Single-particle vs. pair superfluidity in a bilayer system of dipolar bosons

We consider the ground state of a bilayer system of dipolar bosons, where dipoles are oriented by an external field in the direction perpendicular to the parallel planes. Quantum Monte Carlo methods are used to calculate the ground-state energy, the one-body and two-body density matrix, and the superfluid response as a function of the separation between layers. We find that by decreasing the interlayer distance for fixed value of the strength of the dipolar interaction, the system undergoes a quantum phase transition from a single-particle to a pair superfluid. The single-particle superfluid is characterized by a finite value of both the atomic condensate and the super-counterfluid density. The pair superfluid phase is found to be stable against formation of many-body cluster states and features a gap in the spectrum of elementary excitations.Comment: 4 figure

Impact of cyclone IDAI on the Hydrographic Services - The Case of Mozambique

The deadliest tropical cyclone in 2019 was the Intense Tropical Cyclone Idai in the South-West Indian Ocean, which killed over 1,303 people in Mozambique, Malawi, Zimbabwe, and Madagascar. In this study, the impacts of cyclone Idai on the Mozambican Hydrographic Services is presented. The study has identified the need to settle an appropriate Disaster Risk and Management System in National Hydrographic Services, as well as, the need to strengthen the capacity of the National Hydrographic Services to respond to natural disasters and develop standard operating procedures where the support from international community may be of paramount importance

Características petrográficas y geoquímicas de rocas basálticas de la península de cabo corrientes (serranía de baudó), colombia

Petrographic and chemical analyses were perfomed on eight rock samples from the Cabo Corrientes Peninsula. Based on these analses the existence of an oceanic basaltic association which is represented by basalts, spilitic basalts, spilites and komatiitic basalts was stablished; these rocks suffered an intens sodic metasomatism clearly shown in the chemical analyses and in the mineralogical assemblage. It is not clear if these metasomatism has been produced by deep ocean hydrothermal metamorfism as sugested by the presence of albitization and zeolites. It is concluded that the basaltic rocks of the Peninsula on both sides of the Utria fault and specially the ones to the west of it, is tectonically uplifted oceanic crust. A similar origin can be assumed for the rocks of other peninsulas which, like the Cabo Corrientes, are western apophyses of the Baudo Sarrania (i.e.) the peninsulas located North and South of Bahias Cupica and Solano. There is a great similarity with therocks of Gorgona Island.Mediante análisis petrográficos y químicos detallados de ocho muestras de roca provenientes de la península de Cabo Corrientes se establece la presencia de una asociación basáltica de tipo oceánico, representada por basaltos, basaltos espitilizados, espilitas y basaltos komatiíticos. Estas rocas presentan un intenso metasomatismo sódico, reconocible mineralógicamente y reflejado claramente en los análisis químicos. Sin embargo, no es claro si este metasomatismo es efecto de un metamorfismo hidrotermal de fondo oceánico como lo sugieren la albitización y las ceolitas presentes.Se concluye que: Las rocas basálticas de la península, situadas a ambos lados de la falla de Utria y especialmente al Oeste de esta, corresponden a rocas de fondo oceánico (corteza) levantadas tectónicamente. Se asume una situación similar para otras penínsulas que como la de Cabo Corrientes, están a manera de "apéndices" occidentales de la Serranía de Baudó, como son las situadas al Norte y Sur del Golfo de Cupica y Bahía Solano. La similitud con rocas presentes en la Isla de Gorgona parece evidente

Special geometry for arbitrary signatures

In this paper we generalize special geometry to arbitrary signatures in target space. We formulate the definitions in a precise mathematical setting and give a translation to the coordinate formalism used in physics. For the projective case, we first discuss in detail projective Kaehler manifolds, appearing in N=1 supergravity. We develop a new point of view based on the intrinsic construction of the line bundle. The topological properties are then derived and the Levi-Civita connection in the projective manifold is obtained as a particular projection of a Levi-Civita connection in a `mother' manifold with one extra complex dimension. The origin of this approach is in the superconformal formalism of physics, which is also explained in detail. Finally, we specialize these results to projective special Kaehler manifolds and provide explicit examples with different choices of signature.Comment: LaTeX, 83 pages; v2: typos corrected, version to be published in Handbook of pseudo-Riemannian Geometry and Supersymmetry, IRMA Lectures in Mathematics and Theoretical Physic

Hidden dimers and the matrix maps: Fibonacci chains re-visited

The existence of cycles of the matrix maps in Fibonacci class of lattices is well established. We show that such cycles are intimately connected with the presence of interesting positional correlations among the constituent `atoms' in a one dimensional quasiperiodic lattice. We particularly address the transfer model of the classic golden mean Fibonacci chain where a six cycle of the full matrix map exists at the centre of the spectrum [Kohmoto et al, Phys. Rev. B 35, 1020 (1987)], and for which no simple physical picture has so far been provided, to the best of our knowledge. In addition, we show that our prescription leads to a determination of other energy values for a mixed model of the Fibonacci chain, for which the full matrix map may have similar cyclic behaviour. Apart from the standard transfer-model of a golden mean Fibonacci chain, we address a variant of it and the silver mean lattice, where the existence of four cycles of the matrix map is already known to exist. The underlying positional correlations for all such cases are discussed in details.Comment: 14 pages, 2 figures. Submitted to Physical Review

Spin reversal in Fe8 under fast pulsed magnetic fields

We report measurements on magnetization reversal in the Fe8 molecular magnet using fast pulsed magnetic fields of 1.5 kT s−1 and in the temperature range of 0.6–4.1 K. We observe and analyze the temperature dependence of the reversal process, which involves in some cases several resonances. Our experiments allow observation of resonant quantum tunneling of magnetization up to a temperature of ~4 K. We also observe shifts in the maxima of the relaxation within each resonance field with temperature that suggest the emergence of a thermal instability—a combination of spin reversal and self-heating that may result in a magnetic deflagration process. The results are mainly understood in the framework of thermally-activated quantum tunneling transitions in combination with emergence of a thermal instability

Spin reversal in Fe8 under fast pulsed magnetic fields

We report measurements on magnetization reversal in the Fe8 molecular magnet using fast pulsed magnetic fields of 1.5 kT s−1 and in the temperature range of 0.6–4.1 K. We observe and analyze the temperature dependence of the reversal process, which involves in some cases several resonances. Our experiments allow observation of resonant quantum tunneling of magnetization up to a temperature of ~4 K. We also observe shifts in the maxima of the relaxation within each resonance field with temperature that suggest the emergence of a thermal instability—a combination of spin reversal and self-heating that may result in a magnetic deflagration process. The results are mainly understood in the framework of thermally-activated quantum tunneling transitions in combination with emergence of a thermal instability

Field induced magnetic transition and metastability in Co substituted Mn2SbMn_{2}Sb

A detailed investigation of first order ferrimagnetic (FRI) to antiferromagnetic (AFM) transition in Co (15%) doped $Mn_2Sb$ is carried out. These measurements demonstrate anomalous thermomagnetic irreversibility and glass-like frozen FRI phase at low temperatures. The irreversibility arising between the supercooling and superheating spinodals is distinguised in an ingenious way from the irreversibility arising due to kinetic arrest. Field annealing measurements shows reentrant FRI-AFM-FRI transition with increasing temperature. These measurements also show that kinetic arrest band and supercooling band are anitcorrelated i.e regions which are kinetically arrested at higher temperature have lower supercooling temperature and vice versa.Comment: 10 pages, 8 figure

Periodic features in the Dynamic Structure Factor of the Quasiperiodic Period-doubling Lattice

We present an exact real-space renormalization group (RSRG) method for evaluating the dynamic structure factor of an infinite one-dimensional quasiperiodic period-doubling (PD) lattice. We observe that for every normal mode frequency of the chain, the dynamic structure factor $S(q,\omega)$ always exhibits periodicity with respect to the wave vector $q$ and the presence of such periodicity even in absence of translational invariance in the system is quite surprising. Our analysis shows that this periodicity in $S(q,\omega)$ actually indicates the presence of delocalized phonon modes in the PD chain. The Brillouin Zones of the lattice are found to have a hierarchical structure and the dispersion relation gives both the acoustic as well as optical branches. The phonon dispersion curves have a nested structure and we have shown that it is actually the superposition of the dispersion curves of an infinite set of periodic lattices.Comment: 9 pages, 3 postscript figures, REVTeX, To appear in Phys. Rev. B (1 February 1998-I