213 research outputs found
The influence of medium effects on the gross structure of hybrid stars
We investigate the influence of medium effects on the structure of hybrid
stars, i.e. neutron stars possessing a quark matter core. We found that medium
effects reduce the extent of a pure quark matter phase in the interior of a
hybrid star significantly in favor of a mixed phase of quark and hadronic
matter. Over a wide range of the strong coupling constant - which parameterizes
the influence of medium effects - quark matter is able to exist at least in a
mixed phase in the interior of neutron stars.Comment: 20 pages, LaTeX, 4 inline eps-figures, 4 gif-figures, extended
discussion, to be published in Nucl. Phys. A. Also available at
http://theorie.physik.uni-giessen.de/~schertle/HybSta
Vortex Holography
We show that the Abelian Higgs field equations in the four dimensional anti
de Sitter spacetime have a vortex line solution. This solution, which has
cylindrical symmetry in AdS, is a generalization of the flat spacetime
Nielsen-Olesen string. We show that the vortex induces a deficit angle in the
AdS spacetime that is proportional to its mass density. Using the AdS/CFT
correspondence, we show that the mass density of the string is uniform and dual
to the discontinuity of a logarithmic derivative of correlation function of the
boundary scalar operator.Comment: LaTeX, 20 pages, 4 eps figures, references and two paragraphs added,
to appear in Nucl. Phys.
Non-adiabatic geometrical quantum gates in semiconductor quantum dots
In this paper we study the implementation of non-adiabatic geometrical
quantum gates with in semiconductor quantum dots. Different quantum information
enconding/manipulation schemes exploiting excitonic degrees of freedom are
discussed. By means of the Aharanov-Anandan geometrical phase one can avoid the
limitations of adiabatic schemes relying on adiabatic Berry phase; fast
geometrical quantum gates can be in principle implementedComment: 5 Pages LaTeX, 10 Figures include
An infinite family of convex Brunnian links in
This paper proves that convex Brunnian links exist for every dimension by constructing explicit examples. These examples are three-component
links which are higher-dimensional generalizations of the Borromean rings.Comment: 10 pages, 4 figure
Novel point mutation in the extracellular domain of the granulocyte colony-stimulating factor (G-CSF) receptor in a case of severe congenital neutropenia hyporesponsive to G-CSF treatment
Severe congenital neutropenia (SCN) is a heterogeneous condition
characterized by a drastic reduction in circulating neutrophils and a
maturation arrest of myeloid progenitor cells in the bone marrow. Usually
this condition can be successfully treated with granulocyte
colony-stimulating factor (G-CSF). Here we describe the identification of
a novel point mutation in the extracellular domain of the G-CSF receptor
(G-CSF-R) in an SCN patient who failed to respond to G-CSF treatment. When
this mutant G-CSF-R was expressed in myeloid cells, it was defective in
both proliferation and survival signaling. This correlated with diminished
activation of the receptor complex as determined by signal transducer and
activator of transcription (STAT) activation, although activation of STAT5
was more affected than STAT3. Interestingly, the mutant receptor showed
normal affinity for ligand, but a reduced number of ligand binding sites
compared with the wild-type receptor. This suggests that the mutation in
the extracellular domain affects ligand-receptor complex formation with
severe consequences for intracellular signal transduction. Together these
data add to our understanding of the mechanisms of cytokine receptor
signaling, emphasize the role of GCSFR mutations in the etiology of SCN,
and implicate such mutations in G-CSF hyporesponsiveness
Exotic smooth structures on 4-manifolds with zero signature
For every integer , we construct infinite families of mutually
nondiffeomorphic irreducible smooth structures on the topological -manifolds
and (2k-1)(\CP#\CPb), the connected sums of
copies of and \CP#\CPb.Comment: 6 page
On the Exact Evaluation of Certain Instances of the Potts Partition Function by Quantum Computers
We present an efficient quantum algorithm for the exact evaluation of either
the fully ferromagnetic or anti-ferromagnetic q-state Potts partition function
Z for a family of graphs related to irreducible cyclic codes. This problem is
related to the evaluation of the Jones and Tutte polynomials. We consider the
connection between the weight enumerator polynomial from coding theory and Z
and exploit the fact that there exists a quantum algorithm for efficiently
estimating Gauss sums in order to obtain the weight enumerator for a certain
class of linear codes. In this way we demonstrate that for a certain class of
sparse graphs, which we call Irreducible Cyclic Cocycle Code (ICCC_\epsilon)
graphs, quantum computers provide a polynomial speed up in the difference
between the number of edges and vertices of the graph, and an exponential speed
up in q, over the best classical algorithms known to date
Exotic Smooth Structures on Small 4-Manifolds
Let M be either CP^2#3CP^2bar or 3CP^2#5CP^2bar. We construct the first
example of a simply-connected symplectic 4-manifold that is homeomorphic but
not diffeomorphic to M.Comment: 11 page
Medium effects in strange quark matter and strange stars
We investigate the properties of strange quark matter at zero temperature
including medium effects. The quarks are considered as quasiparticles which
acquire an effective mass generated by the interaction with the other quarks of
the dense system. The effective quark masses are derived from the zero momentum
limit of the dispersion relations following from an effective quark propagator
obtained from resumming one-loop self energy diagrams in the hard dense loop
approximation. This leads to a thermodynamic selfconsistent description of
strange quark matter as an ideal Fermi gas of quasiparticles. Within this
approach we find that medium effects reduce the overall binding energy with
respect to of strange quark matter. For realistic values of the
strong coupling constant strange quark matter is not absolutely stable. The
application to pure strange quark matter stars shows that medium effects have,
nevertheless, no impact on the mass-radius relation of the stars. However, a
phase transition to hadronic matter at the surface of the stars becomes more
likely.Comment: 16 pages, LaTeX, 14 eps-figures included. To be published in Nuclear
Physics
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