3,920 research outputs found
Critical Endpoint and Inverse Magnetic Catalysis for Finite Temperature and Density Quark Matter in a Magnetic Background
In this article we study chiral symmetry breaking for quark matter in a
magnetic background, , at finite temperature and quark chemical
potential, , making use of the Ginzburg-Landau effective action formalism.
As a microscopic model to compute the effective action we use the renormalized
quark-meson model. Our main goal is to study the evolution of the critical
endpoint, , as a function of the magnetic field strength, and
investigate on the realization of inverse magnetic catalysis at finite chemical
potential. We find that the phase transition at zero chemical potential is
always of the second order; for small and intermediate values of ,
moves towards small , while for larger it moves
towards moderately larger values of . Our results are in agreement with
the inverse magnetic catalysis scenario at finite chemical potential and not
too large values of the magnetic field, while at larger direct magnetic
catalysis sets in.Comment: 6 pages, 2 figure
The cohomology of the Grassmannian is a -module
The integral singular cohomology ring of the Grassmann variety parametrizing r-dimensional subspaces in the n-dimensional complex vector space is naturally an irreducible representation of the Lie algebra gl n ðZÞ of all the n n matrices with integral entries. The simplest case, r 1⁄4 1, recovers the well known fact that any vector space is a module over the Lie algebra of its own endomorphisms. The other extremal case, r 1⁄4 ∞; corresponds to the bosonic vertex representation of the Lie algebra gl ∞ ðZÞ on the polynomial ring in infinitely many indeterminates, due to Date, Jimbo, Kashiwara and Miwa. In the present article we provide the structure of this irreducible representation explicitly, by means of a distinguished Hasse-Schmidt derivation ation on an exterior algebra, borrowed from Schubert Calculus
Aircraft control via variable cant-angle winglets
Copyright @ 2008 American Institute of Aeronautics and AstronauticsThis paper investigates a novel method for the control of "morphing" aircraft. The concept consists of a pair of winglets; with adjustable cant angle, independently actuated and mounted at the tips of a baseline flying wing. The general philosophy behind the concept was that for specific flight conditions such as a coordinated turn, the use of two control devices would be sufficient for adequate control. Computations with a vortex lattice model and subsequent wind-tunnel tests demonstrate the viability of the concept, with individual and/or dual winglet deflection producing multi-axis coupled control moments. Comparisons between the experimental and computational results showed reasonable to good agreement, with the major discrepancies thought to be due to wind-tunnel model aeroelastic effects.This work has been supported by a Marie Curie excellence research grant funded by the European Commission
Hot Quark Matter with an Axial Chemical Potential
We analyze the phase diagram of hot quark matter in presence of an axial
chemical potential, . The latter is introduced to mimic the chirality
transitions induced, in hot Quantum Chromodynamics, by the strong sphaleron
configurations. In particular, we study the curvature of the critical line at
small , the effects of a finite quark mass and of a vector interaction.
Moreover, we build the mixed phase at the first order phase transition line,
and draw the phase diagram in the chiral density and temperature plane. We
finally compute the full topological susceptibility in presence of a background
of topological charge.Comment: 12 pages, 7 figures. Few references added, short discussion included.
Final version appearing on Phys. Rev.
Dressed Polyakov loop and phase diagram of hot quark matter under magnetic field
We evaluate the dressed Polyakov loop for hot quark matter in strong magnetic
field. To compute the finite temperature effective potential, we use the
Polyakov extended Nambu-Jona Lasinio model with eight-quark interactions taken
into account. The bare quark mass is adjusted in order to reproduce the
physical value of the vacuum pion mass. Our results show that the dressed
Polyakov loop is very sensitive to the strenght of the magnetic field, and it
is capable to capture both the deconfinement crossover and the chiral
crossover. Besides, we compute self-consistently the phase diagram of the
model. We find a tiny split of the two aforementioned crossovers as the
strength of the magnetic field is increased. Concretely, for the largest value
of magnetic field investigated here, , the split is of the order
of . A qualitative comparison with other effective models and recent
Lattice results is also performed.Comment: 10 pages, 3 figures, RevTeX4-1 styl
Dual modulation VCSEL-based sustainable transceiver for SSB DMT signals transmission
Single sideband DMT signal performance is analyzed in order to achieve high capacity and high spectral efficiency over 50-km uncompensated SMF. A sustainable implementation of the SSB DMT-based transceiver is proposed by means of a VCSEL source and a dual-modulator scheme, providing SSB without optical filtering and Hilbert transform implementation. Moreover, Kramers-Kronig detection, made possible by SSB, is studied at the receiver to effectively compensate the chromatic dispersion with direct detection
Native NIR-emitting single colour centres in CVD diamond
Single-photon sources are a fundamental element for developing quantum
technologies, and sources based on colour centres in diamonds are among the
most promising candidates. The well-known NV centres are characterized by
several limitations, thus few other defects have recently been considered. In
the present work, we characterize in detail native efficient single colour
centres emitting in the near infra-red in both standard IIa single-crystal and
electronic-grade polycrystalline commercial CVD diamond samples. In the former
case, a high-temperature annealing process in vacuum is necessary to induce the
formation/activation of luminescent centres with good emission properties,
while in the latter case the annealing process has marginal beneficial effects
on the number and performances of native centres in commercially available
samples. Although displaying significant variability in several photo physical
properties (emission wavelength, emission rate instabilities, saturation
behaviours), these centres generally display appealing photophysical properties
for applications as single photon sources: short lifetimes, high emission rates
and strongly polarized light. The native centres are tentatively attributed to
impurities incorporated in the diamond crystal during the CVD growth of
high-quality type IIa samples, and offer promising perspectives in
diamond-based photonics.Comment: 27 pages, 10 figures. Submitted to "New Journal of Phsyics",
NJP-100003.R
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