2,513 research outputs found
Identification of Colour Reconnection using Factorial Correlator
A new signal is proposed for the colour reconnection in the hadronic decay of
W+ W- in e+e- collisions. Using Pythia Monte Carlo it is shown that this
signal, being based on the factorial correlator, is more sensitive than the
ones using only averaged quantities.Comment: 6 pages 1 postscript figur
Spin filtering and magnetoresistance in ballistic tunnel junctions
We theoretically investigate magnetoresistance (MR) effects in connection
with spin filtering in quantum-coherent transport through tunnel junctions
based on non-magnetic/semimagnetic heterostructures. We find that spin
filtering in conjunction with the suppression/enhancement of the spin-dependent
Fermi seas in semimagnetic contacts gives rise to (i) spin-split kinks in the
MR of single barriers and (ii) a robust beating pattern in the MR of double
barriers with a semimagnetic well. We believe these are unique signatures for
quantum filtering.Comment: Added references + corrected typo
Topological insulators and superconductors
Topological insulators are new states of quantum matter which can not be
adiabatically connected to conventional insulators and semiconductors. They are
characterized by a full insulating gap in the bulk and gapless edge or surface
states which are protected by time-reversal symmetry. These topological
materials have been theoretically predicted and experimentally observed in a
variety of systems, including HgTe quantum wells, BiSb alloys, and BiTe
and BiSe crystals. We review theoretical models, materials properties
and experimental results on two-dimensional and three-dimensional topological
insulators, and discuss both the topological band theory and the topological
field theory. Topological superconductors have a full pairing gap in the bulk
and gapless surface states consisting of Majorana fermions. We review the
theory of topological superconductors in close analogy to the theory of
topological insulators.Comment: 55 pages, 44 figures, Review article commissioned by the Review of
Modern Physics. Please help us to improve the article by emailing us your
comments and missing reference
The Present State of Organic Xenobiotics in the Chesapeake Bay - A Synthesis Paper
This manuscript discusses the results of the first two and one half years of a three-year study designed to determine the present state of xenobiotic compounds in the Chesapeake Bay. It shows that polynuclear aromatic hydrocarbons are the most frequently encountered compounds and are the most abundant. Concentrations are highest in the Northern Bay with several sources implicated. During this study an apparent dumping of the pesticide, DDT, occurred. Either the quantity disposed of was small enough or the assimulation capacity was large enough that no adverse effects were noted. The detection by us of 6-phenyldodecane in bottom sediments of the Patapsco River and its detection in a nearby industrial outfall by the Monsanto Research Corporation shows that chemicals entering the River can be dispersed throughout the system and can enter the Chesapeake Bay
Heavy quark polarizations of in the general two Higgs doublet model
The polarizations of the heavy quark ( or ) in the process have been calculated in the general two Higgs doublet model.
The CP violating normal polarization of the top quark can reach 8%, and for the bottom quark, while it is zero in the standard model. The
longitudinal and transverse polarizations of the bottom quark can be
significantly different from those in SM and consequently could aslo be used as
the probe of the new physics.Comment: 12 pages, discussion on statistic significance added, version to
appear in PR
Fluctuation-Induced First Order Transition between the Quantum Hall Liquid and Insulator
We study the phase transition between the quantum Hall liquid state and the
insulating state within the framework of the Chern-Simons-Landau-Ginzburg
theory of the quantum Hall effect. For the transition induced by a background
periodic potential in the absence of disorder, the model is described by a
relativistic scalar field coupled to the Chern-Simons gauge field. For this
system, we show that the transition is of the first order, induced by the
fluctuations of the gauge field, rather than second order, with statistical
angle-dependent scaling exponent.Comment: 5 pages, REVTEX 3.0, two PostScript pictures appended, preprint
SU-ITP-94-
Modification of the Landau-Lifshitz Equation in the Presence of a Spin-Polarized Current in CMR and GMR Materials
We derive a continuum equation for the magnetization of a conducting
ferromagnet in the presence of a spin-polarized current. Current effects enter
in the form of a topological term in the Landau-Lifshitz equation . In the
stationary situation the problem maps onto the motion of a classical charged
particle in the field of a magnetic monopole. The spatial dependence of the
magnetization is calculated for a one-dimensional geometry and suggestions for
experimental observation are made. We also consider time-dependent solutions
and predict a spin-wave instability for large currents.Comment: 4 two-column pages in RevTex, 3 ps-figure
Radiative Higgs Boson Decays H\to f\bar{f}\gamma Beyond the Standard Model
Neutral Higgs boson radiative decays of the form h_0, H, A \to
f\bar{f}\gamma, in the light fermion limit $m_f->0, are calculated in the two
Higgs doublet model at one-loop level. Comparisons with the calculation within
the standard model are given, which indicates that these two models are
distinguishable in the decay mode fermion-antifermion -photon. Our results show
that the concerned process may stand as an implement to identify the Higgs
belongings in case there is a intermediate mass Higgs detected.Comment: 13 pages in Revtex, version to appear in Phys. Rev.
Collective excitations in double-layer quantum Hall systems
We study the collective excitation spectra of double-layer quantum-Hall
systems using the single mode approximation. The double-layer in-phase density
excitations are similar to those of a single-layer system. For out-of-phase
density excitations, however, both inter-Landau-level and intra-Landau-level
double-layer modes have finite dipole oscillator strengths. The oscillator
strengths at long wavelengths for the latter transitions are shifted upward by
interactions by identical amounts proportional to the interlayer Coulomb
coupling. The intra-Landau-level out-of-phase mode has a gap when the ground
state is incompressible except in the presence of spontaneous inter-layer
coherence. We compare our results with predictions based on the
Chern-Simons-Landau-Ginzburg theory for double-layer quantum Hall systems.Comment: RevTeX, 21 page
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