229 research outputs found
New Strong Interactons at the Tevatron ?
Recent results from CDF indicate that the inclusive cross section for jets
with GeV is significantly higher than that predicted by QCD. We
describe here a simple flavor-universal variant of the ``coloron" model of Hill
and Parke that can accommodate such a jet excess, and which is not in
contradiction with other experimental data. As such, the model serves as a
useful baseline with which to compare both the data and other models proposed
to describe the jet excess. An interesting theoretical feature of the model is
that if the global chiral symmetries of the quarks remain unbroken in the
confining phase of the coloron interaction, it realizes the possibility that
the ordinary quarks are composite particles.Comment: added contributions to scattering cross-sections; 10
pages, LaTeX, includes 1 figure. Full postscript version at
http://smyrd.bu.edu/htfigs/htfigs.htm
Muon-Spin Rotation Spectra in the Mixed Phase of High-T_c Superconductors : Thermal Fluctuations and Disorder Effects
We study muon-spin rotation (muSR) spectra in the mixed phase of highly
anisotropic layered superconductors, specifically Bi_2+xSr_2-xCaCu_2O_8+delta
(BSCCO), by modeling the fluid and solid phases of pancake vortices using
liquid-state and density functional methods. The role of thermal fluctuations
in causing motional narrowing of muSR lineshapes is quantified in terms of a
first-principles theory of the flux-lattice melting transition. The effects of
random point pinning are investigated using a replica treatment of liquid state
correlations and a replicated density functional theory. Our results indicate
that motional narrowing in the pure system, although substantial, cannot
account for the remarkably small linewidths obtained experimentally at
relatively high fields and low temperatures. We find that satisfactory
agreement with the muSR data for BSCCO in this regime can be obtained through
the ansatz that this ``phase'' is characterized by frozen short-range
positional correlations reflecting the structure of the liquid just above the
melting transition. This proposal is consistent with recent suggestions of a
``pinned liquid'' or ``glassy'' state of pancake vortices in the presence of
pinning disorder. Our results for the high-temperature liquid phase indicate
that measurable linewidths may be obtained in this phase as a consequence of
density inhomogeneities induced by the pinning disorder. The results presented
here comprise a unified, first-principles theoretical treatment of muSR spectra
in highly anisotropic layered superconductors in terms of a controlled set of
approximations.Comment: 50 pages Latex file, including 10 postscript figure
Separation of spin and charge in paired spin-singlet quantum Hall states
We propose a series of paired spin-singlet quantum Hall states, which exhibit
a separation of spin and charge degrees of freedom. The fundamental excitations
over these states, which have filling fraction \nu=2/(2m+1) with m an odd
integer, are spinons (spin-1/2 and charge zero) or fractional holons (charge
+/- 1/(2m+1) and spin zero). The braid statistics of these excitations are
non-abelian. The mechanism for the separation of spin and charge in these
states is topological: spin and charge excitations are liberated by binding to
a vortex in a p-wave pairing condensate. We briefly discuss related, abelian
spin-singlet states and possible transitions.Comment: 4 pages, uses revtex
jFuzzyLogic: a Java Library to Design Fuzzy Logic Controllers According to the Standard for Fuzzy Control Programming
Fuzzy Logic Controllers are a specific model of Fuzzy Rule Based Systems suitable for engineering
applications for which classic control strategies do not achieve good results or for when it is too difficult
to obtain a mathematical model. Recently, the International Electrotechnical Commission has published
a standard for fuzzy control programming in part 7 of the IEC 61131 norm in order to offer a well defined
common understanding of the basic means with which to integrate fuzzy control applications in control
systems. In this paper, we introduce an open source Java library called jFuzzyLogic which offers a fully
functional and complete implementation of a fuzzy inference system according to this standard, providing
a programming interface and Eclipse plugin to easily write and test code for fuzzy control applications.
A case study is given to illustrate the use of jFuzzyLogic.McGill Uninversity, Genome QuebecSpanish Government
TIN2011-28488Andalusian Government
P10-TIC-685
Precise calculation of parity nonconservation in cesium and test of the standard model
We have calculated the 6s-7s parity nonconserving (PNC) E1 transition
amplitude, E_{PNC}, in cesium. We have used an improved all-order technique in
the calculation of the correlations and have included all significant
contributions to E_{PNC}. Our final value E_{PNC} = 0.904 (1 +/- 0.5 %) \times
10^{-11}iea_{B}(-Q_{W}/N) has half the uncertainty claimed in old calculations
used for the interpretation of Cs PNC experiments. The resulting nuclear weak
charge Q_{W} for Cs deviates by about 2 standard deviations from the value
predicted by the standard model.Comment: 24 pages, 8 figure
Coherent Phonons in Carbon Nanotubes and Graphene
We review recent studies of coherent phonons (CPs) corresponding to the
radial breathing mode (RBM) and G-mode in single-wall carbon nanotubes (SWCNTs)
and graphene. Because of the bandgap-diameter relationship, RBM-CPs cause
bandgap oscillations in SWCNTs, modulating interband transitions at terahertz
frequencies. Interband resonances enhance CP signals, allowing for chirality
determination. Using pulse shaping, one can selectively excite
speci!c-chirality SWCNTs within an ensemble. G-mode CPs exhibit
temperature-dependent dephasing via interaction with RBM phonons. Our
microscopic theory derives a driven oscillator equation with a
density-dependent driving term, which correctly predicts CP trends within and
between (2n+m) families. We also find that the diameter can initially increase
or decrease. Finally, we theoretically study the radial breathing like mode in
graphene nanoribbons. For excitation near the absorption edge, the driving term
is much larger for zigzag nanoribbons. We also explain how the armchair
nanoribbon width changes in response to laser excitation.Comment: 48 pages, 41 figure
Probabilistic reasoning with a bayesian DNA device based on strand displacement
We present a computing model based on the DNA strand displacement technique which performs Bayesian inference. The model will take single stranded DNA as input data, representing the presence or absence of a specific molecular signal (evidence). The program logic encodes the prior probability of a disease and the conditional probability of a signal given the disease playing with a set of different DNA complexes and their ratios. When the input and program molecules interact, they release a different pair of single stranded DNA species whose relative proportion represents the application of Bayes? Law: the conditional probability of the disease given the signal. The models presented in this paper can empower the application of probabilistic reasoning in genetic diagnosis in vitro
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
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