1,615 research outputs found
Competing Quantum Orderings in Cuprate Superconductors: A Minimal Model
We present a minimal model for cuprate superconductors. At the unrestricted
mean-field level, the model produces homogeneous superconductivity at large
doping, striped superconductivity in the underdoped regime and various
antiferromagnetic phases at low doping and for high temperatures. On the
underdoped side, the superconductor is intrinsically inhomogeneous and global
phase coherence is achieved through Josephson-like coupling of the
superconducting stripes. The model is applied to calculate experimentally
measurable ARPES spectra.Comment: 5 pages, 4 eps included figure
A New Class of Exact Hairy Black Hole Solutions
We present a new class of black hole solutions with minimally coupled scalar
field in the presence of a negative cosmological constant. We consider a
one-parameter family of self-interaction potentials parametrized by a
dimensionless parameter . When , we recover the conformally invariant
solution of the Martinez-Troncoso-Zanelli (MTZ) black hole. A non-vanishing
signals the departure from conformal invariance. All solutions are
perturbatively stable for negative black hole mass and they may develop
instabilities for positive mass. Thermodynamically, there is a critical
temperature at vanishing black hole mass, where a higher-order phase transition
occurs, as in the case of the MTZ black hole. Additionally, we obtain a branch
of hairy solutions which undergo a first-order phase transition at a second
critical temperature which depends on and it is higher than the MTZ
critical temperature. As , this second critical temperature diverges.Comment: 18 pages, 6 figures, minor changes, references added, published
versio
The 1:1 resonance in Extrasolar Systems: Migration from planetary to satellite orbits
We present families of symmetric and asymmetric periodic orbits at the 1/1
resonance, for a planetary system consisting of a star and two small bodies, in
comparison to the star, moving in the same plane under their mutual
gravitational attraction. The stable 1/1 resonant periodic orbits belong to a
family which has a planetary branch, with the two planets moving in nearly
Keplerian orbits with non zero eccentricities and a satellite branch, where the
gravitational interaction between the two planets dominates the attraction from
the star and the two planets form a close binary which revolves around the
star. The stability regions around periodic orbits along the family are
studied. Next, we study the dynamical evolution in time of a planetary system
with two planets which is initially trapped in a stable 1/1 resonant periodic
motion, when a drag force is included in the system. We prove that if we start
with a 1/1 resonant planetary system with large eccentricities, the system
migrates, due to the drag force, {\it along the family of periodic orbits} and
is finally trapped in a satellite orbit. This, in principle, provides a
mechanism for the generation of a satellite system: we start with a planetary
system and the final stage is a system where the two small bodies form a close
binary whose center of mass revolves around the star.Comment: to appear in Cel.Mech.Dyn.Ast
Knowledge recombination and inventor networks: The asymmetric effects of embeddedness on knowledge reuse and impact
Ministry of Education, Singapore under its Academic Research Funding Tier
Quantum Breaking Time Scaling in the Superdiffusive Dynamics
We show that the breaking time of quantum-classical correspondence depends on
the type of kinetics and the dominant origin of stickiness. For sticky dynamics
of quantum kicked rotor, when the hierarchical set of islands corresponds to
the accelerator mode, we demonstrate by simulation that the breaking time
scales as with the transport exponent
that corresponds to superdiffusive dynamics. We discuss also other
possibilities for the breaking time scaling and transition to the logarithmic
one with respect to
Note on Varying Speed of Light Cosmologies
The various requirements on a consistent varying speed of light (`VSL')
theory are surveyed, giving a short check-list of issues that should be
satisfactorily handled by such theories.Comment: 6 pages; to appear in the GRG Journa
On the dynamics of Extrasolar Planetary Systems under dissipation. Migration of planets
We study the dynamics of planetary systems with two planets moving in the
same plane, when frictional forces act on the two planets, in addition to the
gravitational forces. The model of the general three-body problem is used.
Different laws of friction are considered. The topology of the phase space is
essential in understanding the evolution of the system. The topology is
determined by the families of stable and unstable periodic orbits, both
symmetric and non symmetric. It is along the stable families, or close to them,
that the planets migrate when dissipative forces act. At the critical points
where the stability along the family changes, there is a bifurcation of a new
family of stable periodic orbits and the migration process changes route and
follows the new stable family up to large eccentricities or to a chaotic
region. We consider both resonant and non resonant planetary systems. The 2/1,
3/1 and 3/2 resonances are studied. The migration to larger or smaller
eccentricities depends on the particular law of friction. Also, in some cases
the semimajor axes increase and in other cases they are stabilized. For
particular laws of friction and for special values of the parameters of the
frictional forces, it is possible to have partially stationary solutions, where
the eccentricities and the semimajor axes are fixed.Comment: Accepted in Celestial Mechanics and Dynamical Astronom
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