68 research outputs found
Discreteness of the spectrum of the compactified D=11 supermembrane with non-trivial winding
We analyze the Hamiltonian of the compactified D=11 supermembrane with
non-trivial central charge in terms of the matrix model constructed recently by
some of the authors. Our main result provides a rigorous proof that the quantum
Hamiltonian of the supersymmetric model has compact resolvent and thus its
spectrum consists of a discrete set of eigenvalues with finite multiplicity.Comment: 16 pages, final versio
Transition from Diffusive to Localized Regimes in Surface Corrugated Optical Waveguides
Exact calculations of the transmittance of surface corrugated optical
waveguides are presented. The elastic scattering of diffuse light or other
electromagnetic waves from a rough surface induces a diffusive transport along
the waveguide axis. As the length of the corrugated part of the waveguide
increases, a transition from the diffusive to the localized regime is observed.
This involves an analogy with electron conduction in nanowires, and hence, a
concept analogous to that of ``resistance'' can be introduced. We show an
oscillatory behavior of both the elastic mean free path and the localization
length versus the wavelength.Comment: 3 pages, REVTEX, 3 PS figure
Logistic regression for simulating damage occurrence on a fruit grading line
Many factors influence the incidence of mechanical damage in fruit handled on a grading line. This makes it difficult to address damage estimation from an analytical point of view. During fruit transfer from one element of a grading line to another, damage occurs as a combined effect of machinery roughness and the intrinsic susceptibility of fruit. This paper describes a method to estimate bruise probability by means of logistic regression, using data yielded by specific laboratory tests. Model accuracy was measured via the statistical significance of its parameters and its classification ability. The prediction model was then linked to a simulation model through which impacts and load levels, similar to those of real grading lines, could be generated. The simulation output sample size was determined to yield reliable estimations. The process makes it possible to derive a suitable line design and the type of fruit that should be handled to maintain bruise levels within European Union (EU) Standards. A real example with peaches was carried out with the aid of the software implementation SIMLINÂź, developed by the authors and registered by Madrid Technical University. This kind of tool has been demanded by inter-professional associations and grading lines designers in recent year
Wess-Zumino-Witten and fermion models in noncommutative space
We analyze the connection between Wess-Zumino-Witten and free fermion models
in two-dimensional noncommutative space. Starting from the computation of the
determinant of the Dirac operator in a gauge field background, we derive the
corresponding bosonization recipe studying, as an example, bosonization of the
U(N) Thirring model. Concerning the properties of the noncommutative
Wess-Zumino-Witten model, we construct an orbit-preserving transformation that
maps the standard commutative WZW action into the noncommutative one.Comment: 27 pages, 1 figure. LaTex fil
Dual-Composite Right-Left Handed Transmission Lines for the Design of Compact Diplexers
In this study, the use of dual-composite right-left-handed (D-CRLH) transmission lines is proposed for the design of diplexers. The D-CRLH diplexers present advantages over conventional diplexers such as smaller size (especially in the ultra high frequency band). The design procedure and the design equations are presented in this paper. The non-linear phase response of a D-CRLH transmission line has been used to design diplexers at any arbitrary frequencies. Finally, two diplexers have been designed and manufactured: one for quite near frequencies and the other for further ones. The simulation results show good agreement with the measurements. A sensitivity analysis has been provided to show the robustness of this kind of circuits
Electronic Properties of Ultra-Thin Aluminum Nanowires
We have carried out first principles electronic structure and total energy
calculations for a series of ultrathin aluminum nanowires, based on structures
obtained by relaxing the model wires of Gulseren et al. The number of
conducting channels is followed as the wires radius is increased. The results
suggest that pentagonal wires should be detectable, as the only ones who can
yield a channel number between 8 and 10.Comment: 9 pages + 3 figures, to appear on Surface Scienc
A thermophysical study of the melting process in alkyl chain metal n-alkanoates: The thallium (I) series
The peculiar thermal behavior of the thallium(I) n-alkanoates series (consisting in several transitions between polymorphic and mesomorphic phases) in comparison with other metallic n-alkanoates series is stated. The allowance of highly accurate adiabatic heat capacity data permits a study of the CH2CH2 contributions to the lattice heat capacity curve at low temperature. Moreover, in this series an anomalous gradual enhancement of the lattice heat capacity has been interpreted from vibrational spectroscopy results as a noncooperative effect due to the internal hindered rotation of the alkyl chain (formation of gauche defects, even in the solid state). The thermodynamics of the âstepwise melting processâ from the totally ordered solid at low temperature to the isotropic liquid is based on a revised lattice heat-capacity curve. This was used to evaluate the energy and entropy not only of the clear first order transitions present in the series but also of the described noncooperative effect. The CH2CH2 enthalpy and entropy contribution for this series is estimated and a comparison with the published values for other series is carried out. Moreover, the texture of the mesophases is revealed by polarized light microscopy. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69602/2/JCPSA6-111-8-3590-1.pd
Asâ(Ag) sulphide veins in the Spanish Central System: further evidence for a hydrothermal event of Permian age
The Spanish Central System (SCS) has been subjected to repeated deformation and fluid flow events which have produced
both sulphide-bearing and barren vein systems. Although several hydrothermal episodes took place between 300 and 100 Ma,
fluid circulation during the Permian was especially important, giving rise to a range of different types of deposits. This study
presents a multidisciplinary approach leading to the characterisation of the chemistry and age of the hydrothermal fluids that
produced the Asâ(Ag) mineralised stockwork of MoÂŽnica mine (Bustaviejo, Madrid). Fluid inclusion data indicate the presence
of two different fluids. An initial ore stage (I) formed from a low- to moderate salinity (3â8 wt.% eq. NaCl) H2OâNaClâCO2â
CH4 fluid, at minimum trapping temperature of 350±15 ÂșC and 0.3 kbar. A second H2OâNaCl fluid is found in three types of
fluid inclusions: a high temperature and low salinity type (340±20 ÂșC; 0.8â3.1 wt.% eq. NaCl) also associated to ore stage I, a
moderate temperature and very low salinity type (160â255 ÂșC; 0â1.5 wt.% eq. NaCl) represented in ore stage III, and a very
low temperature and hypersaline type (60â70 ÂșC; 30â35 wt.% NaCl), unrelated to the mineralising stages and clearly
postdating the previous types. 40Arâ39Ar dating on muscovite from the early AsâFe stage (I) has provided an age of 286±4
Ma, synchronous with the late emplacement phases of La Cabrera plutonic massif (288±5 Ma) and with other Permian
hydrothermal events like SnâW skarns and Wâ(Sn) sulphide veins. ÎŽ18O of water in equilibrium with stage I quartz (5.3â
7.7x), ÎŽD of water in equilibrium with coexisting muscovite (-16.0â° to -2.0â°), and sulphide ÎŽ34S (1.5â3.6â°) values are
compatible with waters that leached metamorphic rocks. The dominant mechanism of the Asâ(Ag) deposition was mixing and
dilution processes between aqueousâcarbonic and aqueous fluids for stage I (AsâFe), and nearly isobaric cooling processes for
stages II (ZnâCuâSn) and III (PbâAg). The origin and hydrothermal evolution of Asâ(Ag) veins is comparable to other
hydrothermal Permian events in the Spanish Central System
Morita Duality and Large-N Limits
We study some dynamical aspects of gauge theories on noncommutative tori. We
show that Morita duality, combined with the hypothesis of analyticity as a
function of the noncommutativity parameter Theta, gives information about
singular large-N limits of ordinary U(N) gauge theories, where the large-rank
limit is correlated with the shrinking of a two-torus to zero size. We study
some non-perturbative tests of the smoothness hypothesis with respect to Theta
in theories with and without supersymmetry. In the supersymmetric case this is
done by adapting Witten's index to the present situation, and in the
nonsupersymmetric case by studying the dependence of energy levels on the
instanton angle. We find that regularizations which restore supersymmetry at
high energies seem to preserve Theta-smoothness whereas nonsupersymmetric
asymptotically free theories seem to violate it. As a final application we use
Morita duality to study a recent proposal of Susskind to use a noncommutative
Chern-Simons gauge theory as an effective description of the Fractional Hall
Effect. In particular we obtain an elegant derivation of Wen's topological
order.Comment: 41 pages, Harvmac. Some corrections to section 6.3. Comments added on
Hall Effec
Insertion (22;9)(q11;q34q21) in a patient with chronic myeloid leukemia characterized by fluorescence in situ hybridization
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