1,632 research outputs found
Quantum Condensates in Nuclear Matter: Problems
In connection with the contribution "Quantum Condensates in Nuclear Matter"
some problems are given to become more familiar with the techniques of
many-particle physics.Comment: 8 pages, 1 figur
Aberrant location of inhibitory synaptic marker proteins in the hippocampus of dystrophin-deficient mice
Duchenne muscular dystrophy (DMD) is a neuromuscular disease that arises from mutations in the dystrophin-encoding gene. Apart from muscle pathology, cognitive impairment, primarily of developmental origin, is also a significant component of the disorder. Convergent lines of evidence point to an important role for dystrophin in regulating the molecular machinery of central synapses. The clustering of neurotransmitter receptors at inhibitory synapses, thus impacting on synaptic transmission, is of particular significance. However, less is known about the role of dystrophin in influencing the precise expression patterns of proteins located within the pre- and postsynaptic elements of inhibitory synapses. To this end, we exploited molecular markers of inhibitory synapses, interneurons and dystrophin-deficient mouse models to explore the role of dystrophin in determining the stereotypical patterning of inhibitory connectivity within the cellular networks of the hippocampus CA1 region. In tissue from wild-type (WT) mice, immunoreactivity of neuroligin2 (NL2), an adhesion molecule expressed exclusively in postsynaptic elements of inhibitory synapses, and the vesicular GABA transporter (VGAT), a marker of GABAergic presynaptic elements, were predictably enriched in strata pyramidale and lacunosum moleculare. In acute contrast, NL2 and VGAT immunoreactivity was relatively evenly distributed across all CA1 layers in dystrophin-deficient mice. Similar changes were evident with the cannabinoid receptor 1, vesicular glutamate transporter 3, parvalbumin, somatostatin and the GABAA receptor alpha1 subunit. The data show that in the absence of dystrophin, there is a rearrangement of the molecular machinery, which underlies the precise spatio-temporal pattern of GABAergic synaptic transmission within the CA1 sub-field of the hippocampus
Pions in the quark matter phase diagram
The relationship between mesonic correlations and quantum condensates in the
quark matter phase diagram is explored within a quantum field theoretical
approach of the Nambu and Jona-Lasinio (NJL) type. Mean-field values in the
scalar meson and diquark channels are order parameters signalling the
occurrence of quark condensates, entailing chiral symmetry breaking (chi SB)
and color superconductivity (2SC) in quark matter. We investigate the spectral
properties of scalar and pseudoscalar meson excitations in the phase diagram in
Gaussian approximation and show that outside the chi SB region where the pion
is a zero-width bound state, there are two regions where it can be considered
as a quasi-bound state with a lifetime exceeding that of a typical heavy-ion
collision fireball: (A) the high-temperature chi SB crossover region at low
densities and (B) the high-density color superconducting phase at temperatures
below 100 MeV.Comment: presented by D. Zablocki at the Joint Meeting
Heidelberg-Liege-Paris-Wroclaw (HLPW08), Spa, Belgium, 6-8 March 2008, 10
pages, 5 figures, LaTeX, uses aip-6s.clo, aipproc.cls and aipxfm.sty
(included
Color neutrality effects in the phase diagram of the PNJL model
The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is
analyzed imposing the constraint of color charge neutrality. Main effects of
this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain
in the T-mu plane, a shift of the critical point to lower temperatures and a
coexistence of chiSB and two-flavor superconducting phases. The effects can be
understood in view of the presence of a nonvanishing color chemical potential
mu_8, which is necessary to compensate the color charge density rho_8 induced
by the nonvanishing Polyakov-loop mean field phi_3.Comment: 8 pages, 4 figures, figures added, minor text modification
Bound States and Superconductivity in Dense Fermi Systems
A quantum field theoretical approach to the thermodynamics of dense Fermi
systems is developed for the description of the formation and dissolution of
quantum condensates and bound states in dependence of temperature and density.
As a model system we study the chiral and superconducting phase transitions in
two-flavor quark matter within the NJL model and their interrelation with the
formation of quark-antiquark and diquark bound states. The phase diagram of
quark matter is evaluated as a function of the diquark coupling strength and a
coexistence region of chiral symmetry breaking and color superconductivity is
obtained at very strong coupling. The crossover between Bose-Einstein
condensation (BEC) of diquark bound states and condensation of diquark
resonances (Cooper pairs) in the continuum (BCS) is discussed as a Mott effect.
This effect consists in the transition of bound states into the continuum of
scattering states under the influence of compression and heating. We explain
the physics of the Mott transition with special emphasis on role of the Pauli
principle for the case of the pion in quark matter.Comment: 16 pages, 5 figure
Recommended from our members
A Search for Dark Higgs Bosons
Recent astrophysical and terrestrial experiments have motivated the proposal
of a dark sector with GeV-scale gauge boson force carriers and new Higgs
bosons. We present a search for a dark Higgs boson using 516 fb-1 of data
collected with the BABAR detector. We do not observe a significant signal and
we set 90% confidence level upper limits on the product of the Standard
Model-dark sector mixing angle and the dark sector coupling constant.Comment: 7 pages, 5 postscript figures, published version with improved plots
for b/w printin
Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV
A search for new physics is presented based on an event signature of at least
three jets accompanied by large missing transverse momentum, using a data
sample corresponding to an integrated luminosity of 36 inverse picobarns
collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector
at the LHC. No excess of events is observed above the expected standard model
backgrounds, which are all estimated from the data. Exclusion limits are
presented for the constrained minimal supersymmetric extension of the standard
model. Cross section limits are also presented using simplified models with new
particles decaying to an undetected particle and one or two jets
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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