Pairing in a two-component ultracold Fermi gas: Phases with broken-space symmetries

We explore the phase diagram of a two-component ultracold atomic Fermi gas interacting with zero-range forces in the limit of weak coupling. We focus on the dependence of the pairing gap and the free energy on the variations in the number densities of the two species while the total density of the system is held fixed. As the density asymmetry is increased, the system exhibits a transition from a homogenous Bardeen-Cooper-Schrieffer (BCS) phase to phases with spontaneously broken global space symmetries. One such realization is the deformed Fermi surface superfluidity (DFS) which exploits the possibility of deforming the Fermi surfaces of the species into ellipsoidal form at zero total momentum of Cooper pairs. The critical asymmetries at which the transition from DFS to the unpaired state occurs are larger than those for the BCS phase. In this precritical region the DFS phase lowers the pairing energy of the asymmetric BCS state. We compare quantitatively the DFS phase to another realization of superconducting phases with broken translational symmetry: the single-plane-wave Larkin-Ovchinnikov-Fulde-Ferrell phase, which is characterized by a nonvanishing center-of-mass momentum of the Cooper pairs. The possibility of the detection of the DFS phase in the time-of-flight experiments is discussed and quantified for the case of 6Li atoms trapped in two different hyperfine states.

Broken colinearity of the amphioxus Hox cluster.

Background In most eumetazoans studied so far, Hox genes determine the identity of structures along the main body axis. They are usually linked in genomic clusters and, in the case of the vertebrate embryo, are expressed with spatial and temporal colinearity. Outside vertebrates, temporal colinearity has been reported in the cephalochordate amphioxus (the least derived living relative of the chordate ancestor) but only for anterior and central genes, namely Hox1 to Hox4 and Hox6. However, most of the Hox gene expression patterns in amphioxus have not been reported. To gain global insights into the evolution of Hox clusters in chordates, we investigated a more extended expression profile of amphioxus Hox genes. Results Here we report an extended expression profile of the European amphioxus Branchiostoma lanceolatum Hox genes and describe that all Hox genes, except Hox13, are expressed during development. Interestingly, we report the breaking of both spatial and temporal colinearity for at least Hox6 and Hox14, which thus have escaped from the classical Hox code concept. We show a previously unidentified Hox6 expression pattern and a faint expression for posterior Hox genes in structures such as the posterior mesoderm, notochord, and hindgut. Unexpectedly, we found that amphioxus Hox14 had the most divergent expression pattern. This gene is expressed in the anterior cerebral vesicle and pharyngeal endoderm. Amphioxus Hox14 expression represents the first report of Hox gene expression in the most anterior part of the central nervous system. Nevertheless, despite these divergent expression patterns, amphioxus Hox6 and Hox14 seem to be still regulated by retinoic acid. Conclusions Escape from colinearity by Hox genes is not unusual in either vertebrates or amphioxus and we suggest that those genes escaping from it are probably associated with the patterning of lineage-specific morphological traits, requiring the loss of those developmental constraints that kept them colinear.

Encryption methods using formal power series rings

Recently there has been a great deal of work on noncommutative algebraic cryptography. This involves the use of noncommutative algebraic objects as the platforms for encryption systems. Most of this work, such as the Anshel-Anshel-Goldfeld scheme, the Ko-Lee scheme and the Baumslag-Fine-Xu Modular group scheme use nonabelian groups as the basic algebraic object. Some of these encryption methods have been successful and some have been broken. It has been suggested that at this point further pure group theoretic research, with an eye towards cryptographic applications, is necessary.In the present study we attempt to extend the class of noncommutative algebraic objects to be used in cryptography. In particular we explore several different methods to use a formal power series ring R && x1; :::; xn && in noncommuting variables x1; :::; xn as a base to develop cryptosystems. Although R can be any ring we have in mind formal power series rings over the rationals Q. We use in particular a result of Magnus that a finitely generated free group F has a faithful representation in a quotient of the formal power series ring in noncommuting variables.

La formació d'una política exterior per a l'Índia. La visita de Nehru a l'Espanya republicana durant la Guerra Civil

L'objectiu ha estat posar en relació dues realitats que fins al moment havien estat considerades completament alienes, com són l’Índia i Espanya. La recerca de fonts per a les relacions bilaterals de tot tipus es va iniciar al segle XIX. A partir d’aquest moment apareixen tres camps fonamentals on aprofundir. D’una banda tenim les relacions diplomàtiques i la seva vessant política a partir del segle XX. El desenvolupament de representacions consulars té a veure amb el creixement de l’activitat econòmica amb l’Índia britànica, especialment en el camp del proveïment de primeres matèries (cotó i jute). En aquest sentit, la recuperació de les relacions econòmiques va ser clau per al posterior mutu reconeixement diplomàtic el 1957 quan l’Índia ja era un estat independent. Entre mig queden anys de malvolença degut a la vinculació de Nehru amb el govern republicà durant la Guerra Civil i la posició de l’Índia en el cas d’Espanya a l’ONU. Un altre camp d’interès per a les relacions bilaterals es centra en la missió de Bombay que a partir de 1920 fou administrada per jesuïtes catalans, valencians i aragonesos. Finalment, un seguiment de la premsa i la intel•lectualitat espanyola mostra com l’Índia es va convertir a partir de 1920 en un nou focus d’interès informatiu i pel món acadèmic, com no ho havia estat fins llavors. Aquest descobriment de l’Índia per part de viatgers, artistes i periodistes obra una nova via d’intercanvi que es veurà trucada per la Guerra Civil i el posterior establiment d’un règim que destruí el teixit intel•lectual del país.

Primordial Perturbations in Einstein-Aether theories

El nostre objectiu es l'estudi d'extensions de la Relativitat General i, en particular, estem interessats en les teories que continguin camps vectorials addicionals. En aquests tipus de teories es necessari imposar que el vector ha de tenir norma fixa per evitar la presència d'un fantasma o grau de llibertat amb terme cinètic negatiu, i això implica que la simetria Lorentz està trencada espontàniament. El camp del aether només interactua gravitatòriament i la seva presència es difícil de detectar, no obstant això, durant inflació les fluctuacions del buit a escales petites d'un camp lleuger pot deixar una empremta en observables com les anisotropies del fons de radiació de microones. Les fluctuacions del Einstein-aether es comporten com els camps sense massa i això fa que inflació generi modes de longitud de ona llarga en els sectors escalar i vectorial. Hem estudiat la signatura del Einstein-aether dins l'espectre de pertorbacions primordials lluny del límit de de Sitter de inflació. Aquests modes escalars i vectorials poden deixar una empremta significativa en la radiació de fons de microones en funció dels paràmetres del model. Les observacions del fons de radiació de microones imposen restriccions fenomenològiques que redueixen els límits existents per aquesta classe de teoria. Amb aquest estudi del aether també esperem millorar el coneixement que tenim de una classe més ampla de teories que exhibeixen el mateix tipus de trencament de simetria.

Avaluació i intervenció psicoeducativa en les relacions materno/paterno-filials en famílies desestructurades

Anàlisi, avaluació i intervenció psicoeducativa en un programa assistencial i de suport a les relacions materno/paternofilials en famílies desestructurades. Els usuaris són els pares i les mares separats o divorciats (i els seus fills menors) amb conflictes entre ells i on ha estat el jutge qui ha establert el règim de visites. Es dóna suport i orientació als progenitors i als menors que acudeixen al centre per a fer l'intercanvi o l'estada del menor amb el progenitor no custodi, per a facilitar i millorar la relació entre les parts (menors, part custòdia i part no-custòdia).

Modelling structural zeros in compositional data

This analysis was stimulated by the real data analysis problem of householdexpenditure data. The full dataset contains expenditure data for a sample of 1224 households. The expenditure is broken down at 2 hierarchical levels: 9 major levels (e.g. housing, food, utilities etc.) and 92 minor levels. There are also 5 factors and 5 covariates at the household level. Not surprisingly, there are a small number of zeros at the major level, but many zeros at the minor level. The question is how best to model the zeros. Clearly, models that tryto add a small amount to the zero terms are not appropriate in general as at least some of the zeros are clearly structural, e.g. alcohol/tobacco for households that are teetotal. The key question then is how to build suitable conditional models. For example, is the sub-composition of spendingexcluding alcohol/tobacco similar for teetotal and non-teetotal households?In other words, we are looking for sub-compositional independence. Also, what determines whether a household is teetotal? Can we assume that it is independent of the composition? In general, whether teetotal will clearly depend on the household level variables, so we need to be able to model this dependence. The other tricky question is that with zeros on more than onecomponent, we need to be able to model dependence and independence of zeros on the different components. Lastly, while some zeros are structural, others may not be, for example, for expenditure on durables, it may be chance as to whether a particular household spends money on durableswithin the sample period. This would clearly be distinguishable if we had longitudinal data, but may still be distinguishable by looking at the distribution, on the assumption that random zeros will usually be for situations where any non-zero expenditure is not small.While this analysis is based on around economic data, the ideas carry over tomany other situations, including geological data, where minerals may be missing for structural reasons (similar to alcohol), or missing because they occur only in random regions which may be missed in a sample (similar to the durables)

Assessing the Precision of Compositional Data in a Stratified Double Stage Cluster Sample: Application to the Swiss Earnings Structure Survey

Precision of released figures is not only an important quality feature of official statistics,it is also essential for a good understanding of the data. In this paper we show a casestudy of how precision could be conveyed if the multivariate nature of data has to betaken into account. In the official release of the Swiss earnings structure survey, the totalsalary is broken down into several wage components. We follow Aitchison's approachfor the analysis of compositional data, which is based on logratios of components. Wefirst present diferent multivariate analyses of the compositional data whereby the wagecomponents are broken down by economic activity classes. Then we propose a numberof ways to assess precision

L'ambient urbà i la criminalitat. Robatoris contra el patrimoni a la ciutat de Girona

L’estudi de la criminalitat és multifactorial, cal destriar en la mesura del possible els factorsambientals, d’entorn urbà, que poden jugar el paper de facilitadors de la delinqüència. Lestipologies delictives són diverses i amb motivacions "mòbils" diferenciats, el que confereixdificultats a l’estudi de la criminalitat, és per aquesta raó que es trien dues tipologies derobatoris contra el patrimoni per ser analitzats: robatoris amb força a interior de domicili(vivenda) i els furts, en un marc de ciutat petita-mitjana, com és el cas de Girona. Elconeixement per part de l’autor del marc urbà n’és un part essencial per desenvolupar l’estudi.Un dels objectius finalistes és aconseguir avançar en estudis de diagnosi criminal de les ciutats;així com en el coneixement dels patrons espaials que tenen les tipologies delictives i lainfluència de les característiques del disseny urbà sobre la criminalitat. La metodologia ques’implementarà serà: recerca bibliogràfica, estadística descriptiva i inferencial, sistemesd’informació geogràfica, així com la deducció a partir de la visualització de la cartografiagenerada i un treball de camp de les zones d’alta ocurrència delictiva dels delictes esmentats.Pel que fa a les hipòtesis principals: els robatoris contra el patrimoni no es concentren en àreesdegradades urbanísticament sinó ans el contrari en ambients urbans cuidats. Aquesta hipòtesies contraposa a la teoria criminal de la "Broken Windows", que esmenta que els espais urbansdegradats és on hi ha menys ocupació d’espai públic i més delinqüència. Una altra hipòtesiimportant és que els espais percebuts com a segurs, respecte les tipologies delictivesesmentades, són els més insegurs

A genealogical conceptual model using ontologies

Roughly fifteen years ago, the Church of Jesus Christ of Latter-day Saints published a new proposed standard file format. They call it GEDCOM. It was designed to allow different genealogy programs to exchange data.Five years later, in may 2000, appeared the GENTECH Data Modeling Project, with the support of the Federation of Genealogical Societies (FGS) and other American genealogical societies. They attempted to define a genealogical logic data model to facilitate data exchange between different genealogical programs. Although genealogists deal with an enormous variety of data sources, one of the central concepts of this data model was that all genealogical data could be broken down into a series of short, formal genealogical statements. It was something more versatile than only export/import data records on a predefined fields. This project was finally absorbed in 2004 by the National Genealogical Society (NGS).Despite being a genealogical reference in many applications, these models have serious drawbacks to adapt to different cultural and social environments. At the present time we have no formal proposal for a recognized standard to represent the family domain.Here we propose an alternative conceptual model, largely inherited from aforementioned models. The design is intended to overcome their limitations. However, its major innovation lies in applying the ontological paradigm when modeling statements and entities.

Critical ruptures in a bundle of slowly relaxing fibers

We study the damage enhanced creep rupture of disordered materials by means of a fiber bundle model. Broken fibers undergo a slow stress relaxation modeled by a Maxwell element whose stress exponent m can vary in a broad range. Under global load sharing we show that due to the strength disorder of fibers, the lifetime ʧ of the bundle has sample-to-sample fluctuations characterized by a log-normal distribution independent of the type of disorder. We determine the Monkman-Grant relation of the model and establish a relation between the rupture life tʄ and the characteristic time tm of the intermediate creep regime of the bundle where the minimum strain rate is reached, making possible reliable estimates of ʧ from short term measurements. Approaching macroscopic failure, the deformation rate has a finite time power law singularity whose exponent is a decreasing function of m. On the microlevel the distribution of waiting times is found to have a power law behavior with m-dependent exponents different below and above the critical load of the bundle. Approaching the critical load from above, the cutoff value of the distributions has a power law divergence whose exponent coincides with the stress exponent of Maxwell elements

Música, sociedad y mestizaje a través del sonido del fagot

La sociedad, la música y la cultura son elementos que van relacionados desde la Antigüedad. Hoy en día, los medios de comunicación han abierto las fronteras de lo que hasta hace pocas décadas eran barreras geográficamente impenetrables. El siglo XXI comienza como un siglo en el que la hibridación cultural es un hecho, la música está cada vez más construida desde la mezcla de elementos. Los músicos que actualmente se están formando lo hacen absorbiendo elementos de músicas y culturas que fueron muy distintas hace tiempo y hoy no lo son más. El acceso a Internet, la relación entre los propios individuos conviviendo con gente de otros países nos presenta un panorama, en lo musical, de apertura como nunca antes se había visto hasta ahora. Hoy por hoy cualquier músico, con cualquier instrumento puede verse, de un modo natural, interpretando músicas que rompen de algún modo con el hilo conductor que la historia de esos instrumentos ha llevado hasta el presente.

Persecution perpetuated: The medieval origins of anti-semitic violence in Nazi Germany

How persistent are cultural traits? This paper uses data on anti-Semitism in Germany and finds continuity at the local level over more than half a millennium. When the Black Death hit Europe in 1348-50, killing between one third and one half of the population, its cause was unknown. Many contemporaries blamed the Jews. Cities all over Germany witnessed mass killings of their Jewish population. At the same time, numerous Jewish communities were spared these horrors. We use plague pogroms as an indicator for medieval anti-Semitism. Pogroms during the Black Death are a strong and robust predictor of violence against Jews in the 1920s, and of votes for the Nazi Party. In addition, cities that saw medieval anti-Semitic violence also had higher deportation rates for Jews after 1933, were more likely to see synagogues damaged or destroyed in the Night of Broken Glass in 1938, and their inhabitants wrote more anti-Jewish letters to the editor of the Nazi newspaper Der Stürmer.

Ordered structures in rotating ultracold Bose gases

Two-dimentional systems of trapped samples of few cold bosonic atoms submitted to strong rotation around the perpendicular axis may be realized in optical lattices and microtraps. We investigate theoretically the evolution of ground state structures of such systems as the rotational frequency Omega increases. Various kinds of ordered structures are observed. In some cases, hidden interference patterns exhibit themselves only in the pair correlation function; in some other cases explicit broken-symmetry structures appear that modulate the density. For N < 10 atoms, the standard scenario, valid for large sytems is absent, and is only gradually recovered as N increases. On the one hand, the Laughlin state in the strong rotational regime contains ordered structures much more similar to a Wigner molecule than to a fermionic quantum liquid. On the other hand, in the weak rotational regime, the possibility to obtain equilibrium states, whose density reveals an array of vortices, is restricted to the vicinity of some critical values of the rotational frequency Omega.