Pilot Wave model that includes creation and annihilation of particles

The purpose of this paper is to come up with a Pilot Wave model of quantum field theory that incorporates particle creation and annihilation without sacrificing determinism. This has been previously attempted in an article by the same author titled "Incorporating particle creation and annihilation in Pilot Wave model", in a much less satisfactory way. In this paper I would like to "clean up" some of the things. In particular, I would like to get rid of a very unnatural concept of "visibility" of particles, which makes the model much simpler. On the other hand, I would like to add a mechanism for decoherence, which was absent in the previous version.Comment: 9 pages, no figure

Gravity and Matter in Causal Set Theory

The goal of this paper is to propose an approach to the formulation of dynamics for causal sets and coupled matter fields. We start from the continuum version of the action for a Klein-Gordon field coupled to gravity, and rewrite it first using quantities that have a direct correspondent in the case of a causal set, namely volumes, causal relations, and timelike lengths, as variables to describe the geometry. In this step, the local Lagrangian density $L(f;x)$ for a set of fields $f$ is recast into a quasilocal expression $L_0(f;p,q)$ that depends on pairs of causally related points $p \prec q$ and is a function of the values of $f$ in the Alexandrov set defined by those points, and whose limit as $p$ and $q$ approach a common point $x$ is $L(f;x)$. We then describe how to discretize $L_0(f;p,q)$, and use it to define a discrete action.Comment: 13 pages, no figures; In version 2, friendlier results than in version 1 are obtained following much shorter derivation

A Numerical Study of Transport and Shot Noise at 2D Hopping

We have used modern supercomputer facilities to carry out extensive Monte Carlo simulations of 2D hopping (at negligible Coulomb interaction) in conductors with the completely random distribution of localized sites in both space and energy, within a broad range of the applied electric field $E$ and temperature $T$, both within and beyond the variable-range hopping region. The calculated properties include not only dc current and statistics of localized site occupation and hop lengths, but also the current fluctuation spectrum. Within the calculation accuracy, the model does not exhibit $1/f$ noise, so that the low-frequency noise at low temperatures may be characterized by the Fano factor $F$. For sufficiently large samples, $F$ scales with conductor length $L$ as $(L_c/L)^{\alpha}$, where $\alpha=0.76\pm 0.08 < 1$, and parameter $L_c$ is interpreted as the average percolation cluster length. At relatively low $E$, the electric field dependence of parameter $L_c$ is compatible with the law $L_c\propto E^{-0.911}$ which follows from directed percolation theory arguments.Comment: 17 pages, 8 figures; Fixed minor typos and updated reference

Causal Sets: Quantum gravity from a fundamentally discrete spacetime

In order to construct a quantum theory of gravity, we may have to abandon certain assumptions we were making. In particular, the concept of spacetime as a continuum substratum is questioned. Causal Sets is an attempt to construct a quantum theory of gravity starting with a fundamentally discrete spacetime. In this contribution we review the whole approach, focusing on some recent developments in the kinematics and dynamics of the approach.Comment: 10 pages, review of causal sets based on talk given at the 1st MCCQG conferenc

A Numerical Study of Coulomb Interaction Effects on 2D Hopping Transport

We have extended our supercomputer-enabled Monte Carlo simulations of hopping transport in completely disordered 2D conductors to the case of substantial electron-electron Coulomb interaction. Such interaction may not only suppress the average value of hopping current, but also affect its fluctuations rather substantially. In particular, the spectral density $S_I (f)$ of current fluctuations exhibits, at sufficiently low frequencies, a $1/f$-like increase which approximately follows the Hooge scaling, even at vanishing temperature. At higher $f$, there is a crossover to a broad range of frequencies in which $S_I (f)$ is nearly constant, hence allowing characterization of the current noise by the effective Fano factor F\equiv S_I(f)/2e \left. For sufficiently large conductor samples and low temperatures, the Fano factor is suppressed below the Schottky value (F=1), scaling with the length $L$ of the conductor as $F = (L_c / L)^{\alpha}$. The exponent $\alpha$ is significantly affected by the Coulomb interaction effects, changing from $\alpha = 0.76 \pm 0.08$ when such effects are negligible to virtually unity when they are substantial. The scaling parameter $L_c$, interpreted as the average percolation cluster length along the electric field direction, scales as $L_c \propto E^{-(0.98 \pm 0.08)}$ when Coulomb interaction effects are negligible and $L_c \propto E^{-(1.26 \pm 0.15)}$ when such effects are substantial, in good agreement with estimates based on the theory of directed percolation.Comment: 19 pages, 7 figures. Fixed minor typos and updated reference

Identification of TUB as a novel candidate gene influencing body weight in humans

Previously, we identified a locus on 11p influencing obesity in families with type 2 diabetes. Based on mouse studies, we selected TUB as a functional candidate gene and performed association studies to determine whether this controls obesity. We analyzed the genotypes of 13 single nucleotide polymorphisms (SNPs) around TUB in 492 unrelated type 2 diabetic patients with known BMI values. One SNP (rs1528133) was found to have a significant effect on BMI (1.54 kg/m(2), P = 0.006). This association was confirmed in a population enriched for type 2 diabetes, using 750 individuals who were not selected for type 2 diabetes. Two SNPs in linkage disequilibrium with rs1528133 and mapping to the 3' end of TUB, rs2272382, and rs2272383 also affected BMI by 1.3 kg/m2 (P = 0.016 and P = 0.010, respectively). Combined analysis confirmed this association (P = 0.005 and P = 0.002, respectively). Moreover, comparing 349 obese subjects (BMI >30 kg/m(2)) from the combined cohort with 289 normal subjects (BMI <25 kg/m(2)) revealed that the protective alleles have a lower frequency in obese subjects (odds ratio 1.32 [95% CI 1.04-1.67], P = 0.022). Altogether, data from the tubby mouse as well as these data suggest that TUB could be an important factor in controlling the central regulation of body weight in humans

Various spin-polarization states beyond the maximum-density droplet: a quantum Monte Carlo study

Using variational quantum Monte Carlo method, the effect of Landau-level mixing on the lowest-energy--state diagram of small quantum dots is studied in the magnetic field range where the density of magnetic flux quanta just exceeds the density of electrons. An accurate analytical many-body wave function is constructed for various angular momentum and spin states in the lowest Landau level, and Landau-level mixing is then introduced using a Jastrow factor. The effect of higher Landau levels is shown to be significant; the transition lines are shifted considerably towards higher values of magnetic field and certain lowest-energy states vanish altogether.Comment: 4 pages, 2 figures. Submitted to Phys. Rev.