60,021 research outputs found
String bit models of two-dimensional quantum gravity coupled with matter
We extend the formalism of Hamiltonian string bit models of quantum gravity
type in two spacetime dimensions to include couplings to particles. We find
that the single-particle closed and open universe models respectively behave
like empty open and closed universes, and that a system of two distinguishable
particles in a closed universe behaves like an empty closed universe. We then
construct a metamodel that contains all such models, and find that its
transition amplitude is exactly the same as the sl(2) gravity model.Comment: 24 pages, LaTeX2e; typos corrected, references adde
Proof of a positivity conjecture of M. Kontsevich on non-commutative cluster variables
We prove a conjecture of Kontsevich, which asserts that the iterations of the
noncommutative rational map are given by
noncommutative Laurent polynomials with nonnegative integer coefficients.Comment: 13 pages; This paper supersedes the first author's preprint "A step
towards the cluster positivity conjecture" (arXiv:1103.2726). The main
improvement is that we give expressions in terms of subpaths of certain
lattice path
A String Bit Hamiltonian Approach to Two-Dimensional Quantum Gravity
Motivated by the formalism of string bit models, or quantum matrix models, we
study a class of simple Hamiltonian models of quantum gravity type in two
space-time dimensions. These string bit models are special cases of a more
abstract class of models defined in terms of the sl(2) subalgebra of the
Virasoro algebra. They turn out to be solvable and their scaling limit
coincides in special cases with known transfer matrix models of two-dimensional
quantum gravity.Comment: 24 pages, no figure; LaTeX2
On Inhomogeneity of a String Bit Model for Quantum Gravity
We study quantum gravitational effect on a two-dimensional open universe with
one particle by means of a string bit model. We find that matter is necessarily
homogeneously distributed if the influence of the particle on the size of the
universe is optimized.Comment: 16 pages, LaTeX2
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Attachment styles as predictors of Facebook-related jealousy and surveillance in romantic relationships
This is the post-print of the Article. The official published version can be accessed from the link below - Copyright @ 2012 John Wiley & SonsFacebook has become ubiquitous over the past five years, yet few studies have examined its role within romantic relationships. In two studies, we tested attachment anxiety and avoidance as predictors of Facebook-related jealousy and surveillance (i.e., checking a romantic partner’s Facebook page). Study 1 found that anxiety was positively associated, and avoidance negatively associated, with Facebook jealousy and surveillance. The association of anxiety with Facebook jealousy was mediated in part by lower trust. Study 2 replicated this finding, and daily diary results further showed that over a one-week period, anxiety was positively associated, and avoidance negatively associated, with Facebook surveillance. The association of anxiety with greater surveillance was mediated in part by daily experiences of jealousy
Neutrino oscillations and Big Bang Nucleosynthesis
We outline how relic neutrino asymmetries may be generated in the early
universe via active-sterile neutrino oscillations. We discuss possible
consequences for big bang nucleosynthesis, within the context of a particular
4-neutrino model.Comment: 6 pages. Talk given at NuFACT'01 workshop, Tsukuba, Japan (May 2001
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Distributed Strain Sensing Using Electrical Time Domain Reflectometry With Nanocomposites
The abelian projection revisited
Abelian projection is reanalysed in the frame of the SU(N) Higgs model. The
extension to QCD is discussed. It is shown that dual superconductivity of the
vacuum is an intrinsic property independent of the choice of the abelian
projection.Comment: 3 pages, 1 figure, Lattice2003(topology
Short-duration lensing events: I. wide-orbit planets? free-floating low-mass objects? or high-velocity stars?
Short duration lensing events tend to be generated by low-mass lenses or by
lenses with high transverse velocities. Furthermore, for any given lens mass
and speed, events of short duration are preferentially caused by nearby lenses
(mesolenses) that can be studied in detail, or else by lenses so close to the
source star that finite-source-size effects may be detected, yielding
information about both the Einstein ring radius and the surface of the lensed
star. Planets causing short-duration events may be in orbits with any
orientation, and may have semimajor axes smaller than an AU, or they may reach
the outer limits of their planetary systems, in the region corresponding to the
Solar System's Oort Cloud. They can have masses larger than Jupiter's or
smaller than Pluto's. Lensing therefore has a unique potential to expand our
understanding of planetary systems. A particular advantage of lensing is that
it can provide precision measurements of system parameters, including the
masses of and projected separation between star and planet. We demonstrate how
the parameters can be extracted and show that a great deal can be learned. For
example, it is remarkable that the gravitational mass of nearby free-floating
planet-mass lenses can be measured by complementing observations of a
photometric event with deep images that detect the planet itself. A fraction of
short events may be caused by high-velocity stars located within a kpc. Many
high-velocity lenses are likely to be neutron stars that received large natal
kicks. Other high-speed stars may be members of the halo population. Still
others may be hypervelocity stars that have been ejected from the Galactic
Center, or runaway stars escaped from close binaries, possibly including the
progenitor binaries of Type Ia supernovae.Comment: 17 pages; 2 figures; submitted to ApJ 3 July 200
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