4,019 research outputs found
Quantum interference oscillations of the superparamagnetic blocking in an Fe8 molecular nanomagnet
We show that the dynamic magnetic susceptibility and the superparamagnetic
blocking temperature of an Fe8 single molecule magnet oscillate as a function
of the magnetic field Hx applied along its hard magnetic axis. These
oscillations are associated with quantum interferences, tuned by Hx, between
different spin tunneling paths linking two excited magnetic states. The
oscillation period is determined by the quantum mixing between the ground S=10
and excited multiplets. These experiments enable us to quantify such mixing. We
find that the weight of excited multiplets in the magnetic ground state of Fe8
amounts to approximately 11.6%.Comment: Accepted in Phys. Rev. Let
Aperture-free star formation rate of SDSS star-forming galaxies
Large area surveys with a high number of galaxies observed have undoubtedly
marked a milestone in the understanding of several properties of galaxies, such
as star-formation history, morphology, and metallicity. However, in many cases,
these surveys provide fluxes from fixed small apertures (e.g. fibre), which
cover a scant fraction of the galaxy, compelling us to use aperture corrections
to study the global properties of galaxies. In this work, we derive the current
total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming
galaxies, using an empirically based aperture correction of the measured flux for the first time, thus minimising the uncertainties associated
with reduced apertures. All the fluxes have been
extinction-corrected using the ratio free from aperture
effects. The total SFR for 210,000 SDSS star-forming galaxies has been
derived applying pure empirical and aperture
corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey.
We find that, on average, the aperture-corrected SFR is 0.65dex higher
than the SDSS fibre-based SFR. The relation between the SFR and stellar mass
for SDSS star-forming galaxies (SFR--) has been obtained, together
with its dependence on extinction and equivalent width. We
compare our results with those obtained in previous works and examine the
behaviour of the derived SFR in six redshift bins, over the redshift range . The SFR-- sequence derived here is in
agreement with selected observational studies based on integral field
spectroscopy of individual galaxies as well as with the predictions of recent
theoretical models of disc galaxies
Mixing Effects in the Crystallization of Supercooled Quantum Binary Liquids
By means of Raman spectroscopy of liquid microjets we have investigated the
crystallization process of supercooled quantum liquid mixtures composed of
parahydrogen (pH) diluted with small amounts of up to 5\% of either neon or
orthodeuterium (oD), and of oD diluted with either Ne or pH. We
show that the introduction of Ne impurities affects the crystallization
kinetics in both the pH-Ne and oD-Ne mixtures in terms of a significant
reduction of the crystal growth rate, similarly to what found in our previous
work on supercooled pH-oD liquid mixtures [M. K\"uhnel et {\it al.},
Phys. Rev. B \textbf{89}, 180506(R) (2014)]. Our experimental results, in
combination with path-integral simulations of the supercooled liquid mixtures,
suggest in particular a correlation between the measured growth rates and the
ratio of the effective particle sizes originating from quantum delocalization
effects. We further show that the crystalline structure of the mixture is also
affected to a large extent by the presence of the Ne impurities, which likely
initiate the freezing process through the formation of Ne crystallites.Comment: 19 pages, 7 figures, submitted to J. Chem. Phy
Convergence of Ginzburg-Landau functionals in 3-d superconductivity
In this paper we consider the asymptotic behavior of the Ginzburg- Landau
model for superconductivity in 3-d, in various energy regimes. We rigorously
derive, through an analysis via {\Gamma}-convergence, a reduced model for the
vortex density, and we deduce a curvature equation for the vortex lines. In a
companion paper, we describe further applications to superconductivity and
superfluidity, such as general expressions for the first critical magnetic
field H_{c1}, and the critical angular velocity of rotating Bose-Einstein
condensates.Comment: 45 page
Large magnetic dipole moments for neutrinos with arbitrary masses
We show that there is a general sort of models in which it is possible to
have large magnetic dipole moments for neutrinos while keeping their masses
arbitrarily small. Some examples of these models are considered.Comment: REVTEX, 8 pages, 2 .eps figure
Remark on the vectorlike nature of the electromagnetism and the electric charge quantization
In this work we study the structure of the electromagnetic interactions and
the electric charge quantization in gauge theories of electroweak interactions
based on semi-simple groups. We show that in the standard model of the
electroweak interactions the structure of the electromagnetic interactions is
strongly correlated to the quantization pattern of the electric charges. We
examine these two questions also in all possible chiral bilepton gauge models
of the electroweak interactions. In all they we can explain the vectorlike
nature of the electromagnetic interactions and the electric charge quantization
together demanding nonvanishing fermion masses and the anomaly cancellations.Comment: 17 pages, latex, no figure
DYNAMICAL SOLUTION OF A MODEL WITHOUT ENERGY BARRIERS
In this note we study the dynamics of a model recently introduced by one of
us, that displays glassy phenomena in absence of energy barriers. Using an
adiabatic hypothesis we derive an equation for the evolution of the energy as a
function of time that describes extremely well the glassy behaviour observed in
Monte Carlo simulations.Comment: 11 pages, LaTeX, 3 uuencoded figure
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