1,507 research outputs found
Local Primitive Causality and the Common Cause Principle in Quantum Field Theory
If \{A(V)\} is a net of local von Neumann algebras satisfying standard axioms
of algebraic relativistic quantum field theory and V_1 and V_2 are spacelike
separated spacetime regions, then the system (A(V_1),A(V_2),\phi) is said to
satisfy the Weak Reichenbach's Common Cause Principle iff for every pair of
projections A \in A(V_1), B \in A(V_2) correlated in the normal state \phi
there exists a projection C belonging to a von Neumann algebra associated with
a spacetime region V contained in the union of the backward light cones of V_1
and V_2 and disjoint from both V_1 and V_2, a projection having the properties
of a Reichenbachian common cause of the correlation between A and B. It is
shown that if the net has the local primitive causality property then every
local system (A(V_1),A(V_2),\phi) with a locally normal and locally faithful
state \phi and open bounded V_1 and V_2 satisfies the Weak Reichenbach's Common
Cause Principle.Comment: 14 pages, Late
Quantum Probability Theory
The mathematics of classical probability theory was subsumed into classical
measure theory by Kolmogorov in 1933. Quantum theory as nonclassical
probability theory was incorporated into the beginnings of noncommutative
measure theory by von Neumann in the early thirties, as well. To precisely this
end, von Neumann initiated the study of what are now called von Neumann
algebras and, with Murray, made a first classification of such algebras into
three types. The nonrelativistic quantum theory of systems with finitely many
degrees of freedom deals exclusively with type I algebras. However, for the
description of further quantum systems, the other types of von Neumann algebras
are indispensable. The paper reviews quantum probability theory in terms of
general von Neumann algebras, stressing the similarity of the conceptual
structure of classical and noncommutative probability theories and emphasizing
the correspondence between the classical and quantum concepts, though also
indicating the nonclassical nature of quantum probabilistic predictions. In
addition, differences between the probability theories in the type I, II and
III settings are explained. A brief description is given of quantum systems for
which probability theory based on type I algebras is known to be insufficient.
These illustrate the physical significance of the previously mentioned
differences.Comment: 28 pages, LaTeX, typos removed and some minor modifications for
clarity and accuracy made. This is the version to appear in Studies in the
History and Philosophy of Modern Physic
Magnetic Monopole in Noncommutative Space-Time and Wu-Yang Singularity-Free Gauge Transformations
We investigate the validity of the Dirac Quantization Condition (DQC) for
magnetic monopoles in noncommutative space-time. We use an approach which is
based on an extension of the method introduced by Wu and Yang. To study the
effects of noncommutativity of space-time, we consider the gauge
transformations of gauge fields and use the corresponding deformed
Maxwell's equations. Using a perturbation expansion in the noncommutativity
parameter , we show that the DQC remains unmodified up to the first
order in the expansion parameter. The result is obtained for a class of
noncommutative source terms, which reduce to the Dirac delta function in the
commutative limit.Comment: 18 pages. Relation to relevant literature clarified in the
conclusions, 6 references adde
Examining a reduced jet-medium coupling in Pb+Pb collisions at the Large Hadron Collider
Recent data on the nuclear modification factor of jet fragments in
2.76 ATeV Pb+Pb collisions at the Large Hadron Collider (LHC) indicate that the
jet-medium coupling in a Quark-Gluon Plasma (QGP) is reduced at LHC energies
and not compatible with the coupling deduced from data at the Relativistic
Hadron Collider (RHIC). We estimate the reduction factor from a combined fit to
the available data on and the elliptic flow
at ATeV over a transverse momentum
range 10-100 GeV and a broad impact parameter, b, range. We use a simple
analytic "polytrope" model () to investigate
the dynamical jet-energy loss model dependence. Varying a=0-1 interpolates
between weakly-coupled and strongly-coupled models of jet-energy dependence
while z=0-2 covers a wide range of possible jet-path dependencies from elastic
and radiative to holographic string mechanisms. Our fit to LHC data indicates
an approximate 40% reduction of the coupling from RHIC to LHC and
excludes energy-loss models characterized by a jet-energy exponent with a>1/3.
In particular, the rapid rise of with >10 GeV combined with the
slow variation of the asymptotic at the LHC rules out popular
exponential geometric optics models (a=1). The LHC data are compatible with
pQCD-like energy-loss models where the jet-medium coupling is
reduced by approximately 10% between RHIC and LHC.Comment: 10 pages, 7 figures, version published in Physical Review
Fourier Harmonics of High-pT Particles Probing the Fluctuating Intitial Condition Geometries in Heavy-Ion Collisions
Second Fourier harmonics of jet quenching have been thoroughly explored in
the literature and shown to be sensitive to the underlying jet path-length
dependence of energy loss and the differences between the mean eccentricity
predicted by Glauber and CGC/KLN models of initial conditions. We compute the
jet path-length dependence of energy-loss for higher azimuthal harmonics of
jet-fragments in a generalized model of energy-loss for RHIC energies and find,
however, that even the high- second moment is most sensitive to the poorly
known early-time evolution during the first fm/c. Moreover, we demonstrate that
higher-jet harmonics are remarkably insensitive to the initial conditions,
while the different vs. correlations
between the moments of monojet and dijet nuclear modifications factors remain a
most sensitive probe to differentiate between Glauber and CGC/KLN initial state
sQGP geometries.Comment: 6 pages, 7 figures, updated figures, version accepted for publication
in Phys. Rev.
Open Charm and Beauty at Ultrarelativistic Heavy Ion Colliders
Important goals of RHIC and LHC experiments with ion beams include the
creation and study of new forms of matter, such as the Quark Gluon Plasma.
Heavy quark production and attenuation will provide unique tomographic probes
of that matter. We predict the suppression pattern of open charm and beauty in
collisions at RHIC and LHC energies based on the DGLV formalism of
radiative energy loss. A cancelation between effects due to the
energy dependence of the high slope and heavy quark energy loss is
predicted to lead to surprising similarity of heavy quark suppression at RHIC
and LHC.Comment: 4 pages, 6 *.eps files combined into 4 figure
Differential freezeout and pion interferometry at RHIC from covariant transport theory
Puzzling discrepancies between recent pion interferometry data on Au+Au
reactions at s^1/2 = 130 and 200 AGeV from RHIC and predictions based on ideal
hydrodynamics are analyzed in terms of covariant parton transport theory. The
discrepancies of out and longitudinal radii are significantly reduced when the
finite opacity of the gluon plasma is taken into account.Comment: 4 pages, 3 EPS figures. Submitted to PR
Di-Jet Conical Correlations Associated with Heavy Quark Jets in anti--de Sitter Space/Conformal Field Theory Correspondence
We show that far zone Mach and diffusion wake ``holograms'' produced by
supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT)
correspondence do not lead to observable conical angular correlations in the
strict supergravity limit if Cooper-Frye hadronization is
assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is
shown to produce an apparent sonic boom azimuthal angle distribution that is
roughly independent of the heavy quark's velocity. Our results indicate that a
measurement of the dependence of the away-side correlations on the velocity of
associated identified heavy quark jets at the BNL Relativistic Heavy Ion
Collider and CERN LHC will provide a direct test of the nonperturbative
dynamics involved in the coupling between jets and the strongly-coupled
Quark-Gluon Plasma (sQGP) implied by AdS/CFT correspondence.Comment: 4 pages, 2 figures, version published in Physical Review Letter
Near Zone Navier-Stokes Analysis of Heavy Quark Jet Quenching in an =4 SYM Plasma
The near zone energy-momentum tensor of a supersonic heavy quark jet moving
through a strongly-coupled SYM plasma is analyzed in terms of
first-order Navier-Stokes hydrodynamics. It is shown that the hydrodynamical
description of the near quark region worsens with increasing quark velocities.
For realistic quark velocities, , the non-hydrodynamical region is
located at a narrow band surrounding the quark with a width of approximately
in the direction parallel to the quark's motion and with a length of
roughly in the perpendicular direction. Our results can be
interpreted as an indication of the presence of coherent Yang-Mills fields
where deviation from hydrodynamics is at its maximum. In the region where
hydrodynamics does provide a good description of the system's dynamics, the
flow velocity is so small that all the nonlinear terms can be dropped. Our
results, which are compatible with the thermalization timescales extracted from
elliptic flow measurements, suggest that if AdS/CFT provides a good description
of the RHIC system, the bulk of the quenched jet energy has more than enough
time to locally thermalize and become encoded in the collective flow. The
resulting flow pattern close to the quark, however, is shown to be considerably
different than the superposition of Mach cones and diffusion wakes observed at
large distances.Comment: new revised version, 11 figures, as published in PR
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