arXiv subjects

José Luis V. Cerdeira

Publications and source records attributed to José Luis V. Cerdeira.

7 recordsLinked to original sources

arXiv2026

On the quantum statistical relation and the covariant phase space Hamiltonian

We show how the covariant phase space Hamiltonian can be constructed in theories in which some of the fields have gauge freedoms. The addition to the action of boundary terms that guarantee the well-posedness of a variational principle and its exact gauge invariance for the prescribed boundary conditions turn out to be essential in this construction. The same ingredients are essential in the use of the action in the framework of Gibbons and Hawking's Euclidean approach to Quantum Gravity and we show how the on-shell action constructed with a Lagrangian with those properties can be expressed in terms of the covariant phase space Hamiltonian. We compute the Hamiltonian of several theories, one of which has Chern--Simons terms, using our prescription and show that, in black-hole backgrounds, the Hamiltonian gives directly the quantum statistical relation including terms related to non-gravitational charges and chemical potentials, as expected.

hep-th↗

arXiv2026

$α'$ corrections to self-dual gravitational instantons

We study the $α'$ corrections to self-dual gravitational instantons in the context of the four-dimensional Cano--Ruipérez action, which can be obtained by the compactification of the Bergshoeff--de Roo heterotic string effective action on $\mathbb{T}^{6}$ followed by a truncation and a field redefinition. We show that the metric of spaces of self-dual curvature does not receive any corrections, but their (initially trivial) dilaton and axion fields do, owing to their couplings to Gauss--Bonnet and Pontrjagin densities. We find the generic form of the corrections of the dilaton and axion fields for the Gibbons--Hawking multi-instanton solutions and their explicit form for the particular cases of the Euclidean Taub--NUT and Eguchi--Hanson spaces. We construct the boundary terms required to define a well-posed Dirichlet variational principle in the Euclidean Cano--Ruipérez theory, including the contributions associated with the Gauss--Bonnet and Pontrjagin terms. The boundary terms are normalized for asymptotically-locally-Euclidean solutions, and we evaluate with them the Euclidean action of the $α'$-corrected Eguchi--Hanson instanton showing that the total action receives no corrections to first order in $α'$. We also show that, at zeroth order in $α'$, one can construct Euclidean solutions similar to the string theory D-instanton with non-trivial dilaton and axion on the background of a self-dual purely gravitational instanton which remains unmodified. We also compute the $α'$ corrections to these solutions.

hep-th↗

arXiv2025

Higher-form symmetries in supergravity, scalar charges and black-hole thermodynamics

Minimal 5-dimensional supergravity compactified on a circle gives the T$^{3}$ model of $\mathcal{N}=2,d=4$ supergravity, whose duality group is SL$(2,\mathbb{R})$. We study exhaustively the relations between all the local and global symmetries of both theories and between the corresponding conserved currents and charges, including the on-shell closed generalized Komar charges associated to isometries. We find that the 2-dimensional subgroup of SL$(2,\mathbb{R})$ that does not include electric-magnetic transformations is realized as a higher-form symmetry group that acts on the 5-dimensional metric and vector field. Using the generalized Komar charges we compute the Smarr formulas for black holes, showing that they are identical once the relations between all the 5- and 4-dimensional thermodynamical quantities are taken into account, which is only possible if certain constraints on the fields are satisfied. We notice that on-shell closed 5-dimensional 3-form charges give, upon dimensional reduction, on-shell closed 3-form currents and 2-form charges. The dimensional reduction of the 5-dimensional generalized Komar 3-form charge associated to a Killing vector gives a new 4-dimensional on-shell closed 3-form current which must be associated to a new global symmetry of the theory when it admits that Killing vector. Some of the results that we have derived are valid for theories of Einstein--Maxwell-like theories of $(p+1)$-forms with Chern--Simons terms, which includes 11-dimensional supergravity as a particular example.

hep-th↗

arXiv2025

On-shell Lagrangians as total derivatives and the generalized Komar charge

Lagrangians which transform homogeneously under a global transformation of the fields (a global rescaling, for instance) can be written on-shell as a total derivative which has a universal, solution-independent expression, using a functional version of the Euler theorem for homogeneous functions. We study the uniqueness of this expression and how this result can be used in the construction of generalized Komar charges.

hep-th↗

arXiv2025

The Komar charge in presence of the Holst term and the gravitational Witten effect

In the first-order formalism, the Einstein--Hilbert action can be modified by the addition of a Holst term multiplied by the Barbero parameter $α$. This modification breaks parity although it does not affect the equations of motion. We show that the standard Komar charge is also modified by the addition of a topological term multiplied by the Barbero parameter $α$. For the Killing vector that generates time translations, the value of the Komar integral at infinity is modified by the addition of a term proportional to the NUT charge $N$ and the parity-breaking Barbero parameter. Thus, as in the standard Witten effect, a non-vanishing NUT charge $N$ induces a non-vanishing mass $αN$.

hep-th↗

arXiv2025

A note on the calculation of the Komar integral in the Lorentzian Taub-NUT spacetime

It has recently been shown that one can derive consistent thermodynamical expressions in the Lorentzian Taub--NUT spacetime keeping the Misner-string singularities and taking into account their contributions in the Komar integrals. We show how the same results are obtained when the Mister-string singularities are removed by using Misner's procedure because, even though the complete spacetime has no such singularities anymore, they are unavoidable in all spacelike hypersurfaces which are used in the Komar integrals. Different choices of hypersurfaces may contain different strings and lead to different physics, though.

gr-qc↗

arXiv2023

Non-Lorentzian expansions of the Lorentz force and kinematical algebras

We consider non-Lorentzian expansions, Galilean and Carrollian, of the Lorentz force equation in which both the particle position and the electro-magnetic field are expanded. There are two well-known limits in the case of a constant field, called electric and magnetic, that are studied separately. We show that the resulting equations of motion follow equivalently from considering a non-linear realisation of a certain infinite-dimensional algebras.

hep-th↗