9,408 research outputs found
Probing the topological structure of the QCD vacuum with overlap fermions
Overlap fermions implement exact chiral symmetry on the lattice and are thus
an appropriate tool for investigating the chiral and topological structure of
the QCD vacuum. We study various chiral and topological aspects on
Luescher-Weisz-type quenched gauge field configurations using overlap fermions
as a probe. Particular emphasis is placed upon the analysis of the spectral
density and the localisation properties of the eigenmodes as well as on the
local structure of topological charge fluctuations.Comment: 8 pages, 6 figures, talk given at the Workshop on Computational
Hadron Physics, Nicosia, Cyprus, September 14-17, 2005; v2: Fig.6 corrected,
statistics in Fig. 4-6 increased, minor text change
Experimental investigation of the radial structure of energetic particle driven modes
Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often
excited by energetic particles (EPs) in tokamak plasmas. One of the main open
questions concerning EP driven instabilities is the non-linear evolution of the
mode structure. The aim of the present paper is to investigate the properties
of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs)
observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG)
discharges. This paper focuses on the changes in the mode structure of
BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown
that in case of the observed down-chirping BAEs the changes in the radial
structure are smaller than the uncertainty of our measurement. This behaviour
is most probably the consequence of that BAEs are normal modes, thus their
radial structure strongly depends on the background plasma parameters rather
than on the EP distribution. In the case of rapidly upward chirping EGAMs the
analysis consistently shows shrinkage of the mode structure. The proposed
explanation is that the resonance in the velocity space moves towards more
passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio
A giant ring-like structure at 0.78<z<0.86 displayed by GRBs
According to the cosmological principle, Universal large-scale structure is
homogeneous and isotropic. The observable Universe, however, shows complex
structures even on very large scales. The recent discoveries of structures
significantly exceeding the transition scale of 370 Mpc pose a challenge to the
cosmological principle.
We report here the discovery of the largest regular formation in the
observable Universe; a ring with a diameter of 1720 Mpc, displayed by 9 gamma
ray bursts (GRBs), exceeding by a factor of five the transition scale to the
homogeneous and isotropic distribution. The ring has a major diameter of
and a minor diameter of at a distance of 2770 Mpc in the 0.78<z<0.86
redshift range, with a probability of of being the result of
a random fluctuation in the GRB count rate.
Evidence suggests that this feature is the projection of a shell onto the
plane of the sky. Voids and string-like formations are common outcomes of
large-scale structure. However, these structures have maximum sizes of 150 Mpc,
which are an order of magnitude smaller than the observed GRB ring diameter.
Evidence in support of the shell interpretation requires that temporal
information of the transient GRBs be included in the analysis.
This ring-shaped feature is large enough to contradict the cosmological
principle. The physical mechanism responsible for causing it is unknown.Comment: Accepted for publication in MNRAS, 13 pages, 8 figures and 4 table
Neutrino oscillations with disentanglement of a neutrino from its partners
We bring attention to the fact that in order to understand existing data on
neutrino oscillations, and to design future experiments, it is imperative to
appreciate the role of quantum entanglement. Once this is accounted for, the
resulting energy-momentum conserving phenomenology requires a single new
parameter related to disentanglement of a neutrino from its partners. This
parameter may not be CP symmetric. We illustrate the new ideas, with
potentially measurable effects, in the context of a novel experiment recently
proposed by Gavrin, Gorbachev, Veretenkin, and Cleveland. The strongest impact
of our ideas is on the resolution of various anomalies in neutrino oscillations
and on neutrino propagation in astrophysical environments.Comment: 6 page
Curvature energy effects on strange quark matter nucleation at finite density
We consider the effects of the curvature energy term on thermal strange quark
matter nucleation in dense neutron matter. Lower bounds on the temperature at
which this process can take place are given and compared to those without the
curvature term.Comment: PlainTex, 6 pp., IAG-USP Rep.5
Equation of state for the MCFL phase and its implications for compact star models
Using the solutions of the gap equations of the magnetic-color-flavor-locked
(MCFL) phase of paired quark matter in a magnetic field, and taking into
consideration the separation between the longitudinal and transverse pressures
due to the field-induced breaking of the spatial rotational symmetry, the
equation of state (EoS) of the MCFL phase is self-consistently determined. This
result is then used to investigate the possibility of absolute stability, which
turns out to require a field-dependent bag constant to hold. That is, only if
the bag constant varies with the magnetic field, there exists a window in the
magnetic field vs. bag constant plane for absolute stability of strange matter.
Implications for stellar models of magnetized (self-bound) strange stars and
hybrid (MCFL core) stars are calculated and discussed.Comment: 11 pp. 11 figure
THE CONFLUENCE RATIO OF THE TRANSYLVANIAN BASIN RIVERS
There are many possibilities to assess the hydrological and geomorphological evolution of a territory. Among them, one remarks the confluence ratio of the rivers belonging to different catchment areas. The values of this indicator may provide information regarding the stage of evolution of the fluvial landforms in the Transylvanian Basin. Also, the values may serve for the calculation of other parameters of catchment areas like: the degree of finishing of the drainage basin for its corresponding order, the density of river segments within a catchment area etc. To calculate the confluence ratio, 35 catchment areas of different orders have been selected. The confluence ratio varies between 3.04 and 6.07. The large range of values demonstrates the existence of a heterogeneous lithology and of morphological and hydrographical contrasts from one catchment area to the other. The existence of values above 5, correlated also with observations in the field, reveals an accelerated dynamics of the geomorphological processes in those catchment areas. This dynamic is mainly supported by the high landform fragmentation due to the first order rivers. In contrast, the catchment areas that have a confluence ratio below 5 are in a more advanced stage of evolution with stable slopes, unable to initiate new first order river segments
Scaling Relations and Exponents in the Growth of Rough Interfaces Through Random Media
The growth of a rough interface through a random media is modelled by a
continuous stochastic equation with a quenched noise. By use of the Novikov
theorem we can transform the dependence of the noise on the interface height
into an effective temporal correlation for different regimes of the evolution
of the interface. The exponents characterizing the roughness of the interface
can thus be computed by simple scaling arguments showing a good agreement with
recent experiments and numerical simulations.Comment: 4 pages, RevTex, twocolumns, two figures (upon request). To appear in
Europhysics Letter
Immune cell profile of sentinel lymph nodes in patients with malignant melanoma - FOXP3+ cell density in cases with positive sentinel node status is associated with unfavorable clinical outcome
BACKGROUND: Besides being a preferential site of early metastasis, the sentinel lymph node (SLN) is also a privileged site of T-cell priming, and may thus be an appropriate target for investigating cell types involved in antitumor immune reactions. METHODS: In this retrospective study we determined the prevalence of OX40+ activated T lymphocytes, FOXP3+ (forkhead box P3) regulatory T cells, DC-LAMP+ (dendritic cell-lysosomal associated membrane protein) mature dendritic cells (DCs) and CD123+ plasmacytoid DCs by immunohistochemistry in 100 SLNs from 60 melanoma patients. Density values of each cell type in SLNs were compared to those in non-sentinel nodes obtained from block dissections (n = 37), and analyzed with regard to associations with clinicopathological parameters and disease outcome. RESULTS: Sentinel nodes showed elevated amount of all cell types studied in comparison to non-sentinel nodes. Metastatic SLNs had higher density of OX40+ lymphocytes compared to tumor-negative nodes, while no significant difference was observed in the case of the other cell types studied. In patients with positive sentinel node status, high amount of FOXP3+ cells in SLNs was associated with shorter progression-free (P = 0.0011) and overall survival (P = 0.0014), while no significant correlation was found in the case of sentinel-negative patients. The density of OX40+, CD123+ or DC-LAMP+ cells did not show significant association with the outcome of the disease. CONCLUSIONS: Taken together, our results are compatible with the hypothesis of functional competence of sentinel lymph nodes based on the prevalence of the studied immune cells. The density of FOXP3+ lymphocytes showed association with progression and survival in patients with positive SLN status, while the other immune markers studied did not prove of prognostic importance. These results, together with our previous findings on the prognostic value of activated T cells and mature DCs infiltrating primary melanomas, suggest that immune activation-associated markers in the primary tumor may have a higher impact than those in SLNs on the prognosis of the patients. On the other hand, FOXP3+ cell density in SLNs, but not in the primary tumor, was found predictive of disease outcome in melanoma patients
Nucleation of quark matter bubbles in neutron stars
The thermal nucleation of quark matter bubbles inside neutron stars is
examined for various temperatures which the star may realistically encounter
during its lifetime. It is found that for a bag constant less than a critical
value, a very large part of the star will be converted into the quark phase
within a fraction of a second. Depending on the equation of state for neutron
star matter and strange quark matter, all or some of the outer parts of the
star may subsequently be converted by a slower burning or a detonation.Comment: 13 pages, REVTeX, Phys.Rev.D (in press), IFA 93-32. 5 figures (not
included) available upon request from [email protected]
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