7,043 research outputs found
Dynamical Formation of Disoriented Chiral Condensates
We study the dynamical formation of disoriented chiral condensates in very
high energy nucleus-nucleus collisions using Bjorken hydrodynamics and
relativistic nucleation theory. It is the dynamics of the first order
confinement phase transition which controls the evolution of the system. Every
bubble or fluctuation of the new, hadronic, phase obtains its own chiral
condensate with a probability determined by the Boltzmann weight of the finite
temperature effective potential of the linear sigma model. We evaluate domain
size and chiral angle distributions, which can be used as initial conditions
for the solution of semiclassical field equations.Comment: 17 pages, latex and 10 ps figures available at
http://www.nbi.dk/~vischer/dcc.htm
Collective Motion of Polarized Dipolar Fermi Gases in the Hydrodynamic Regime
Recently, a seminal STIRAP experiment allowed the creation of 40K-87Rb
molecules in the rovibrational ground state [K.-K. Ni et al., Science 322, 231
(2008)]. In order to describe such a polarized dipolar Fermi gas in the
hydrodynamic regime, we work out a variational time-dependent Hartree-Fock
approach. With this we calculate dynamical properties of such a system as, for
instance, the frequencies of the low-lying excitations and the time-of-flight
expansion. We find that the dipole-dipole interaction induces anisotropic
breathing oscillations in momentum space. In addition, after release from the
trap, the momentum distribution becomes asymptotically isotropic, while the
particle density becomes anisotropic
Eisenstein series and automorphic representations
We provide an introduction to the theory of Eisenstein series and automorphic
forms on real simple Lie groups G, emphasising the role of representation
theory. It is useful to take a slightly wider view and define all objects over
the (rational) adeles A, thereby also paving the way for connections to number
theory, representation theory and the Langlands program. Most of the results we
present are already scattered throughout the mathematics literature but our
exposition collects them together and is driven by examples. Many interesting
aspects of these functions are hidden in their Fourier coefficients with
respect to unipotent subgroups and a large part of our focus is to explain and
derive general theorems on these Fourier expansions. Specifically, we give
complete proofs of the Langlands constant term formula for Eisenstein series on
adelic groups G(A) as well as the Casselman--Shalika formula for the p-adic
spherical Whittaker function associated to unramified automorphic
representations of G(Q_p). In addition, we explain how the classical theory of
Hecke operators fits into the modern theory of automorphic representations of
adelic groups, thereby providing a connection with some key elements in the
Langlands program, such as the Langlands dual group LG and automorphic
L-functions. Somewhat surprisingly, all these results have natural
interpretations as encoding physical effects in string theory. We therefore
also introduce some basic concepts of string theory, aimed toward
mathematicians, emphasising the role of automorphic forms. In particular, we
provide a detailed treatment of supersymmetry constraints on string amplitudes
which enforce differential equations of the same type that are satisfied by
automorphic forms. Our treatise concludes with a detailed list of interesting
open questions and pointers to additional topics which go beyond the scope of
this book.Comment: 326 pages. Detailed and example-driven exposition of the subject with
highlighted applications to string theory. v2: 375 pages. Substantially
extended and small correction
Properties of exotic matter for heavy ion searches
We examine the properties of both forms of strange matter, small lumps of strange quark matter (strangelets) and of strange hadronic matter (Metastable Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and future heavy ion searches. The strong and weak decays are discussed separately to distinguish between long-lived and short-lived candidates where the former ones are detectable in present heavy ion experiments while the latter ones in future heavy ion experiments, respectively. We find some long-lived strangelet candidates which are highly negatively charged with a mass to charge ratio like a anti deuteron (M/Z 2) but masses of A=10 to 16. We predict also many short-lived candidates, both in quark and in hadronic form, which can be highly charged. Purely hyperonic nuclei like the (2 02 ) are bound and have a negative charge while carrying a positive baryon number. We demonstrate also that multiply charmed exotics (charmlets) might be bound and can be produced at future heavy ion colliders
Quantum Fluctuations in Dipolar Bose Gases
We investigate the influence of quantum fluctuations upon dipolar Bose gases
by means of the Bogoliubov-de Gennes theory. Thereby, we make use of the local
density approximation to evaluate the dipolar exchange interaction between the
condensate and the excited particles. This allows to obtain the Bogoliubov
spectrum analytically in the limit of large particle numbers. After discussing
the condensate depletion and the ground-state energy correction, we derive
quantum corrected equations of motion for harmonically trapped dipolar Bose
gases by using superfluid hydrodynamics. These equations are subsequently
applied to analyze the equilibrium configuration, the low-lying oscillation
frequencies, and the time-of-flight dynamics. We find that both atomic magnetic
and molecular electric dipolar systems offer promising scenarios for detecting
beyond mean-field effects.Comment: Published in PR
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