Effective Lagrangian of unitary Fermi gas from ε\varepsilon expansion

Using $\varepsilon$ expansion technique proposed in \cite{Nishida:2006br} we derive an effective Lagrangian (Ginzburg-Landau-like functional) of the degenerate unitary Fermi gas to the next-to-leading (NLO) order in $\varepsilon.$ It is demonstrated that for many realistic situations it is sufficient to retain leading order (LO) terms in the derivative expansion. The functional is used to study vortex structure in the symmetric gas, and interface between normal and superfluid phases in the polarized gas. The resulting surface free energy is about four times larger than the value previously quoted in the literature.Comment: 17 pages, 4 figure

Annotated catalogue of the Tachinidae (Insecta, Diptera) of the Afrotropical Region, with the description of seven new genera

The Tachinidae of the Afrotropical Region are catalogued and seven genera and eight species are newly described. There are 237 genera and 1126 species recognized, of which 101 genera and 1043 species are endemic to the region. The catalogue is based on examination of the primary literature comprising about 525 references as well as numerous name-bearing types and other specimens housed in collections. Taxa are arranged hierarchically and alphabetically under the categories of subfamily, tribe, genus, subgenus (where recognized), species, and rarely subspecies. Nomenclatural information is provided for all genusgroup and species-group names, including lists of synonyms (mostly restricted to Afrotropical taxa) and name-bearing type data. Species distributions are recorded by country within the Afrotropical Region and by larger geographical divisions outside the region. Additional information is given in the form of notes, numbering about 300 in the catalogue section. Seven genera and eight species are described as new: Afrophylax Cerretti & O’Hara with type species Sturmia aureiventris Villeneuve, 1910, gen. n. (Exoristinae, Eryciini); Austrosolieria Cerretti & O’Hara with type species Austrosolieria londti Cerretti & O’Hara, gen. n. and sp. n. (South Africa) and Austrosolieria freidbergi Cerretti & O’Hara, sp. n. (Malawi) (Tachininae, Leskiini); Carceliathrix Cerretti & O’Hara with type species Phorocera crassipalpis Villeneuve, 1938, gen. n. (Exoristinae, Eryciini); Filistea Cerretti & O’Hara with type species Viviania aureofasciata Curran, 1927, gen. n. and Filistea verbekei Cerretti & O’Hara, sp. n. (Cameroon, D.R. Congo, Uganda) (Exoristinae, Blondeliini); Mesnilotrix Cerretti & O’Hara with type species Dexiotrix empiformis Mesnil, 1976, gen. n. (Dexiinae, Dexiini); Myxophryxe Cerretti & O’Hara with type species Phorocera longirostris Villeneuve, 1938, gen. n., Myxophryxe murina Cerretti & O’Hara, sp. n. (South Africa), Myxophryxe regalis Cerretti & O’Hara, sp. n. (South Africa), and Myxophryxe satanas Cerretti & O’Hara, sp. n. (South Africa) (Exoristinae, Goniini); and Stiremania Cerretti & O’Hara with type species Stiremania karoo Cerretti & O’Hara, gen. n. and sp. n. (South Africa), and Stiremania robusta Cerretti & O’Hara, sp. n. (South Africa) (Exoristinae, Goniini). Paraclara Bezzi, 1908 is transferred from the Cylindromyiini to the Hermyini, comb. n. Sarrorhina Villeneuve, 1936 is transferred from the Minthoini to the Graphogastrini, comb. n. Three genera are newly recorded from the Afrotropical Region: Madremyia Townsend, 1916 (Eryciini); Paratrixa Brauer & Bergenstamm, 1891 (Blondeliini); and Simoma Aldrich, 1926 (Goniini). Three genera previously recorded from the Afrotropical Region are no longer recognized from the region: Calozenillia Townsend, 1927 (Palaearctic, Oriental and Australasian regions); Eurysthaea Robineau-Desvoidy, 1863 (Palaearctic, Oriental and Australasian regions); and Trixa Meigen, 1824 (Palaearctic and Oriental regions). Two species are newly recorded from the Afrotropical Region: Amnonia carmelitana Kugler, 1971 (Ethiopia, Kenya); and Simoma grahami Aldrich, 1926 (Namibia). Three species previously recorded from the Afrotropical Region are no longer recognized from the region: Euthera peringueyi Bezzi, 1925 (Oriental Region); Hamaxia incongrua Walker, 1860 (Palaearctic, Oriental and Australasian regions); Leucostoma tetraptera (Meigen, 1824) (Palaearctic Region). New replacement names are proposed for five preoccupied names of Afrotropical species: Billaea rubida O’Hara & Cerretti for Phorostoma rutilans Villeneuve, 1916, preoccupied in the genus Billaea Robineau-Desvoidy, 1830 by Musca rutilans Fabricius, 1781, nom. n.; Cylindromyia braueri O’Hara & Cerretti for Ocyptera nigra Villeneuve, 1918, preoccupied in the genus Cylindromyia Meigen, 1803 by Glossidionophora nigra Bigot, 1885, nom. n.; Cylindromyia rufohumera O’Hara & Cerretti for Ocyptera scapularis Villeneuve, 1944, preoccupied in the genus Cylindromyia Meigen, 1803 by Ocyptera scapularis Loew, 1845, nom. n.; Phytomyptera longiarista O’Hara & Cerretti for Phytomyzoneura aristalis Villeneuve, 1936, preoccupied in the genus Phytomyptera Rondani, 1845 by Phasiostoma aristalis Townsend, 1915, nom. n.; and Siphona (Siphona) pretoriana O’Hara & Cerretti for Siphona laticornis Curran, 1941, preoccupied in the genus Siphona Meigen, 1803 by Actia laticornis Malloch, 1930, nom. n. New type species fixations are made under the provisions of Article 70.3.2 of the ICZN Code for two genus-group names: Lydellina Villeneuve, 1916, type species newly fixed as Lydellina villeneuvei Townsend, 1933 (valid genus name); and Sericophoromyia Austen, 1909, type species newly fixed as Tachina quadrata Wiedemann, 1830 (synonym of Winthemia Robineau-Desvoidy, 1830). Lectotypes are designated for the following nine nominal species based on examination of one or more syntypes of each: Degeeria crocea Villeneuve, 1950; Degeeria semirufa Villeneuve, 1950; Erycia brunnescens Villeneuve, 1934; Exorista oculata Villeneuve, 1910; Kiniatilla tricincta Villeneuve, 1938; Myxarchiclops caffer Villeneuve, 1916; Ocyptera linearis Villeneuve, 1936; Peristasisea luteola Villeneuve, 1934; and Phorocera crassipalpis Villeneuve, 1938. The following four genus-group names that were previously treated as junior synonyms or subgenera are recognized as valid generic names: Bogosiella Villeneuve, 1923, status revived; Dyshypostena Villeneuve, 1939, status revived; Perlucidina Mesnil, 1952, status revived; and Thelymyiops Mesnil, 1950, status n. The following six species-group names that were previously treated as junior synonyms are recognized as valid species names: Besseria fossulata Bezzi, 1908, status revived; Degeeria cinctella Villeneuve, 1950, status revived (as Medina cinctella (Villeneuve)); Nemoraea miranda intacta Villeneuve, 1916, status revived (as Nemoraea intacta Villeneuve); Succingulum exiguum Villeneuve, 1935, status revived (as Trigonospila exigua (Villeneuve)); Wagneria rufitibia abbreviata Mesnil, 1950, status n. (as Periscepsia abbreviata (Mesnil)); and Wagneria rufitibia nudinerva Mesnil, 1950, status n. (as Periscepsia nudinerva (Mesnil)). The following 25 new or revived combinations are proposed: Afrophylax aureiventris (Villeneuve, 1910), comb. n.; Blepharella orbitalis (Curran, 1927), comb. n.; Bogosiella pomeroyi Villeneuve, 1923, comb. revived; Brachychaetoides violacea (Curran, 1927), comb. n.; Carceliathrix crassipalpis (Villeneuve, 1938), comb. n.; Charitella whitmorei (Cerretti, 2012), comb. n.; Dyshypostena edwardsi (van Emden, 1960), comb. n.; Dyshypostena tarsalis Villeneuve, 1939, comb. revived; Estheria buccata (van Emden, 1947), comb. n.; Estheria surda (Curran, 1933), comb. n.; Filistea aureofasciata (Curran, 1927), comb. n.; Madremyia setinervis (Mesnil, 1968), comb. n.; Mesnilotrix empiformis (Mesnil, 1976), comb. n.; Myxophryxe longirostris (Villeneuve, 1938), comb. n.; Nealsomyia chloronitens (Mesnil, 1977), comb. n.; Nealsomyia clausa (Curran, 1940), comb. n.; Nilea longicauda (Mesnil, 1970), comb. n.; Paratrixa aethiopica Mesnil, 1952, comb. revived; Paratrixa stammeri Mesnil, 1952, comb. revived; Perlucidina africana (Jaennicke, 1867), comb. n.; Perlucidina perlucida (Karsch, 1886), comb. revived; Prolophosia retroflexa (Villeneuve, 1944), comb. n.; Sturmia profana (Karsch, 1888), comb. n.; additionally, Ceromasia rufiventris Curran, 1927 is treated as an unplaced species of Goniini, comb. n. and Hemiwinthemia stuckenbergi Verbeke, 1973 is treated as an unplaced species of Leskiini, comb. n. New or revived generic and specific synonymies are proposed for the following nine names: Afrosturmia Curran, 1927 with Blepharella Macquart, 1851, syn. n.; Archiphania van Emden, 1945 with Catharosia Rondani, 1868, syn. revived; Besseria longicornis Zeegers, 2007 with Besseria fossulata Bezzi, 1908 (current name Besseria fossulata), syn. n.; Dexiomera Curran, 1933 with Estheria Robineau-Desvoidy, 1830, syn. n.; Hemiwinthemia francoisi Verbeke, 1973 with Nemoraea capensis Schiner, 1868 (current name Smidtia capensis), syn. n.; Kinangopana van Emden, 1960 with Dyshypostena Villeneuve, 1939, syn. n.; Metadrinomyia Shima, 1980 with Charitella Mesnil, 1957, syn. n.; Phorocera majestica Curran, 1940 with Phorocera longirostris Villeneuve, 1938 (current name Myxophryxe longirostris), syn. n.; and Podomyia discalis Curran, 1939 with Antistasea fimbriata Bischof, 1904 (current name Antistasea fimbriata), syn. n

Measurement of the Zero Crossing in a Feshbach Resonance of Fermionic 6-Li

We measure a zero crossing in the scattering length of a mixture of the two lowest hyperfine states of 6-Li. To locate the zero crossing, we monitor the decrease in temperature and atom number arising from evaporation in a CO2 laser trap as a function of magnetic field B. The temperature decrease and atom loss are minimized for B=528(4) G, consistent with no evaporation. We also present preliminary calculations using potentials that have been constrained by the measured zero crossing and locate a broad Feshbach resonance at approximately 860 G, in agreement with previous theoretical predictions. In addition, our theoretical model predicts a second and much narrower Feshbach resonance near 550 G.Comment: Five pages, four figure

Three-body problem in Fermi gases with short-range interparticle interaction

We discuss 3-body processes in ultracold two-component Fermi gases with short-range intercomponent interaction characterized by a large and positive scattering length $a$. It is found that in most cases the probability of 3-body recombination is a universal function of the mass ratio and $a$, and is independent of short-range physics. We also calculate the scattering length corresponding to the atom-dimer interaction.Comment: 4 pages, 2 figure

Three-body recombination in a three-state Fermi gas with widely tunable interactions

We investigate the stability of a three spin state mixture of ultracold fermionic $^6$Li atoms over a range of magnetic fields encompassing three Feshbach resonances. For most field values, we attribute decay of the atomic population to three-body processes involving one atom from each spin state and find that the three-body loss coefficient varies by over four orders of magnitude. We observe high stability when at least two of the three scattering lengths are small, rapid loss near the Feshbach resonances, and two unexpected resonant loss features. At our highest fields, where all pairwise scattering lengths are approaching $a_t = -2140 a_0$, we measure a three-body loss coefficient $L_3 \simeq 5\times 10^{-22} \mathrm{cm}^6/\mathrm{s}$ and a trend toward lower decay rates for higher fields indicating that future studies of color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be feasible

Auger decay, Spin-exchange, and their connection to Bose-Einstein condensation of excitons in Cu_2O

In view of the recent experiments of O'Hara, et al. on excitons in Cu_2O, we examine the interconversion between the angular-momentum triplet-state excitons and the angular-momentum singlet-state excitons by a spin-exchange process which has been overlooked in the past. We estimate the rate of this particle-conserving mechanism and find a substantially higher value than the Auger process considered so far. Based on this idea, we give a possible explanation of the recent experimental observations, and make certain predictions, with the most important being that the singlet-state excitons in Cu_2O is a very serious candidate for exhibiting the phenomenon of Bose-Einstein condensation.Comment: 4 pages, RevTex, 1 ps figur

Numerical simulation of exciton dynamics in Cu2O at ultra low temperatures within a potential trap

We have studied theoretically the relaxation behaviour of excitons in cuprous oxide (Cu2O) at ultra low temperatures when excitons are confined within a potential trap by solving numerically the Boltzmann equation. As relaxation processes, we have included in this paper deformation potential phonon scattering, radiative and non-radiative decay and Auger decay. The relaxation kinetics has been analysed for temperatures in the range between 0.3K and 5K. Under the action of deformation potential phonon scattering only, we find for temperatures above 0.5K that the excitons reach local equilibrium with the lattice i.e. that the effective local temperature is coming down to bath temperature, while below 0.5K a non-thermal energy distribution remains. Interestingly, for all temperatures the global spatial distribution of excitons does not reach the equilibrium distribution, but stays at a much higher effective temperature. If we include further a finite lifetime of the excitons and the two-particle Auger decay, we find that both the local and the global effective temperature are not coming down to bath temperature. In the first case we find a Bose-Einstein condensation (BEC) to occur for all temperatures in the investigated range. Comparing our results with the thermal equilibrium case, we find that BEC occurs for a significantly higher number of excitons in the trap. This effect could be related to the higher global temperature, which requires an increased number of excitons within the trap to observe the BEC. In case of Auger decay, we do not find at any temperature a BEC due to the heating of the exciton gas

Bark Thickness in Coast Redwood (Sequoia sempervirens (D.Don) Endl.) Varies According to Tree- and Crown Size, Stand Structure, Latitude and Genotype

Research Highlights: Bark thickness (BT) in coastal redwood (Sequoia sempervirens (D.Don) Endl.) varies in accordance with tree size, crown ratio, position within the canopy, height along the tree stem, genetic identity and latitude. However, current BT predictive equations do not account for such variability, leading to inaccurate BT estimations. We present improved BT models to increase the accuracy of BT estimates for coastal redwood in northern California. Background and Objectives: BT is an important metric that has many practical applications in forest management. However, BT varies substantially across species and environments, as well as across individuals and populations. Our objectives were to investigate BT along various gradients of change, with factors accounting for genetics, tapering of BT along the tree bole, differences in BT according to tree crown position within the stand, and the latitude. Materials and Methods: We collected BT data throughout most of redwood’s natural range along a north–south latitudinal gradient. Subsets of these data were used to examine the influence of particular variables on BT while holding the other variables constant. Results: Regionally, the bark was thicker among more xeric southern redwoods and thinner among more mesic northern redwoods. We found that the BT of codominant, intermediate and suppressed trees was around 8%, 14%, and 18% thicker, respectively, than bark of the same size dominant tree. Redwood trees growing in the partial shade of an overstory had thicker bark than trees growing in even-aged stands and incorporating genetic identity yielded major improvements in the BT model estimates, suggesting that BT is under genetic control. Bark thickness decreased with increasing height along the tree stem, with notable differences in the BT above and below breast height. Conclusions: We recommend utilizing the best available BT equations (over standard ‘bark factors’) in forest science, modeling and management applications. We also recommend the adoption of our drilling method for BT measurement on larger trees due to the potential for error associated with traditional bark gauge measurements

Stress Dependence of Exciton Relaxation Processes in Cu2O

A comprehensive study of the exciton relaxation processes in Cu2O has led to some surprises. We find that the ortho-para conversion rate becomes slower at high stress, and that the Auger nonradiative recombination rate increases with stress, with apparently no Auger recombination at zero stress. These results have important consequences for the pursuit of Bose-Einstein condensation of excitons in a harmonic potential.Comment: 10 figures, 1 tabl

Mean-Field vs Monte-Carlo equation of state for the expansion of a Fermi superfluid in the BCS-BEC crossover

The equation of state (EOS) of a Fermi superfluid is investigated in the BCS-BEC crossover at zero temperature. We discuss the EOS based on Monte-Carlo (MC) data and asymptotic expansions and the EOS derived from the extended BCS (EBCS) mean-field theory. Then we introduce a time-dependent density functional, based on the bulk EOS and Landau's superfluid hydrodynamics with a von Weizs\"acker-type correction, to study the free expansion of the Fermi superfluid. We calculate the aspect ratio and the released energy of the expanding Fermi cloud showing that MC EOS and EBCS EOS are both compatible with the available experimental data of $^6$Li atoms. We find that the released energy satisfies an approximate analytical formula that is quite accurate in the BEC regime. For an anisotropic droplet, our numerical simulations show an initially faster reversal of anisotropy in the BCS regime, later suppressed by the BEC fluid.Comment: 13 pages, 3 figures, presented to the 15th International Laser Physics Workshop (Lausanne, July 24-28, 2006); to be published in Laser Physic