Exact ground states and correlation functions of chain and ladder models of interacting hardcore bosons or spinless fermions

By removing one empty site between two occupied sites, we map the ground states of chains of hardcore bosons and spinless fermions with infinite nearest-neighbor repulsion to ground states of chains of hardcore bosons and spinless fermions without nearest-neighbor repulsion respectively, and ultimately in terms of the one-dimensional Fermi sea. We then introduce the intervening-particle expansion, where we write correlation functions in such ground states as a systematic sum over conditional expectations, each of which can be ultimately mapped to a one-dimensional Fermi-sea expectation. Various ground-state correlation functions are calculated for the bosonic and fermionic chains with infinite nearest-neighbor repulsion, as well as for a ladder model of spinless fermions with infinite nearest-neighbor repulsion and correlated hopping in three limiting cases. We find that the decay of these correlation functions are governed by surprising power-law exponents.Comment: 20 pages, 18 figures, RevTeX4 clas

A GENERALIZED STOCHASTIC DOMINANCE PROGRAM FOR THE IBM PC

A microcomputer program to perform Generalized Stochastic Dominance (GSD), Quasi-Second Degree Dominance (SSD), and Quasi-First Degree Stochastic Dominance (FSD) is described. The program is designed to run on IBM-compatible personal computers with a Hercules or CGA graphics adapter. It is menu-driven and has options for GSD, quasi-FSD, quasi-SSD, graphics, and calculations of premiums associated with use of dominant distributions.Research and Development/Tech Change/Emerging Technologies,

Ghost Cosmology: Exact Solutions, Transitions Between Standard Cosmologies and Ghost Dark Energy/Matter Evolution

The recently proposed infrared modification of gravity through the introduction of a ghost scalar field results in a number of interesting cosmological and phenomenological implications. In this paper, we derive the exact cosmological solutions for a number of scenarios where at late stages, the ghost behaves like dark matter, or dark energy. The full solutions give valuable information about the non-linear regime beyond the asymptotic first order analysis presented in the literature. The generic feature is that these ghost cosmologies give rise to smooth transitions between radiation dominated phases (or more general power-law expansions) at early epochs and ghost dark matter resp. ghost dark energy dominated late epochs. The current age of our universe places us right at the non-linear transition phase. By studying the evolution backwards in time, we find that the dominance of the ghost over ordinary baryonic matter and radiative contributions persists back to the earliest times such that the Friedmann-Robertson-Walker geometry is dictated to a good approximation by the ghost alone. We also find that the Jeans instability occurs in the ghost dark energy scenario at late times, while it is absent in the ghost dark matter scenario.Comment: 31 pages, 9 figures; added references, clarified a few minor point

An Exploratory Study On Systems Security And Hacker Hiring

We conducted an exploratory study to enhance understanding on systems security and hacker hiring.  Increased understanding on these issues will assist firms in developing effective guidelines for mitigating problems associated with potential attacks and in designing recruitment procedures for hiring hackers.  Specifically, we examine the impact of corporate security policies on perceived systems security; the impact of internal (external) systems security audits on perceived systems security; and the willingness of firms in hiring hackers.

An Empirical Investigation Of Hacking Behavior

Currently, very limited research is available to help researchers and firms understand the behavior of hackers.  As a result, misconceptions about hackers are formed based on lack of understanding about technology and failure in recognizing the differences among hackers.  We use addiction, intrinsic motivation (state), and self-monitoring (trait) theories to explain hacking.   We obtained 62 usable responses from hackers who completed our online research instrument.  Our findings showed that intrinsically motivated hackers were less discouraged by the possibility of being discovered and the rules imposed by regulatory authorities; however, no significant result was reported for rules imposed by the profession.  Individuals with high motivation to hack were found to be less discouraged by all three deterrence measures.  Participants who perceived hacking to be more consistent with their internal cues were less discouraged by the possibility of being discovered and the rules imposed by regulatory authorities; however, no significant difference was found for rules imposed by the profession.  Finally, contrary to our expectation, low self-monitors were more discouraged by all three deterrence measures than high self-monitors.  Additional research is needed to provide insight into this finding