23,127 research outputs found
Deconfinement vs. chiral symmetry and higher representation matter
The interplay of deconfinement and chiral symmetry restoration are considered
in terms of effective theories. We generalize the earlier model studies by
considering fermions in higher representations, and study the finite
temperature phase diagrams of SU(2) and SU(3) gauge theories with two fermion
flavors in fundamental, adjoint or two-index symmetric representations. We
discuss our results in relation to recent lattice simulations on these theories
and outline possible applications in the context of dynamical electroweak
symmetry breaking.Comment: 13 pages, 6 figure
Enskog Theory for Polydisperse Granular Mixtures II. Sonine Polynomial Approximation
The linear integral equations defining the Navier-Stokes (NS) transport
coefficients for polydisperse granular mixtures of smooth inelastic hard disks
or spheres are solved by using the leading terms in a Sonine polynomial
expansion. Explicit expressions for all the NS transport coefficients are given
in terms of the sizes, masses, compositions, density and restitution
coefficients. In addition, the cooling rate is also evaluated to first order in
the gradients. The results hold for arbitrary degree of inelasticity and are
not limited to specific values of the parameters of the mixture. Finally, a
detailed comparison between the derivation of the current theory and previous
theories for mixtures is made, with attention paid to the implication of the
various treatments employed to date.Comment: 26 pages, to be published in Phys. Rev.
Potential Terrorist Uses of Highway-Borne Hazardous Materials, MTI Report 09-03
The Department of Homeland Security (DHS) has requested that the Mineta Transportation Institutes National Transportation Security Center of Excellence (MTI NTSCOE) provide any research it has or insights it can provide on the security risks created by the highway transportation of hazardous materials. This request was submitted to MTI/NSTC as a National Transportation Security Center of Excellence. In response, MTI/NTSC reviewed and revised research performed in 2007 and 2008 and assembled a small team of terrorism and emergency-response experts, led by Center Director Brian Michael Jenkins, to report on the risks of terrorists using highway shipments of flammable liquids (e.g., gasoline tankers) to cause casualties anywhere, and ways to reduce those risks. This report has been provided to DHS. The teams first focus was on surface transportation targets, including highway infrastructure, and also public transportation stations. As a full understanding of these materials, and their use against various targets became revealed, the team shifted with urgency to the far more plentiful targets outside of surface transportation where people gather and can be killed or injured. However, the team is concerned to return to the top of the use of these materials against public transit stations and recommends it as a separate subject for urgent research
Electromagnetic Moments of the Baryon Decuplet
We compute the leading contributions to the magnetic dipole and electric
quadrupole moments of the baryon decuplet in chiral perturbation theory. The
measured value for the magnetic moment of the is used to determine
the local counterterm for the magnetic moments. We compare the chiral
perturbation theory predictions for the magnetic moments of the decuplet with
those of the baryon octet and find reasonable agreement with the predictions of
the large-- limit of QCD. The leading contribution to the quadrupole
moment of the and other members of the decuplet comes from one--loop
graphs. The pionic contribution is shown to be proportional to (and so
will not contribute to the quadrupole moment of nuclei), while the
contribution from kaons has both isovector and isoscalar components. The chiral
logarithmic enhancement of both pion and kaon loops has a coefficient that
vanishes in the limit. The third allowed moment, the magnetic octupole,
is shown to be dominated by a local counterterm with corrections arising at two
loops. We briefly mention the strange counterparts of these moments.Comment: Uses harvmac.tex, 15 pages with 3 PostScript figures packed using
uufiles. UCSD/PTH 93-22, QUSTH-93-05, Duke-TH-93-5
1/N_c Expansion of the Heavy Baryon Isgur-Wise Functions
The 1/N_c expansion of the heavy baryon Isgur-Wise functions is discussed.
Because of the contracted SU(2N_f) light quark spin-flavor symmetry, the
universality relations among the Isgur-Wise functions of \Lambda_b to \Lambda_c
and \Sigma_b^{(*)} to \Sigma_c^{(*)} are valid up to the order of 1/N_c^2.Comment: 7 pages, latex, no figures, to appear in Phys. Rev.
Coupling single molecule magnets to quantum circuits
In this work we study theoretically the coupling of single molecule magnets
(SMMs) to a variety of quantum circuits, including microwave resonators with
and without constrictions and flux qubits. The main results of this study is
that it is possible to achieve strong and ultrastrong coupling regimes between
SMM crystals and the superconducting circuit, with strong hints that such a
coupling could also be reached for individual molecules close to constrictions.
Building on the resulting coupling strengths and the typical coherence times of
these molecules (of the order of microseconds), we conclude that SMMs can be
used for coherent storage and manipulation of quantum information, either in
the context of quantum computing or in quantum simulations. Throughout the work
we also discuss in detail the family of molecules that are most suitable for
such operations, based not only on the coupling strength, but also on the
typical energy gaps and the simplicity with which they can be tuned and
oriented. Finally, we also discuss practical advantages of SMMs, such as the
possibility to fabricate the SMMs ensembles on the chip through the deposition
of small droplets.Comment: 23 pages, 12 figure
The O VI Absorbers Toward PG0953+415: High Metallicity, Cosmic-Web Gas Far From Luminous Galaxies
The spectrum of the low-redshift QSO PG0953+415 shows two strong, intervening
O VI absorption systems. To study the nature of these absorbers, we have used
the Gemini Multiobject Spectrograph to conduct a deep spectroscopic galaxy
redshift survey in the 5' x 5' field centered on the QSO. This survey is fully
complete for r' < 19.7 and is 73% complete for r' < 21.0. We find three
galaxies at the redshift of the higher-z O VI system (z = 0.14232) including a
galaxy at projected distance rho = 155 kpc. We find no galaxies in the Gemini
field at the redshift of the lower-z O VI absorber (z = 0.06807), which
indicates that the nearest galaxy is more than 195 kpc away or has L < 0.04 L*.
Previous shallower surveys covering a larger field have shown that the z =
0.06807 O VI absorber is affiliated with a group/filament of galaxies, but the
nearest known galaxy has rho = 736 kpc. The z = 0.06807 absorber is notable for
several reasons. The absorption profiles reveal simple kinematics indicative of
quiescent material. The H I line widths and good alignment of the H I and metal
lines favor photoionization and, moreover, the column density ratios imply a
high metallicity: [M/H] = -0.3 +/- 0.12. The z = 0.14232 O VI system is more
complex and less constrained but also indicates a relatively high metallicity.
Using galaxy redshifts from SDSS, we show that both of the PG0953+415 O VI
absorbers are located in large-scale filaments of the cosmic web. Evidently,
some regions of the web filaments are highly metal enriched. We discuss the
origin of the high-metallicity gas and suggest that the enrichment might have
occurred long ago (at high z).Comment: Submitted for publication in the Astrophysical Journal Letters. Figs.
1 and 2 compressed for astro-ph. High-resolution version available at
http://www.astro.umass.edu/~tripp/astro/qualitypreps/pg0953tripp.pd
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