1,372 research outputs found
From the chiral magnetic wave to the charge dependence of elliptic flow
The quark-gluon plasma formed in heavy ion collisions contains charged chiral
fermions evolving in an external magnetic field. At finite density of electric
charge or baryon number (resulting either from nuclear stopping or from
fluctuations), the triangle anomaly induces in the plasma the Chiral Magnetic
Wave (CMW). The CMW first induces a separation of the right and left chiral
charges along the magnetic field; the resulting dipolar axial charge density in
turn induces the oppositely directed vector charge currents leading to an
electric quadrupole moment of the quark-gluon plasma. Boosted by the strong
collective flow, the electric quadrupole moment translates into the charge
dependence of the elliptic flow coefficients, so that
(at positive net charge). Using the latest quantitative simulations of the
produced magnetic field and solving the CMW equation, we make further
quantitative estimates of the produced splitting and its centrality
dependence. We compare the results with the available experimental data.Comment: Contains 12 pages, 6 figures, written as a proceeding for the talk of
Y. Burnier at the conference "P and CP-odd Effects in Hot and Dense Matter
2012" held in BN
Chiral helix in AdS/CFT with flavor
The D3/D7 holographic model aims at a better approximation to QCD by adding
to N=4 SYM theory N_f of N=2 supersymmetric hypermultiplets in the fundamental
representation of SU(N_c) -- the "flavor fields" representing the quarks.
Motivated by a recent observation of the importance of the Wess-Zumino-like
(WZ) term for realizing the chiral magnetic effect within this model, we
revisit the phase diagram of the finite temperature, massless D3/D7 model in
the presence of external electric/magnetic fields and at finite chemical
potential. We point out that the A-V-V triangle anomaly represented by the WZ
term in the D7 brane probe action implies the existence of new phases that have
been overlooked in the previous studies. In the case of an external magnetic
field and at finite chemical potential, we find a "chiral helix" phase in which
the U(1)_A angle of D7 brane embedding increases monotonically along the
direction of the magnetic field -- this is a geometric realization of the
chiral spiral phase in QCD. We also show that in the case of parallel electric
and magnetic fields (E,B) there exists a phase in which the D7 brane
spontaneously begins to rotate, so that the U(1)_A angle changes as a function
of time -- this may be called the "spontaneous rotation" phase; it is a
geometrical realization of a phase with non-zero chiral chemical potential. Our
results call for a more thorough study of the (T,B,E,\mu) phase diagram of the
massless D3/D7 model taking a complete account of the WZ term.
We also speculate about the possible phase diagram in the massive case.Comment: 25 pages, 7 figure
Nonperturbative Determination of Heavy Meson Bound States
In this paper we obtain a heavy meson bound state equation from the heavy
quark equation of motion in heavy quark effective theory (HQET) and the heavy
meson effective field theory we developed very recently. The bound state
equation is a covariant extention of the light-front bound state equation for
heavy mesons derived from light-front QCD and HQET. We determine the covariant
heavy meson wave function variationally by minimizing the binding energy
. Subsequently the other basic HQET parameters and
, and the heavy quark masses and can also be
consistently determined.Comment: 15 pages, 1 figur
Evolution of Non-Gaussian Hydrodynamic Fluctuations
In the context of the search for the QCD critical point using non-Gaussian fluctuations, we obtain the evolution equations for non-Gaussian cumulants to the leading order of the systematic expansion in the magnitude of thermal fluctuations. We develop a diagrammatic technique in which the leading order contributions are given by tree diagrams. We introduce a Wigner transform for multipoint correlators and derive the evolution equations for three- and four-point Wigner functions for the problem of nonlinear stochastic diffusion with multiplicative noise
Fluctuation dynamics in a relativistic fluid with a critical point
To describe dynamics of bulk and fluctuations near the QCD critical point we develop general relativistic fluctuation formalism for a fluid carrying baryon charge. Feedback of fluctuations modifies hydrodynamic coefficients including bulk viscosity and conductivity and introduces nonlocal and noninstantaneous terms in constitutive equations. We perform necessary ultraviolet (short-distance) renormalization to obtain cutoff-independent deterministic equations suitable for numerical implementation. We use the equations to calculate the universal nonanalytic small-frequency dependence of transport coefficients due to fluctuations (long-time tails). Focusing on the critical mode we show how this general formalism matches existing Hydro+ description of fluctuations near the QCD critical point and nontrivially extends it inside and outside of the critical region
Holographic Pomeron and the Schwinger mechanism
We revisit the problem of dipole-dipole scattering via exchanges of soft Pomerons in the context of holographic QCD. We show that a single closed string exchange contribution to the eikonalized dipole-dipole scattering amplitude yields a Regge behavior of the elastic amplitude; the corresponding slope and intercept are different from previous results obtained by a variational analysis of semiclassical surfaces. We provide a physical interpretation of the semiclassical worldsheets driving the Regge behavior for (-t)>0 in terms of worldsheet instantons. The latter describe the Schwinger mechanism for string pair creation by an electric field, where the longitudinal electric field E L=σ Ttanh(χ/2) at the origin of this nonperturbative mechanism is induced by the relative rapidity χ of the scattering dipoles. Our analysis naturally explains the diffusion in the impact parameter space encoded in the Pomeron exchange; in our picture, it is due to the Unruh temperature of accelerated strings under the electric field. We also argue for the existence of a "micro-fireball" in the middle of the transverse space due to the soft Pomeron exchange, which may be at the origin of the thermal character of multiparticle production in ep/pp collisions. After summing over uncorrelated multi-Pomeron exchanges, we find that the total dipole-dipole cross section obeys the Froissart unitarity bound
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Studies in theoretical high energy particle physics
This report discusses research in string theory; solitons; supersymmetry; conformed field theory; and quarks
Interplay of Reggeon and photon in pA collisions
We discuss the effects of the electromagnetic interaction in high-energy proton collisions with nuclei of large Z at strong coupling λ=g2Nc. Using the holographic dual limit of large Nc>λ1, we describe the Reggeon exchange as a twisted surface and show that it gets essentially modified by the electromagnetic interaction
Internal kinematics of spiral galaxies in distant clusters. Part II. Observations and data analysis
We have conducted an observing campaign with FORS at the ESO-VLT to explore
the kinematical properties of spiral galaxies in distant galaxy clusters. Our
main goal is to analyse transformation- and interaction processes of disk
galaxies within the special environment of clusters as compared to the
hierarchical evolution of galaxies in the field. Spatially resolved MOS-spectra
have been obtained for seven galaxy clusters at 0.3<z<0.6 to measure rotation
velocities of cluster members. For three of the clusters, Cl0303+17, Cl0413-65,
and MS1008-12, for which we presented results including a TF-diagram in Ziegler
et al. 2003, we describe here in detail the observations and data analysis.
Each of them was observed with two setups of the standard FORS MOS-unit.With
typical exposure times of >2 hours we reach an S/N>5 in the emission lines
appropriate for the deduction of the galaxies' internal rotation velocities
from [OII], Hbeta, or [OIII] profiles. Preselection of targets was done on the
basis of available redshifts as well as from photometric and morphological
information gathered from own observations, archive data, and from the
literature. Emphasis was laid on the definition of suitable setups to avoid the
typical restrictions of the standard MOS unit for this kind of observations. In
total we assembled spectra of 116 objects of which 50 turned out to be cluster
members. Position velocity diagrams, finding charts as well as tables with
photometric, spectral, and structural parameters of individual galaxies are
presented.Comment: 18 pages, 6 figures, accepted for publication in Astronomy and
Astrophysics. A version with full resolution figures can be downloaded from
http://www.uni-sw.gwdg.de/~vwgroup/publications.htm
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