Extracting information from non adiabatic dynamics: excited symmetric states of the Bose-Hubbard model

Using Fourier transform on a time series generated by unitary evolution, we extract many-body eigenstates of the Bose-Hubbard model corresponding to low energy excitations, which are generated when the insulator-superfluid phase transition is realized in a typical experiment. The analysis is conducted in a symmetric external potential both without and with and disorder. A simple classification of excitations in the absence disorder is provided. The evolution is performed assuming the presence of the parity symmetry in the system rendering many-body quantum states either symmetric or antisymmetric. Using symmetry-breaking technique, those states are decomposed into elementary one-particle processes.Comment: inv. talk at 5th Workshop on Quantum Chaos and Localization Phenomena, Warsaw 201

Shifts in Assemblage of Foraging Bats at Mammoth Cave National Park Following Arrival of White-Nose Syndrome

The arrival of white-nose syndrome (WNS) to North America in 2006, and the subsequent decline in populations of cave-hibernating bats have potential long-term implications for communities of forest-dwelling bats in affected regions. Severe declines in wintering populations of bats should lead to concomitant shifts in the composition and relative abundance of species during the staging, maternity, and swarming seasons in nearby forested habitats. We examined capture rates of bats collected in mist nets from 2009 to 2016 to evaluate summer patterns in abundance of species pre- and post-arrival of WNS to Mammoth Cave National Park, KY. The data demonstrated a significant change in overall relative abundances. Myotis septentrionalis (Northern Long-eared Myotis) was the most commonly captured species pre-WNS but declined to 18.5% of its original abundance. Nycticeius humeralis (Evening Bat), uncommonly caught in mist nets pre-WNS, demonstrated the largest increase in capture success following arrival of WNS to the Park, followed by Eptesicus fuscus (Big Brown Bat) and Lasiurus borealis (Eastern Red Bat). These data suggest that losses of cave-hibernating bats to WNS may be leading to a restructuring of foraging bat assemblages in nearby forested habitats, with species less affected by WNS potentially exploiting niche space vacated by bats succumbing to infection with WNS

Low temperature expansion for the 3-d Ising Model

We compute the weak coupling expansion for the energy of the three dimensional Ising model through 48 excited bonds. We also compute the magnetization through 40 excited bonds. This was achieved via a recursive enumeration of states of fixed energy on a set of finite lattices. We use a linear combination of lattices with a generalization of helical boundary conditions to eliminate finite volume effects.Comment: 10 pages, IASSNS-HEP-92/42, BNL-4767

Series expansions without diagrams

We discuss the use of recursive enumeration schemes to obtain low and high temperature series expansions for discrete statistical systems. Using linear combinations of generalized helical lattices, the method is competitive with diagramatic approaches and is easily generalizable. We illustrate the approach using the Ising model and generate low temperature series in up to five dimensions and high temperature series in three dimensions. The method is general and can be applied to any discrete model. We describe how it would work for Potts models.Comment: 24 pages, IASSNS-HEP-93/1

The contribution of star-forming galaxies to the cosmic radio background

Recent measurements of the temperature of the sky in the radio band, combined with literature data, have convincingly shown the existence of a cosmic radio background with an amplitude of $\sim 1$ K at 1 GHz and a spectral energy distribution that is well described by a power law with index $\alpha \simeq -0.6$. The origin of this signal remains elusive, and it has been speculated that it could be dominated by the contribution of star-forming galaxies at high redshift \change{if the far infrared-radio correlation $q(z)$ evolved} in time. \change{We fit observational data from several different experiments by the relation $q(z) \simeq q_0 - \beta \log(1+z)$ with $q_0 = 2.783 \pm 0.024$ and $\beta = 0.705 \pm 0.081$ and estimate the total radio emission of the whole galaxy population at any given redshift from the cosmic star formation rate density at that redshift. It is found that} star-forming galaxies can only account for $\sim$13 percent of the observed intensity of the cosmic radio background.Comment: 5 pages, 3 figure

(Never) Mind your p's and q's: Von Neumann versus Jordan on the Foundations of Quantum Theory

In two papers entitled "On a new foundation [Neue Begr\"undung] of quantum mechanics," Pascual Jordan (1927b,g) presented his version of what came to be known as the Dirac-Jordan statistical transformation theory. As an alternative that avoids the mathematical difficulties facing the approach of Jordan and Paul A. M. Dirac (1927), John von Neumann (1927a) developed the modern Hilbert space formalism of quantum mechanics. In this paper, we focus on Jordan and von Neumann. Central to the formalisms of both are expressions for conditional probabilities of finding some value for one quantity given the value of another. Beyond that Jordan and von Neumann had very different views about the appropriate formulation of problems in quantum mechanics. For Jordan, unable to let go of the analogy to classical mechanics, the solution of such problems required the identication of sets of canonically conjugate variables, i.e., p's and q's. For von Neumann, not constrained by the analogy to classical mechanics, it required only the identication of a maximal set of commuting operators with simultaneous eigenstates. He had no need for p's and q's. Jordan and von Neumann also stated the characteristic new rules for probabilities in quantum mechanics somewhat differently. Jordan (1927b) was the first to state those rules in full generality. Von Neumann (1927a) rephrased them and, in a subsequent paper (von Neumann, 1927b), sought to derive them from more basic considerations. In this paper we reconstruct the central arguments of these 1927 papers by Jordan and von Neumann and of a paper on Jordan's approach by Hilbert, von Neumann, and Nordheim (1928). We highlight those elements in these papers that bring out the gradual loosening of the ties between the new quantum formalism and classical mechanics.Comment: New version. The main difference with the old version is that the introduction has been rewritten. Sec. 1 (pp. 2-12) in the old version has been replaced by Secs. 1.1-1.4 (pp. 2-31) in the new version. The paper has been accepted for publication in European Physical Journal

Low Temperature Expansions for Potts Models

On simple cubic lattices, we compute low temperature series expansions for the energy, magnetization and susceptibility of the three-state Potts model in D=2 and D=3 to 45 and 39 excited bonds respectively, and the eight-state Potts model in D=2 to 25 excited bonds. We use a recursive procedure which enumerates states explicitly. We analyze the series using Dlog Pade analysis and inhomogeneous differential approximants.Comment: (17 pages + 8 figures

The Abundance of New Kind of Dark Matter Structures

A new kind of dark matter structures, ultracompact minihalos (UCMHs) was proposed recently. They would be formed during the radiation dominated epoch if the large density perturbations are existent. Moreover, if the dark matter is made up of weakly interacting massive particles, the UCMHs can have effect on cosmological evolution because of the high density and dark matter annihilation within them. In this paper, one new parameter is introduced to consider the contributions of UCMHs due to the dark matter annihilation to the evolution of cosmology, and we use the current and future CMB observations to obtain the constraint on the new parameter and then the abundance of UCMHs. The final results are applicable for a wider range of dark matter parametersComment: 4 pages, 1 tabl

From 10 Kelvin to 10 TeraKelvin: Insights on the Interaction Between Cosmic Rays and Gas in Starbursts

Recent work has both illuminated and mystified our attempts to understand cosmic rays (CRs) in starburst galaxies. I discuss my new research exploring how CRs interact with the ISM in starbursts. Molecular clouds provide targets for CR protons to produce pionic gamma rays and ionization, but those same losses may shield the cloud interiors. In the densest molecular clouds, gamma rays and Al-26 decay can provide ionization, at rates up to those in Milky Way molecular clouds. I then consider the free-free absorption of low frequency radio emission from starbursts, which I argue arises from many small, discrete H II regions rather than from a "uniform slab" of ionized gas, whereas synchrotron emission arises outside them. Finally, noting that the hot superwind gas phase fills most of the volume of starbursts, I suggest that it has turbulent-driven magnetic fields powered by supernovae, and that this phase is where most synchrotron emission arises. I show how such a scenario could explain the far-infrared radio correlation, in context of my previous work. A big issue is that radio and gamma-ray observations imply CRs also must interact with dense gas. Understanding how this happens requires a more advanced understanding of turbulence and CR propagation.Comment: Conference proceedings for "Cosmic-ray induced phenomenology in star-forming environments: Proceedings of the 2nd Session of the Sant Cugat Forum of Astrophysics" (April 16-19, 2012). 16 pages, 5 figure