50,473 research outputs found
Short-term hot-hardness characteristics of five case hardened steels
Short-term hot-hardness studies were performed with carburized and hardened AISI 8620, CBS 1000, CBS 1000M, CBS 600, and Vasco X-2 steels. Case and core hardness measurements were made at temperatures from 294 to 811 K (70 to 1000 F). The data were compared with data for high-speed tool steels and AISI 52100. The materials tested can be ranked as follows in order of decreasing hot-hardness retention: (1) Vasco X-2; equivalent to through-hardened tool steels up to 644 K (700 F) above which Vasco X-2 is inferior; (2) CBS 1000, (3) CBS 1000M; (4) CBS 6000; better hardness retention at elevated temperatures than through-hardened AISI 52100; and (5) AISI 8620. For the carburized steels, the change in hardness with temperature of the case and core are similar for a given material. The short-term hot hardness of these materials can be predicted with + or - 1 point Rockwell C
Fatigue life of 120 mm bore ball bearings at 600 deg F with fluorocarbon, polyphenyl ether, and synthetic paraffinic base lubricants
High temperature tests to determine fatigue life of 120mm bore ball bearings with fluorocarbon, polyphenyl ether, and synthetic base paraffin base lubricant
Determining the underlying Fermi surface of strongly correlated superconductors
The notion of a Fermi surface (FS) is one of the most ingenious concepts
developed by solid state physicists during the past century. It plays a central
role in our understanding of interacting electron systems. Extraordinary
efforts have been undertaken, both by experiment and by theory, to reveal the
FS of the high temperature superconductors (HTSC), the most prominent strongly
correlated superconductors. Here, we discuss some of the prevalent methods used
to determine the FS and show that they lead generally to erroneous results
close to half filling and at low temperatures, due to the large superconducting
gap (pseudogap) below (above) the superconducting transition temperature. Our
findings provide a perspective on the interplay between strong correlations and
superconductivity and highlight the importance of strong coupling theories for
the characterization as well as the determination of the underlying FS in ARPES
experiments
Electronic structure of strongly correlated d-wave superconductors
We study the electronic structure of a strongly correlated d-wave
superconducting state. Combining a renormalized mean field theory with direct
calculation of matrix elements, we obtain explicit analytical results for the
nodal Fermi velocity, v_F, the Fermi wave vector, k_F, and the momentum
distribution, n_k, as a function of hole doping in a Gutzwiller projected
d-wave superconductor. We calculate the energy dispersion, E_k, and spectral
weight of the Gutzwiller-Bogoliubov quasiparticles, and find that the spectral
weight associated with the quasiparticle excitation at the antinodal point
shows a non monotonic behavior as a function of doping. Results are compared to
angle resolved photoemission spectroscopy (ARPES) of the high temperature
superconductors.Comment: final version, comparison to experiments added, 4+ pages, 4 figure
A necessary flexibility condition of a nondegenerate suspension in Lobachevsky 3-space
We show that some combination of the lengths of all edges of the equator of a
flexible suspension in Lobachevsky 3-space is equal to zero (each length is
taken either positive or negative in this combination).Comment: 20 pages, 13 figure
The Link between General Relativity and Shape Dynamics
We show that one can construct two equivalent gauge theories from a linking
theory and give a general construction principle for linking theories which we
use to construct a linking theory that proves the equivalence of General
Relativity and Shape Dynamics, a theory with fixed foliation but spatial
conformal invariance. This streamlines the rather complicated construction of
this equivalence performed previously. We use this streamlined argument to
extend the result to General Relativity with asymptotically flat boundary
conditions. The improved understanding of linking theories naturally leads to
the Lagrangian formulation of Shape Dynamics, which allows us to partially
relate the degrees of freedom.Comment: 19 pages, LaTeX, no figure
Optimal Alignment Sensing of a Readout Mode Cleaner Cavity
Critically coupled resonant optical cavities are often used as mode cleaners
in optical systems to improve the signal to noise ratio (SNR) of a signal that
is encoded as an amplitude modulation of a laser beam. Achieving the best SNR
requires maintaining the alignment of the mode cleaner relative to the laser
beam on which the signal is encoded. An automatic alignment system which is
primarily sensitive to the carrier field component of the beam will not, in
general, provide optimal SNR. We present an approach that modifies traditional
dither alignment sensing by applying a large amplitude modulation on the signal
field, thereby producing error signals that are sensitive to the signal
sideband field alignment. When used in conjunction with alignment actuators,
this approach can improve the detected SNR; we demonstrate a factor of 3
improvement in the SNR of a kilometer-scale detector of the Laser
Interferometer Gravitational-wave Observatory. This approach can be generalized
to other types of alignment sensors
Finite Size Effect on Correlation Functions of a Bose Gas in a Trap and Destruction of the Order Parameter by Phase Fluctuations
The influence of the finite sizes on the coherent properties of 3D Bose
systems is considered. As is shown, the correlation functions of a Bose gas in
a trap have essential differences from analogous correlation functions in an
infinite system. Thus, the anomalous correlation function vanishes due to the
divergency of phase fluctuations which destruct the order parameter too. The
normal correlation function decays exponentially in time for sufficiently large
time interval.Comment: 10 pages, RevTex4, some references have been added some changes in
text are mad
Heterotic Line Bundle Standard Models
In a previous publication, arXiv:1106.4804, we have found 200 models from
heterotic Calabi-Yau compactifications with line bundles, which lead to
standard models after taking appropriate quotients by a discrete symmetry and
introducing Wilson lines. In this paper, we construct the resulting standard
models explicitly, compute their spectrum including Higgs multiplets, and
analyze some of their basic properties. After removing redundancies we find
about 400 downstairs models, each with the precise matter spectrum of the
supersymmetric standard model, with one, two or three pairs of Higgs doublets
and no exotics of any kind. In addition to the standard model gauge group, up
to four Green-Schwarz anomalous U(1) symmetries are present in these models,
which constrain the allowed operators in the four-dimensional effective
supergravity. The vector bosons associated to these anomalous U(1) symmetries
are massive. We explicitly compute the spectrum of allowed operators for each
model and present the results, together with the defining data of the models,
in a database of standard models accessible at
http://www-thphys.physics.ox.ac.uk/projects/CalabiYau/linebundlemodels/index.html.
Based on these results we analyze elementary phenomenological properties. For
example, for about 200 models all dimension four and five proton decay
violating operators are forbidden by the additional U(1) symmetries.Comment: 55 pages, Latex, 3 pdf figure
The B-L/Electroweak Hierarchy in Smooth Heterotic Compactifications
E8 X E8 heterotic string and M-theory, when appropriately compactified, can
give rise to realistic, N=1 supersymmetric particle physics. In particular, the
exact matter spectrum of the MSSM, including three right-handed neutrino
supermultiplets, one per family, and one pair of Higgs-Higgs conjugate
superfields is obtained by compactifying on Calabi-Yau manifolds admitting
specific SU(4) vector bundles. These "heterotic standard models" have the
SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge group of the standard model augmented by
an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L
gauge symmetry be spontaneously broken by a vacuum expectation value of at
least one right-handed sneutrino. In a previous paper, we presented the results
of a renormalization group analysis showing that B-L gauge symmetry is indeed
radiatively broken with a B-L/electroweak hierarchy of O(10) to O(10^{2}). In
this paper, we present the details of that analysis, extending the results to
include higher order terms in tan[beta]^{-1} and the explicit spectrum of all
squarks and sleptons.Comment: 60 pages, 6 figure
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