Non-linear Response of the trap model in the aging regime : Exact results in the strong disorder limit

We study the dynamics of the one dimensional disordered trap model presenting a broad distribution of trapping times $p(\tau) \sim 1/\tau^{1+\mu}$, when an external force is applied from the very beginning at $t=0$, or only after a waiting time $t_w$, in the linear as well as in the non-linear response regime. Using a real-space renormalization procedure that becomes exact in the limit of strong disorder $\mu \to 0$, we obtain explicit results for many observables, such as the diffusion front, the mean position, the thermal width, the localization parameters and the two-particle correlation function. In particular, the scaling functions for these observables give access to the complete interpolation between the unbiased case and the directed case. Finally, we discuss in details the various regimes that exist for the averaged position in terms of the two times and the external field.Comment: 27 pages, 1 eps figur

On the Initial Conditions for Brane Inflation

String theory gives rise to various mechanisms to generate primordial inflation, of which ``brane inflation'' is one of the most widely considered. In this scenario, inflation takes place while two branes are approaching each other, and the modulus field representing the separation between the branes plays the role of the inflaton field. We study the phase space of initial conditions which can lead to a sufficiently long period of cosmological inflation, and find that taking into account the possibility of nonvanishing initial momentum can significantly change the degree of fine tuning of the required initial conditions.Comment: 11 pages, 2 figure

Abelian duality on globally hyperbolic spacetimes

We study generalized electric/magnetic duality in Abelian gauge theory by combining techniques from locally covariant quantum field theory and Cheeger-Simons differential cohomology on the category of globally hyperbolic Lorentzian manifolds. Our approach generalizes previous treatments using the Hamiltonian formalism in a manifestly covariant way and without the assumption of compact Cauchy surfaces. We construct semi-classical configuration spaces and corresponding presymplectic Abelian groups of observables, which are quantized by the CCR-functor to the category of C*-algebras. We demonstrate explicitly how duality is implemented as a natural isomorphism between quantum field theories. We apply this formalism to develop a fully covariant quantum theory of self-dual fields

Mobile app as a tool to collect health data: a survey on vaccination against COVID-19

Objective. To evaluate the feasibility of using a mobile app to collect health-related data and the impact of this data collection method on the results obtained, using the COVID-19 vaccination attitude assessment as an example. Material and methods. A survey was conducted on attitudes towards COVID-19 vaccination using the «Know Your Heart» mobile app. A total of 1,770 Arkhangelsk region residents aged 35—74 years who participated in the ЭССЕ-РФ3 survey conducted in the Arkhangelsk region in 2021 were invited to install the application and take part in the survey. Multiple logistic regression analysis was used to evaluate factors related to application installation and survey participation. Results. Of the total number of subjects invited to participate in the study, 611 (34.5%) installed the mobile app, and 150 (8.5%) participated in the survey. Subjects under 65 were more likely to install the application than those 65—74, as were subjects with a steady job versus those without one. Subjects under 65 years of age showed a higher responding rate to the invitation to participate in the mobile survey. Individuals who abused alcohol were less likely to agree to participate in the mobile survey. The majority of respondents are vaccinated against COVID-19 (81%). Vaccinated subjects and those confident in the effectiveness of nonspecific preventive measures were more likely to have positive attitudes towards vaccination. Conclusion. The low response rate to the survey resulting in an unrepresentative sample determined the low effectiveness of the survey using the mobile app. When overcoming these obstacles, mobile applications have the potential to be used in scientific research due to their high speed, accessibility, and ease of data collection

Ground-state clusters of two-, three- and four-dimensional +-J Ising spin glasses

A huge number of independent true ground-state configurations is calculated for two-, three- and four-dimensional +- J spin-glass models. Using the genetic cluster-exact approximation method, system sizes up to N=20^2,8^3,6^4 spins are treated. A ``ballistic-search'' algorithm is applied which allows even for large system sizes to identify clusters of ground states which are connected by chains of zero-energy flips of spins. The number of clusters n_C diverges with N going to infinity. For all dimensions considered here, an exponential increase of n_C appears to be more likely than a growth with a power of N. The number of different ground states is found to grow clearly exponentially with N. A zero-temperature entropy per spin of s_0=0.078(5)k_B (2d), s_0=0.051(3)k_B (3d) respectively s_0=0.027(5)k_B (4d) is obtained.Comment: large extensions, now 12 pages, 9 figures, 27 reference

Random Mass Dirac Fermions in Doped Spin-Peierls and Spin-Ladder systems: One-Particle Properties and Boundary Effects

Quasi-one-dimensional spin-Peierls and spin-ladder systems are characterized by a gap in the spin-excitation spectrum, which can be modeled at low energies by that of Dirac fermions with a mass. In the presence of disorder these systems can still be described by a Dirac fermion model, but with a random mass. Some peculiar properties, like the Dyson singularity in the density of states, are well known and attributed to creation of low-energy states due to the disorder. We take one step further and study single-particle correlations by means of Berezinskii's diagram technique. We find that, at low energy $\epsilon$, the single-particle Green function decays in real space like $G(x,\epsilon) \propto (1/x)^{3/2}$. It follows that at these energies the correlations in the disordered system are strong -- even stronger than in the pure system without the gap. Additionally, we study the effects of boundaries on the local density of states. We find that the latter is logarithmically (in the energy) enhanced close to the boundary. This enhancement decays into the bulk as $1/\sqrt{x}$ and the density of states saturates to its bulk value on the scale $L_\epsilon \propto \ln^2 (1/\epsilon)$. This scale is different from the Thouless localization length $\lambda_\epsilon\propto\ln (1/\epsilon)$. We also discuss some implications of these results for the spin systems and their relation to the investigations based on real-space renormalization group approach.Comment: 26 pages, LaTex, 9 PS figures include

Effective spinless fermions in the strong coupling Kondo model

Starting from the two-orbital Kondo-lattice model with classical t_2g spins, an effective spinless fermion model is derived for strong Hund coupling J_H with a projection technique. The model is studied by Monte Carlo simulations and analytically using a uniform hopping approximation. The results for the spinless fermion model are in remarkable agreement with those of the original Kondo-lattice model, independent of the carrier concentration, and even for moderate Hund coupling J_H. Phase separation, the phase diagram in uniform hopping approximation, as well as spectral properties including the formation of a pseudo-gap are discussed for both the Kondo-lattice and the effective spinless fermion model in one and three dimensions.Comment: Revtex4, 10 pages, 15 figures, typos correcte

Los métodos de diagnóstico de la sarna sarcóptica en cerdos

Poster apresentado no II Congreso Ibérico de Epidemiologia Veterinária, que decorreu em Barcelona, na FVUAB de 2 a 5 de Fevereiro de 2010.El ácaro astigmatídeo Sarcoptes scabiei (Figura 1), que causa la sarna, es una especie adaptada a diferentes hospedadores y con especial importancia en el cerdo. La sarna es una enfermedad parasitaria de la piel comunes en los animales estabulados o explotados en virtud de las malas condiciones de higiene y por lo general se produce a finales de invierno o principios de primavera. La importancia económica de la enfermedad se asocia con disminución en la producción, con la devaluación de los canales en el matadero y el uso continuo de acaricidas en los animales infectados (Damriyasa et al., 2004)

Calculation of ground states of four-dimensional +or- J Ising spin glasses

Ground states of four-dimensional (d=4) EA Ising spin glasses are calculated for sizes up to 7x7x7x7 using a combination of a genetic algorithm and cluster-exact approximation. The ground-state energy of the infinite system is extrapolated as e_0=-2.095(1). The ground-state stiffness (or domain wall) energy D is calculated. A D~L^{\Theta} behavior with \Theta=0.65(4) is found which confirms that the d=4 model has an equilibrium spin-glass-paramagnet transition for non-zero T_c.Comment: 5 pages, 3 figures, 31 references, revtex; update of reference