123,600 research outputs found
Large Momenta Fluctuations Of Charm Quarks In The Quark-Gluon Plasma
We show that large fluctuations of D mesons kinetic energy (or momentum)
distributions might be a signature of a phase transition to the quark gluon
plasma (QGP). In particular, a jump in the variance of the momenta or kinetic
energy, as a function of a control parameter (temperature or Fermi energy at
finite baryon densities) might be a signature for a first order phase
transition to the QGP. This behaviour is completely consistent with the order
parameter defined for a system of interacting quarks at zero temperature and
finite baryon densities which shows a jump in correspondance to a first order
phase transition to the QGP. The shows exactly the same behavior of
the order parameter and of the variance of the D mesons. We discuss
implications for relativistic heavy ion collisions within the framework of a
transport model and possible hints for experimental data.Comment: 4 pages 3 figure
Strongly interacting bosons in a disordered optical lattice
Disorder, prevalent in nature, is intimately involved in such spectacular
effects as the fractional quantum Hall effect and vortex pinning in type-II
superconductors. Understanding the role of disorder is therefore of fundamental
interest to materials research and condensed matter physics. Universal
behavior, such as Anderson localization, in disordered non-interacting systems
is well understood. But, the effects of disorder combined with strong
interactions remains an outstanding challenge to theory. Here, we
experimentally probe a paradigm for disordered, strongly-correlated bosonic
systems-the disordered Bose-Hubbard (DBH) model-using a Bose-Einstein
condensate (BEC) of ultra-cold atoms trapped in a completely characterized
disordered optical lattice. We determine that disorder suppresses condensate
fraction for superfluid (SF) or coexisting SF and Mott insulator (MI) phases by
independently varying the disorder strength and the ratio of tunneling to
interaction energy. In the future, these results can constrain theories of the
DBH model and be extended to study disorder for strongly-correlated fermionic
particles.Comment: 15 pages, 4 figures updated to correct errors in referencing previous
wor
Hardcore bosons on checkerboard lattices near half filling: geometric frustration, vanishing charge order and fractional phase
We study a spinless hardcore boson model on checkerboard lattices by Green
function Monte Carlo method. At half filling, the ground state energy is
obtained up to lattice and extrapolated to infinite size, the
staggered pseudospin magnetization is found to vanish in the thermodynamic
limit. Thus the charge order is absent in this system. Away from
half filling, two defects induced by each hole (particle) may carry fractional
charge (). For one hole case, we study how the defect-defect
correlation changes with , which is the ratio between the hopping integral
and cyclic exchange, equals to when . Moreover, we argue that
these fractional defects may propagate independently when the concentration of
holes (or defects) is large enough
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