7,681 research outputs found
Characterizing the Larkin-Ovchinnikov-Fulde-Ferrel phase induced by the chromomagnetic instability
We discuss possible destinations from the chromomagnetic instability in color
superconductors with Fermi surface mismatch . In the two-flavor
superconducting (2SC) phase we calculate the effective potential for color
vector potentials which are interpreted as the net momenta of
pairing in the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) phase. When
where is the gap energy, the effective
potential suggests that the instability leads to a LOFF-like state which is
characterized by color-rotated phase oscillations with small . In the
vicinity of the magnitude of continuously
increases from zero as the effective potential has negative larger curvature at
vanishing that is the Meissner mass squared. In the gapless 2SC
(g2SC) phase, in contrast, the effective potential has a minimum at
even when the negative Meissner mass squared
is infinitesimally small. Our results imply that the chromomagnetic instability
found in the gapless phase drives the system toward the LOFF state with
.Comment: 6 pages, 3 figures; fatal typo about the conclusion corrected;
reference adde
Confinement Properties in the Multi-Instanton System
We investigate the confinement properties in the multi-instanton system,
where the size distribution is assumed to be for the large
instanton size . We find that the instanton vacuum gives the area law
behavior of the Wilson loop, which indicates existence of the linear confining
potential. In the multi-instanton system, the string tension increases
monotonously with the instanton density, and takes the standard value for the density . Thus, instantons
directly relate to color confinement properties.Comment: Talk presented by M. Fukushima at ``Lattice '97'', the International
Symposium on Lattice Field Theory, 22 - 26 July 1997, in Edinburgh, Scotland,
3 pages, Plain Late
Dielectric correction to the Chiral Magnetic Effect
We derive an electric current density in the presence of a magnetic
field and a chiral chemical potential . We show that has
not only the anomaly-induced term (i.e. Chiral Magnetic
Effect) but also a non-anomalous correction which comes from interaction
effects and expressed in terms of the susceptibility. We find the correction
characteristically dependent on the number of quark flavors. The numerically
estimated correction turns out to be a minor effect on heavy-ion collisions but
can be tested by the lattice QCD simulation.Comment: 4 pages, 1 figur
Views of the Chiral Magnetic Effect
My personal views of the Chiral Magnetic Effect are presented, which starts
with a story about how we came up with the electric-current formula and
continues to unsettled subtleties in the formula. There are desirable features
in the formula of the Chiral Magnetic Effect but some considerations would lead
us to even more questions than elucidations. The interpretation of the produced
current is indeed very non-trivial and it involves a lot of confusions that
have not been resolved.Comment: 19 pages, no figure; typos corrected, references significantly
updated, to appear in Lect. Notes Phys. "Strongly interacting matter in
magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Ye
Instability of a gapless color superconductor with respect to inhomogeneous fluctuations
We systematically apply density functional theory to determine the kind of
inhomogeneities that spontaneously develop in a homogeneous gapless phase of
neutral two-flavor superfluid quark matter. We consider inhomogeneities in the
quark and electron densities and in the phases and amplitude of the order
parameter. These inhomogeneities are expected to lead the gapless phase to a
BCS-normal coexisting phase, a Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state
with phase oscillations alone, and a LOFF state with amplitude oscillations. We
find that which of them the homogeneous system tends towards depends
sensitively on the chemical potential separation between up and down quarks and
the gradient energies.Comment: 15 pages, 3 figures; corrected Eq. (36) and changed content
associated with d quark clustering instabilit
Effective Model Approach to the Dense State of QCD Matter
The first-principle approach to the dense state of QCD matter, i.e. the
lattice-QCD simulation at finite baryon density, is not under theoretical
control for the moment. The effective model study based on QCD symmetries is a
practical alternative. However the model parameters that are fixed by hadronic
properties in the vacuum may have unknown dependence on the baryon chemical
potential. We propose a new prescription to constrain the effective model
parameters by the matching condition with the thermal Statistical Model. In the
transitional region where thermal quantities blow up in the Statistical Model,
deconfined quarks and gluons should smoothly take over the relevant degrees of
freedom from hadrons and resonances. We use the Polyakov-loop coupled
Nambu--Jona-Lasinio (PNJL) model as an effective description in the quark side
and show how the matching condition is satisfied by a simple ansatz on the
Polyakov loop potential. Our results favor a phase diagram with the chiral
phase transition located at slightly higher temperature than deconfinement
which stays close to the chemical freeze-out points.Comment: 8 pages, 4 figures; Talk at International Workshop on High Density
Nuclear Matter, Cape Town, South Africa, April 6-9, 201
Magnetic-field Induced Screening Effect and Collective Excitations
We explicitly construct the fermion propagator in a magnetic field background
B to take the lowest Landau-level approximation. We analyze the energy and
momentum dependence in the polarization tensor and discuss the collective
excitations. We find there appear two branches of collective modes in one of
two transverse gauge particles; one represents a massive and attenuated gauge
particle and the other behaves similar to the zero sound at finite density.Comment: 5 pages, 3 figures; references on the zero sound added and typos
correcte
Asymptotics for the Wiener sausage among Poissonian obstacles
We consider the Wiener sausage among Poissonian obstacles. The obstacle is
called hard if Brownian motion entering the obstacle is immediately killed, and
is called soft if it is killed at certain rate. It is known that Brownian
motion conditioned to survive among obstacles is confined in a ball near its
starting point. We show the weak law of large numbers, large deviation
principle in special cases and the moment asymptotics for the volume of the
corresponding Wiener sausage. One of the consequence of our results is that the
trajectory of Brownian motion almost fills the confinement ball.Comment: 19 pages, Major revision made for publication in J. Stat. Phy
Are You Tampering With My Data?
We propose a novel approach towards adversarial attacks on neural networks
(NN), focusing on tampering the data used for training instead of generating
attacks on trained models. Our network-agnostic method creates a backdoor
during training which can be exploited at test time to force a neural network
to exhibit abnormal behaviour. We demonstrate on two widely used datasets
(CIFAR-10 and SVHN) that a universal modification of just one pixel per image
for all the images of a class in the training set is enough to corrupt the
training procedure of several state-of-the-art deep neural networks causing the
networks to misclassify any images to which the modification is applied. Our
aim is to bring to the attention of the machine learning community, the
possibility that even learning-based methods that are personally trained on
public datasets can be subject to attacks by a skillful adversary.Comment: 18 page
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