Strong Coupling Correction in Superfluid 3^3He in Aerogel

Effects of impurity scatterings on the strong coupling (SC) contribution, stabilizing the ABM (axial) pairing state, to the quartic term of the Ginzburg-Landau (GL) free energy of superfluid $^3$He are theoretically studied to examine recent observations suggestive of an anomalously small SC effect in superfluid $^3$He in aerogels. To study the SC corrections, two approaches are used. One is based on a perturbation in the short-range repulsive interaction, and the other is a phenomenological approach used previously for the bulk liquid by Sauls and Serene [Phys.Rev.B 24, 183 (1981)]. It is found that the impurity scattering favors the BW pairing state and shrinks the region of the ABM pairing state in the T-P phase diagram. In the phenomenological approach, the resulting shrinkage of the ABM region is especially substantial and, if assuming an anisotropy over a large scale in aerogel, leads to justifying the phase diagrams determined experimentally.Comment: 19 pages, 9 figures, Accepted for publication in Phys. Rev.

Vortex core transitions in superfluid 3He in globally anisotropic aerogels

Core structures of a single vortex in A-like and B-like phases of superfluid 3He in uniaxially compressed and stretched aerogels are studied by numerically solving Ginzburg-Landau equations derived microscopically. It is found that, although any uniaxial deformation leads to a wider A-like phase with the axial pairing in the pressure-temperature phase diagram, the vortex core states in the two phases in aerogel depend highly on the type of deformation. In a compressed aerogel, the first-order vortex core transition (VCT) previously seen in the bulk B phase appears at any pressure in the B-like phase while no strange vortex core is expected in the corresponding A-like phase. By contrast, in a stretched aerogel, the VCT in the B-like phase is lost while another VCT is expected to occur between a nonunitary core and a polar one in the A-like phase. Experimental search for these results is hoped to understand correlation between superfluid 3He and aerogel structure.Comment: 7 pages, 6 figures Text was changed. Resubmitted versio

Superfluid 3^3He in globally isotropic random media

Recent theoretical and experimental studies of superfluid $^3$He in aerogels with a global anisotropy, e.g., due to an external stress, have definitely shown that the A-like phase with an equal spin pairing (ESP) in such aerogel samples is in the ABM (or, axial) pairing state. In this paper, the A-like phase of superfluid $^3$He in globally {\it isotropic} aerogel is studied in details by assuming a weakly disordered system in which singular topological defects are absent. Through calculation of the free energy, a disordered ABM state is found to be the best candidate of the pairing state of the globally isotropic A-like phase. Further, it is found through a one-loop renormalization group calculation that the coreless continuous vortices (or, vortex-skyrmions) are irrelevant to the long-distance behavior of the disorder-induced textures, and that the superfluidity is maintained in spite of lack of the conventional off-diagonal long range order. Therefore, the globally isotropic A-like phase at weak disorder is, like in the case with a global stretched anisotropy, a superfluid glass with the ABM pairing.Comment: Revised version accepted for publication in Phys.Rev.

Strong Coupling Corrections to the Ginzburg-Landau Theory of Superfluid ^{3}He

In the Ginzburg-Landau theory of superfluid $^{3}$He, the free energy is expressed as an expansion of invariants of a complex order parameter. Strong coupling effects, which increase with increasing pressure, are embodied in the set of coefficients of these order parameter invariants\cite{Leg75,Thu87}. Experiments can be used to determine four independent combinations of the coefficients of the five fourth order invariants. This leaves the phenomenological description of the thermodynamics near $T_{c}$ incomplete. Theoretical understanding of these coefficients is also quite limited. We analyze our measurements of the magnetic susceptibility and the NMR frequency shift in the $B$-phase which refine the four experimental inputs to the phenomenological theory. We propose a model based on existing experiments, combined with calculations by Sauls and Serene\cite{Sau81} of the pressure dependence of these coefficients, in order to determine all five fourth order terms. This model leads us to a better understanding of the thermodynamics of superfluid $^{3}$He in its various states. We discuss the surface tension of bulk superfluid $^{3}$He and predictions for novel states of the superfluid such as those that are stabilized by elastic scattering of quasiparticles from a highly porous silica aerogel.Comment: 9 pages, 7 figures, 2 table

Can Variations of (HNMR)-H-1 Chemical Shifts in Benzene Substituted with an Electron-Accepting (NO2)/Donating (NH2) Group be Explained in Terms of Resonance Effects of Substituents?

The classical textbook explanation of variations of (HNMR)-H-1 chemical shifts in benzenes bearing an electron-donating (NH2) or an electron-withdrawing (NO2) group in terms of substituent resonance effects was examined by analyzing molecular orbital contributions to the total shielding. It was found that the -electronic system showed a more pronounced shielding effect on all ring hydrogen atoms, relative to benzene, irrespective of substituent +R/-R effects. For the latter, this was in contrast to the traditional explanations of downfield shift of nitrobenzene proton resonances, which were found to be determined by the sigma-electronic system and oxygen in-plane lone pairs. In aniline, the +R effect of NH2 group can be used to fully explain the upfield position of meta-H signals and partly the upfield position of para-H signals, the latter also being influenced by the sigma-system. The position of the lowest frequency signal of ortho-Hs was fully determined by sigma-electrons.This is peer-reviewed version of the following article: Baranac-Stojanović, M. Can Variations of 1H NMR Chemical Shifts in Benzene Substituted with an Electron-Accepting (NO2)/Donating (NH2) Group Be Explained in Terms of Resonance Effects of Substituents? Chemistry - An Asian Journal 2018, 13 (7), 877–881. [https://doi.org/10.1002/asia.201800137]Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3181

Superfluid nanomechanical resonator for quantum nanofluidics

We have developed a nanomechanical resonator, for which the motional degree of freedom is a superfluid 4He oscillating flow confined to precisely defined nanofluidic channels. It is composed of an in-cavity capacitor measuring the dielectric constant, which is coupled to a superfluid Helmholtz resonance within nanoscale channels, and it enables sensitive detection of nanofluidic quantum flow. We present a model to interpret the dynamics of our superfluid nanomechanical resonator, and we show how it can be used for probing confined geometry effects on thermodynamic functions. We report isobaric measurements of the superfluid fraction in liquid 4He at various pressures, and the onset of quantum turbulence in restricted geometry.Comment: 10 pages, 11 figure

Determination of a phoneme set for Acazulco Otomí. Linguistic fieldwork in Ndöngü, San Jerónimo Acazulco

Þessi ritgerð fjallar um hið dauðvona mesóameríska tungumál San Jerónimo Acazulco otomí sem er upprunið í Mið-Mexíkó og tilheyrir oto-mangue málaættinni. Rauði þráðurinn í ritgerðinni er hljóðfræði og hljóðkerfisfræði og sett er fram yfirgripsmikil hljóðfræðileg lýsing á tungumálinu ásamt því að hljóðön þess eru ákvörðuð. Í mismunandi rannsóknum á afbrigðum otomí tungumála hafa samhljóðakerfi verið skoðuð á marga vegu. Acazulco otomí hefur merkilegt samhljóðakerfi en tungumálið hefur til að mynda þrískipta aðgreiningu milli raddaðra, óraddaðra og fráblásinna lokhljóða, ásamt þrýstihljóðum, málgerðafræðileg fágæti á borð við órödduð nefhljóð og nándarhljóð ásamt aðblásturskerfi. Hljóðkerfi Acazulco otomí varðveitir marga þætti sem finna má í endurgerðum orðmyndum á fyrri stigum oto-mangue tungumála. Af þeim sökum er tungumálið dýrmæt heimild fyrir rannsóknir á oto-pame tungumálum í Mexíkó, bæði hvað varðar málgerðafræði og söguleg málvísindi. Efni ritgerðarinnar má rekja til vettvangsferðar sem var hluti af mun stærra, þverfræðilegu verkefni sem málvísindamenn, mannfræðingar og fornleifafræðingar komu að. Enn fremur var verkefnið almenn skrásetning á tungumáli sem hefur lítt verið rannsakað. Það mætti tala um nokkurs konar endur-lífgunarferli en upptökum af frásögnum, helgisiðum o.s.frv. var safnað og þær skráðar og hljóðritaðar. Hljóðkerfisleg greining er nauðsynleg svo hægt sé að búa til hagnýtt ritmál fyrir tungumál og sýnt verður hvernig hægt er að tákna hljóð tungumálsins skriflega. Ritmál er veigamikill þáttur er kemur að endurlífgun og varðveislu tungumála.This thesis discusses the moribund Mesoamerican language San Jerónimo Acazulco Otomí of central Mexico, a member of the Oto-Manguean language family. In the thesis, I will focus on the phonetics and phonology of the language and provide a comprehensive phonolog-ical description as well as determining a phoneme set for the language. Different studies of Otomian language varieties have dealt with the conso-nant systems in various ways. Acazulco Otomí has a remarkable consonant inventory, which, in addition to a three-way voiced/unvoiced/aspiration contrast in its stops, includes ejective stops and typological rarities like un-voiced nasals and approximants, as well as a system of preaspiration. The sound system of Acazulco Otomí preserves many features that it shares with reconstructed earlier stages of Oto-Manguean languages; therefore, the lan-guage is a valuable source in typological and historical linguistic studies of Oto-Pamean languages of Mexico. Moreover, this thesis is a result of a field work trip, which was part of a larger interdisciplinary project carried out by linguists, anthropologists, and archæologists. Furthermore, it was part of a general documentation of an understudied language and revitalization process, collecting and transcribing recordings of tales, rituals, etc. A phonological analysis is essential in the process of designing a practical orthogra-phy for a language, and through my analysis, I will discuss how to represent the sounds of the language orthographically. An orthography is a crucial aspect in the revitalization process and the possibilities for an endangered language to survive.Esta tesis tiene por objeto la lengua moribunda otomí de San Jerónimo de Acazulco (centro de México), perteneciente a la familia otomangue. En esta tesis me ocuparé de la fonética y la fonología de este idioma, aportando una descripción fonológica exhaustiva y estableciendo su repertorio de fonemas. Los sistemas consonánticos de las variedades de la lengua otomí han sido descritos diversamente por distintos estudios. El otomí de Acazulco tiene un inventario de consonantes notable, que, además de las tres formas de contraste —sonora, sorda y aspirada— en sus oclusivas, incluye oclusivas eyectivas y rarezas tipológicas tales como nasales sordas y aproximantes, así como un sistema de preaspiración. El sistema fonético del otomí de Acazulco conserva muchas características de las anteriores etapas reconstruidas de las lenguas otomangues, por lo que este idioma es una fuente valiosa para los estudios de tipología y de lingüística histórica de las lenguas otopameanas de México. Por otra parte, esta tesis es el resultado de un viaje de trabajo de campo incardinado en un proyecto interdisciplinario más extenso, que fue llevado a cabo por lingüistas, antropólogos y arqueólogos. Además, formaba parte de una documentación general de una lengua poco estudiada y de su proceso de revitalización, con la recolección y transcripción de grabaciones de cuentos, rituales, etc. El análisis fonológico es esencial en el diseño de una ortograía práctica para un idioma, y a través de mi análisis, trataré cómo representar de esta lengua ortográficamente. La ortograía es un aspecto crucial en el proceso de revitalización y para las oportunidades de supervivencia de una lengua amenazada

Islændinges udtale af dansk. En sammenlignende analyse af lydsystemerne i islandsk og dansk, og islandske studerendes danskudtale

Denne opgave består af to dele. I den første del præsenteres en analyse af lydsystemerne i islandsk og dansk, hvori ligheder såvel som forskelle mellem de to sprog gøres rede for, samt andre træk som er fremtrædende i sprogenes lydsystemer hver for sig. I anden del diskuteres i lyset af analysen i opgavens første del, de udtalefaktorer som er sværest for islændinge der lærer dansk. Disse faktorer er resultater som jeg er kommet frem til efter at have undervist i et kursus i dansk fonetik og udtale ved Islands Universitet i foråret 2011, hvor jeg gennem semestret løbende har lyttet til og fulgt de studerendes udtale, både i timerne og i lydoptagelser som har været en vigtig del af undervisningen. Jeg viser også resultaterne af en undersøgelse af de studerendes tilegnelse af danske udtaletræk, og diskuterer samtidig også hvilke der er svære at komme af med. Denne opgave er endvidere en del af en lingvistisk tradition, og både i brødtekst og i fodnoter vil der være eksempler som kaster lys over fælles og forskellige træk i verdens sprog hvorved vi ser islandsk og dansk fra et bredere, typologisk perspektiv