Two performances of the "Return of Alpamis" : current performance-practice in the Uzbek oral epic of the Sheraban school

The present study attempts to clarify the issues of text composition and poetic style within the Uzbek oral poetic genre known as the doston (dastan). It focuses on four short oral poetic texts: two recordings of two identical sections of the Alpamis doston sung by a single bard (baxsi) in 1990 and in 1991. Due to the fact that researchers within Uzbekistan and other former Soviet republics of Central Asia have paid little attention to issues of "improvisation" and "memorization," even such a modest attempt at multiple recording can help to state the relevant questions more clearly. A close analysis of the four texts demonstrates how the techniques of oral composition intersect with poetic style. This analysis is aided at times by interviews with and explanations from the bard. In addition, these interviews and observations of the bard and his immediate environment reveal aspects of the baxsi profession that he viewed as having significance.Not

Singular order parameter interaction at nematic quantum critical point in two dimensional electron systems

We analyze the infrared behavior of effective N-point interactions between order parameter fluctuations for nematic and other quantum critical electron systems with a scalar order parameter in two dimensions. The interactions exhibit a singular momentum and energy dependence and thus cannot be represented by local vertices. They diverge for all N greater or equal 4 in a collinear static limit, where energy variables scale to zero faster than momenta, and momenta become increasingly collinear. The degree of divergence is not reduced by any cancellations and renders all N-point interactions marginal. A truncation of the order parameter action at quartic or any other finite order is therefore not justified. The same conclusion can be drawn for the effective action describing fermions coupled to a U(1) gauge field in two dimensions.Comment: 18 pages, 1 figur

Determinant Bounds and the Matsubara UV Problem of Many-Fermion Systems

It is known that perturbation theory converges in fermionic field theory at weak coupling if the interaction and the covariance are summable and if certain determinants arising in the expansion can be bounded efficiently, e.g. if the covariance admits a Gram representation with a finite Gram constant. The covariances of the standard many--fermion systems do not fall into this class due to the slow decay of the covariance at large Matsubara frequency, giving rise to a UV problem in the integration over degrees of freedom with Matsubara frequencies larger than some Omega (usually the first step in a multiscale analysis). We show that these covariances do not have Gram representations on any separable Hilbert space. We then prove a general bound for determinants associated to chronological products which is stronger than the usual Gram bound and which applies to the many--fermion case. This allows us to prove convergence of the first integration step in a rather easy way, for a short--range interaction which can be arbitrarily strong, provided Omega is chosen large enough. Moreover, we give - for the first time - nonperturbative bounds on all scales for the case of scale decompositions of the propagator which do not impose cutoffs on the Matsubara frequency.Comment: 29 pages LaTe

Spectral Function of 2D Fermi Liquids

We show that the spectral function for single-particle excitations in a two-dimensional Fermi liquid has Lorentzian shape in the low energy limit. Landau quasi-particles have a uniquely defined spectral weight and a decay rate which is much smaller than the quasi-particle energy. By contrast, perturbation theory and the T-matrix approximation yield spurious deviations from Fermi liquid behavior, which are particularly pronounced for a linearized dispersion relation.Comment: 6 pages, LaTeX2e, 5 EPS figure

Analysis of Shroud Options in Support of the Human Exploration of Mars

In support of the Mars Design Reference Architecture (DRA) 5.0, the NASA study team analyzed several shroud options for use on the Ares V launch vehicle.1,2 These shroud options included conventional "large encapsulation" shrouds with outer diameters ranging from 8.4 to 12.9 meters (m) and overall lengths of 22.0 to 54.3 meters, along with a "nosecone-only" shroud option used for Mars transfer vehicle component delivery. Also examined was a "multi-use" aerodynamic encapsulation shroud used for launch, Mars aerocapture, and entry, descent, and landing of the cargo and habitat landers. All conventional shroud options assessed for use on the Mars launch vehicles were the standard biconic design derived from the reference shroud utilized in the Constellation Program s lunar campaign. It is the purpose of this paper to discuss the technical details of each of these shroud options including material properties, structural mass, etc., while also discussing both the volume and mass of the various space transportation and surface system payload elements required to support a "minimum launch" Mars mission strategy, as well as the synergy, potential differences and upgrade paths that may be required between the Lunar and Mars mission shrouds

Renormalized perturbation theory for Fermi systems: Fermi surface deformation and superconductivity in the two-dimensional Hubbard model

Divergencies appearing in perturbation expansions of interacting many-body systems can often be removed by expanding around a suitably chosen renormalized (instead of the non-interacting) Hamiltonian. We describe such a renormalized perturbation expansion for interacting Fermi systems, which treats Fermi surface shifts and superconductivity with an arbitrary gap function via additive counterterms. The expansion is formulated explicitly for the Hubbard model to second order in the interaction. Numerical soutions of the self-consistency condition determining the Fermi surface and the gap function are calculated for the two-dimensional case. For the repulsive Hubbard model close to half-filling we find a superconducting state with d-wave symmetry, as expected. For Fermi levels close to the van Hove singularity a Pomeranchuk instability leads to Fermi surfaces with broken square lattice symmetry, whose topology can be closed or open. For the attractive Hubbard model the second order calculation yeilds s-wave superconductivity with a weakly momentum dependent gap, whose size is reduced compared to the mean-field result.Comment: 18 pages incl. 6 figure

GALEX FUV Observations of Comet C/2004 Q2 (Machholz): The Ionization Lifetime of Carbon

We present a measurement of the lifetime of ground state atomic carbon, C(^3P), against ionization processes in interplanetary space and compare it to the lifetime expected from the dominant physical processes likely to occur in this medium. Our measurement is based on analysis of a far ultraviolet (FUV) image of comet C/2004 Q2 (Machholz) recorded by the Galaxy Evolution Explorer (GALEX) on 2005 March 1. The bright CI 1561 A and 1657 A multiplets dominate the GALEX FUV band. We used the image to create high S/N radial profiles that extended beyond one million km from the comet nucleus. Our measurements yielded a total carbon lifetime of 7.1 -- 9.6 x 10^5 s (scaled to 1 AU). Which compares favorably to calculations assuming solar photoionization, solar wind proton change exchange and solar wind electron impact ionization are the dominant processes occurring in this medium and that comet Machholz was embedded in the slow solar wind. The shape of the CI profiles inside 3x10^5 km suggests that either the CO lifetime is shorter than previously thought and/or a shorter-lived carbon-bearing parent molecule, such as CH_4 is providing the majority of the carbon in this region of the coma of comet Machholz.Comment: 26 pages, 6 figures, accepted for publication in the Astrophysical Journa

Functional renormalization group approach to correlated fermion systems

Numerous correlated electron systems exhibit a strongly scale-dependent behavior. Upon lowering the energy scale, collective phenomena, bound states, and new effective degrees of freedom emerge. Typical examples include (i) competing magnetic, charge, and pairing instabilities in two-dimensional electron systems, (ii) the interplay of electronic excitations and order parameter fluctuations near thermal and quantum phase transitions in metals, (iii) correlation effects such as Luttinger liquid behavior and the Kondo effect showing up in linear and non-equilibrium transport through quantum wires and quantum dots. The functional renormalization group is a flexible and unbiased tool for dealing with such scale-dependent behavior. Its starting point is an exact functional flow equation, which yields the gradual evolution from a microscopic model action to the final effective action as a function of a continuously decreasing energy scale. Expanding in powers of the fields one obtains an exact hierarchy of flow equations for vertex functions. Truncations of this hierarchy have led to powerful new approximation schemes. This review is a comprehensive introduction to the functional renormalization group method for interacting Fermi systems. We present a self-contained derivation of the exact flow equations and describe frequently used truncation schemes. Reviewing selected applications we then show how approximations based on the functional renormalization group can be fruitfully used to improve our understanding of correlated fermion systems.Comment: Review article, final version, 59 pages, 28 figure

Fermion loops, loop cancellation and density correlations in two dimensional Fermi systems

We derive explicit results for fermion loops with an arbitrary number of density vertices in two dimensions at zero temperature. The 3-loop is an elementary function of the three external momenta and frequencies, and the N-loop can be expressed as a linear combination of 3-loops with coefficients that are rational functions of momenta and frequencies. We show that the divergencies of single loops for low energy and small momenta cancel each other when loops with permuted external variables are summed. The symmetrized N-loop, i.e. the connected N-point density correlation function of the Fermi gas, does not diverge for low energies and small momenta. In the dynamical limit, where momenta scale to zero at fixed finite energy variables, the symmetrized N-loop vanishes as the (2N-2)-th power of the scale parameter.Comment: 24 pages (including 3 EPS figures), LaTeX2e; submitted to Phys. Rev.

A packet of letters

1 volume, 19 pages. One of 45 numbered copies. The type of A Packet of Letters is 18 pt. Bodoni and was set by Mollohan Typesetting of West Warwick, Rhode Island. It was printed on Nideggen paper on a hand fed Vandercook Press. The binding is by Stuart Einhorn of Providence, R.I.A Packet of Letters was published in an edition of 45 ... --Colophon. Title and text in red and black on title page. Bound at the head of the text with white-coated metal spiral binding. Text is attached to a cloth cover binder with an off-center opening in front. A mounted paper label with title and author name is split to allow the cover opening. Library has copy no. 31 Keywords: woodcuts, literacy, World War II, letters from a son serving in the military during WWII to his mother.https://digitalcommons.risd.edu/specialcollections_artistsbooks/1214/thumbnail.jp