Thermodynamics in the NC disc

We study the thermodynamics of a scalar field on a noncommutative disc implementing the boundary as the limit case of an interaction with an appropriately chosen confining background. We explicitly obtain expressions for thermodynamic potentials of gases of particles obeying different statistics. In order to do that, we derive an asymptotic expansion for the density of the zeros of Laguerre polynomials. As a result we prove that the Bose-Einstein condensation in the noncommutative disc does not take place.Fil: Franchino Viñas, Sebastián Alberto. Universitat Jena; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Pisani, P.. Facultad de Ciencias Exactas, Universidad Nacional de la Plata; Argentin

Formalismo de línea de mundo en teorías no conmutativas

La unificación de las fuerzas descriptas en el modelo estándar y gravitatoria en una teoría de la gravedad cuántica es quizás el problema más importante, desde el punto de vista teórico, a resolver por la física actual. La teoría cuántica de campos (TCC) no conmutativa (NC) se ha establecido en los últimos años como un posible modelo efectivo de la gravedad cuántica debido, fundamentalmente, a las benignas propiedades de renormalización que han demostrado tener algunos modelos dentro de este marco. El objetivo de esta tesis es la implementación de las técnicas del formalismo de línea de mundo (FLM), las cuales ya han demostrado su eficacia en el estudio de las TCC usuales, al cálculo de cantidades a un bucle de diversos modelos de TCC NC. El principal resultado consiste en el análisis a un bucle del modelo de Grosse-Wulkenhaar utilizando el FLM. Asimismo, mostramos como adaptar el FLM a modelos no conmutativos de campos escalares autointeractuantes en el plano Moyal. En el camino de esta adaptación, encontramos los desarrollos (para tiempo propio pequeño) del núcleo de calor de operadores con potenciales singulares y no locales; estos resultan de interés tanto por su posible aplicacion física como por su contenido matemático.Facultad de Ciencias Exacta

Propagator from nonperturbative worldline dynamics

We use the worldline representation for correlation functions together with numerical path integral methods to extract nonperturbative information about the propagator to all orders in the coupling in the quenched limit (small-Nf expansion). Specifically, we consider a simple two-scalar field theory with cubic interaction (S²QED) in four dimensions as a toy model for QED-like theories. Using a worldline regularization technique, we are able to analyze the divergence structure of all-order diagrams and to perform the renormalization of the model nonperturbatively. Our method gives us access to a wide range of couplings and coordinate distances. We compute the pole mass of the S²QED electron and observe sizable nonperturbative effects in the strong-coupling regime arising from the full photon dressing. We also find indications for the existence of a critical coupling where the photon dressing compensates the bare mass such that the electron mass vanishes. The short distance behavior remains unaffected by the photon dressing in accordance with the power-counting structure of the model.Facultad de Ciencias Exacta

Asymptotic freedom for λφ4⁎ QFT in Snyder-de Sitter space

We analyze the model of a self-interacting φ4⁎ scalar field theory in Snyder–de Sitter space. After analytically computing the one-loop beta functions in the small noncommutativity and curvature limit, we solve numerically the corresponding system of differential equations, showing that in this limit the model possesses at least one regime in which the theory is asymptotically free. Moreover, in a given region of the parameter space we also observe a peculiar running of the parameter associated to the curvature, which changes its sign and therefore can be interpreted as a transition from an IR de-Sitter space to and UV anti-de Sitter one.Facultad de Ciencias Exacta

Vacuum effective actions and mass-dependent renormalization in curved space

We review past and present results on the non-local form-factors of the effective action of semiclassical gravity in two and four dimensions computed by means of a covariant expansion of the heat kernel up to the second order in the curvatures. We discuss the importance of these form-factors in the construction of mass-dependent beta functions for the Newton's constant and the other gravitational couplings.Comment: 26 pages, review prepared for the special issue of Universe collecting the contributions for the workshop "Quantum Fields - from Fundamental Concepts to Phenomenological Questions" (Mainz 26-28 September 2018), covers the results of 1803.06948 and 1812.0046

Quantum vacuum fluctuations and the principle of virtual work in inhomogeneous backgrounds

We discuss several aspects of the stress-energy tensor for a quantum scalar field in an inhomogeneous background, the latter being modeled by a variable mass. Using a perturbative approach, dimensional regularization, and adiabatic subtraction, we present all-order formal expressions for the stress-energy tensor. Importantly, we provide an explicit proof of the principle of virtual work for Casimir forces, taking advantage of the conservation law for the renormalized stress-energy tensor. We discuss also discontinuity-induced divergences. For the particular case of planar inhomogeneities, we corroborate the perturbative results with a WKB-inspired expansion.Fil: Franchino Viñas, Sebastián Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mantiñan, M. N.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; ArgentinaFil: Mazzitelli, Francisco Diego. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin

Magnetic properties of a Fermi gas in a noncommutative phase space

Motivated by the strong constraints to noncommutative quantum theories coming from Gamma Ray Bursts and the precision attained by SQUID devices in measuring magnetic fields, we study in this article the thermodynamic behaviour of a Fermi gas subject to the action of a background magnetic field, in two and three dimensional space with noncommutative coordinates and momenta. An explicit expression is obtained for the magnetization and magnetic susceptibility of the gas, both for Landau’s diamagnetism and Pauli’s paramagnetism. We are lead in this way to an upper bound θ≲(10Gev)⁻² for the noncommutative parameter.Facultad de Ciencias Exacta

Local Neumann semitransparent layers: Resummation, pair production, and duality

We consider local semitransparent Neumann boundary conditions for a quantum scalar field as imposed by a quadratic coupling to a source localized on a flat codimension-one surface. Upon a proper regularization to give meaning to the interaction, we interpret the effective action as a theory in a first-quantized phase space. We compute the relevant heat kernel to all order in a homogeneous background and quadratic order in perturbations, giving a closed expression for the corresponding effective action in D=4. In the dynamical case, we analyze the pair production caused by a harmonic perturbation and a Sauter pulse. Notably, we prove the existence of a strong/weak duality that links this Neumann field theory to the analog Dirichlet one.Fil: Ahmadiniaz, N.. Helmholtz-Zentrum Dresden-Rossendorf; AlemaniaFil: Franchino Viñas, Sebastián Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Manzo, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Mazzitelli, Francisco Diego. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin