175 research outputs found
The Chern-Simons diffusion rate in strongly coupled N=4 SYM plasma in an external magnetic field
We calculate the Chern-Simons diffusion rate in a strongly coupled N=4 SUSY
Yang-Mills plasma in the presence of a constant external magnetic flux
via the holographic correspondence. Due to the strong interactions between the
charged fields and non-Abelian gauge fields, the external Abelian magnetic
field affects the thermal Yang-Mills dynamics and increases the diffusion rate,
regardless of its strength. We obtain the analytic results for the Chern-Simons
diffusion rate both in the weak and strong magnetic field limits. In the latter
limit, we show that the diffusion rate scales as and this can be
understood as a result of a dynamical dimensional reduction.Comment: 10 pages, 1 figure, typos corrected, comments adde
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
Chiral magnetic wave at finite baryon density and the electric quadrupole moment of quark-gluon plasma in heavy ion collisions
Chiral Magnetic Wave (CMW) is a gapless collective excitation of quark-gluon
plasma in the presence of external magnetic field that stems from the interplay
of Chiral Magnetic (CME) and Chiral Separation Effects (CSE); it is composed by
the waves of the electric and chiral charge densities coupled by the axial
anomaly. We consider CMW at finite baryon density and find that it induces the
electric quadrupole moment of the quark-gluon plasma produced in heavy ion
collisions: the "poles" of the produced fireball (pointing outside of the
reaction plane) acquire additional positive electric charge, and the "equator"
acquires additional negative charge. We point out that this electric quadrupole
deformation lifts the degeneracy between the elliptic flows of positive and
negative pions leading to , and estimate the magnitude
of the effect.Comment: 4 pages, 3 figure
Dynamics of the Chiral Magnetic Effect in a weak magnetic field
We investigate the real-time dynamics of the chiral magnetic effect in
quantum electrodynamics (QED) and quantum chromodynamics (QCD). We consider a
field configuration of parallel (chromo)electric and (chromo)magnetic fields
with a weak perpendicular electromagnetic magnetic field. The chiral magnetic
effect induces an electromagnetic current along this perpendicular magnetic
field, which we will compute using linear response theory. We discuss specific
results for a homogeneous sudden switch-on and a pulsed (chromo)electric field
in a static and homogeneous (chromo)magnetic field. Our methodology can be
easily extended to more general situations. The results are useful for
investigating the chiral magnetic effect with heavy ion collisions and with
lasers that create strong electromagnetic fields. As a side result we obtain
the rate of chirality production for massive fermions in parallel electric and
magnetic fields that are static and homogeneous.Comment: 13 pages, 7 figures, revte
Electromagnetic field evolution in relativistic heavy-ion collisions
The hadron string dynamics (HSD) model is generalized to include the creation
and evolution of retarded electromagnetic fields as well as the influence of
the magnetic and electric fields on the quasiparticle propagation. The
time-space structure of the fields is analyzed in detail for non-central Au+Au
collisions at 200 GeV. It is shown that the created magnetic
field is highly inhomogeneous but in the central region of the overlapping
nuclei it changes relatively weakly in the transverse direction. For the impact
parameter 10 fm the maximal magnetic field - perpendicularly to the
reaction plane - is obtained of order 5 for a very short time
0.2 fm/c, which roughly corresponds to the time of a maximal overlap of
the colliding nuclei. We find that at any time the location of the maximum in
the distribution correlates with that of the energy density of the
created particles. In contrast, the electric field distribution, being also
highly inhomogeneous, has a minimum in the center of the overlap region.
Furthermore, the field characteristics are presented as a function of the
collision energy and the centrality of the collisions. To explore the effect of
the back reaction of the fields on hadronic observables a comparison of HSD
results with and without fields is exemplified. Our actual calculations show no
noticeable influence of the electromagnetic fields - created in heavy-ion
collisions - on the effect of the electric charge separation with respect to
the reaction plane.Comment: 17 pages, 22 figures, title changed by editor, accepted for PR
Deconfinement and Chiral Symmetry Restoration in a Strong Magnetic Background
We perform a model study of deconfinement and chiral symmetry restoration in
a strong magnetic background. We use a Nambu-Jona Lasinio model with the
Polyakov loop, taking into account a possible dependence of the coupling on the
Polyakov loop expectation value, as suggested by the recent literature. Our
main result is that, within this model, the deconfinement and chiral crossovers
of QCD in strong magnetic field are entangled even at the largest value of
considered here, namely (that is,
Tesla). The amount of split that we measure is, at this value of , of the
order of 2%. We also study briefly the role of the 8-quark term on the
entanglement of the two crossovers. We then compare the phase diagram of this
model with previous results, as well as with available Lattice data.Comment: 12 pages, 6 figures, RevTeX 4-1 style. Some reference added. Some
typos corrected. To appear on Physical Review
Human breast tissue cancer diagnosis by Raman spectroscopy
Abstract. Differences between Raman spectra of normal, malignant and benign tissues have been recorded and analyzed as a method for the early detection of cancer. To the best of our knowledge, this is one of the most statistically reliable research (67 patients) on Raman spectroscopy-based diagnosis of breast cancers among the world women population. The paper demonstrates that Raman spectroscopy is a promising new tool for real-time diagnosis of tissue abnormalities
Chiral Magnetic Effect on the Lattice
We review recent progress on the lattice simulations of the chiral magnetic
effect. There are two different approaches to analyze the chiral magnetic
effect on the lattice. In one approach, the charge density distribution or the
current fluctuation is measured under a topological background of the gluon
field. In the other approach, the topological effect is mimicked by the chiral
chemical potential, and the induced current is directly measured. Both
approaches are now developing toward the exact analysis of the chiral magnetic
effect.Comment: to appear in Lect. Notes Phys. "Strongly interacting matter in
magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Ye
Lattice QCD Simulations in External Background Fields
We discuss recent results and future prospects regarding the investigation,
by lattice simulations, of the non-perturbative properties of QCD and of its
phase diagram in presence of magnetic or chromomagnetic background fields.
After a brief introduction to the formulation of lattice QCD in presence of
external fields, we focus on studies regarding the effects of external fields
on chiral symmetry breaking, on its restoration at finite temperature and on
deconfinement. We conclude with a few comments regarding the effects of
electromagnetic background fields on gluodynamics.Comment: 31 pages, 10 figures, minor changes and references added. To appear
in Lect. Notes Phys. "Strongly interacting matter in magnetic fields"
(Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye
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