions. We show that the energy-momentum tensor reproduces the Hall viscosity and other parity violating terms of first order in the torsion. We also consider the modifications of the constitutive relations, and classify the corresponding susceptibilities. An entropy current consistent with zero production of entropy in equilibrium is constructed.

hep-th↗

arXiv2014

Second-order partition function of a non-interacting chiral fluid in 3+1 dimensions

We compute the partition function for non-interacting chiral fermions at second order in a derivative expansion of an arbitrary time-independent gravitational and gauge background. We find that Pauli-Villars regularization of the vacuum part is needed to get consistent results. We use our results to discuss some features of the non-dissipative constitutive relations of second order hydrodynamics.

hep-th↗

arXiv2014

Parity odd equilibrium partition function in 2+1 dimensions

We use Schwinger's proper time method to compute the parity odd contributions to the U(1) current and energy-momentum tensor of an ideal gas of fermions in 2+1 dimensions in the presence of static gauge and gravitational backgrounds. From these results the equilibrium partition function at first order in the derivative expansion is explicitly obtained by integration. The form of the computed partition function is consistent with general arguments based on Kaluza-Klein and gauge invariance.

hep-th↗

arXiv2013

Parity violating gravitational response and anomalous constitutive relations

We compute the parity violating part of the time-dependent gravitational response function of an ideal gas of Weyl fermions up to third order in the derivative expansion and give its full tensorial structure. Our main results are two functions that parametrize the energy-momentum tensor in terms of gauge-invariant combinations of vector and tensor metric perturbations. The zero frequency limit of these functions is related with the anomalous constitutive relations and with the full anomalous partition function in the presence of gauge and mixed anomalies. In particular, our results imply the existence of a previously unknown invariant contribution to the parity-odd partition function at third derivative order that we explicitly construct. Beyond the static limit, the gravitational response function may provide valuable insights into time-dependent phenomena driven by anomalies.

hep-th↗

arXiv2013

Kinetic theory and evolution of cosmological fluctuations with neutrino number asymmetry

We derive a kinetic equation for chiral matter at non-zero chemical potential that governs the response of the parity odd part of the distribution function to perturbations of the Robertson-Walker metric. The derivation is based on a recent evaluation of the gravitational polarization tensor at non-zero chemical potential. We also provide the equations for gravity waves that follow from the anisotropic stress tensor describing the lepton asymmetry. These equations can be used to assess the effects that a non-zero neutrino chemical potential would have on the evolution of cosmological perturbations.

hep-th↗

arXiv2012

Hydrodynamics in 1+1 dimensions with gravitational anomalies

The constraints imposed on hydrodynamics by the structure of gauge and gravitational anomalies are studied in two dimensions. By explicit integration of the consistent gravitational anomaly, we derive the equilibrium partition function at second derivative order. This partition function is then used to compute the parity-violating part of the covariant energy-momentum tensor and the transport coefficients.

hep-th↗

arXiv2011

Analytical approach to relaxation dynamics of condensed Bose gases

The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.

cond-mat.quant-gas↗

arXiv2010

Hamiltonian formulation of the effective kinetic theory for superfluid Fermi liquids

We present in a local form the time dependent effective description of a superfluid Fermi liquid which includes Landau damping effects at $T\neq 0$. This is achieved by the introduction of an additional variable, the quasiparticle distribution function, which obeys a simple kinetic equation. The transport equation is coupled with first order equations for the Goldstone mode and the particle density. We prove that a main feature of this formulation is its Hamiltonian structure relative to a certain Poisson bracket. We construct the Hamiltonian to quadratic order.

cond-mat.quant-gas↗