19,116 research outputs found
Can CPT Symmetry Be Tested With K^0 vs \bar{K}^0--> \pi^+\pi^-\pi^0 Decays?
We show that the CP-violating effect in K^0 vs \bar K^0-->\pi^+\pi^-\pi^0
decays differs from that in K_{\rm L}-->\pi^+\pi^-, K_{\rm L}-->\pi^0\pi^0 or
the semileptonic K_{\rm L} transitions, if there exists CPT violation in
K^0-\bar{K}^0 mixing. A delicate measurement of this difference in the KTeV
experiment and at the \phi factory will provide a new test of CPT symmetry in
the neutral kaon system.Comment: RevTex 6 pages. Phys. Rev. D (in printing
Parton recombination at all
Hadron production at all in heavy-ion collisions in the framework of
parton recombination is reviewed. It is shown that the recombination of thermal
and shower partons dominates the hadron spectra in the intermediate
region. In collisions, the physics of particle production at any
is basically the same as at . The Cronin effect is described as a
result of the final-state instead of the initial-state interaction. The
suppression of at high is due to the reduction of the soft
parton density on the deuteron side, thus resulting in less pions produced by
recombination, an explanation that requires no new physics. In
collisions large ratio is obtained because the thermal partons can
contribute to the formation of proton more than they do to the pion.Comment: 12 pages + 5 figures. Invited talk at Hard Probes 200
High transverse momentum suppression and surface effects in Cu+Cu and Au+Au collisions within the PQM model
We study parton suppression effects in heavy-ion collisions within the Parton
Quenching Model (PQM). After a brief summary of the main features of the model,
we present comparisons of calculations for the nuclear modification and the
away-side suppression factor to data in Au+Au and Cu+Cu collisions at 200 GeV.
We discuss properties of light hadron probes and their sensitivity to the
medium density within the PQM Monte Carlo framework.Comment: Comments: 6 pages, 8 figures. To appear in the proceedings of Hot
Quarks 2006: Workshop for Young Scientists on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May
200
Phenomenology of Jet Quenching in Heavy Ion Collisions
We derive an analytical expression for the quenching factor in the strong
quenching limit where the spectrum of hard partons is dominated by
surface emission. We explore the phenomenological consequences of different
scaling laws for the energy loss and calculate the additional suppression of
the away-side jet.Comment: Substantially modified manuscrip
A Shape Theorem for Riemannian First-Passage Percolation
Riemannian first-passage percolation (FPP) is a continuum model, with a
distance function arising from a random Riemannian metric in . Our main
result is a shape theorem for this model, which says that large balls under
this metric converge to a deterministic shape under rescaling. As a
consequence, we show that smooth random Riemannian metrics are geodesically
complete with probability one
Schwinger Algebra for Quaternionic Quantum Mechanics
It is shown that the measurement algebra of Schwinger, a characterization of
the properties of Pauli measurements of the first and second kinds, forming the
foundation of his formulation of quantum mechanics over the complex field, has
a quaternionic generalization. In this quaternionic measurement algebra some of
the notions of quaternionic quantum mechanics are clarified. The conditions
imposed on the form of the corresponding quantum field theory are studied, and
the quantum fields are constructed. It is shown that the resulting quantum
fields coincide with the fermion or boson annihilation-creation operators
obtained by Razon and Horwitz in the limit in which the number of particles in
physical states .Comment: 20 pages, Plain Te
Convex Dynamics and Applications
This paper proves a theorem about bounding orbits of a time dependent
dynamical system. The maps that are involved are examples in convex dynamics,
by which we mean the dynamics of piecewise isometries where the pieces are
convex. The theorem came to the attention of the authors in connection with the
problem of digital halftoning. \textit{Digital halftoning} is a family of
printing technologies for getting full color images from only a few different
colors deposited at dots all of the same size. The simplest version consist in
obtaining grey scale images from only black and white dots. A corollary of the
theorem is that for \textit{error diffusion}, one of the methods of digital
halftoning, averages of colors of the printed dots converge to averages of the
colors taken from the same dots of the actual images. Digital printing is a
special case of a much wider class of scheduling problems to which the theorem
applies. Convex dynamics has roots in classical areas of mathematics such as
symbolic dynamics, Diophantine approximation, and the theory of uniform
distributions.Comment: LaTex with 9 PostScript figure
Implications of Weak-Interaction Space Deformation for Neutrino Mass Measurements
The negative values for the squares of both electron and muon neutrino masses
obtained in recent experiments are explained as a possible consequence of a
change in metric within the weak-interaction volume in the energy-momentum
representation. Using a model inspired by a combination of the general theory
of relativity and the theory of deformation for continuous media, it is shown
that the negative value of the square of the neutrino mass can be obtained
without violating allowed physical limits. The consequence is that the negative
value is not necessary unphysical.Comment: 12 pages, 5 figures, LaTe
Gravitomagnetism in Quantum Mechanics
We give a systematic treatment of the quantum mechanics of a spin zero
particle in a combined electromagnetic field and a weak gravitational field,
which is produced by a slow moving matter source. The analysis is based on the
Klein-Gordon equation expressed in generally covariant form and coupled
minimally to the electromagnetic field. The Klein-Gordon equation is recast
into Schroedinger equation form (SEF), which we then analyze in the
non-relativistic limit. We include a discussion of some rather general
observable physical effects implied by the SEF, concentrating on
gravitomagnetism. Of particular interest is the interaction of the orbital
angular momentum of the particle with the gravitomagnetic field.Comment: 9 page
Constant Rank Bimatrix Games are PPAD-hard
The rank of a bimatrix game (A,B) is defined as rank(A+B). Computing a Nash
equilibrium (NE) of a rank-, i.e., zero-sum game is equivalent to linear
programming (von Neumann'28, Dantzig'51). In 2005, Kannan and Theobald gave an
FPTAS for constant rank games, and asked if there exists a polynomial time
algorithm to compute an exact NE. Adsul et al. (2011) answered this question
affirmatively for rank- games, leaving rank-2 and beyond unresolved.
In this paper we show that NE computation in games with rank , is
PPAD-hard, settling a decade long open problem. Interestingly, this is the
first instance that a problem with an FPTAS turns out to be PPAD-hard. Our
reduction bypasses graphical games and game gadgets, and provides a simpler
proof of PPAD-hardness for NE computation in bimatrix games. In addition, we
get:
* An equivalence between 2D-Linear-FIXP and PPAD, improving a result by
Etessami and Yannakakis (2007) on equivalence between Linear-FIXP and PPAD.
* NE computation in a bimatrix game with convex set of Nash equilibria is as
hard as solving a simple stochastic game.
* Computing a symmetric NE of a symmetric bimatrix game with rank is
PPAD-hard.
* Computing a (1/poly(n))-approximate fixed-point of a (Linear-FIXP)
piecewise-linear function is PPAD-hard.
The status of rank- games remains unresolved
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