Browsing by Author "Loewe, Marcelo"

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    ζ-function for a model with spectral dependent boundary conditions
    (2025) Falomir, Horacio; Loewe, Marcelo; Muñoz, Enrique; Rojas Gómez-Lobo, Juan Cristóbal
    We explore the meromorphic structure of the zeta-function associated with the boundary eigenvalue problem of a modified Sturm-Liouville operator subject to spectral-dependent boundary conditions at one end of a segment of length l. We find that it presents isolated simple poles that follow the general rule valid for second-order differential operator subject to standard local boundary conditions. We employ our results to evaluate the determinant of the operator and the Casimir energy of the system it describes, and study its dependence on l for both the massive and the massless cases.
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    Temperature fluctuations in a relativistic gas: Pressure corrections and possible consequences in the deconfinement transition
    (2024) Castaño Yepes, Jorge David; Loewe, Marcelo; Muñoz, Enrique; Rojas Gómez-Lobo, Juan Cristóbal
    In this work, we study the effects of random temperature fluctuations on the partition function of a quantum system by means of the replica method. This picture provides a conceptual model for a quantum nonequilibrium system, depicted as an ensemble of subsystems at different temperatures, randomly distributed with respect to a given mean value. We then assume the temperature displays stochastic fluctuations T ¼ T0 þ δT with respect to its ensemble average value T0, with zero mean standard deviation δT ¼0 and δT2 ¼ Δ. By means of the replica method, we obtain the average grand canonical potential, leading to the equation of state and the corresponding excess pressure caused by these fluctuations with respect to the equilibrium system at a uniform temperature. Our findings reveal an increase in pressure as the system’s ensemble average temperature T0 rises, consistently exceeding the pressure observed in an equilibrium state. We applied our general formalism to three paradigmatic physical systems; the relativistic Fermi gas, the ideal gas of photons, and a gas of non-Abelian gauge fields (gluons) in the noninteracting limit. Finally, we explore the implications for the deconfinement transition in the context of the simple bag model, where we show that the critical temperature decreases.