Testing lorentz and CPT invariance with ultracold neutrons

In this paper we investigate, within the standard model extension framework, the influence of Lorentz- and CPT-violating terms on gravitational quantum states of ultracold neutrons. Using a semiclassical wave packet, we derive the effective nonrelativistic Hamiltonian which describes the neutrons vertical motion by averaging the contributions from the perpendicular coordinates to the free falling axis. We compute the physical implications of the Lorentz- and CPT-violating terms on the spectra. The comparison of our results with those obtained in the GRANIT experiment leads to an upper bound for the symmetries-violation c(mu nu)(n) coefficients. We find that ultracold neutrons are sensitive to the a(i)(n) and e(i)(n) coefficients, which thus far are unbounded by experiments in the neutron sector. We propose two additional problems involving ultracold neutrons which could be relevant for improving our current bounds; namely, gravity-resonance spectroscopy and neutron whispering gallery wave.CONACyT [234745, 234774

Electro and magneto statics of topological insulators as modeled by planar, spherical and cylindrical θ\theta boundaries: Green function approach

The Green function (GF) method is used to analyze the boundary effects produced by a Chern Simons (CS) extension to electrodynamics. We consider the electromagnetic field coupled to a $\theta$ term that is piecewise constant in different regions of space, separated by a common interface $\Sigma$, the $\theta$ boundary, model which we will refer to as $\theta$ electrodynamics ($\theta$ ED). This model provides a correct low energy effective action for describing topological insulators (TI). In this work we construct the static GF in $\theta$ ED for different geometrical configurations of the $\theta$ boundary, namely: planar, spherical and cylindrical $\theta$ interfaces. Also we adapt the standard Green theorem to include the effects of the $\theta$ boundary. These are the most important results of our work, since they allow to obtain the corresponding static electric and magnetic fields for arbitrary sources and arbitrary boundary conditions in the given geometries. Also, the method provides a well defined starting point for either analytical or numerical approximations in the cases where the exact analytical calculations are not possible. Explicit solutions for simple cases in each of the aforementioned geometries for $\theta$ boundaries are provided. The adapted Green theorem is illustrated by studying the problem of a point like electric charge interacting with a planar TI with prescribed boundary conditions. Our generalization, when particularized to specific cases, is successfully compared with previously reported results, most of which have been obtained by using the methods of images.Comment: 24 pages, 4 figures, accepted for publication in PRD. arXiv admin note: text overlap with arXiv:1511.0117

Numerical test of the Cardy-Jacobsen conjecture in the site-diluted Potts model in three dimensions

We present a microcanonical Monte Carlo simulation of the site-diluted Potts model in three dimensions with eight internal states, partly carried out in the citizen supercomputer Ibercivis. Upon dilution, the pure model's first-order transition becomes of the second-order at a tricritical point. We compute accurately the critical exponents at the tricritical point. As expected from the Cardy-Jacobsen conjecture, they are compatible with their Random Field Ising Model counterpart. The conclusion is further reinforced by comparison with older data for the Potts model with four states.Comment: Final version. 9 pages, 9 figure

War and Economics: Spanish Civil War Finances Revisited

This paper reviews how the Spanish civil war was financed. We present new evidence to show that the two combatant parties, the Republican government and the Franco administration followed similar financial strategies. In both cases money creation, rather than new taxes or the issue of debt, was the main mechanism used to cover the expenses of the war. We argue, contrary to the established knowledge, that both sides consumed a similar amount of domestic and foreign resources. We also argue that the Spanish Republic did not lose the war because of a lack of means. International factors, such as the Non-Intervention agreement promoted by France and Great Britain, and the military setbacks of the Republican army during the first year of the war, were decisive for Franco’s victory in 1939.Spain, civil war, financial resources

The out-equilibrium 2D Ising spin glass: almost, but not quite, a free-field theory

We consider the spatial correlation function of the two-dimensional Ising spin glass under out-equilibrium conditions. We pay special attention to the scaling limit reached upon approaching zero temperature. The field-theory of a non-interacting field makes a surprisingly good job at describing the spatial shape of the correlation function of the out-equilibrium Edwards-Anderson Ising model in two dimensions.Comment: 20 pages + 5 Figure

Effect of Dilution on First Order Transitions: The Three Dimensional Three States Potts Model

We have studied numerically the effect of quenched site dilution on a first order phase transition in three dimensions. We have simulated the site diluted three states Potts model studying in detail the second order region of its phase diagram. We have found that the $\nu$ exponent is compatible with the one of the three dimensional diluted Ising model whereas the $\eta$ exponent is definitely different.Comment: RevTex. 6 pages and 6 postscript figure