1,935,669 research outputs found
Tachyonic crystals and the laminar instability of the perturbative vacuum in asymptotically free gauge theories
Lattice Monte Carlo studies in SU(3) gauge theory have shown that the
topological charge distribution in the vacuum is dominated by thin coherent
membranes of codimension one arranged in a layered, alternating-sign sandwich.
A similar lamination of topological charge occurs in the 2D model.
In holographic QCD, the observed topological charge sheets are naturally
interpreted as branes wrapped around an .. With this interpretation,
the laminated array of topological charge membranes observed on the lattice can
be identified as a "tachyonic crystal", a regular, alternating-sign array of
and branes that arises as the final state of the decay of a
non-BPS brane via the tachyonic mode of the attached string. In the gauge
theory, the homogeneous, space-filling brane represents the perturbative
gauge vacuum, which is unstable toward lamination associated with a marginal
tachyonic boundary perturbation . For the
model, the cutoff field theory can be cast as the low energy limit
of an open string theory in background gauge and tachyon fields
and . This allows a detailed comparison with large field theory
results and provides strong support for the tachyonic crystal interpretation of
the gauge theory vacuum.Comment: 21 pages, 3 figure
Small Instantons in and Sigma Models
The anomalous scaling behavior of the topological susceptibility in
two-dimensional sigma models for is studied using the
overlap Dirac operator construction of the lattice topological charge density.
The divergence of in these models is traced to the presence of small
instantons with a radius of order (= lattice spacing), which are directly
observed on the lattice. The observation of these small instantons provides
detailed confirmation of L\"{u}scher's argument that such short-distance
excitations, with quantized topological charge, should be the dominant
topological fluctuations in and , leading to a divergent
topological susceptibility in the continuum limit. For the \CP models with
the topological susceptibility is observed to scale properly with the
mass gap. These larger models are not dominated by instantons, but rather
by coherent, one-dimensional regions of topological charge which can be
interpreted as domain wall or Wilson line excitations and are analogous to
D-brane or ``Wilson bag'' excitations in QCD. In Lorentz gauge, the small
instantons and Wilson line excitations can be described, respectively, in terms
of poles and cuts of an analytic gauge potential.Comment: 33 pages, 12 figure
Casimir force for cosmological domain walls
We calculate the vacuum fluctuations that may affect the evolution of
cosmological domain walls. Considering domain walls, which are classically
stable and have interaction with a scalar field, we show that explicit symmetry
violation in the interaction may cause quantum bias that can solve the
cosmological domain wall problem.Comment: 15 pages, 2figure
Air conditioning system and component therefore distributing air flow from opposite directions
The air conditioning system comprises a plurality of separate air conditioning units coupled to a common supply duct such that air may be introduced into the supply duct in two opposite flow directions. A plurality of outlets such as registers or auxiliary or branch ducts communicate with the supply duct and valve means are disposed in the supply duct at at least some of the outlets for automatically channelling a controllable amount of air from the supply duct to the associated outlet regardless of the direction of air flow within the supply duct. The valve means comprises an automatic air volume control apparatus for distribution within the air supply duct into which air may be introduced from two opposite directions. The apparatus incorporates a freely swinging movable vane in the supply duct to automatically channel into the associated outlet only the deflected air flow which has the higher relative pressure
The Fundamental Commutator For Massless Particles
It is discussed that the usual Heisenberg commutation relation (CR) is not a
proper relation for massless particles and then an alternative is obtained. The
canonical quantization of the free electromagnetic(EM)fields based on the field
theoretical generalization of this alternative is carried out. Without imposing
the normal ordering condition,the vacuum energy is automatically zero.This can
be considered as a solution to the EM fields vacuum catastrophe and a step
toward managing the cosmologial constant problem at least for the EM fields
contribution to the state of vacuum.Comment: 12 pages,no figures,To appear in Mod.Phys.Ltt.
Thermal -Brane Boundary States from Green-Schwarz Superstrings
In this paper we thermalize the type II superstrings in the GS formulation by
applying the TFD formalism. The thermal boundary conditions on the thermal
Hilbert space are obtained from the BPS -brane boundary conditions at zero
temperature. We show that thermal boundary states can be obtained by
thermalization from the BPS -branes at zero temperature. These new states
can be interpreted as thermal -branes. Next, we discuss the supersymmetry
breaking of the thermal string in the TFD approach. We identify the broken
supersymmetry with the -transformation while the
-transformation is preserved. Also, we compute the thermal partition
function and the entropy of the thermal string.Comment: 23 pages, LATeX fil
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