214 research outputs found
Remarks on monopoles in Abelian projected continuum Yang-Mills theories
A possible mechanism accounting for monopole configurations in continuum
Yang-Mills theories is discussed. The presence of the gauge fixing term is
taken into account.Comment: Contribution to LHP2001, 9-18 July 2001, Cairns, Australi
DC and AC Josephson Effect in a Superconductor-Luttinger Liquid-Superconductor System
We calculate both the DC and the AC Josephson current through a
one-dimensional system of interacting electrons, connected to two
superconductors by tunnel junctions. We treat the (repulsive) Coulomb
interaction in the framework of the one-channel, spin- Luttinger model.
The Josephson current is obtained for two geometries of experimental relevance:
a quantum wire and a ring. At zero temperature, the critical current is found
to decay algebraically with increasing distance between the junctions. The
decay is characterized by an exponent which depends on the strength of the
interaction. At finite temperatures , lower than the superconducting
transition temperature , there is a crossover from algebraic to
exponential decay of the critical current as a function of , at a distance
of the order of . Moreover, the dependence of critical current
on temperature shows non-monotonic behavior. If the Luttinger liquid is
confined to a ring of circumference , coupled capacitively to a gate voltage
and threaded by a magnetic flux, the Josephson current shows remarkable parity
effects under the variation of these parameters. For some values of the gate
voltage and applied flux, the ring acts as a -junction. These features are
robust against thermal fluctuations up to temperatures on the order of . For the wire-geometry, we have also studied the AC-Josephson
effect. The amplitude and the phase of the time-dependent Josephson current are
affected by electron-electron interactions. Specifically, the amplitude shows
pronounced oscillations as a function of the bias voltage due to the difference
between the velocities of spin and charge excitations in the Luttinger liquid.
Therefore, the AC Josephson effect can be used as a tool for the observation o
Resonant cancellation of off-resonant effects in a multilevel qubit
Off-resonant effects are a significant source of error in quantum
computation. This paper presents a group theoretic proof that off-resonant
transitions to the higher levels of a multilevel qubit can be completely
prevented in principle. This result can be generalized to prevent unwanted
transitions due to qubit-qubit interactions. A simple scheme exploiting dynamic
pulse control techniques is presented that can cancel transitions to higher
states to arbitrary accuracy.Comment: 4 pages, Revtex, submitted for publicatio
Dynamical gluon mass generation from <A^2> in linear covariant gauges
We construct the multiplicatively renormalizable effective potential for the
mass dimension two local composite operator A^2 in linear covariant gauges. We
show that the formation of is energetically favoured and that the gluons
acquire a dynamical mass due to this gluon condensate. We also discuss the
gauge parameter independence of the resultant vacuum energy.Comment: 21 pages. 14 .eps figures. v2: minor modifications. v3: version
accepted for publication in JHE
Interacting one dimensional electron gas with open boundaries
We discuss the properties of interacting electrons on a finite chain with
open boundary conditions. We extend the Haldane Luttinger liquid description to
these systems and study how the presence of the boundaries modifies various
correlation functions. In view of possible experimental applications to quantum
wires, we analyse how tunneling measurements can reveal the underlying
Luttinger liquid properties. The two terminal conductance is calculated. We
also point out possible applications to quasi one dimensional materials and
study the effects of magnetic impurities.Comment: 38 pages, ReVTeX, 7 figures (available upon request
On the infrared scaling solution of SU(N) Yang-Mills theories in the maximally Abelian gauge
An improved method for extracting infrared exponents from functional
equations is presented. The generalizations introduced allow for an analysis of
quite complicated systems such as Yang-Mills theory in the maximally Abelian
gauge. Assuming the absence of cancellations in the appropriately renormalized
integrals the only consistent scaling solution yields an infrared enhanced
diagonal gluon propagator in support of the Abelian dominance hypothesis. This
is explicitly shown for SU(2) and subsequently verified for SU(N), where
additional interactions exist. We also derive the most infrared divergent
scaling solution possible for vertex functions in terms of the propagators'
infrared exponents. We provide general conditions for the existence of a
scaling solution for a given system and comment on the cases of linear
covariant gauges and ghost anti-ghost symmetric gauges.Comment: 23 pages, 10 figures; version coincides with version published in
EPJ
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
Effect of event selection on jetlike correlation measurement in d+Au collisions at sNN=200 GeV
AbstractDihadron correlations are analyzed in sNN=200 GeV d+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions
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