2,295 research outputs found
Anelastic spectroscopy study of the spin-glass and cluster spin-glass phases of LaSrCuO
The anelastic spectra of LaSrCuO have been measured at
liquid He temperatures slightly below and above the concentration which is considered to separate the spin-glass phase from the
cluster spin-glass (CSG) phase. For all the elastic energy loss
functions show a step below the temperature of freezing into
the CSG state, similarly to what found in samples well within the CSG phase,
but with a smaller amplitude. The excess dissipation in the CSG state is
attributed to the motion of the domain walls between the clusters of
antiferromagnetically correlated spin. These results are in agreement with the
recent proposal, based on inelastic neutron scattering, of an electronic phase
separation between regions with and , at least for
Comment: 5 pages, 3 figures, submitted to Phys. Rev.
Leptoproduction of J/psi
We study leptoproduction of at large within the
nonrelativistic QCD (NRQCD) factorization formalism. The cross section is
dominated by color-octet terms that are of order . The color-singlet
term, which is of order , is shown to be a small contribution to
the total cross section. We also calculate the tree diagrams for color-octet
production at order in a region of phase space where there is no
leading color-octet contribution. We find that in this regime the color-singlet
contribution dominates. We argue that non-perturbative corrections arising from
diffractive leptoproduction, higher twist effects, and higher order terms in
the NRQCD velocity expansion should be suppressed as is increased.
Therefore, the color-octet matrix elements can be reliably extracted from this process.
Finally, we point out that an experimental measurement of the polarization of
leptoproduced will provide an excellent test of the NRQCD
factorization formalism.Comment: 33 pages latex. 10 figures. Uses revtex, epsf, and rotate macros.
This paper is also available via the UW phenomenology archives at
http://phenom.physics.wisc.edu/pub/preprints
aily Stock Market Forecast from Textual Web Data
ABSTRACT Data mining can be described as "making better use of data". Every human being is increasingly faced with unmanageable amounts of data, hence, data mining or knowledge discovery apparently affects all of us. It is therefore recognized as one of the key research areas. Ideally, we would like to develop techniques for "making better use of any kind of data for any purpose". However, we argue that this goal is too demanding yet. It may sometimes be more promising to develop techniques applicable to specific data and with a specific goal in mind. In this paper, we describe such an application driven data mining system. Our aim is to predict stock markets using information contained in articles published on the Web. Mostly textual articles appearing in the leading and influential financial newspapers are taken as input. From those articles the daily closing values of major stock market indices in Asia, Europe and America are predicted. Textual statements contain not only the effect (e.g. the stocks plummet) but also why it happened (e.g. because of weakness in the dollar and consequently a weakening of the treasury bonds). Exploiting textual information in addition to numeric time series data increases the quality of the input. Hence improved predictions are expected
Self generated randomness, defect wandering and viscous flow in stripe glasses
We show that the competition between interactions on different length scales,
as relevant for the formation of stripes in doped Mott insulators, can cause a
glass transition in a system with no explicitly quenched disorder. We
analytically determine a universal criterion for the emergence of an
exponentially large number of metastable configurations that leads to a finite
configurational entropy and a landscape dominated viscous flow. We demonstrate
that glassines is unambiguously tied to a new length scale which characterizes
the typical length over which defects and imperfections in the stripe pattern
are allowed to wander over long times.Comment: 17 pages, 9 figure
Systematic Study of Short Range Antiferromagnetic Order and The Spin-Glass State in Lightly Doped La2-xSrxCuO4
Systematic measurements of the magnetic susceptibility were performed on
single crystals of lightly doped La2-xSrxCuO4 (x=0.03, 0.04 and 0.05). For all
samples the temperature dependence of the in-plane magnetic susceptibility
shows typical spin-glass features with spin-glass transition temperatures Tg of
6.3K, 5.5K and 5.0K for x=0.03, 0.04 and 0.05, respectively. The canonical
spin-glass order parameter extracted from the in-plane susceptibility of all
the samples follows a universal scaling curve. On the other hand, the
out-of-plane magnetic susceptibility deviates from Curie law below a
temperature Tdv, higher than Tg. Comparing with previous neutron scattering
results with an instrumental energy resolution of 0.25 meV from Wakimoto et
al., the x-dependence of Tdv is qualitatively the same as that of Tel, the
temperature below which the elastic magnetic scattering develops around (pi,
pi). Thus, a revised magnetic phase diagram in the lightly doped region of
La2-xSrxCuO4 is proposed. The Curie constants calculated from the in-plane
susceptibility are independent of the Sr concentration. On the basis of the
cluster spin-glass model, this fact might reflect an inhomogeneous distribution
of doped holes in the CuO2 plane, such as in a stripe structure.Comment: 7 pages, 6 figure
High-Field Quasiparticle Tunneling in Bi_2Sr_2CaCu_2O_8+delta: Negative Magnetoresistance in the Superconducting State
We report on the c-axis resistivity rho_c(H) in Bi_2Sr_2CaCu_2O_{8+\delta}
that peaks in quasi-static magnetic fields up to 60 T. By suppressing the
Josephson part of the two-channel (Cooper pair/quasiparticle) conductivity
\sigma_c (H), we find that the negative slope of \rho_c(H) above the peak is
due to quasiparticle tunneling conductivity \sigma_q(H) across the CuO_2 layers
below H_{c2}. At high fields (a) \sigma_q(H) grows linearly with H, and (b)
\rho_c(T) tends to saturate (sigma_c \neq 0) as T->0, consistent with the
scattering at the nodes of the d-gap. A superlinear sigma_q(H) marks the normal
state above T_c.Comment: 4p., 5 fig. (.eps), will be published in Phys. Rev. Let
The quantum superalgebra : deformed para-Bose operators and root of unity representations
We recall the relation between the Lie superalgebra and para-Bose
operators. The quantum superalgebra , defined as usual in terms
of its Chevalley generators, is shown to be isomorphic to an associative
algebra generated by so-called pre-oscillator operators satisfying a number of
relations. From these relations, and the analogue with the non-deformed case,
one can interpret these pre-oscillator operators as deformed para-Bose
operators. Some consequences for (Cartan-Weyl basis,
Poincar\'e-Birkhoff-Witt basis) and its Hopf subalgebra are
pointed out. Finally, using a realization in terms of ``-commuting''
-bosons, we construct an irreducible finite-dimensional unitary Fock
representation of and its decomposition in terms of
representations when is a root of unity.Comment: 15 pages, LaTeX (latex twice), no figure
Primary choriocarcinoma of the renal pelvis presenting as intracerebral hemorrhage: a case report and review of the literature
<p>Abstract</p> <p>Introduction</p> <p>A choriocarcinoma is a malignant neoplasm normally arising in the gestational trophoblast, gonads and, less frequently, the retroperitoneum, mediastinum and pineal gland. Primary choriocarcinomas of the renal pelvis are extremely rare.</p> <p>Case presentation</p> <p>We report a case of primary choriocarcinoma of the renal pelvis in a 38-year-old Greek woman of reproductive age, presenting with a sudden development of intracerebral hemorrhage due to metastatic lesions. The diagnosis was established with a renal biopsy, along with an elevated serum level of beta-human chorionic gonadotropin. An extensive diagnostic work up confirmed the origin of the choriocarcinoma to be the renal pelvis.</p> <p>Conclusion</p> <p>Extragonadal choriocarcinomas are rare neoplasms that require extensive laboratory and imaging studies to exclude a gonadal origin. Moreover, this is the first case of severe intracerebral hemorrhage as the initial presentation of primary choriocarcinoma of the renal pelvis. Nonetheless, choriocarcinomas should be considered in the differential diagnosis of women of reproductive age.</p
Spin and Chirality Effects in Antler-Topology Processes at High Energy Colliders
We perform a model-independent investigation of spin and chirality
correlation effects in the antler-topology processes
at high energy colliders with polarized
beams. Generally the production process
can occur not only through the -channel exchange of vector bosons,
, including the neutral Standard Model (SM) gauge bosons,
and , but also through the - and -channel exchanges of new
neutral states, and , and the -channel
exchange of new doubly-charged states, . The general set of
(non-chiral) three-point couplings of the new particles and leptons allowed in
a renormalizable quantum field theory is considered. The general spin and
chirality analysis is based on the threshold behavior of the excitation curves
for pair production in collisions with
longitudinal and transverse polarized beams, the angular distributions in the
production process and also the production-decay angular correlations. In the
first step, we present the observables in the helicity formalism. Subsequently,
we show how a set of observables can be designed for determining the spins and
chiral structures of the new particles without any model assumptions. Finally,
taking into account a typical set of approximately chiral invariant scenarios,
we demonstrate how the spin and chirality effects can be probed experimentally
at a high energy collider.Comment: 50 pages, 14 figures, 6 tables, matches version published in EPJ
Microwave amplification with nanomechanical resonators
Sensitive measurement of electrical signals is at the heart of modern science
and technology. According to quantum mechanics, any detector or amplifier is
required to add a certain amount of noise to the signal, equaling at best the
energy of quantum fluctuations. The quantum limit of added noise has nearly
been reached with superconducting devices which take advantage of
nonlinearities in Josephson junctions. Here, we introduce a new paradigm of
amplification of microwave signals with the help of a mechanical oscillator. By
relying on the radiation pressure force on a nanomechanical resonator, we
provide an experimental demonstration and an analytical description of how the
injection of microwaves induces coherent stimulated emission and signal
amplification. This scheme, based on two linear oscillators, has the advantage
of being conceptually and practically simpler than the Josephson junction
devices, and, at the same time, has a high potential to reach quantum limited
operation. With a measured signal amplification of 25 decibels and the addition
of 20 quanta of noise, we anticipate near quantum-limited mechanical microwave
amplification is feasible in various applications involving integrated
electrical circuits.Comment: Main text + supplementary information. 14 pages, 3 figures (main
text), 18 pages, 6 figures (supplementary information
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