434 research outputs found
A Matrix Model for QCD: QCD Colour is Mixed
We use general arguments to show that coloured QCD states when restricted to
gauge invariant local observables are mixed. This result has important
implications for confinement: a pure colourless state can never evolve into two
coloured states by unitary evolution. Furthermore, the mean energy in such a
mixed coloured state is infinite. Our arguments are confirmed in a matrix model
for QCD that we have developed using the work of Narasimhan and Ramadas and
Singer. This model, a -dimensional quantum mechanical model for gluons
free of divergences and capturing important topological aspects of QCD, is
adapted to analytical and numerical work. It is also suitable to work on large
QCD. As applications, we show that the gluon spectrum is gapped and also
estimate some low-lying levels for and 3 (colors).
Incidentally the considerations here are generic and apply to any non-abelian
gauge theory.Comment: 16 pages, 3 figures. V2: comments regarding infinite energy and
confinement adde
Spontaneous Breaking of Lorentz Symmetry and Vertex Operators for Vortices
We first review the spontaneous Lorentz symmetry breaking in the presence of
massless gauge fields and infraparticles. This result was obtained long time
ago in the context of rigorious quantum field theory by Frohlich et. al. and
reformulated by Balachandran and Vaidya using the notion of superselection
sectors and direction-dependent test functions at spatial infinity for the
non-local observables. Inspired by these developments and under the assumption
that the spectrum of the electric charge is quantized, (in units of a
fundamental charge e) we construct a family of vertex operators which create
winding number k, electrically charged Abelian vortices from the vacuum (zero
winding number sector) and/or shift the winding number by k units. In
particular, we find that for rotating vortices the vertex operator at level k
shifts the angular momentum of the vortex by k \frac{{\tilde q}}{q}, where
\tilde q is the electric charge of the quantum state of the vortex and q is the
charge of the vortex scalar field under the U(1) gauge field. We also show
that, for charged-particle-vortex composites angular momentum eigenvalues shift
by k \frac{{\tilde q}}{q}, {\tilde q} being the electric charge of the
charged-particle-vortex composite. This leads to the result that for
\frac{{\tilde q}}{q} half-odd integral and for odd k our vertex operators flip
the statistics of charged-particle-vortex composites from bosons to fermions
and vice versa. For fractional values of \frac{{\tilde q}}{q}, application of
vertex operator on charged-particle-vortex composite leads in general to
composites with anyonic statistics.Comment: Published version, 15+1 pages, 1 figur
Novel Edge States in Self-Dual Gravity
In contrast to the Einstein-Hilbert action, the action for self-dual gravity
contains vierbeins. They are eleminated at the level of observables by an
gauge condition implied by the action. We argue that despite
this condition, new "edge" or superselected state vectors corresponding to maps
of the spheres at infinity to arise. They
are characterised by new quantum numbers and they lead to mixed states. For
black holes, they arise both at the horizon and the spatial infinity and may be
relevant for the black hole information paradox. Similar comments can be made
about the Einstein-Palatini action which uses vierbeins.Comment: 15 pages, reference added, some minor notational changes - no changes
in conclusio
Magnetic Domains and Surface Effects in Hollow Maghemite Nanoparticles
In the present work, we investigate the magnetic properties of ferrimagnetic
and noninteracting maghemite (g-Fe2O3) hollow nanoparticles obtained by the
Kirkendall effect. From the experimental characterization of their magnetic
behavior, we find that polycrystalline hollow maghemite nanoparticles are
characterized by low superparamagnetic-to-ferromagnetic transition
temperatures, small magnetic moments, significant coercivities and
irreversibility fields, and no magnetic saturation on external magnetic fields
up to 5 T. These results are interpreted in terms of the microstructural
parameters characterizing the maghemite shells by means of an atomistic Monte
Carlo simulation of an individual spherical shell model. The model comprises
strongly interacting crystallographic domains arranged in a spherical shell
with random orientations and anisotropy axis. The Monte Carlo simulation allows
discernment between the influence of the structure polycrystalline and its
hollow geometry, while revealing the magnetic domain arrangement in the
different temperature regimes.Comment: 26 pages, 8 figures. In press in Phys. Rev.
Pensions and Intertemporal Choice: Evidence from the U.S. Military
SSRN-id2383874We study a choice made by over 20,000 U.S. military personnel annually between
the High-3 and Redux retirement plans. Compared to High-3, Redux offers a
2 billion in future retirement
payments
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