19,356 research outputs found
Perturbing Around A Warped Product Of AdS_4 and Seven-Ellipsoid
We compute the spin-2 Kaluza-Klein modes around a warped product of AdS_4 and
a seven-ellipsoid. This background with global G_2 symmetry is related to a
U(N) x U(N) N=1 superconformal Chern-Simons matter theory with sixth order
superpotential. The mass-squared in AdS_4 is quadratic in G_2 quantum number
and KK excitation number. We determine the dimensions of spin-2 operators using
the AdS/CFT correspondence. The connection to N=2 theory preserving SU(3) x
U(1)_R is also discussed.Comment: 21pp; The second and last paragraphs of section 2, the footnotes 1
and 2 added and to appear in JHE
Temperature-dependent errors in nuclear lattice simulations
We study the temperature dependence of discretization errors in nuclear
lattice simulations. We find that for systems with strong attractive
interactions the predominant error arises from the breaking of Galilean
invariance. We propose a local "well-tempered" lattice action which eliminates
much of this error. The well-tempered action can be readily implemented in
lattice simulations for nuclear systems as well as cold atomic Fermi systems.Comment: 33 pages, 17 figure
From Marginal Deformations to Confinement
We consider type IIB supergravity backgrounds which describe marginal
deformations of the Coulomb branch of N=4 super Yang-Mills theory with SO(4) x
SO(2) global symmetry. Wilson loop calculations indicate that certain
deformations enhance the Coulombic attraction between quarks and anti-quarks at
the UV conformal fixed-point. In the IR region, these deformations can induce a
transition to linear confinement.Comment: 14 pages, 4 figures, minor corrections, comments and references adde
How Muscles Function - The Work Loop Technique
Anna Ahn discusses Bob Josephsonâs 1985 paper entitled: âMechanical power output from striated muscle during cyclic contractionâ
Dark matter annihilation at cosmological redshifts: possible relic signal from annihilation of weakly interacting massive particles
We discuss the possibility to observe the products of dark matter
annihilation that was going on in the early Universe. Of all the particles that
could be generated by this process we consider only photons, as they are both
uncharged and easily detectable. The earlier the Universe was, the higher the
dark matter concentration and the annihilation rate (proportional to )
were. However, the emission from the very early Universe cannot reach us
because of the opacity. The main part of the signal was generated at the moment
the Universe had just become transparent for the photons produced by the
annihilation. Thus, the dark matter annihilation in the early Universe should
have created a sort of relic emission. We obtain its flux and the spectrum.
If weakly interacting massive particles (WIMPs) constitute dark matter, it is
shown that we may expect an extragalactic gamma-ray signal in the energy range
0.5 - 20 {MeV} with a maximum near 8 {MeV}. We show that an experimentally
observed excess in the gamma-ray background at 0.5 - 20 {MeV} could be created
by the relic WIMPs annihilation only if the dark matter structures in the
universe had appeared before the universe became transparent for the
annihilation products (). We discuss in more detail physical
conditions whereby this interpretation could be possible.Comment: 8 pages, 3 figure
James Webb Space Telescope Deployment Brushless DC Motor Characteristics Analysis
A DC motor's performance is usually characterized by a series of tests, which are conducted by pass/fail criteria. In most cases, these tests are adequate to address the performance characteristics under environmental and loading effects with some uncertainties and decent power/torque margins. However, if the motor performance requirement is very stringent, a better understanding of the motor characteristics is required. The purpose of this paper is to establish a standard way to extract the torque components of the brushless motor and gear box characteristics of a high gear ratio geared motor from the composite geared motor testing and motor parameter measurement. These torque components include motor magnetic detent torque, Coulomb torque, viscous torque, windage torque, and gear tooth sliding torque. The Aerospace Corp bearing torque model and MPB torque models are used to predict the Coulomb torque of the motor rotor bearings and to model the viscous components. Gear tooth sliding friction torque is derived from the dynamo geared motor test data. With these torque data, the geared motor mechanical efficiency can be estimated and provide the overall performance of the geared motor versus several motor operating parameters such as speed, temperature, applied current, and transmitted power
Die Spacer Thickness Reproduction for Central Incisor Crown Fabrication with Combined Computer-aided Design and 3D Printing Technology: An in vitro Study
Statement of problem
The inability to control die spacer thickness has been reported. However, little information is available on the congruency between the computer-aided design parameters for die spacer thickness and the actual printout. Purpose
The purpose of this study was to evaluate the accuracy and precision of the die spacer thickness achieved by combining computer-aided design and 3-dimensional printing technology. Material and Methods
An ivorine maxillary central incisor was prepared for a ceramic crown. The prepared tooth was duplicated by using polyvinyl siloxane duplicating silicone, and 80 die-stone models were produced from Type IV dental stone. The dies were randomly divided into 5 groups with assigned die spacer thicknesses of 25 ÎŒm, 45 ÎŒm, 65 ÎŒm, 85 ÎŒm, and 105 ÎŒm (n=16). The printed resin copings, obtained from a printer (ProJet DP 3000; 3D Systems), were cemented onto their respective die-stone models with self-adhesive resin cement and stored at room temperature until sectioning into halves in a buccolingual direction. The internal gap was measured at 5 defined locations per side of the sectioned die. Images of the printed resin coping/die-stone model internal gap dimensions were obtained with an inverted bright field metallurgical microscope at Ă100 magnification. The acquired digital image was calibrated, and measurements were made using image analysis software. Mixed models (α=.05) were used to evaluate accuracy. A false discovery rate at 5% was used to adjust for multiple testing. Coefficient of variation was used to determine the precision for each group and was evaluated statistically with the Wald test (α=.05). Results
The accuracy, expressed in terms of the mean differences between the prescribed die spacer thickness and the measured internal gap (standard deviation), was 50 ÎŒm (11) for the 25 ÎŒm group simulated die spacer thickness, 30 ÎŒm (10) for the 45 ÎŒm group, 15 ÎŒm (14) for the 65 ÎŒm group, 3 ÎŒm (23) for the 85 ÎŒm group, and -10 ÎŒm (32) for the 105 ÎŒm group. The precision mean of the measurements, expressed as a coefficient of variation, ranged between 14% and 33% for the 5 groups. Conclusions
For the accuracy evaluation, statistically significant differences were found for all the groups, except the group of 85 ÎŒm. For the precision assessment, the coefficient of variation was above 10% for all groups, showing the printerâs inability to reproduce the uniform internal gap within the same group
Energy, Central Charge, and the BPS Bound for 1+1 Dimensional Supersymmetric Solitons
We consider one-loop quantum corrections to soliton energies and central
charges in the supersymmetric and sine-Gordon models in 1+1
dimensions. In both models, we unambiguously calculate the correction to the
energy in a simple renormalization scheme and obtain ,
in agreement with previous results. Furthermore, we show that there is an
identical correction to the central charge, so that the BPS bound remains
saturated in the one-loop approximation. We extend these results to arbitrary
1+1 dimensional supersymmetric theories.Comment: 15 pages, RevTeX; v2: generalized energy result, added minor
clarifications, and fixed typos; v3: more minor clarifications and
corrections; v4: fixed factor of 2 in eq. (25); v5: fixed minor error in eq.
(55
A Deformation of Twistor Space and a Chiral Mass Term in N=4 Super Yang-Mills Theory
Super twistor space admits a certain (super) complex structure deformation
that preserves the Poincare subgroup of the symmetry group PSL(4|4) and depends
on 10 parameters. In a previous paper [hep-th/0502076], it was proposed that in
twistor string theory this deformation corresponds to augmenting N=4 super
Yang-Mills theory by a mass term for the left-chirality spinors. In this paper
we analyze this proposal in more detail. We calculate 4-particle scattering
amplitudes of fermions, gluons and scalars and show that they are supported on
holomorphic curves in the deformed twistor space.Comment: 52 pages, 15 figure
Are There Any New Vacua of Gauged N=8 Supergravity in Four Dimensions?
We consider the most general SU(3) singlet space of gauged N=8 supergravity
in four-dimensions. The SU(3)-invariant six scalar fields in the theory can be
viewed in terms of six real four-forms. By exponentiating these four-forms, we
eventually obtain the new scalar potential. For the two extreme limits, we
reproduce the previous results found by Warner in 1983. In particular, for the
N=1 G_2 critical point, we find the constraint surface parametrized by three
scalar fields on which the cosmological constant has the same value. We obtain
the BPS domain-wall solutions for restricted scalar submanifold. We also
describe the three-dimensional mass-deformed superconformal Chern-Simons matter
theory dual to the above supersymmetric flows in four-dimensions.Comment: 44p; the main text and appendices improved for compact
presentation;the acknowledgments added and to appear in IJMP
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