1,363 research outputs found
Hamiltonian approach to QCD in Coulomb gauge - a survey of recent results
I report on recent results obtained within the Hamiltonian approach to QCD in
Coulomb gauge. Furthermore this approach is compared to recent lattice data,
which were obtained by an alternative gauge fixing method and which show an
improved agreement with the continuum results. By relating the Gribov
confinement scenario to the center vortex picture of confinement it is shown
that the Coulomb string tension is tied to the spatial string tension. For the
quark sector a vacuum wave functional is used which explicitly contains the
coupling of the quarks to the transverse gluons and which results in
variational equations which are free of ultraviolet divergences. The
variational approach is extended to finite temperatures by compactifying a
spatial dimension. The effective potential of the Polyakov loop is evaluated
from the zero-temperature variational solution. For pure Yang--Mills theory,
the deconfinement phase transition is found to be second order for SU(2) and
first order for SU(3), in agreement with the lattice results. The corresponding
critical temperatures are found to be and , respectively. When quarks are included, the deconfinement
transition turns into a cross-over. From the dual and chiral quark condensate
one finds pseudo-critical temperatures of and , respectively, for the deconfinement and chiral transition.Comment: Talk given by H. Reinhardt at "5th Winter Workshop on
Non-Perturbative Quantum Field Theory", 22-24 March 2017, Sophia-Antipolis,
France. arXiv admin note: text overlap with arXiv:1609.09370,
arXiv:1510.03286, arXiv:1607.0814
Partial spin freezing in the quasi-two-dimensional La2(Cu,Li)O4
In conventional spin glasses, the magnetic interaction is not strongly
anisotropic and the entire spin system freezes at low temperature. In
La2(Cu,Li)O4, for which the in-plane exchange interaction dominates the
interplane one, only a fraction of spins with antiferromagnetic correlations
extending to neighboring planes become spin-glass. The remaining spins with
only in-plane antiferromagnetic correlations remain spin-liquid at low
temperature. Such a novel partial spin freezing out of a spin-liquid observed
in this cold neutron scattering study is likely due to a delicate balance
between disorder and quantum fluctuations in the quasi-two dimensional S=1/2
Heisenberg system.Comment: 4 pages, 4 figure
Field-induced coupled superconductivity and spin density wave order in the Heavy Fermion compound CeCoIn5
The high field superconducting state in CeCoIn5 has been studied by
transverse field muon spin rotation measurements with an applied field parallel
to the crystallographic c-axis close to the upper critical field Hc2 = 4.97 T.
At magnetic fields >= 4.8 T the muon Knight shift is enhanced and the
superconducting transition changes from second order towards first order as
predicted for Pauli-limited superconductors. The field and temperature
dependence of the transverse muon spin relaxation rate sigma reveal
paramagnetic spin fluctuations in the field regime from 2 T < H < 4.8 T. In the
normal state close to Hc2 correlated spin fluctuations as described by the self
consistent renormalization theory are observed. The results support the
formation of a mode-coupled superconducting and antiferromagnetically ordered
phase in CeCoIn5 for H directed parallel to the c-axis.Comment: 5 paes, 4 figure
Chiral Correction to the Spin Fluctuation Feedback in two-dimensional p-wave Superconductors
We consider the stability of the superconducting phase for spin-triplet
p-wave pairing in a quasi-two-dimensional system. We show that in the absence
of spin-orbit coupling there is a chiral contribution to spin fluctuation
feedback which is related to spin quantum Hall effect in a chiral
superconducting phase. We show that this mechanism supports the stability of a
chiral p-wave state.Comment: 8 pages. The final version is accepted for publication in Europhys
Let
Observation of two time scales in the ferromagnetic manganite La(1-x)Ca(x)MnO(3), x = 0.3
We report new zero-field muon spin relaxation and neutron spin echo
measurements in ferromagnetic (FM) (La,Ca)MnO3 which taken together suggest two
spatially separated regions in close proximity possessing very different Mn-ion
spin dynamics. One region corresponds to an extended cluster which displays
'critical slowing down' near Tc and an increasing volume fraction below Tc. The
second region possesses more slowly fluctuating spins and a decreasing volume
fraction below Tc. These data are discussed in terms of the growth of small
polarons into overlapping regions of correlated spins below Tc, resulting in a
microscopically inhomogeneous FM transition.Comment: 10 pages, 3 figure
Timing Studies on RXTE Observations of SAX J2103.5+4545
SAX J2103.5+4545 has been continuously monitored for 900 days by
Rossi X-ray Timing Explorer (RXTE) since its outburst in July 2002. Using these
observations and previous archival RXTE observations of SAX J2103.5+4545, we
refined the binary orbital parameters and find the new orbital period as P=
(12.66536 0.00088) days and the eccentricity as 0.4055 0.0032. With
these new orbital parameters, we constructed the pulse frequency and pulse
frequency derivative histories of the pulsar and confirmed the correlation
between X-ray flux and pulse frequency derivative presented by Baykal, Stark
and Swank (2002). We constructed the power spectra for the fluctuations of
pulse frequency derivatives and found that the power law index of the noise
spectra is 2.13 0.6. The power law index is consistent with random walk
in pulse frequency derivative and is the steepest among the HMXRBs.
X-ray spectra analysis confirmed the inverse correlation trend between
power-law index and X-ray flux found by Baykal, Stark and Swank (2002).Comment: 23 pages, 7 figures, revised version accepted for publication in
MNRA
- …