3,830 research outputs found
Magnetic Monopole Content of Hot Instantons
We study the Abelian projection of an instanton in as a
function of temperature (T) and non-trivial holonomic twist () of the
Polyakov loop at infinity. These parameters interpolate between the circular
monopole loop solution at T=0 and the static 't Hooft-Polyakov
monopole/anti-monopole pair at high temperature.Comment: 3 pages, LATTICE98(confine), LaTeX, PostScript figures include
Thermodynamics of Lattice QCD with massless quarks and chiral 4-fermion interactions
We have simulated lattice QCD with an irrelevant 4-fermion interaction and 2
zero mass quarks. The chiral phase transition is observed to be second order
and we discuss extraction of critical exponents.Comment: LATTICE98(hightemp
Simplicial Chiral Models
Principal chiral models on a d-1 dimensional simplex are introduced and
studied analytically in the large limit. The and
models are explicitly solved. Relationship with standard lattice models and
with few-matrix systems in the double scaling limit are discussed.Comment: 6 pages, PHYZZ
Green's Functions from Quantum Cluster Algorithms
We show that cluster algorithms for quantum models have a meaning independent
of the basis chosen to construct them. Using this idea, we propose a new method
for measuring with little effort a whole class of Green's functions, once a
cluster algorithm for the partition function has been constructed. To explain
the idea, we consider the quantum XY model and compute its two point Green's
function in various ways, showing that all of them are equivalent. We also
provide numerical evidence confirming the analytic arguments. Similar
techniques are applicable to other models. In particular, in the recently
constructed quantum link models, the new technique allows us to construct
improved estimators for Wilson loops and may lead to a very precise
determination of the glueball spectrum.Comment: 15 pages, LaTeX, with four figures. Added preprint numbe
Enviropod handbook: A guide to preparation and use of the Environmental Protection Agency's light-weight aerial camera system
The use of the Environmental Protection Agency (EPA) Enviropod camera system is detailed in this handbook which contains a step-by-step guide for mission planning, flights, film processing, indexing, and documentation. Information regarding Enviropod equipment and specifications is included
On the Eikonal Approximation in AdS Space
We explore the eikonal approximation to graviton exchange in AdS_5 space, as
relevant to scattering in gauge theories. We restrict ourselves to the regime
where conformal invariance of the dual gauge theory holds, and to large 't
Hooft coupling where the computation involves pure gravity. We give a heuristic
argument, a direct loop computation, and a shock wave derivation. The scalar
propagator in AdS_3 plays a key role, indicating that even at strong coupling,
two-dimensional conformal invariance controls high-energy four-dimensional
gauge-theory scattering.Comment: 22 pages, 2 figures; published version: updated references and
several clarifying remarks adde
Spin-String Interaction in QCD Strings
I consider the question of the interaction between a QCD string and the spin
of a quark or an antiquark on whose worldline the string terminates. The
problem is analysed from the point of view of a string representation for the
expectation value of a Wilson loop for a spin-half particle. A string
representation of the super Wilson loop is obtained starting from an effective
string representation of a Wilson Loop. The action obtained in this manner is
invariant under a worldline supersymmetry and has a boundary term which
contains the spin-string interaction. For rectangular loops the spin-string
interaction vanishes and there is no spin-spin term in the resulting heavy
quark potential. On the other hand if an allowance is made for the finite
intrinsic thickness of the flux-tube, by assuming that the spin-string
interaction takes place not just at the boundary of the string world-sheet but
extends to a distance of the order of the intrinsic thickness of the flux tube,
then we do obtain a spin-spin interaction which falls as the fifth power of the
distance. Such a term was previously suggested by Kogut and Parisi in the
context of a flux-tube model of confinement.Comment: 19 pages, 1 figure; Published version with added discussion and
references in section
A study of storm-induced variations in the littoral sediment transport patterns of central Monterey Bay
This 2009 study focuses on identifying sources for littoral sediment, littoral transport trends, and how both vary from summer to winter conditions. Littoral transport in central Monterey Bay were determined using grain size, heavy mineral petrography, and alongshore transport estimates generated by changes in swell direction. The amount of heavy minerals along the coast varies seasonally, and the winter erosion of Aromas sandstone paleo-dunes as well as the summer progradation of offshore bar sediments are possible contributors to coastal mineral assemblages. Heavy mineral deposition within the study area supports the conclusion that there are two dominant littoral cells in Monterey Bay isolated by the Monterey Submarine Canyon: a year-round Pajaro cell that transports sediment southward along the coast from the Pajaro River Mouth, and a seasonal Salinas cell that transports sediment northward from the Salinas River Mouth during summer W-SW swell conditions. Similarities in beach composition across the canyon is thought to be generated by a combination of seasonal mixing of fluvial material from the Pajaro and Salinas watersheds, and the erosion of the Aromas Sandstones
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