WorldWideScience

Sample records for backcalculating layer moduli

  1. System Identification Method for Evaluating the Effect of Thickness Error on Backcalculated Pavement Layer Moduli

    Institute of Scientific and Technical Information of China (English)

    ZHONG Yan-hui; WANG Fu-ming; ZHANG Bei; CAI Ying-chun

    2004-01-01

    Based on system identification theory and FWD testing data, the effect of thickness error on backcalculating pavement layer moduli is studied and the method of singular value decomposition (SVD) is presented to solve the morbidity problem of sensitivity matrix in this paper.The results show that the thickness error has great effects on the backcalculated pavement layer moduli. The error of backcalculated moduli can be controlled within the range of ±15% by limiting the thickness error within the range of ±5%.

  2. Will Nonlinear Backcalculation Help?

    DEFF Research Database (Denmark)

    Ullidtz, Per

    2000-01-01

    Backcalculation of FWD data often results in unrealistic moduli. The modulus of the subgrade may be two to three times the expected value, and the modulus of an intermediate granular material may be lower than the subgrade modulus. If stresses or strains measured in the pavement are compared with...... theoretical values, the agreement is often poor.All theoretical models for calculating pavement response are based on a number of simplifications with respect to reality and must be verified experimentally. Most models assume that all pavement layers consist of linear elastic materials. This paper...

  3. Will Nonlinear Backcalculation Help?

    DEFF Research Database (Denmark)

    Ullidtz, Per

    demonstrates, that treating the subgrade as a nonlinear elastic material, can result in more realistic moduli and a much better agreement between measured and calculated stresses and strains.The response of nonlinear elastic materials can be calculated using the Finite Element Method (FEM). A much simpler...... approach is to use the Method of Equivalent Thicknesses (MET), modified for a nonlinear subgrade. The paper includes an example where moduli backcalculated using FEM, linear elastic theory and MET are compared. Stresses and strains predicted by the three methods are also compared to measured values. For...

  4. Effective elastic moduli of polymer-layered silicate nanocomposites

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Polymer-layered silicate (PLS) nanocomposites exhibit some mechanical properties that are much better than conventional polymer filled composites. A relatively low content of layered silicate yields a significant enhancement of material performance. After the volume fraction of clay reaches a relatively low "critical value"; however, further increasing does not show a greater stiffening effect. This phenomenon is contrary to previous micromechanical pre-dictions and is not understood well. Based on the analysis on the microstructures of PLS nanocomposites, the present note provides an insight into the physical micromechanisms of the above unexpected phenomenon. The Mori-Tanaka scheme and a numerical method are employed to estimate the effec-tive elastic moduli of such a composite.

  5. Moduli Redefinitions and Moduli Stabilisation

    OpenAIRE

    Conlon, Joseph P.; Pedro, Francisco G.

    2010-01-01

    Field redefinitions occur in string compactifications at the one loop level. We review arguments for why such redefinitions occur and study their effect on moduli stabilisation and supersymmetry breaking in the LARGE volume scenario. For small moduli, although the effect of such redefinitions can be larger than that of the $\\alpha'$ corrections in both the K\\"ahler and scalar potentials, they do not alter the structure of the scalar potential. For the less well motivated case of large moduli,...

  6. Estimating frame bulk and shear moduli of two double porosity layers by ultrasound transmission.

    Science.gov (United States)

    Bai, Ruonan; Tinel, Alain; Alem, Abdellah; Franklin, Hervé; Wang, Huaqing

    2016-08-01

    The acoustic plane wave transmission by water saturated double porosity media is investigated. Two samples of double porosity media assumed to obey Berryman and Wang (BW) extension (Berryman and Wang, 1995, 2000) of Biot's theory in the low frequency regime are under consideration: ROBU® (pure binder-free borosilicate glass 3.3 manufactured to form the individual grains) and Tobermorite 11Å (the individual porous cement grains show irregular shapes). The de facto gap existing between theoretical and experimental data can be minimized by modifying adequately two of the parameters estimated from triaxial tests: the frame bulk and shear moduli. The frequency dependent imaginary parts that follow necessary from the minimization are in relation with the energy losses due to contact relaxation and friction between grains. PMID:27209582

  7. Analytical Approaches for Addressing The Variation in Back-Calculated Age-Length Relationships for Fish

    OpenAIRE

    Shephard, Samuel; Jackson, Donald C.

    2009-01-01

    Estimating an age-length relationship is a routine aspect of many fisheries studies and is simplified by the use of commercially available computer programs. These computer programs may be misleading since a result can be produced irrespective of the quality or the extent of the data, and there is some concern that back-calculated age-length relationships are sensitive to the sample size and composition. We investigated this issue by comparing estimates of mean back-calculated lengths at age ...

  8. Cosmology of Light Moduli

    OpenAIRE

    Choi, Kiwoon; Chun, Eung Jin; Kim, Hang Bae

    1998-01-01

    In string/M-theory with a large compactification radius, some axion-like moduli can be much lighter than the gravitino. Generic moduli in gauge-mediated supersymmetry breaking models also have a mass far below the weak scale. Motivated by these, we examine the cosmological implications of light moduli for the mass range from the weak scale to an extremely small scale of order 10^{-26} eV, and obtain an upper bound on the initial moduli misalignment for both cases with and without a late entro...

  9. Heterotic Moduli Stabilization

    CERN Document Server

    Cicoli, Michele; Westphal, Alexander

    2013-01-01

    We perform a systematic analysis of moduli stabilization for weakly coupled heterotic string theory compactified on smooth Calabi-Yau three-folds. We focus on both supersymmetric and supersymmetry breaking vacua of generic (0,2) compactifications obtained by minimising the total (F + D)-term scalar potential. After reviewing how to stabilise all the geometric moduli in a supersymmetric way by including fractional fluxes, non-perturbative and threshold effects, we show that the inclusion of \\alpha' corrections leads to new de Sitter or nearly Minkowski vacua which break supersymmetry spontaneously. The minimum lies at moderately large volumes of all the geometric moduli, at perturbative values of the string coupling and at the right phenomenological value of the GUT gauge coupling. However the structure of the heterotic 3-form flux used for complex structure moduli stabilization does not contain enough freedom to tune the superpotential. This results in the generic prediction of high-scale supersymmetry breaki...

  10. Heterotic moduli stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Cicoli, M. [Bologna Univ. (Italy). Dipt. Fisica ed Astronomia; INFN, Bologna (Italy); Adbus Salam ICTP, Trieste (Italy); De Alwis, S. [Adbus Salam ICTP, Trieste (Italy); Colorado Univ., Boulder, CO (United States). UCB 390 Physics Dept.; Westphal, A. [DESY Hamburg (Germany). Theory Group

    2013-04-15

    We perform a systematic analysis of moduli stabilization for weakly coupled heterotic string theory compactified on smooth Calabi-Yau three-folds. We focus on both supersymmetric and supersymmetry breaking vacua of generic (0,2) compactifications obtained by minimising the total (F+D)-term scalar potential. After reviewing how to stabilise all the geometric moduli in a supersymmetric way by including fractional fluxes, non-perturbative and threshold effects, we show that the inclusion of {alpha}' corrections leads to new de Sitter or nearly Minkowski vacua which break supersymmetry spontaneously. The minimum lies at moderately large volumes of all the geometric moduli, at perturbative values of the string coupling and at the right phenomenological value of the GUT gauge coupling. However the structure of the heterotic 3-form flux used for complex structure moduli stabilization does not contain enough freedom to tune the superpotential. This results in the generic prediction of high-scale supersymmetry breaking around the GUT scale. We finally provide a dynamical derivation of anisotropic compactifications with stabilized moduli which allow for perturbative gauge coupling unification around 10{sup 16} GeV.

  11. Moduli-induced baryogenesis

    International Nuclear Information System (INIS)

    We study a scenario for baryogenesis in modular cosmology and discuss its implications for the moduli stabilization mechanism and the supersymmetry (SUSY) breaking scale. If moduli fields dominate the Universe and decay into the standard model particles through diatonic couplings, the right amount of baryon asymmetry can be generated through CP violating decay of gluino into quark and squark followed by baryon-number violating squark decay. We find that, in the KKLT-type moduli stabilization, at least two non-perturbative terms are required to obtain a sizable CP phase, and that the successful baryogenesis is possible for the soft SUSY breaking mass heavier than O(1) TeV. A part of the parameter space for successful baryogenesis can be probed at the collider experiments, dinucleon decay search experiment, and the measurements of electric dipole moments of neutron and electron. It is also shown that similar baryogenesis works in the case of the gravitino- or the saxion-dominated Universe.

  12. Moduli-induced baryogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Ishiwata, Koji; Jeong, Kwang Sik [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Kashiwa (Japan). Kavli IPMU, TODIAS

    2013-12-15

    We study a scenario for baryogenesis in modular cosmology and discuss its implications for the moduli stabilization mechanism and the supersymmetry (SUSY) breaking scale. If moduli fields dominate the Universe and decay into the standard model particles through diatonic couplings, the right amount of baryon asymmetry can be generated through CP violating decay of gluino into quark and squark followed by baryon-number violating squark decay. We find that, in the KKLT-type moduli stabilization, at least two non-perturbative terms are required to obtain a sizable CP phase, and that the successful baryogenesis is possible for the soft SUSY breaking mass heavier than O(1) TeV. A part of the parameter space for successful baryogenesis can be probed at the collider experiments, dinucleon decay search experiment, and the measurements of electric dipole moments of neutron and electron. It is also shown that similar baryogenesis works in the case of the gravitino- or the saxion-dominated Universe.

  13. Moduli of Trigonal Curves

    CERN Document Server

    Stankova-Frenkel, Z E

    1997-01-01

    We study the moduli of trigonal curves. We establish the exact upper bound of ${36(g+1)}/(5g+1)$ for the slope of trigonal fibrations. Here, the slope of any fibration $X\\to B$ of stable curves with smooth general member is the ratio Hodge class $\\lambda$ on the moduli space $\\bar{\\mathfrak{M}}_g$ to the base $B$. We associate to a trigonal family $X$ a canonical rank two vector bundle $V$, and show that for Bogomolov-semistable $V$ the slope satisfies the stronger inequality ${\\delta_B}/{\\lambda_B}\\leq 7+{6}/{g}$. We further describe the rational Picard group of the {trigonal} locus $\\bar{\\mathfrak T}_g$ in the moduli space $\\bar{\\mathfrak{M}}_g$ of genus $g$ curves. In the even genus case, we interpret the above Bogomolov semistability condition in terms of the so-called Maroni divisor in $\\bar{\\mathfrak T}_g$.

  14. Can backcalculation models unravel complex larval growth histories in a tropical freshwater fish?

    Science.gov (United States)

    Starrs, D; Ebner, B C; Fulton, C J

    2013-07-01

    This experimental study compared the precision and accuracy of the biological intercept (BI), modified fry (MF) and time-varying growth (TVG) backcalculation models in estimating the early growth of the tropical freshwater purple-spotted gudgeon Mogurnda adspersa. Larvae were reared up to 41 days post hatching under two temperatures and four different feeding regimes. Food and temperature treatments induced complex growth profiles among fish, and although total length (LT ) and otolith radius were related under all conditions, some uncoupling was evident in the otolith-somatic-growth (OSG) relationship of fish subjected to periods of changing food availability. Furthermore, otolith growth was found to be significantly influenced by temperature, but not by food availability. Analysis of backcalculation residuals by linear mixed effects modelling revealed that BI and TVG were equally precise in predicting somatic growth, with the highest accuracy provided by TVG. The performance of all the three models declined as the OSG relationship weakened under low-food conditions, with maximum errors estimated to be 39, 60 and 36% of observed LT for the BI, MF and TVG models, respectively. The need for careful validation of backcalculation models is emphasized when examining fishes subjected to variable environmental conditions, and when exploring the differential influence of temperature and food on fish LT and otolith growth. PMID:23808694

  15. Moduli-Induced Vacuum Destabilisation

    OpenAIRE

    Conlon, Joseph P.; Pedro, Francisco G.

    2010-01-01

    We look for ways to destabilise the vacuum. We describe how dense matter environments source a contribution to moduli potentials and analyse the conditions required to initiate either decompactification or a local shift in moduli vevs. We consider astrophysical objects such as neutron stars as well as cosmological and black hole singularities. Regrettably neutron stars cannot destabilise realistic Planck coupled moduli, which would require objects many orders of magnitude denser. However grav...

  16. Moduli of weighted hyperplane arrangements

    CERN Document Server

    Lahoz, Martí; Macrí, Emanuele; Stellari, Paolo

    2015-01-01

    This book focuses on a large class of geometric objects in moduli theory and provides explicit computations to investigate their families. Concrete examples are developed that take advantage of the intricate interplay between Algebraic Geometry and Combinatorics. Compactifications of moduli spaces play a crucial role in Number Theory, String Theory, and Quantum Field Theory – to mention just a few. In particular, the notion of compactification of moduli spaces has been crucial for solving various open problems and long-standing conjectures. Further, the book reports on compactification techniques for moduli spaces in a large class where computations are possible, namely that of weighted stable hyperplane arrangements.

  17. Inflationary Predictions and Moduli Masses

    CERN Document Server

    Das, Kumar; Maharana, Anshuman

    2015-01-01

    A generic feature of inflationary models in supergravity/string constructions is vacuum misalignment for the moduli fields. The associated production of moduli particles leads to an epoch in the post-inflationary history in which the energy density is dominated by cold moduli particles. This modification of the post-inflationary history implies that the preferred range for the number of e-foldings between horizon exit of the modes relevant for CMB observations and the end of inflation $(N_k)$ depends on moduli masses. This in turn implies that the precision CMB observables $n_s$ and $r$ are sensitive to moduli masses. We analyse this sensitivity for some representative models of inflation and find the effect to be highly relevant for confronting inflationary models with observations.

  18. Analytical approaches for addressing the variation in back-calculated age-length relationships for fish.

    Science.gov (United States)

    Shephard, Samuel; Jackson, Donald C

    2009-12-01

    Estimating an age-length relationship is a routine aspect of many fisheries studies and is simplified by the use of commercially available computer programs. These computer programs may be misleading since a result can be produced irrespective of the quality or the extent of the data, and there is some concern that back-calculated age-length relationships are sensitive to the sample size and composition. We investigated this issue by comparing estimates of mean back-calculated lengths at age and growth rates derived from subsets of a large sample of wild channel catfish Ictalurus punctatus (N=788) collected in 2001 and 2002 from 9 rivers in Mississippi, United States. Estimates of growth rate varied among subsets consisting of individual year class (2-6) of channel catfish separated from the overall sample. For nine subsets, comprising randomly-selected and increasing proportions of the overall sample (20%-100% at 10% increments of the overall sample), growth was similar. However, growth differed for a subset representing a random 10% of the overall sample. Lengths at age and growth rates derived from each of the 2001 and 2002 components of the sample both differed. All results were significant at P < 0.05. PMID:24575181

  19. Moduli spaces in algebraic geometry

    International Nuclear Information System (INIS)

    This volume of the new series of lecture notes of the Abdus Salam International Centre for Theoretical Physics contains the lecture notes of the School on Algebraic Geometry which took place at the Abdus Salam International Centre for Theoretical Physics from 26 July to 13 August 1999. The school consisted of 2 weeks of lecture courses and one week of conference. The topic of the school was moduli spaces. More specifically the lectures were divided into three subtopics: principal bundles on Riemann surfaces, moduli spaces of vector bundles and sheaves on projective varieties, and moduli spaces of curves

  20. Supergravity gaugings and moduli superpotentials

    International Nuclear Information System (INIS)

    These lecture notes describe the method of N=4 supergravity gaugings used as a four-dimensional effective Lagrangian description of the moduli superpotentials generated by superstring vacua with fluxes. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  1. Supergravity gaugings and moduli superpotentials

    Energy Technology Data Exchange (ETDEWEB)

    Derendinger, J.P. [Physics Institute, Neuchatel University, A.-L. Breguet 1, 2000 Neuchatel (Switzerland)

    2006-05-04

    These lecture notes describe the method of N=4 supergravity gaugings used as a four-dimensional effective Lagrangian description of the moduli superpotentials generated by superstring vacua with fluxes. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  2. Ultransonic velocity measurements in sheared granular layers: Implications for the evolution of dynamic elastic moduli of compositionally-diverse cataclastic fault gouges

    Science.gov (United States)

    Knuth, Matthew William

    The objective of this project was to investigate the mechanical and elastic evolution of laboratory fault gouge analogs during active shear. To do this, I designed, constructed, and implemented a new technique for measuring changes in the elastic properties of granular layers subjected to shear deformation. Granular layers serve as an experimental analog to gouge layers forming in cataclastic faults. The technique combines a double-direct shear configuration with a method of determining ultrasonic elastic compressional and shear wavespeed. Experimental results are divided into chapters based on application to fundamental mechanics or to field cases. The first set of experiments allowed us to develop the technique and apply it to a range of end- member materials including quartz sands, montmorillonite clays, and mixtures of sand and clay. Emphasis is placed on normal stress unload-reload cycles and the resulting behavior as clay content is varied within the layer. We observe consistent decrease in wavespeed with shear for sand, and nonlinear but increasing wavespeed for clay and the sand/clay mixture. The second set of experiments involves the application of this technique to measurements conducted under fluid saturation and controlled pressure conditions, examining the behavior of materials from the Nankai Trough Accretionary Prism under shear. I introduce the effects of variable displacement rate and hold time, with implications for fault stability and rate-and-state frictional sliding. The experiments demonstrate a consistent inverse relationship between sliding velocity and wavespeed, and an increase in wavespeed associated with holds. The third set of experiments deals with velocity through stick-slipping glass beads, which has implications for fundamental granular mechanics questions involving velocity-weakening materials. I find that wavespeed decreases in the time between events and increases at "slips", suggesting a strong control related to changes in

  3. Bending moduli of polymeric surfactant interfaces

    OpenAIRE

    Milner, S.T.; Witten, T. A.

    1988-01-01

    Our recent theory of the free energy and conformations of end-grafted polymer « brushes » is extended to polymers attached to curved surfaces. Several important systems, e.g., layers of polymeric surfactants or of strongly segregated diblock copolymers, can be well described as brushes. By expanding in powers of the curvature the free energy of a brush on a curved surface, the mean and Gaussian bending moduli may be obtained analytically. Results for K and K of monodisperse brushes are consis...

  4. Moduli mediation without moduli-induced gravitino problem

    CERN Document Server

    Akita, Kensuke; Oikawa, Akane; Otsuka, Hajime

    2016-01-01

    We study the moduli-induced gravitino problem within the framework of the phenomenologically attractive mirage mediations. The huge amount of gravitino generated by the moduli decay can be successfully diluted by introducing an extra light modulus field which does not induce the supersymmetry breaking. Since the lifetime of extra modulus field becomes longer than usually considered modulus field, our proposed mechanism is applied to both the low- and high-scale supersymmetry breaking scenarios. We also point out that such an extra modulus field appears in the flux compactification of type II string theory.

  5. Moduli Space of General Connections

    CERN Document Server

    Dubrovskiy, Stanislav

    2010-01-01

    We consider local invariants of general connections (with torsion). The group of origin-preserving diffeomorphisms acts on a space of jets of general connections. Dimensions of moduli spaces of generic connections are calculated. Poincar\\'e series of the geometric structure of connection is constructed, and shown to be a rational function, confirming the finiteness assertion of Tresse.

  6. Generating RSA moduli with a predetermined portion

    OpenAIRE

    Lenstra, Arjen K.

    1998-01-01

    This paper reviews and generalizes a method to generate RSA moduli with a predetermined portion. The potential advantages of the resulting methods are discussed. Both the storage and the computational requirements of the RSA cryptosystem can be considerably reduced. The constructions are as efficient as generation of regular RSA moduli, and the resulting moduli do not seem to offer less security than regular RSA moduli

  7. The moduli space of generalized Morse functions

    OpenAIRE

    Botvinnik, Boris; Madsen, Ib

    2010-01-01

    We study the moduli and determine a homotopy type of the space of all generalized Morse functions on d-manifolds for given d. This moduli space is closely connected to the moduli space of all Morse functions studied in the paper math.AT/0212321, and the classifying space of the corresponding cobordism category.

  8. Moduli Backreaction on Inflationary Attractors

    CERN Document Server

    Roest, Diederik; Werkman, Pelle

    2016-01-01

    We investigate the interplay between moduli dynamics and inflation, focusing on the KKLT-scenario and cosmological $\\alpha$-attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for $\\alpha$-attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory, or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e-folds due to the interplay with moduli.

  9. Moduli spaces of riemannian metrics

    CERN Document Server

    Tuschmann, Wilderich

    2015-01-01

    This book studies certain spaces of Riemannian metrics on both compact and non-compact manifolds. These spaces are defined by various sign-based curvature conditions, with special attention paid to positive scalar curvature and non-negative sectional curvature, though we also consider positive Ricci and non-positive sectional curvature. If we form the quotient of such a space of metrics under the action of the diffeomorphism group (or possibly a subgroup) we obtain a moduli space. Understanding the topology of both the original space of metrics and the corresponding moduli space form the central theme of this book. For example, what can be said about the connectedness or the various homotopy groups of such spaces? We explore the major results in the area, but provide sufficient background so that a non-expert with a grounding in Riemannian geometry can access this growing area of research.

  10. Coherency strain modeling of elastic moduli in Cu/Nb multilayers

    International Nuclear Information System (INIS)

    An anomalous decrease in the elastic moduli of Cu/Nb multilayers has been observed via acoustic wave measurements. The decrease occurs for (111) fcc Cu and (110) bcc Nb layered structures with repeat periods between 1 and 5 nm. The coherency strain model has been used to simulate modulus enhancement in noble/transition metal multilayers. This approach addresses the atomic displacements corresponding with the lattice distortions of biaxially stressed layers. Elastic moduli are derived with respect to higher order differentials of a Born-Mayer type potential for nearest neighbor ions. The elastic moduli anomalies of Cu/Nb multilayers are modelled within this conceptual framework

  11. Moduli interpretation of Eisenstein series

    OpenAIRE

    Khuri-Makdisi, Kamal

    2009-01-01

    Let L >= 3. Using the moduli interpretation, we define certain elliptic modular forms of level Gamma(L) over any field k where 6L is invertible and k contains the Lth roots of unity. These forms generate a graded algebra R_L, which, over C, is generated by the Eisenstein series of weight 1 on Gamma(L). The main result of this article is that, when k=C, the ring R_L contains all modular forms on Gamma(L) in weights >= 2. The proof combines algebraic and analytic techniques, including the actio...

  12. Moduli destabilization via gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Dong-il [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Pedro, Francisco G. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Yeom, Dong-han [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics

    2013-06-15

    We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.

  13. Moduli destabilization via gravitational collapse

    International Nuclear Information System (INIS)

    We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.

  14. Brane Potentials and Moduli Spaces

    International Nuclear Information System (INIS)

    It is shown that the supergravity moduli spaces of D1-D5 and D2-D6 brane systems coincide with those of the Coulomb branches of the associated non-abelian gauge theories. We further discuss situations in which worldvolume brane actions include a potential term generated by probing certain supergravity backgrounds. We find that in many cases, the appearance of the potential is due to the application of the Scherk-Schwarz mechanism. We give some examples and discuss the existence of novel supersymmetric brane configurations. (author)

  15. A Metric for Heterotic Moduli

    CERN Document Server

    Candelas, Philip; McOrist, Jock

    2016-01-01

    Heterotic vacua of string theory are realised, at large radius, by a compact threefold with vanishing first Chern class together with a choice of stable holomorphic vector bundle. These form a wide class of potentially realistic four-dimensional vacua of string theory. Despite all their phenomenological promise, there is little understanding of the metric on the moduli space of these. What is sought is the analogue of special geometry for these vacua. The metric on the moduli space is important in phenomenology as it normalises D-terms and Yukawa couplings. It is also of interest in mathematics, since it generalises the metric, first found by Kobayashi, on the space of gauge field connections, to a more general context. Here we construct this metric, correct to first order in alpha', in two ways: first by postulating a metric that is invariant under background gauge transformations of the gauge field, and also by dimensionally reducing heterotic supergravity. These methods agree and the resulting metric is Ka...

  16. SUGRA chaotic inflation and moduli stabilisation

    International Nuclear Information System (INIS)

    Chaotic inflation predicts a large gravitational wave signal which can be tested by the upcoming Planck satellite. We discuss a SUGRA implementation of chaotic inflation in the presence of moduli fields, and find that inflation does not work with a generic KKLT moduli stabilisation potential. A viable model can be constructed with a fine-tuned moduli sector, but only for a very specific choice of Kaeahler potential. Our analysis also shows that inflation models satisfying ∂iWinf=0 for all inflation sector fields φi can be combined successfully with a fine-tuned moduli sector. (orig.)

  17. Ferromagnetic detection of moduli dark matter

    CERN Document Server

    Vinante, A

    2016-01-01

    We propose a scheme to detect light scalar moduli dark matter, based on measuring the change of magnetization induced in a macroscopic hard ferromagnet. Our method can probe moduli dark matter at the natural coupling to the electron mass over several orders of magnitude in the moduli mass. The most attracting feature of the proposed approach, compared to mechanical ones, is that it relies on a nonresonant detection, allowing to probe a much wider region of the parameter space. This is a crucial point, as long as the theory is not able to predict the moduli mass.

  18. SUGRA chaotic inflation and moduli stabilisation

    Energy Technology Data Exchange (ETDEWEB)

    Davis, S.C. [CEA/Saclay, Gif-sur-Yvette (France). Service de Physique Theorique; Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)

    2008-01-15

    Chaotic inflation predicts a large gravitational wave signal which can be tested by the upcoming Planck satellite. We discuss a SUGRA implementation of chaotic inflation in the presence of moduli fields, and find that inflation does not work with a generic KKLT moduli stabilisation potential. A viable model can be constructed with a fine-tuned moduli sector, but only for a very specific choice of Kaeahler potential. Our analysis also shows that inflation models satisfying {partial_derivative}{sub i}W{sub inf}=0 for all inflation sector fields {phi}{sub i} can be combined successfully with a fine-tuned moduli sector. (orig.)

  19. The Moduli and Gravitino (non)-Problems in Models with Strongly Stabilized Moduli

    CERN Document Server

    Evans, Jason L; Olive, Keith A

    2013-01-01

    In gravity mediated models and in particular in models with strongly stabilized moduli, there is a natural hierarchy between gaugino masses, the gravitino mass and moduli masses: $m_{1/2} \\ll m_{3/2} \\ll m_{\\phi}$. Given this hierarchy, we show that 1) moduli problems associated with excess entropy production from moduli decay and 2) problems associated with moduli/gravitino decays to neutralinos are non-existent. Placed in an inflationary context, we show that the amplitude of moduli oscillations are severely limited by strong stabilization. Moduli oscillations may then never come to dominate the energy density of the Universe. As a consequence, moduli decay to gravitinos and their subsequent decay to neutralinos need not overpopulate the cold dark matter density.

  20. The moduli and gravitino (non)-problems in models with strongly stabilized moduli

    International Nuclear Information System (INIS)

    In gravity mediated models and in particular in models with strongly stabilized moduli, there is a natural hierarchy between gaugino masses, the gravitino mass and moduli masses: m1/2 << m3/2 << mφ. Given this hierarchy, we show that 1) moduli problems associated with excess entropy production from moduli decay and 2) problems associated with moduli/gravitino decays to neutralinos are non-existent. Placed in an inflationary context, we show that the amplitude of moduli oscillations are severely limited by strong stabilization. Moduli oscillations may then never come to dominate the energy density of the Universe. As a consequence, moduli decay to gravitinos and their subsequent decay to neutralinos need not overpopulate the cold dark matter density

  1. Strong moduli stabilization and phenomenology

    CERN Document Server

    Dudas, Emilian; Mambrini, Yann; Mustafayev, Azar; Olive, Keith A

    2013-01-01

    We describe the resulting phenomenology of string theory/supergravity models with strong moduli stabilization. The KL model with F-term uplifting, is one such example. Models of this type predict universal scalar masses equal to the gravitino mass. In contrast, A-terms receive highly suppressed gravity mediated contributions. Under certain conditions, the same conclusion is valid for gaugino masses, which like A-terms, are then determined by anomalies. In such models, we are forced to relatively large gravitino masses (30-1000 TeV). We compute the low energy spectrum as a function of m_{3/2}. We see that the Higgs masses naturally takes values between 125-130 GeV. The lower limit is obtained from the requirement of chargino masses greater than 104 GeV, while the upper limit is determined by the relic density of dark matter (wino-like).

  2. Intermediate Jacobians of moduli spaces

    CERN Document Server

    Arapura, D; Arapura, Donu; Sastry, Pramathanath

    1996-01-01

    Let $SU_X(n,L)$ be the moduli space of rank n semistable vector bundles with fixed determinant L on a smooth projective genus g curve X. Let $SU_X^s(n,L)$ denote the open subset parametrizing stable bundles. We show that if g>3 and n > 1, then the mixed Hodge structure on $H^3(SU_X^s(n, L))$ is pure of type ${(1,2),(2,1)}$ and it carries a natural polarization such that the associated polarized intermediate Jacobian is isomorphic J(X). This is new when deg L and n are not coprime. As a corollary, we obtain a Torelli theorem that says roughly that $SU_X^s(n,L)$ (or $SU_X(n,L)$) determines X. This complements or refines earlier results of Balaji, Kouvidakis-Pantev, Mumford-Newstead, Narasimhan-Ramanan, and Tyurin.

  3. Moduli Space of Topological 2-form Gravity

    OpenAIRE

    Abe, Mitsuko; Nakamichi, A.; Ueno, T.

    1993-01-01

    We propose a topological version of four-dimensional (Euclidean) Einstein gravity, in which anti-self-dual 2-forms and an SU(2) connection are used as fundamental fields. The theory describes the moduli space of conformally self-dual Einstein manifolds. In the presence of a cosmological constant, we evaluate the index of the elliptic complex associated with the moduli space.

  4. Roaming moduli space using dynamical triangulations

    Energy Technology Data Exchange (ETDEWEB)

    Ambjorn, J., E-mail: ambjorn@nbi.dk [Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark); Barkley, J., E-mail: barkley@nbi.dk [Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark); Budd, T.G., E-mail: t.g.budd@uu.nl [Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, NL-3584 CE Utrecht (Netherlands)

    2012-05-11

    In critical as well as in non-critical string theory the partition function reduces to an integral over moduli space after integration over matter fields. For non-critical string theory this moduli integrand is known for genus one surfaces. The formalism of dynamical triangulations provides us with a regularization of non-critical string theory. We show how to assign in a simple and geometrical way a moduli parameter to each triangulation. After integrating over possible matter fields we can thus construct the moduli integrand. We show numerically for c=0 and c=-2 non-critical strings that the moduli integrand converges to the known continuum expression when the number of triangles goes to infinity.

  5. Roaming moduli space using dynamical triangulations

    CERN Document Server

    Ambjorn, J; Budd, T

    2011-01-01

    In critical as well as in non-critical string theory the partition function reduces to an integral over moduli space after integration over matter fields. For non-critical string theory this moduli integrand is known for genus one surfaces. The formalism of dynamical triangulations provides us with a regularization of non-critical string theory. We show how to assign in a simple and geometrical way a moduli parameter to each triangulation. After integrating over possible matter fields we can thus construct the moduli integrand. We show numerically for $c=0$ and $c=-2$ non-critical strings that the moduli integrand converges to the known continuum expression when the number of triangles goes to infinity.

  6. Roaming moduli space using dynamical triangulations

    Science.gov (United States)

    Ambjørn, J.; Barkley, J.; Budd, T. G.

    2012-05-01

    In critical as well as in non-critical string theory the partition function reduces to an integral over moduli space after integration over matter fields. For non-critical string theory this moduli integrand is known for genus one surfaces. The formalism of dynamical triangulations provides us with a regularization of non-critical string theory. We show how to assign in a simple and geometrical way a moduli parameter to each triangulation. After integrating over possible matter fields we can thus construct the moduli integrand. We show numerically for c=0 and c=-2 non-critical strings that the moduli integrand converges to the known continuum expression when the number of triangles goes to infinity.

  7. String Moduli Stabilization at the Conifold

    CERN Document Server

    Blumenhagen, Ralph; Wolf, Florian

    2016-01-01

    We study moduli stabilization for type IIB orientifolds compactified on Calabi-Yau threefolds in the region close to conifold singularities in the complex structure moduli space. The form of the periods implies new phenomena like exponential mass hierarchies even in the regime of negligible warping. Integrating out the heavy conic complex structure modulus leads to an effective flux induced potential for the axio-dilaton and the remaining complex structure moduli containing exponentially suppressed terms that imitate non-perturbative effects. It is shown that this scenario can be naturally combined with the large volume scenario so that all moduli are dynamically stabilized in the dilute flux regime. As an application of this moduli stabilization scheme, a string inspired model of aligned inflation is designed that features a parametrically controlled hierarchy of mass scales.

  8. Back-calculation of surface acceleration from penetration resistances at liquefied sites of 1956 Dunaharaszti earthquake, in Hungary

    Science.gov (United States)

    Bán, Zoltán; Győri, Erzsébet; Horváth, Tibor

    2015-04-01

    Liquefaction and paleoliquefaction studies are being used increasingly to interpret ground motion parameters (acceleration, magnitude, epicenter location) in regions that experience infrequent but damaging earthquakes. These are especially applicable where the most recent damaging earthquakes occurred prior to the development of ground motion instrumentation. In Hungary, a damaging earthquake of magnitude 5.6 occurred in Dunaharaszti in 1956. Its epicenter was located about 5 km from the southern boundary of Budapest. The quake caused serious damages in the epicentral area and in the southern districts of the capital. A Wiechert type seismometer was operated in Budapest 15-20 km from the epicenter but it saturated by the earthquake so instrumental information does not exist about the shaking strength. Ground accelerations caused by the event can be deduced only from the macroseismic intensity values and from the analogies of recent similar earthquakes where strong motion data exist. The epicentral area of Dunaharaszti earthquake was located along the Danube River. Sand boils were observed in some locations that indicated the occurrence of liquefaction. Because their exact locations were recorded at the time of the earthquake, geotechnical measurements could be performed. Therefore an alternative possibility to estimate shaking strength can be the back-analysis of liquefaction field data. Unlike the paleoliquefaction studies, in our case the source of the earthquake and the magnitude is known, our purpose was only to estimate the peak ground acceleration and acceleration-related parameters, such as Arias intensity. Back-calculation of surface acceleration was performed at two locations, where evidences of liquefaction had been observed after the earthquake. On both locations SPT and CPT measurements were carried out, and back-analysis from them was performed with different empirical methods. This allowed the assessment of the selected method's and the used in

  9. Open String Moduli in KKLT Compactifications

    OpenAIRE

    Aharony, Ofer; Antebi, Yaron E; Berkooz, Micha

    2005-01-01

    In the Kachru-Kallosh-Linde-Trivedi (KKLT) de-Sitter construction one introduces an anti-D3-brane that breaks the supersymmetry and leads to a positive cosmological constant. In this paper we investigate the open string moduli associated with this anti-D3-brane, corresponding to its position on the 3-sphere at the tip of the deformed conifold. We show that in the KKLT construction these moduli are very light, and we suggest a possible way to give these moduli a large mass by putting orientifo...

  10. Multi-Skyrmions with orientational moduli

    CERN Document Server

    Canfora, Fabrizio

    2016-01-01

    We analyze the mechanism of condensation of orientational moduli (as introduced in [25]) on multi-Skyrmionic configurations of the four-dimensional Skyrme model. The present analysis reveals interesting novel features. First of all, the orientational moduli tend to decrease the repulsive interactions between Skyrmions, the effect decreasing with the increase of the Baryon number. Moreover, in the case of a single Skyrmion, the appearance of moduli is energetically favorable if finite volume effects are present. Otherwise, in the usual flat topologically trivial case, it is not. In the low energy theory these solutions can be interpreted as Skyrmions with additional isospin degrees of freedom.

  11. A novel length back-calculation approach accounting for ontogenetic changes in the fish length - otolith size relationship during the early life of sprat (Sprattus sprattus)

    DEFF Research Database (Denmark)

    Guenther, Claudia C.; Temming, Axel; Baumann, Hannes;

    2012-01-01

    An individual-based length back-calculation method was developed for juvenile Baltic sprat (Sprattus sprattus), accounting for ontogenetic changes in the relationship between fish length and otolith length. In sprat, metamorphosis from larvae to juveniles is characterized by the coincidence of low......, which is supposed to be critical in determining recruitment strength in Baltic sprat....

  12. Backcalculation of Resilient Modulus of Subgrade Based Two Point Surface Deflections%基于两点路表弯沉反算土基回弹模量的研究

    Institute of Scientific and Technical Information of China (English)

    杨国良; 吴旷怀

    2008-01-01

    基于层状弹性理论,利用远离承载板中心的两点路表变形响应反算土基回弹模量.根据半刚性基层沥青路面常用路面结构组合形式,构建土基回弹模量与两点路表弯沉值之间一一对应的数据库,建立回归模型.由理论弯沉盆和实测弯沉盆的预测结果表明,建立的土基回弹模量回归预测模型具有良好的精度和可靠性,为进一步快速、有效地评定土基的承载能力提供了依据.%Based on the layered elastic theory, the resilient modulus of subgrade was backcalculated using two point surface deflection responses of pavement structure where were further away from the center of bearing plate. According to the combinations of asphalt pavement on semi-rigid road for high-class highways in common use, the database of structural parameters and corresponding two point surface deflections was established and the regressive models were developed to backcalculate the resilient modulus of subgrade. The predictive results of theoretical and measured deflection basins showed that the regressive model of resilient modulus of subgrade was of good accuracy and reliability. It provids evidences to rapidly and effectively evaluate the bearing capacity of subgrade.

  13. Vertex Operators and Moduli Spaces of Sheaves

    CERN Document Server

    Carlsson, Erik

    2009-01-01

    The Nekrasov partition function in supersymmetric quantum gauge theory is mathematically formulated as an equivariant integral over certain moduli spaces of sheaves on a complex surface. In ``Seiberg-Witten Theory and Random Partitions'', Nekrasov and Okounkov studied these integrals using the representation theory of ``vertex operators'' and the infinite wedge representation. Many of these operators arise naturally from correspondences on the moduli spaces, such as Nakajima's Heisenberg operators, and Grojnowski's vertex operators. In this paper, we build a new vertex operator out of the Chern class of a vector bundle on a pair of moduli spaces. This operator has the advantage that it connects to the partition function by definition. It also incorporates the canonical class of the surface, whereas many other studies assume that the class vanishes. When the moduli space is the Hilbert scheme, we present an explicit expression in the Nakajima operators, and the resulting combinatorial identities. We then apply...

  14. K3 surfaces and their moduli

    CERN Document Server

    Farkas, Gavril; Geer, Gerard

    2016-01-01

    This book provides an overview of the latest developments concerning the moduli of K3 surfaces. It is aimed at algebraic geometers, but is also of interest to number theorists and theoretical physicists, and continues the tradition of related volumes like “The Moduli Space of Curves” and “Moduli of Abelian Varieties,” which originated from conferences on the islands Texel and Schiermonnikoog and which have become classics. K3 surfaces and their moduli form a central topic in algebraic geometry and arithmetic geometry, and have recently attracted a lot of attention from both mathematicians and theoretical physicists. Advances in this field often result from mixing sophisticated techniques from algebraic geometry, lattice theory, number theory, and dynamical systems. The topic has received significant impetus due to recent breakthroughs on the Tate conjecture, the study of stability conditions and derived categories, and links with mirror symmetry and string theory. At the same time, the theory of irred...

  15. Dynamic elastic moduli of rocks under pressure

    International Nuclear Information System (INIS)

    Elastic moduli are determined as a function of confining pressure to 10 kb on rocks in which Plowshare shots are to be fired. Numerical simulation codes require accurate information on the mechanical response of the rock medium to various stress levels in order to predict cavity dimensions. The theoretical treatment of small strains in an elastic medium relates the propagation velocity of compressional and shear waves to the elastic moduli. Velocity measurements can provide, as unique code input data, the rigidity modulus, Poisson' ratio and the shear wave velocity, as well as providing checks on independent determinations of the other moduli. Velocities are determined using pulsed electro-mechanical transducers and measuring the time-of-flight in the rock specimen. A resonant frequency of 1 MHz is used to insure that the wavelength exceeds the average grain dimension and is subject to bulk rock properties. Data obtained on a variety of rock types are presented and analyzed. These data are discussed in terms of their relationship to moduli measured by static methods as well as the effect of anisotropy, porosity, and fractures. In general, fractured rocks with incipient cracks show large increases in velocity and moduli in the first 1 to 2 kb of compression as a result of the closing of these voids. After this, the velocities increase much more slowly. Dynamic moduli for these rocks are often 10% higher than corresponding static moduli at low pressure, but this difference decreases as the voids are closed until the moduli agree within experimental error. The discrepancy at low pressure is a result of the elastic energy in the wave pulse being propagated around cracks, with little effect on propagation velocity averaged over the entire specimen. (author)

  16. Moduli stabilization in type IIB orientifolds

    Energy Technology Data Exchange (ETDEWEB)

    Schulgin, W.

    2007-06-04

    This thesis deals with the stabilization of the moduli fields in the compactifications of the type IIB string theory on orientifolds. A concrete procedure for the construction of solutions, in which all moduli fields are fixed, yields the KKLT scenario. We study, on which models the scenario can be applied, if approximations of the original KKLT work are abandoned. We find that in a series of models, namely such without complex-structure moduli the construction of the consistent solutions in the framework of the KKLT scenario is not possible. The nonperturbative effects, like D3 instantons and gaugino condensates are a further component of the KKLT scenario. They lead to the stabilization of the Kaehler moduli. We present criteria for the generation of the superpotential due to the D3 instantons at a Calaby-Yau manifold in presence of fluxes. Furthermore we show that although the presence of the nonperturbative superpotential in the equations of motions is correlated with the switching on of all ISD and IASD fluxes, the deciding criterium for the generation of the nonperturbative superpotential depends only on the fluxes of the type (2,1). Thereafter we discuss two models, in which we stabilize all moduli fields. Thereby it deals with Calabi-Yau orientifolds which have been obtained by a blow-up procedure from the Z{sub 6-II} and Z{sub 2} x Z{sub 4} orientifolds.

  17. Moduli stabilization in type IIB orientifolds

    International Nuclear Information System (INIS)

    This thesis deals with the stabilization of the moduli fields in the compactifications of the type IIB string theory on orientifolds. A concrete procedure for the construction of solutions, in which all moduli fields are fixed, yields the KKLT scenario. We study, on which models the scenario can be applied, if approximations of the original KKLT work are abandoned. We find that in a series of models, namely such without complex-structure moduli the construction of the consistent solutions in the framework of the KKLT scenario is not possible. The nonperturbative effects, like D3 instantons and gaugino condensates are a further component of the KKLT scenario. They lead to the stabilization of the Kaehler moduli. We present criteria for the generation of the superpotential due to the D3 instantons at a Calaby-Yau manifold in presence of fluxes. Furthermore we show that although the presence of the nonperturbative superpotential in the equations of motions is correlated with the switching on of all ISD and IASD fluxes, the deciding criterium for the generation of the nonperturbative superpotential depends only on the fluxes of the type (2,1). Thereafter we discuss two models, in which we stabilize all moduli fields. Thereby it deals with Calabi-Yau orientifolds which have been obtained by a blow-up procedure from the Z6-II and Z2 x Z4 orientifolds

  18. Matrix string theory and its moduli space

    International Nuclear Information System (INIS)

    The correspondence between Matrix String Theory in the strong coupling limit and IIA superstring theory can be shown by means of the instanton solutions of the former. We construct the general instanton solutions of Matrix String Theory which interpolate between given initial and final string configurations. Each instanton is characterized by a Riemann surface of genus h with n punctures, which is realized as a plane curve. We study the moduli space of such plane curves and find out that, at finite N, it is a discretized version of the moduli space of Riemann surfaces: instead of 3h - 3 + n its complex dimensions are 2h - 3 + n, the remaining h dimensions being discrete. It turns out that as N tends to infinity, these discrete dimensions become continuous. We argue that in this limit one recovers the full moduli space of string interaction theory

  19. Accidental Kähler moduli inflation

    International Nuclear Information System (INIS)

    We study a model of accidental inflation in type IIB string theory where inflation occurs near the inflection point of a small Kähler modulus. A racetrack structure helps to alleviate the known concern that string-loop corrections may spoil Kähler Moduli Inflation unless having a significant suppression via the string coupling or a special brane setup. Also, the hierarchy of gauge group ranks required for the separation between moduli stabilization and inflationary dynamics is relaxed. The relaxation becomes more significant when we use the recently proposed D-term generated racetrack model

  20. String instantons, fluxes and moduli stabilization

    CERN Document Server

    Camara, P G; Maillard, T; Pradisi, G

    2007-01-01

    We analyze a class of dual pairs of heterotic and type I models based on freely-acting $\\mathbb{Z}_2 \\times \\mathbb{Z}_2$ orbifolds in four dimensions. Using the adiabatic argument, it is possible to calculate non-perturbative contributions to the gauge coupling threshold corrections on the type I side by exploiting perturbative calculations on the heterotic side, without the drawbacks due to twisted moduli. The instanton effects can then be combined with closed-string fluxes to stabilize most of the moduli fields of the internal manifold, and also the dilaton, in a racetrack realization of the type I model.

  1. Baryogenesis and Late-Decaying Moduli

    OpenAIRE

    Allahverdi, Rouzbeh; Dutta, Bhaskar; Sinha, Kuver

    2010-01-01

    Late-decaying string moduli dilute the baryon asymmetry of the universe created in any previous era. The reheat temperature for such moduli is below a GeV, thus motivating baryogenesis at very low temperatures. We present an extension of the minimal supersymmetric standard model with TeV-scale colored fields that can yield the correct baryon asymmetry of the universe in this context. Modulus decay, which reheats the universe at a temperature below GeV, produces the visible sector fields and n...

  2. Non-special scrolls with general moduli

    OpenAIRE

    Calabri, Alberto; Ciliberto, Ciro; Flamini, Flaminio; Miranda, Rick

    2007-01-01

    In this paper we study smooth, non-special scrolls S of degree d, genus g, with general moduli. In particular, we study the scheme of unisecant curves of a given degree on S. Our approach is mostly based on degeneration techniques.

  3. Tautological algebras of moduli spaces of curves

    NARCIS (Netherlands)

    Faber, C.F.

    2013-01-01

    These are the lecture notes for my course at the 2011 Park City Mathematical Institute on moduli spaces of Riemann surfaces. The two lectures here correspond roughly to the first and second half of the course. The subject of the first lecture is the tautological ring R∗(Mg) of Mg. I recall Mumford’s

  4. Line bundles on moduli and related spaces

    CERN Document Server

    Huebschmann, Johannes

    2009-01-01

    Let G be a Lie goup, let M and N be smooth connected G-manifolds, let f be a smooth G-map from M to N, and let P denote the fiber of f. Given a closed and equivariantly closed relative 2-form for f with integral periods, we construct the principal G-circle bundles with connection on P having the given relative 2-form as curvature. Given a compact Lie group K, a biinvariant Riemannian metric on K, and a closed Riemann surface S of genus s, when we apply the construction to the particular case where f is the familiar relator map from a product of 2s copies of K to K we obtain the principal K-circle bundles on the associated extended moduli spaces which, via reduction, then yield the corresponding line bundles on possibly twisted moduli spaces of representations of the fundamental group of S in K, in particular, on moduli spaces of semistable holomorphic vector bundles or, more precisely, on a smooth open stratum when the moduli space is not smooth. The construction also yields an alternative geometric object, d...

  5. Roaming moduli space using dynamical triangulations

    NARCIS (Netherlands)

    Ambjørn, J.; Barkley, J.; Budd, T.G.

    2012-01-01

    In critical as well as in non-critical string theory the partition function reduces to an integral over modulispace after integration over matter fields. For non-critical string theory this moduli integrand is known for genus one surfaces. The formalism of dynamicaltriangulations provides us with a

  6. Moduli spaces of unitary conformal field theories

    International Nuclear Information System (INIS)

    We investigate various features of moduli spaces of unitary conformal field theories. A geometric characterization of rational toroidal conformal field theories in arbitrary dimensions is presented and discussed in relation to singular tori and those with complex multiplication. We study the moduli space M2 of unitary two-dimensional conformal field theories with central charge c = 2. All the 26 non-exceptional non-isolated irreducible components of M2 are constructed that may be obtained by an orbifold procedure from toroidal theories. The parameter spaces and partition functions are calculated explicitly. All multicritical points and lines are determined, such that all but three of these 26 components are directly or indirectly connected to the space of toroidal theories in M2. Relating our results to those by Dixon, Ginsparg, Harvey on the classification of c = 3/2 superconformal field theories, we give geometric interpretations to all non-isolated orbifolds discussed by them and correct their statements on multicritical points within the moduli space of c = 3/2 superconformal field theories. In the main part of this work, we investigate the moduli space M of N = (4, 4) superconformal field theories with central charge c = 6. After a slight emendation of its global description we give generic partition functions for models contained in M. We explicitly determine the locations of various known models in the component of M associated to K3 surfaces

  7. String loop corrected hypermultiplet moduli spaces

    NARCIS (Netherlands)

    Robles-Llana, D.; Saueressig, Frank; Vandoren, S.

    2007-01-01

    Using constraints from supersymmetry and string perturbation theory, we determine the string loop corrections to the hypermultiplet moduli space of type II strings compactified on a generic Calabi-Yau threefold. The corresponding quaternion-Kähler manifolds are completely encoded in terms of a singl

  8. Moduli Space of Integrable Dirac Structures

    CERN Document Server

    Milani, Vida

    2009-01-01

    In this paper we introduce the notion of integrable Dirac structures on Hermitian modules. The moduli space of the space of integrable Dirac structures is studied. Then a necessary and sufficient condition for the integrability of a Dirac structure is obtained as the solution of a certain partial differential equation.

  9. Monoids of moduli spaces of manifolds

    DEFF Research Database (Denmark)

    Galatius, Søren; Randal-Williams, Oscar

    2010-01-01

    D the better. We prove that in most cases of interest, D can be chosen to be a homotopy commutative monoid. As a consequence we prove that the stable cohomology of many moduli spaces of surfaces with ¿–structure is the cohomology of the  infinite loop space of a certain Thom spectrum MT¿. This was...

  10. Moduli spaces of convex projective structures on surfaces

    DEFF Research Database (Denmark)

    Fock, V. V.; Goncharov, A. B.

    2007-01-01

    We introduce explicit parametrisations of the moduli space of convex projective structures on surfaces, and show that the latter moduli space is identified with the higher Teichmüller space for defined in [V.V. Fock, A.B. Goncharov, Moduli spaces of local systems and higher Teichmüller theory, math...

  11. Hybrid inflation and the moduli problem

    International Nuclear Information System (INIS)

    We revisit some questions in supersymmetric hybrid inflation. We analyze the amount of fine-tuning required in various models, the problem of decay at the end of inflation and the generation of baryons after inflation. We find that the most natural setting for hybrid inflation is in supersymmetric models with nonrenormalizable couplings. Furthermore, we argue that almost inevitably, one of the fields involved is a modulus, with Planck scale variation. The resulting moduli problem can be solved in two ways: either by a massive modulus (which requires some fine-tuning), or an enhanced symmetry point, in which the moduli becomes strongly coupled to the standard model. Various possibilities for baryon production are discussed

  12. Hybrid Inflation and the Moduli Problem

    CERN Document Server

    Berkooz, M; Volansky, T; Berkooz, Micha; Dine, Michael; Volansky, Tomer

    2004-01-01

    We revisit some questions in supersymmetric hybrid inflation (SHI). We analyze the amount of fine tuning required in various models, the problem of decay at the end of inflation and the generation of baryons after inflation. We find that the most natural setting for HI is in supersymmetric models with non-renormalizable couplings. Furthermore, we argue that almost inevitably, one of the fields involved is a modulus, with Planck scale variation. The resulting moduli problem can be solved in two ways: either by a massive modulus (which requires some fine tuning), or an enhanced symmetry point, in which the moduli becomes strongly coupled to the Standard Model. Various possibilities for baryon production are discussed.

  13. More Dual Fluxes and Moduli Fixing

    CERN Document Server

    Aldazabal, G; Font, A; Ibáñez, L E

    2006-01-01

    We generalize the recent proposal that invariance under T-duality leads to additional non-geometric fluxes required so that superpotentials in type IIA and type IIB orientifolds match. We show that invariance under type IIB S-duality requires the introduction of a new set of fluxes leading to further superpotential terms. We find new classes of N=1 supersymmetric Minkowski vacua based on type IIB toroidal orientifolds in which not only dilaton and complex moduli but also Kahler moduli are fixed. The chains of dualities relating type II orientifolds to heterotic and M-theory compactifications suggests the existence of yet further flux degrees of freedom. Restricting to a particular type IIA/IIB or heterotic compactification only some of these degrees of freedom have a simple perturbative and/or geometric interpretation.

  14. Moduli Stabilization in Heterotic $M$-theory

    OpenAIRE

    Choi, Kiwoon; Kim, Hang Bae; Kim, Hyungdo

    1998-01-01

    We examine the stabilization of the two typical moduli, the length $\\rho$ of the eleventh segment and the volume $V$ of the internal six manifold, in compactified heterotic $M$-theory. It is shown that, under certain conditions, the phenomenologically favored vacuum expectation values of $\\rho$ and $V$ can be obtained by the combined effects of multi-gaugino condensations on the hidden wall and the membrane instantons wrapping the three cycle of the internal six manifold.

  15. Moduli Stabilisation using World-sheet Techniques

    International Nuclear Information System (INIS)

    Gepner models provide algebraic constructions of string backgrounds where the compact part of the manifold is represented by internal conformal field theories carrying the correct central charge. We use these ideas to construct cosmological toy models that provide a way for freezing the string moduli. We also look at the effective field theory of the fields in the spectrum and possible ways of inducing inflation. This document is composed of the slides of the presentation. (author)

  16. Braneworld gravity: Influence of the moduli fields

    International Nuclear Information System (INIS)

    We consider the case of a generic braneworld geometry in the presence of one or more moduli fields (e.g., the dilaton) that vary throughout the bulk spacetime. Working in an arbitrary conformal frame, using the generalized junction conditions of gr-qc/0008008 and the Gauss-Codazzi equations, we derive the effective ''induced'' on-brane gravitational equations. As usual in braneworld scenarios, these equations do not form a closed system in that the bulk can exchange both information and stress-energy with the braneworld. We work with an arbitrary number of moduli fields described by an arbitrary sigma model, with arbitrary curvature couplings, arbitrary self interactions, and arbitrary dimension for the bulk. (The braneworld is always codimension one.) Among the novelties we encounter are modifications of the on-brane stress-energy conservation law, anomalous couplings between on-brane gravity and the trace of the on-brane stress-energy tensor, and additional possibilities for modifying the on-brane effective cosmological constant. After obtaining the general stress-energy ''conservation'' law and the ''induced Einstein equations'' we particularize the discussion to two particularly attractive cases: for a (n-2)-brane in ([n-1]+1) dimensions we discuss both the effect of (1) generic variable moduli fields in the Einstein frame, and (2) the effect of a varying dilaton in the string frame. (author)

  17. BCFT moduli space in level truncation

    Science.gov (United States)

    Kudrna, Matěj; Maccaferri, Carlo

    2016-04-01

    We propose a new non-perturbative method to search for marginal deformations in level truncated open string field theory. Instead of studying the flatness of the effective potential for the marginal field (which is not expected to give a one-to-one parametrization of the BCFT moduli space), we identify a new non-universal branch of the tachyon potential which, from known analytic examples, is expected to parametrize the marginal flow in a much larger region of the BCFT moduli space. By a level 18 computation in Siegel gauge we find an increasingly flat effective potential in the non-universal sector, connected to the perturbative vacuum and we confirm that the coefficient of the marginal field ( λ SFT) has a maximum compatible with the value where the solutions stop existing in the standard Sen-Zwiebach approach. At the maximal reachable level the effective potential still deviates from flatness for large values of the tachyon, but the Ellwood invariants stay close to the correct BCFT values on the whole branch and the full periodic moduli space of the cosine deformation is covered.

  18. Supersymmetric moduli stabilization and high-scale inflation

    International Nuclear Information System (INIS)

    We study the back-reaction of moduli fields on the inflaton potential in generic models of F-term inflation. We derive the moduli corrections as a power series in the ratio of Hubble scale and modulus mass. The general result is illustrated with two examples, hybrid inflation and chaotic inflation. We find that in both cases the decoupling of moduli dynamics and inflation requires moduli masses close to the scale of grand unification. For smaller moduli masses the CMB observables are strongly affected.

  19. Supersymmetric moduli stabilization and high-scale inflation

    Directory of Open Access Journals (Sweden)

    Wilfried Buchmuller

    2014-09-01

    Full Text Available We study the back-reaction of moduli fields on the inflaton potential in generic models of F-term inflation. We derive the moduli corrections as a power series in the ratio of Hubble scale and modulus mass. The general result is illustrated with two examples, hybrid inflation and chaotic inflation. We find that in both cases the decoupling of moduli dynamics and inflation requires moduli masses close to the scale of grand unification. For smaller moduli masses the CMB observables are strongly affected.

  20. Note on moduli stabilization, supersymmetry breaking and axiverse

    International Nuclear Information System (INIS)

    We study properties of moduli stabilization in the four dimensional N=1 supergravity theory with heavy moduli and would-be saxion-axion multiplets including light string-theoretic axions. We give general formulation for the scenario that heavy moduli and saxions are stabilized while axions remain light, assuming that moduli are stabilized near the supersymmetric solution. One can find stable vacuum, i.e. nontachyonic saxions, in the non-supersymmetric Minkowski vacua. We also discuss the cases, where the moduli are coupled to the supersymmetry breaking sector and/or moduli have contributions to supersymmetry breaking. Furthermore we study the models with axions originating from matter-like fields. Our analysis on moduli stabilization is applicable even if there are not light axion multiplets. (orig.)

  1. Note on moduli stabilization, supersymmetry breaking and axiverse

    Energy Technology Data Exchange (ETDEWEB)

    Higaki, Tetsutaro [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics

    2011-06-15

    We study properties of moduli stabilization in the four dimensional N=1 supergravity theory with heavy moduli and would-be saxion-axion multiplets including light string-theoretic axions. We give general formulation for the scenario that heavy moduli and saxions are stabilized while axions remain light, assuming that moduli are stabilized near the supersymmetric solution. One can find stable vacuum, i.e. nontachyonic saxions, in the non-supersymmetric Minkowski vacua. We also discuss the cases, where the moduli are coupled to the supersymmetry breaking sector and/or moduli have contributions to supersymmetry breaking. Furthermore we study the models with axions originating from matter-like fields. Our analysis on moduli stabilization is applicable even if there are not light axion multiplets. (orig.)

  2. Effective elastic moduli and interface effects of nano- crystalline materials

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Many properties of nanocrystalline materials are associated with interface effects. Based on their microstructural features, the influence of interfaces on the effective elastic property of nanocrystalline materials is investigated. First, the Mori-Tanaka method is employed to determine the overall effective elastic moduli by considering a nanocrystalline material as a binary composite solid consisting of a crystal or inclusion phase with regular lattice connected by an amorphous-like interface or matrix phase. The effects of strain gradients are then examined on the effective elastic property by using the strain gradient theory to analyze a representative unit cell. Two interface mechanisms are elucidated that influence the effective stiffness and other mechanical properties of materials. One is the softening effect due to the distorted atomic structures and the increased atomic spacings in interface regions, and the other is the baffling effect due to the existence of boundary layers near interfaces.

  3. Fast Overflow Detection in Moduli Set

    Directory of Open Access Journals (Sweden)

    Mehrin Rouhifar

    2011-05-01

    Full Text Available The Residue Number System (RNS is a non weighted system. It supports parallel, high speed, low power and secure arithmetic. Detecting overflow in RNS systems is very important, because if overflow is not detected properly, an incorrect result may be considered as a correct answer. The previously proposed methods or algorithms for detecting overflow need to residue comparison or complete convert of numbers from RNS to binary. We propose a new and fast overflow detection approach for moduli set {2n-1, 2n, 2n+1}, which it is different from previous methods. Our technique implements RNS overflow detection much faster applying a few more hardware than previous methods.

  4. Arithmetic fundamental groups and moduli of curves

    International Nuclear Information System (INIS)

    This is a short note on the algebraic (or sometimes called arithmetic) fundamental groups of an algebraic variety, which connects classical fundamental groups with Galois groups of fields. A large part of this note describes the algebraic fundamental groups in a concrete manner. This note gives only a sketch of the fundamental groups of the algebraic stack of moduli of curves. Some application to a purely topological statement, i.e., an obstruction to the subjectivity of Johnson homomorphisms in the mapping class groups, which comes from Galois group of Q, is explained. (author)

  5. Isomorphism of Compactifications of Vector Bundles Moduli: Nonreduced Moduli

    Directory of Open Access Journals (Sweden)

    N. V. Timofeeva

    2015-12-01

    Full Text Available We continue the study of the compactification of the moduli scheme for Gieseker-semistable vector bundles on a nonsingular irreducible projective algebraic surface S with polarization L, by locally free sheaves. The relation of main components of the moduli functor or admissible semistable pairs and main components of the Gieseker – Maruyama moduli functor (for semistable torsion-free coherent sheaves with the same Hilbert polynomial on the surface S is investigated. The compactification of interest arises when families of Gieseker-semistable vector bundles E on the nonsingular polarized projective surface (S, L are completed by vector bundles E on projective polarized schemes (S, L of special form. The form of the scheme S, of its polarization L and of the vector bundle E is described in the text. The collection ((S, L, E is called a semistable admissible pair. Vector bundles E on the surface (S, L and E on schemes (S, L are supposed to have equal ranks and Hilbert polynomials which are compute with respect to polarizations L and L, respectively. Pairs of the form ((S, L, E named as S-pairs are also included into the class under the scope. Since the purpose is to study the compactification of moduli space for vector bundles, only families which contain S-pairs are considered. We build up the natural transformation of the moduli functor for admissible semistable pairs to the Gieseker – Maruyama moduli functor for semistable torsion-free coherent sheaves on the surface (S, L, with same rank and Hilbert polynomial. It is demonstrated that this natural transformation is inverse to the natural transformation built in the preceding paper and defined by the standard resolution of a family of torsion-free coherent sheaves with a possibly nonreduced base scheme. The functorial isomorphism constructed determines the scheme isomorphism of compactifications of moduli space for semistable vector bundles on the surface (S, L.

  6. BCFT moduli space in level truncation

    CERN Document Server

    Kudrna, Matej

    2016-01-01

    We propose a new non-perturbative method to search for marginal deformations in level truncated open string field theory. Instead of studying the flatness of the effective potential for the marginal field (which is not expected to give a one-to-one parametrization of the BCFT moduli space), we identify a new non-universal branch of the tachyon potential which, from known analytic examples, is expected to parametrize the marginal flow in a much larger region of the BCFT moduli space. By a level 18 computation in Siegel gauge, we find an increasingly flat effective potential in the non-universal sector, connected to the perturbative vacuum and we confirm that the coefficient of the marginal field (lambda_SFT) has a maximum compatible with the value where the solutions stop existing in the standard Sen-Zwiebach approach. At the maximal reachable level, the effective potential still deviates from flatness for large values of the tachyon, but the Ellwood invariants stay close to the correct BCFT values on the whol...

  7. Explicitly Broken Supersymmetry with Exactly Massless Moduli

    CERN Document Server

    Dong, Xi; Zhao, Yue

    2014-01-01

    There is an avatar of the little hierarchy problem of the MSSM in 3-dimensional supersymmetry. We propose a solution to this problem in AdS$_3$ based on the AdS/CFT correspondence. The bulk theory is a supergravity theory in which U(1) $\\times$ U(1) R-symmetry is gauged by Chern-Simons fields. The bulk theory is deformed by a boundary term quadratic in the gauge fields. It breaks SUSY completely and sources an exactly marginal operator in the dual CFT. SUSY breaking is communicated by gauge interactions to bulk scalar fields and their spinor superpartners. Since the R-charges of scalar and spinor differ, this generates a SUSY breaking shift of their masses. The Ward identity facilitates the calculation of these mass shifts to any desired order in the strength of the deformation. Moduli fields are massless $R$-neutral bulk scalars with vanishing potential in the undeformed theory. These properties are maintained to all orders in the deformation despite the fact that moduli couple in the bulk to loops of R-char...

  8. Cosmological Evolution of Brane World Moduli

    CERN Document Server

    Brax, P; Davis, A C; Rhodes, C S; Brax, Ph.

    2003-01-01

    We study cosmological consequences of non-constant brane world moduli in five dimensional brane world models with bulk scalars and two boundary branes. We focus on the case where the brane tension is an exponential function of the bulk scalar field, $U_b \\propto \\exp{(\\alpha \\phi)}$. In the limit $\\alpha \\to 0$, the model reduces to the two-brane model of Randall-Sundrum, whereas larger values of $\\alpha$ allow for a less warped bulk geometry. Using the moduli space approximation we derive the four-dimensional low-energy effective action from a supergravity-inspired five-dimensional theory. For arbitrary values of $\\alpha$, the resulting theory has the form of a bi-scalar-tensor theory. We show that, in order to be consistent with local gravitational observations, $\\alpha$ has to be small (less than $10^{-2}$) and the separation of the branes must be large. We study the cosmological evolution of the interbrane distance and the bulk scalar field for different matter contents on each branes. Our findings indica...

  9. Moduli of double EPW-sextics

    CERN Document Server

    O'Grady, Kieran G

    2011-01-01

    We study the GIT quotient of the symplectic grassmannian parametrizing lagrangian subspaces of \\bigwedge^3{\\mathbb C}^6 by the natural action of SL_6, call it M. This is a compactification of the moduli space of smooth double EPW-sextics: there are strong analogies with the moduli space of cubic 4-folds. We determine the stable points, the irreducible components of the GIT boundary and their dimensions. Our final goal is to understand the period map from M to the Baily-Borel compactification of the relevant period domain modulo an arithmetic group. With this motivation in mind we prove a result which is analogous to a theorem of Laza on cubic 4-folds with simple singularities namely stability of lagrangians whose associated period point lands in the interior of the Baily-Borel compactification. We also analyze the locus in the GIT-boundary of M where the period map is not regular (presumably the indeterminacy locus is contained in the GIT boundary). It turns out to have two irreducible components, one of dime...

  10. Permutation combinatorics of worldsheet moduli space

    Science.gov (United States)

    Freidel, Laurent; Garner, David; Ramgoolam, Sanjaye

    2015-06-01

    Light-cone string diagrams have been used to reproduce the orbifold Euler characteristic of moduli spaces of punctured Riemann surfaces at low genus and with few punctures. Nakamura studied the meromorphic differential introduced by Giddings and Wolpert to characterize light-cone diagrams and introduced a class of graphs related to this differential. These Nakamura graphs were used to parametrize the cells in a light-cone cell decomposition of moduli space. We develop links between Nakamura graphs and realizations of the worldsheet as branched covers. This leads to a development of the combinatorics of Nakamura graphs in terms of permutation tuples. For certain classes of cells, including those of the top dimension, there is a simple relation to Belyi maps, which allows us to use results from Hermitian and complex matrix models to give analytic formulas for the counting of cells at an arbitrarily high genus. For the most general cells, we develop a new equivalence relation on Hurwitz classes which organizes the cells and allows efficient enumeration of Nakamura graphs using the group theory software gap.

  11. Moduli stabilization and the pattern of sparticle spectra

    CERN Document Server

    Choi, Kiwoon

    2008-01-01

    We discuss the pattern of low energy sparticle spectra which appears in some class of moduli stabilization scenario. In case that light moduli are stabilized by non-perturbative effects encoded in the superpotential and a phenomenologically viable de Sitter vacuum is obtained by a sequestered supersymmetry breaking sector, the anomaly-mediated soft terms become comparable to the moduli-mediated ones, leading to a quite distinctive pattern of low energy spacticle masses dubbed the mirage mediation pattern. We also discuss low energy sparticle masses in more general mixed-mediation scenario which includes a comparable size of gauge mediation in addition to the moduli and anomaly mediations.

  12. On the moduli space of semilocal strings and lumps

    OpenAIRE

    Eto, Minoru; Evslin, Jarah; Konishi, Kenichi; Marmorini, Giacomo; Nitta, Muneto; Ohashi, Keisuke; Vinci, Walter; Yokoi, Naoto

    2007-01-01

    We study BPS non-abelian semilocal vortices in U(Nc) gauge theory with Nf flavors, Nf > Nc, in the Higgs phase. The moduli space for arbitrary winding number is described using the moduli matrix formalism. We find a relation between the moduli spaces of the semilocal vortices in a Seiberg-like dual pairs of theories, U(Nc) and U(Nf-Nc). They are two alternative regularizations of a "parent" non-Hausdorff space, which tend to the same moduli space of sigma-model lumps in the infinite gauge cou...

  13. On moduli spaces in AdS{sub 4} supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Alwis, Senarath de [Colorado Univ., Boulder, CO (United States). Dept. of Physics; Louis, Jan [Hamburg Univ. (Germany). Fachbereich 12 - Physik; Hamburg Univ. (Germany). Zentrum fuer Mathematische Physik; McAllister, Liam [Cornell Univ., Ithaca, NY (United States). Dept. of Physics; Triendl, Hagen [CERN, Geneva (Switzerland). Theory Division, Physics Dept.; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie

    2013-12-15

    We study the structure of the supersymmetric moduli spaces of N=1 and N=2 supergravity theories in AdS{sub 4} backgrounds. In the N=1 case, the moduli space cannot be a complex submanifold of the Kaehler field space, but is instead real with respect to the inherited complex structure. In N=2 supergravity the same result holds for the vector multiplet moduli space, while the hypermultiplet moduli space is a Kaehler submanifold of the quaternionic-Kaehler field space. These findings are in agreement with AdS/CFT considerations.

  14. Moduli stabilisation for chiral global models

    Energy Technology Data Exchange (ETDEWEB)

    Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Mayrhofer, Christoph [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Valandro, Roberto [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

    2011-10-15

    We combine moduli stabilisation and (chiral) model building in a fully consistent global set-up in Type IIB/F-theory. We consider compactifications on Calabi-Yau orientifolds which admit an explicit description in terms of toric geometry. We build globally consistent compactifications with tadpole and Freed-Witten anomaly cancellation by choosing appropriate brane set-ups and world-volume fluxes which also give rise to SU(5)- or MSSM-like chiral models. We fix all the Kaehler moduli within the Kaehler cone and the regime of validity of the 4D effective field theory. This is achieved in a way compatible with the local presence of chirality. The hidden sector generating the non-perturbative effects is placed on a del Pezzo divisor that does not have any chiral intersections with any other brane. In general, the vanishing D-term condition implies the shrinking of the rigid divisor supporting the visible sector. However, we avoid this problem by generating rmoduli, that is an hypersurface in a toric ambient space and admits a simple F-theory up-lift. We present explicit choices of brane set-ups and fluxes which lead to three different phenomenological scenarios: the first with GUT-scale strings and TeV-scale SUSY by fine-tuning the background fluxes; the second with an exponentially large value of the volume and TeV-scale SUSY without fine-tuning the background fluxes; and the third with a very anisotropic configuration that leads to TeV-scale strings and two micron-sized extra dimensions. The K3 fibration structure of the Calabi-Yau three-fold is also particularly suitable for cosmological purposes. (orig.)

  15. Dynamical supersymmetry breaking on quantum moduli spaces

    International Nuclear Information System (INIS)

    Supersymmetry breaking by the quantum deformation of a classical moduli space is considered. A simple, non-chiral, renormalizable model is presented to illustrate this mechanism. The well-known, chiral, SU(3) x SU(2) model and its generalizations are shown to break supersymmetry by this mechanism in the limit Λ2>>Λ3. Other supersymmetry breaking models, with classical flat directions that are only lifted quantum mechanically, are presented. Finally, by integrating in vector matter, the strongly coupled region of chiral models with a dynamically generated superpotential is shown to be continuously connected to a weakly coupled description in terms of confined degrees of freedom, with supersymmetry broken at tree level. (orig.)

  16. Compactifications of reductive groups as moduli stacks of bundles

    DEFF Research Database (Denmark)

    Martens, Johan; Thaddeus, Michael

    Let G be a reductive group. We introduce the moduli problem of "bundle chains" parametrizing framed principal G-bundles on chains of lines. Any fan supported in a Weyl chamber determines a stability condition on bundle chains. Its moduli stack provides an equivariant toroidal compactification of ...

  17. Moduli of Flags of Sheaves and their K-theory

    OpenAIRE

    Negut, Andrei

    2012-01-01

    We introduce moduli spaces of flags of sheaves on P^2, and use them to obtain functors between the derived categories of the usual moduli spaces of sheaves on P^2. These functors induce an action of the shuffle algebra on K-theory, by certain explicit formulas.

  18. Description of moduli space of projective structures via fat graphs

    CERN Document Server

    Fock, V V

    1993-01-01

    We give an elementary explicit construction of cell decomposition of the moduli space of projective structures on a two dimensional surface analogous to the decomposition of Penner/Strebel for moduli space of complex structures. The relations between projective structures and $PGL(2,{\\bf C})$ flat connections are also described.

  19. Beauty is attractive: Moduli trapping at enhanced symmetry points

    International Nuclear Information System (INIS)

    We study quantum effects on moduli dynamics arising from the production of particles which are light at special points in moduli space. The resulting forces trap the moduli at these points, which often exhibit enhanced symmetry. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in an expanding universe, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points with the largest number of light particles, which are often the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of light particles and (spontaneously broken) symmetries. In other words, some of the surprising properties of our world might arise not through pure chance or miraculous cancellations, but through a natural selection mechanism during dynamical evolution. (author)

  20. Metastable SUSY breaking, de Sitter moduli stabilisation and Kähler moduli inflation

    Science.gov (United States)

    Krippendorf, Sven; Quevedo, Fernando

    2009-11-01

    We study the influence of anomalous U(1) symmetries and their associated D-terms on the vacuum structure of global field theories once they are coupled to Script N = 1 supergravity and in the context of string compactifications with moduli stabilisation. In particular, we focus on a IIB string motivated construction of the ISS scenario and examine the influence of one additional U(1) symmetry on the vacuum structure. We point out that in the simplest one-Kähler modulus compactification, the original ISS vacuum gets generically destabilised by a runaway behaviour of the potential in the modulus direction. In more general compactifications with several Kähler moduli, we find a novel realisation of the LARGE volume scenario with D-term uplifting to de Sitter space and both D-term and F-term supersymmetry breaking. The structure of soft supersymmetry breaking terms is determined in the preferred scenario where the standard model cycle is not stabilised non-perturbatively and found to be flavour universal. Our scenario also provides a purely supersymmetric realisation of Kähler moduli (blow-up and fibre) inflation, with similar observational properties as the original proposals but without the need to include an extra (non-SUSY) uplifting term.

  1. Stability phenomena in the topology of moduli spaces

    CERN Document Server

    Cohen, Ralph L

    2009-01-01

    The recent proof by Madsen and Weiss of Mumford's conjecture on the stable cohomology of moduli spaces of Riemann surfaces, was a dramatic example of an important stability theorem about the topology of moduli spaces. In this article we give a survey of families of classifying spaces and moduli spaces where "stability phenomena" occur in their topologies. Such stability theorems have been proved in many situations in the history of topology and geometry, and the payoff has often been quite remarkable. In this paper we discuss classical stability theorems such as the Freudenthal suspension theorem, Bott periodicity, and Whitney's embedding theorems. We then discuss more modern examples such as those involving configuration spaces of points in manifolds, holomorphic curves in complex manifolds, gauge theoretic moduli spaces, the stable topology of general linear groups, and pseudoisotopies of manifolds. We then discuss the stability theorems regarding the moduli spaces of Riemann surfaces: Harer's stability the...

  2. On the moduli space of semilocal strings and lumps

    CERN Document Server

    Eto, Minoru; Konishi, Kenichi; Marmorini, Giacomo; Nitta, Muneto; Ohashi, Keisuke; Vinci, Walter; Yokoi, Naoto

    2007-01-01

    We study BPS non-abelian semilocal vortices in U(Nc) gauge theory with Nf flavors, Nf > Nc, in the Higgs phase. The moduli space for arbitrary winding number is described using the moduli matrix formalism. We find a relation between the moduli spaces of the semilocal vortices in a Seiberg-like dual pairs of theories, U(Nc) and U(Nf-Nc). They are two alternative regularizations of a "parent" non-Hausdorff space, which tend to the same moduli space of sigma-model lumps in the infinite gauge coupling limits. We examine the normalizability of the zero-modes and find the somewhat surprising phenomenon that the number of normalizable zero-modes, dynamical fields in the effective action, depends on the point of the moduli space we are considering. We find, in the lump limit, an effective action on the vortex worldsheet, which we compare to that found by Shifman and Yung.

  3. Infinitesimal moduli of G2 holonomy manifolds with instanton bundles

    CERN Document Server

    de la Ossa, Xenia; Svanes, Eirik Eik

    2016-01-01

    We describe the infinitesimal moduli space of pairs $(Y, V)$ where $Y$ is a manifold with $G_2$ holonomy, and $V$ is a vector bundle on $Y$ with an instanton connection. These structures arise in connection to the moduli space of heterotic string compactifications on compact and non-compact seven dimensional spaces, e.g. domain walls. Employing the canonical $G_2$ cohomology $H^*_{{\\check{\\rm d}}_E}(Y,E)$ developed by Reyes-Carri\\'on and Fern\\'andez and Ugarte, we show that the moduli space decomposes into the sum of the bundle moduli $H^1_{{\\check{\\rm d}}_A}(Y,{\\rm End}(V))$ plus the moduli of the $G_2$ structure preserving the instanton condition. The latter piece is contained in $H^1_{{\\check{\\rm d}}_\

  4. Moduli of Riemann surfaces, transcendental aspects

    International Nuclear Information System (INIS)

    These notes are an informal introduction to moduli spaces of compact Riemann surfaces via complex analysis, topology and Hodge Theory. The prerequisites for the first lecture are just basic complex variables, basic Riemann surface theory up to at least the Riemann-Roch formula, and some algebraic topology, especially covering space theory. The first lecture covers moduli in genus 0 and genus 1 as these can be understood using relatively elementary methods, but illustrate many of the points which arise in higher genus. The notes cover more material than was covered in the lectures, and sometimes the order of topics in the notes differs from that in the lectures. We have seen in genus 1 case that M1 is the quotient Γ1/X1 of a contractible complex manifold X1 = H by a discrete group Γ1 = SL2(Z). The action of Γ1 on X1 is said to be virtually free - that is, Γ1 has a finite index subgroup which acts (fixed point) freely on X1. In this section we will generalize this to all g >= 1 - we will sketch a proof that there is a contractible complex manifold Xg, called Teichmueller space, and a group Γg, called the mapping class group, which acts virtually freely on Xg. The moduli space of genus g compact Riemann surfaces is the quotient: Mg = Γg/Xg. This will imply that Mg has the structure of a complex analytic variety with finite quotient singularities. Teichmueller theory is a difficult and technical subject. Because of this, it is only possible to give an overview. In this lecture, we compute the orbifold Picard group of Mg for all g >= 1. Recall that an orbifold line bundle over Mg is a holomorphic line bundle L over Teichmueller space Xg together with an action of the mapping class group Γg on it such that the projection L → Xg is Γg-equivariant. An orbifold section of this line bundle is a holomorphic Γg-equivariant section Xg → L of L. This is easily seen to be equivalent to fixing a level l>= 3 and considering holomorphic line bundles over Mg[l] with an

  5. Higher-Derivative Supergravity and Moduli Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Ciupke, David; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group; Louis, Jan [Hamburg Univ. (Germany). Fachberich Physik; Hamburg Univ. (Germany). Zentrum fuer Mathematische Physik

    2015-05-15

    We review the ghost-free four-derivative terms for chiral superfields in N=1 supersymmetry and supergravity. These terms induce cubic polynomial equations of motion for the chiral auxiliary fields and correct the scalar potential. We discuss the different solutions and argue that only one of them is consistent with the principles of effective field theory. Special attention is paid to the corrections along flat directions which can be stabilized or destabilized by the higher-derivative terms. We then compute these higher-derivative terms explicitly for the type IIB string compactified on a Calabi-Yau orientifold with fluxes via Kaluza-Klein reducing the (α'){sup 3}R{sup 4} corrections in ten dimensions for the respective N=1 Kaehler moduli sector. We prove that together with flux and the known (α'){sup 3}-corrections the higher-derivative term stabilizes all Calabi-Yau manifolds with positive Euler number, provided the sign of the new correction is negative.

  6. Explicitly broken supersymmetry with exactly massless moduli

    Science.gov (United States)

    Dong, Xi; Freedman, Daniel Z.; Zhao, Yue

    2016-06-01

    The AdS/CFT correspondence is applied to an analogue of the little hierarchy problem in three-dimensional supersymmetric theories. The bulk is governed by a super-gravity theory in which a U(1) × U(1) R-symmetry is gauged by Chern-Simons fields. The bulk theory is deformed by a boundary term quadratic in the gauge fields. It breaks SUSY completely and sources an exactly marginal operator in the dual CFT. SUSY breaking is communicated by gauge interactions to bulk scalar fields and their spinor superpartners. The bulk-to-boundary propagator of the Chern-Simons fields is a total derivative with respect to the bulk coordinates. Integration by parts and the Ward identity permit evaluation of SUSY breaking effects to all orders in the strength of the deformation. The R-charges of scalars and spinors differ so large SUSY breaking mass shifts are generated. Masses of R-neutral particles such as scalar moduli are not shifted to any order in the deformation strength, despite the fact that they may couple to R-charged fields running in loops. We also obtain a universal deformation formula for correlation functions under an exactly marginal deformation by a product of holomorphic and anti-holomorphic U(1) currents.

  7. Quiver moduli and small desingularizations of some GIT quotients

    OpenAIRE

    Reineke, Markus

    2015-01-01

    We construct small desingularizations of moduli spaces of semistable quiver representations for indivisible dimension vectors using deformations of stabilites and a dimension estimate for nullcones. We apply this construction to several classes of GIT quotients.

  8. Successfully combining SUGRA hybrid inflation and moduli stabilisation

    Energy Technology Data Exchange (ETDEWEB)

    Davis, S.C. [CEA Centre d' Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique; Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)

    2008-01-15

    Inflation and moduli stabilisation mechanisms work well independently, and many string-motivated supergravitymodels have been proposed for them. However a complete theory will contain both, and there will be (gravitational) interactions between the two sectors. These give corrections to the inflaton potential, which generically ruin inflation. This holds true even for fine-tuned moduli stabilisation schemes. We show that a viable combined model can be obtained if it is the Kaehler functions (G=K+ln vertical stroke W vertical stroke {sup 2}) of the two sectors that are added, rather than the superpotentials (as is usually done). Interaction between the two sectors does still impose some restrictions on the moduli stabilisation mechanism, which are derived. Significantly, we find that the (post-inflation) moduli stabilisation scale no longer needs to be above the inflationary energy scale. (orig.)

  9. Challenges for Large-Field Inflation and Moduli Stabilization

    CERN Document Server

    Buchmuller, Wilfried; Heurtier, Lucien; Westphal, Alexander; Wieck, Clemens; Winkler, Martin Wolfgang

    2015-01-01

    We analyze the interplay between K\\"ahler moduli stabilization and chaotic inflation in supergravity. While heavy moduli decouple from inflation in the supersymmetric limit, supersymmetry breaking generically introduces non-decoupling effects. These lead to inflation driven by a soft mass term, $m_\\varphi^2 \\sim m m_{3/2}$, where $m$ is a supersymmetric mass parameter. This scenario needs no stabilizer field, but the stability of moduli during inflation imposes a large supersymmetry breaking scale, $m_{3/2} \\gg H$, and a careful choice of initial conditions. This is illustrated in three prominent examples of moduli stabilization: KKLT stabilization, K\\"ahler Uplifting, and the Large Volume Scenario. Remarkably, all models have a universal effective inflaton potential which is flattened compared to quadratic inflation. Hence, they share universal predictions for the CMB observables, in particular a lower bound on the tensor-to-scalar ratio, $r \\gtrsim 0.05$.

  10. Aspects of Moduli Stabilization in Type IIB String Theory

    Directory of Open Access Journals (Sweden)

    Shaaban Khalil

    2016-01-01

    Full Text Available We review moduli stabilization in type IIB string theory compactification with fluxes. We focus on KKLT and Large Volume Scenario (LVS. We show that the predicted soft SUSY breaking terms in KKLT model are not phenomenological viable. In LVS, the following result for scalar mass, gaugino mass, and trilinear term is obtained: m0=m1/2=-A0=m3/2, which may account for Higgs mass limit if m3/2~O(1.5 TeV. However, in this case, the relic abundance of the lightest neutralino cannot be consistent with the measured limits. We also study the cosmological consequences of moduli stabilization in both models. In particular, the associated inflation models such as racetrack inflation and Kähler inflation are analyzed. Finally, the problem of moduli destabilization and the effect of string moduli backreaction on the inflation models are discussed.

  11. Metastable SUSY Breaking, de Sitter Moduli Stabilisation and Kähler Moduli Inflation

    CERN Document Server

    Krippendorf, Sven

    2009-01-01

    We study the influence of anomalous U(1) symmetries and their associated D-terms on the vacuum structure of global field theories once they are coupled to N=1 supergravity and in the context of string compactifications with moduli stabilisation. In particular, we focus on a IIB string motivated construction of the ISS scenario and examine the influence of one additional U(1) symmetry on the vacuum structure. We point out that in the simplest one-Kahler modulus compactification, the original ISS vacuum gets generically destabilised by a runaway behaviour of the potential in the modulus direction. In more general compactifications with several Kahler moduli, we find a novel realisation of the LARGE volume scenario with D-term uplifting to de Sitter space and both D-term and F-term supersymmetry breaking. The structure of soft supersymmetry breaking terms is determined in the preferred scenario where the standard model cycle is not stabilised non-perturbatively and found to be flavour universal. Our scenario als...

  12. Lectures on perverse sheaves on instanton moduli spaces

    CERN Document Server

    Nakajima, Hiraku

    2016-01-01

    I will explain my joint paper `Instantons moduli spaces and W-algebras' with A.Braverman, M.Finkelberg, arXiv:1406.2381. I will concentrate on the geometric part, that is a study of perverse sheaves on instanton moduli spaces. I place a particular emphasize on the hyperbolic restriction functor and stable envelop, which are our key tools, and appear also in other situations in geometric representation theory. These are lecture notes for a course in 2015 PCMI.

  13. On stress-dependent elastic moduli and wave speeds

    OpenAIRE

    Destrade, Michel; Ogden, Ray W.

    2013-01-01

    On the basis of the general nonlinear theory of a hyperelastic material with initial stress, initially without consideration of the origin of the initial stress, we determine explicit expressions for the stress-dependent tensor of incremental elastic moduli. In considering three special cases of initial stress within the general framework, namely hydrostatic stress, uniaxial stress and planar shear stress, we then elucidate in general form the dependence of various elastic moduli on the initi...

  14. N=2 Heterotic-Type II duality and bundle moduli

    CERN Document Server

    Alexandrov, Sergei; Pioline, Boris; Valandro, Roberto

    2014-01-01

    Heterotic string compactifications on a $K3$ surface $\\mathfrak{S}$ depend on a choice of hyperk\\"ahler metric, anti-self-dual gauge connection and Kalb-Ramond flux, parametrized by hypermultiplet scalars. The metric on hypermultiplet moduli space is in principle computable within the $(0,2)$ superconformal field theory on the heterotic string worldsheet, although little is known about it in practice. Using duality with type II strings compactified on a Calabi-Yau threefold, we predict the form of the quaternion-K\\"ahler metric on hypermultiplet moduli space when $\\mathfrak{S}$ is elliptically fibered, in the limit of a large fiber and even larger base. The result is in general agreement with expectations from Kaluza-Klein reduction, in particular the metric has a two-stage fibration structure, where the $B$-field moduli are fibered over bundle and metric moduli, while bundle moduli are themselves fibered over metric moduli. A more precise match must await a detailed analysis of $R^2$-corrected ten-dimensiona...

  15. K\\"{a}hler moduli inflation and WMAP7

    CERN Document Server

    Lee, Sunggeun

    2010-01-01

    Inflationary potentials are investigated for specific models in type IIB string theory via flux compactification. As concrete models, we investigate several cases where the internal spaces are weighted projective spaces. The models we consider have two, three, or four K\\"{a}hler moduli. The K\\"{a}hler moduli play a role of inflaton fields and we consider the cases where only one of the moduli behaves as the inflaton field. For the cases with more than two moduli, we choose the diagonal basis for the expression of the Calabi-Yau volume, which can be written down as a function of four-cycle. With the combination of multiple moduli, we can express the multi-dimensional problem as an effective one-dimensional problem. In the large volume scenario, the potentials of these three models turn out to be of the same type. By taking the specific limit of the relation between the moduli and the volume, the potentials are reduced to simpler ones which induce inflation. As a toy model we first consider the simple potential...

  16. Phenomenology of twisted moduli in type I string inspired models

    International Nuclear Information System (INIS)

    We make a first study of the phenomenological implications of twisted moduli in type I intersecting D5-brane models, focussing on the resulting predictions at the LHC using SOFTSUSY to estimate the Higgs and sparticle spectra. Twisted moduli can play an important role in giving a viable string realisation of sequestering in the limit where supersymmetry breaking comes entirely from the twisted moduli. We focus on a particular string inspired version of gaugino mediation in which the first two families are localised at the intersection between D5-branes, whereas the third family and Higgs doublets are allowed to move within the world-volume of one of the branes. The soft supersymmetry breaking third family sfermion mass terms are then in general non-degenerate with the first two families. We place constraints upon parameter space and predictions of flavour changing neutral current effects. Twisted moduli domination is studied and, as well as solving the most serious part of the SUSY flavour problem, is shown to be highly constrained. The constraints are weakened by switching on gravity-mediated contributions from the dilaton and untwisted T-moduli sectors. In the twisted moduli domination limit we predict a stop-heavy MSSM spectrum and quasi-degenerate lightest neutralino and chargino states with wino-dominated mass eigenstates. (author)

  17. Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

    Science.gov (United States)

    Hassanzadegan, Alireza; Guérizec, Romain; Reinsch, Thomas; Blöcher, Guido; Zimmermann, Günter; Milsch, Harald

    2016-06-01

    The static and poroelastic moduli of a porous rock, e.g., the drained bulk modulus, can be derived from stress-strain curves in rock mechanical tests, and the dynamic moduli, e.g., dynamic Poisson's ratio, can be determined by acoustic velocity and bulk density measurements. As static and dynamic elastic moduli are different, a correlation is often required to populate geomechanical models. A novel poroelastic approach is introduced to correlate static and dynamic bulk moduli of outcrop analogues samples, representative of Upper-Malm reservoir rock in the Molasse basin, southwestern Germany. Drained and unjacketed poroelastic experiments were performed at two different temperature levels (30 and 60°). For correlating the static and dynamic elastic moduli, a drained acoustic velocity ratio is introduced, corresponding to the drained Poisson's ratio in poroelasticity. The strength of poroelastic coupling, i.e., the product of Biot and Skempton coefficients here, was the key parameter. The value of this parameter decreased with increasing effective pressure by about 56 ~% from 0.51 at 3 MPa to 0.22 at 73 MPa. In contrast, the maximum change in P- and S-wave velocities was only 3 % in this pressure range. This correlation approach can be used in characterizing underground reservoirs, and can be employed to relate seismicity and geomechanics (seismo-mechanics).

  18. Phenomenological implications of moduli-dominant SUSY breaking

    International Nuclear Information System (INIS)

    We study moduli-dominated SUSY breaking within the framework of string models. This type of SUSY breaking in general leads to non-universal soft masses, i.e. soft scalar masses and gaugino masses. Further gauginos are lighter than sfermions. This non-universality has phenomenologicallyimportant implications. We investigate radiative electroweak symmetry breaking in the mass spectrum derived from moduli-dominated SUSY breaking, where the lightest chargino and neutralino are almost gauginos. Moreover, constraints from the branching ratio of b→sγ and the relic abundance of the LSP are also considered. The mass spectrum of moduli-dominated SUSY breaking is favorable to the experimental bound of the b→sγ decay decreasing its branching ratio. We obtain an upper bound for the gravitino mass from the cosmological constraint. (orig.)

  19. Natural inflation and moduli stabilization in heterotic orbifolds

    Energy Technology Data Exchange (ETDEWEB)

    Ruehle, Fabian; Wieck, Clemens

    2015-03-15

    We study moduli stabilization in combination with inflation in heterotic orbifold compactifications in the light of a large Hubble scale and the favored tensor-to-scalar ratio r∼0.05. To account for a trans-Planckian field range we implement aligned natural inflation. Although there is only one universal axion in heterotic constructions, further axions from the geometric moduli can be used for alignment and inflation. We argue that such an alignment is rather generic on orbifolds, since all non-perturbative terms are determined by modular weights of the involved fields and the Dedekind η function. We present two setups inspired by the mini-landscape models of the Z{sub 6-II} orbifold which realize aligned inflation and stabilization of the relevant moduli. One has a supersymmetric vacuum after inflation, while the other includes a gaugino condensate which breaks supersymmetry at a high scale.

  20. Polycrystalline gamma plutonium's elastic moduli versus temperature

    Energy Technology Data Exchange (ETDEWEB)

    Migliori, Albert [Los Alamos National Laboratory; Betts, J [Los Alamos National Laboratory; Trugman, A [Los Alamos National Laboratory; Mielke, C H [Los Alamos National Laboratory; Mitchell, J N [Los Alamos National Laboratory; Ramos, M [Los Alamos National Laboratory; Stroe, I [WORCESTER POLYTECHNIC INSTITUTE

    2009-01-01

    Resonant ultrasound spectroscopy was used to measure the elastic properties of pure polycrystalline {sup 239}Pu in the {gamma} phase. Shear and longitudinal elastic moduli were measured simultaneously and the bulk modulus was computed from them. A smooth, linear, and large decrease of all elastic moduli with increasing temperature was observed. They calculated the Poisson ratio and found that it increases from 0.242 at 519 K to 0.252 at 571 K. These measurements on extremely well characterized pure Pu are in agreement with other reported results where overlap occurs.

  1. Fixing moduli in exact type IIA flux vacua

    International Nuclear Information System (INIS)

    Type IIA flux compactifications with O6-planes have been argued from a four dimensional effective theory point of view to admit stable, moduli free solutions. We discuss in detail the ten dimensional description of such vacua and present exact solutions in the case when the O6-charge is smoothly distributed. In the localised case, the solution is a half-flat, non-Calabi-Yau metric. Finally, using the ten dimensional description we show how all moduli are stabilised and reproduce precisely the results of de Wolfe et al. (author)

  2. Gauge Coupling Constant Unification With Planck Scale Values Of Moduli

    OpenAIRE

    Bailin, D.; A. Love; Sabra, W. A.; Thomas, S.(Rutgers, The State University of New Jersey, Piscataway, USA)

    1996-01-01

    Convergence of the standard model gauge coupling constants to a common value at around $2\\times 10^{16}$ GeV is studied in the context of orbifold theories where the modular symmetry groups for $T$ and $U$ moduli are broken to subgroups of $PSL(2, Z)$. The values of the moduli required for this unification of coupling constants are studied for this case and also for the case where string unification is accompanied by unification to a gauge group larger then $SU(3)\\times SU(2)\\times U(1).$

  3. Gauge coupling constant unification with Planck scale values of moduli

    CERN Document Server

    Bailin, David; Sabra, W A; Thomas, S

    1996-01-01

    Convergence of the standard model gauge coupling constants to a common value at around 2\\times 10^{16} GeV is studied in the context of orbifold theories where the modular symmetry groups for T and U moduli are broken to subgroups of PSL(2, Z). The values of the moduli required for this unification of coupling constants are studied for this case and also for the case where string unification is accompanied by unification to a gauge group larger then SU(3)\\times SU(2)\\times U(1).

  4. Stabilization of moduli in spacetime with nested warping

    CERN Document Server

    Arun, Mathew Thomas

    2016-01-01

    The absence, so far, of any graviton signatures at the LHC imposes severe constraints on the Randall-Sundrum scenario. Although a generalization to higher dimensions with nested warpings has been shown to avoid these constraints, apart from incorporating several other phenomenologically interesting features, moduli stabilization in such models has been an open question. We demonstrate here how both the moduli involved can be stabilized, employing slightly different mechanisms for the two branches of the theory. This also offers a dynamical mechanism to generate and stabilize the UED scale.

  5. Moduli stabilization in chiral type IIB orientifold models with fluxes

    International Nuclear Information System (INIS)

    We consider type IIB orientifold models on Calabi-Yau spaces with three-form G-flux turned on. These fluxes freeze some of the complex structure moduli and the complex dilaton via an F-term scalar potential. By introducing pairs of D9-D9-bar branes with Abelian magnetic fluxes it is possible to freeze also some of the Kaehler moduli via a D-term potential. Moreover, such magnetic fluxes in general lead to chiral fermions, which make them interesting for string model-building. These issues are demonstrated in a simple toy model based on a Z2xZ2' orbifold

  6. The stable moduli space of Riemann surfaces: Mumford's conjecture

    DEFF Research Database (Denmark)

    Madsen, I.; Weiss, Michael

    2007-01-01

    D. Mumford conjectured in "Towards an enumerative geometry of the moduli space of curves" that the rational cohomology of the stable moduli space of Riemann surfaces is a polynomial algebra generated by certain classes $\\kappa_i$ of dimension $2i$. For the purpose of calculating rational cohomology...... loop space led to a stable homotopy version of Mumford's conjecture, stronger than the original. We prove the stronger version, relying on Harer's stability theorem, Vassiliev's theorem concerning spaces of functions with moderate singularities and methods from homotopy theory....

  7. Moduli spaces of punctured Poincar\\'e disks

    CERN Document Server

    Devadoss, Satyan L; Heath, Timothy; Vashist, Aditi

    2011-01-01

    The Tamari lattice and the associahedron provide methods of measuring associativity on a line. The real moduli space of marked curves captures the space of such associativity. We consider a natural generalization by considering the moduli space of marked particles on the Poincar\\'{e} disk, extending Tamari's notion of associativity based on nesting. A geometric and combinatorial construction of this space is provided, which appears in Kontsevich's deformation quantization, Voronov's swiss-cheese operad, and Kajiura and Stasheff's open-closed string theory.

  8. The Geometry and Moduli of K3 Surfaces

    OpenAIRE

    Harder, Andrew; Thompson, Alan

    2015-01-01

    These notes will give an introduction to the theory of K3 surfaces. We begin with some general results on K3 surfaces, including the construction of their moduli space and some of its properties. We then move on to focus on the theory of polarized K3 surfaces, studying their moduli, degenerations and the compactification problem. This theory is then further enhanced to a discussion of lattice polarized K3 surfaces, which provide a rich source of explicit examples, including a large class of l...

  9. Degenerations of the moduli spaces of vector bundles on curves

    International Nuclear Information System (INIS)

    Let Y be a smooth projective curve of genus g and UY = UY (n; d) the moduli space of (semi-stable) vector bundles on Y of rank n and degree d. One strategy for studying the variety UY in depth is by the method of degeneration (or specialization), namely one specializes Y to a curve X0, say with only one singularity which is an ordinary double point. One would have a moduli object UX0 on X0 such that UY specializes to UX0 and one expects a close relationship between UX0 and the moduli space UX on the normalisation X of X0. Since the genus of X is (g-1), one would then obtain a machinery for studying UY , especially its properties which are amenable to specialization, by induction on g. This strategy was employed by Gieseker to prove a conjecture of Newstead and Ramanan for moduli spaces in rank 2, namely that the Chern classes ci of the smooth projective variety UY (2; 1) vanish for i > 1/2 dimUY (2; 1), i.e. i >= (2g - 1), since dimUY (2; 1) = (4g - 3). A similar one was employed by M.S. Narasimhan and T.R. Ramadas to prove what is called the factorisation rule in the rank two case and recently it has been generalized to arbitrary rank by Xiaotao Sun. Gieseker constructed a moduli object GX0 on X0 (we do not denote this by UX0 since this will stand for a moduli space of torsion free sheaves on X0) such that it has nice singularities and UY (2; 1) specializes to GX0 . Further, he gave a concrete realization of GX0 via the moduli space UX(2; 1), which helps in solving the conjecture of Newstead and Ramanan by induction on the genus. Recently, in collaboration with D.S. Nagaraj, we have been able to generalize Gieseker's construction of GX0 for arbitrary rank. A good part of these lectures is devoted to outlining this construction. Our method for the global construction is quite different from that of Gieseker; it consists in relating the Gieseker moduli space to that of torsion free sheaves on X0, an aspect which does not figure in Gieseker's work. We give also a

  10. Moduli Vacuum Misalignment and Precise Predictions in String Inflation

    CERN Document Server

    Cicoli, Michele; Maharana, Anshuman; Quevedo, Fernando

    2016-01-01

    The predictions for all the cosmological observables of any inflationary model depend on the number of e-foldings which is sensitive to the post-inflationary history of the universe. In string models the generic presence of light moduli leads to a late-time period of matter domination which lowers the required number of e-foldings and, in turn, modifies the exact predictions of any inflationary model. In this paper we compute exactly the shift of the number of e-foldings in Kaehler moduli inflation which is determined by the magnitude of the moduli initial displacement caused by vacuum misalignment and the moduli decay rates. We find that the preferred number of e-foldings gets reduced from 50 to 45, causing a modification of the spectral index at the percent level. Our results illustrate the importance of understanding the full post-inflationary evolution of the universe in order to derive precise predictions in string inflation. To perform this task it is crucial to work in a setting where there is good con...

  11. The Moduli Space in the Gauged Linear Sigma Model

    CERN Document Server

    Fan, Huijun; Ruan, Yongbin

    2016-01-01

    This is a survey article for the mathematical theory of Witten's Gauged Linear Sigma Model, as developed recently by the authors. Instead of developing the theory in the most general setting, in this paper we focus on the description of the moduli.

  12. Bounds on Scalar Masses in Theories of Moduli Stabilization

    CERN Document Server

    Acharya, Bobby Samir; Kuflik, Eric

    2014-01-01

    In recent years it has been realised that pre-BBN decays of moduli can be a significant source of dark matter production, giving a `non-thermal WIMP miracle' and substantially reduced fine-tuning in cosmological axion physics. We study moduli masses and sharpen the claim that moduli dominated the pre-BBN Universe. We conjecture that in any string theory with stabilized moduli there will be at least one modulus field whose mass is of order (or less than) the gravitino mass and we prove this for a large class of models based on Calabi-Yau extra dimensions. Cosmology then generically requires the gravitino mass not be less than about 30 TeV and the cosmological history of the Universe is non-thermal prior to BBN. Stable LSP's produced in these decays can account for the observed dark matter if they are `wino-like,' which is consistent with the PAMELA data for positrons and antiprotons. With WIMP dark matter, there is an upper limit on the gravitino mass of order 250 TeV. We briefly consider implications for the ...

  13. Quantum cohomology of moduli spaces of genus zero stable curves

    OpenAIRE

    Fontanari, Claudio

    2007-01-01

    We investigate the (small) quantum cohomology ring of the moduli spaces of stable n-pointed curves of genus 0. In particular, we determine an explicit presentation in the case n=5 and we outline a computational approach to the case n=6.

  14. Bohr--Sommerfeld Lagrangians of moduli spaces of Higgs bundles

    DEFF Research Database (Denmark)

    Biswas, Indranil; Gammelgaard, Niels Leth; Logares, Marina

    Let $X$ be a compact connected Riemann surface of genus at least two. Let $M_H(r,d)$ denote the moduli space of semistable Higgs bundles on $X$ of rank $r$ and degree $d$. We prove that the compact complex Bohr-Sommerfeld Lagrangians of $M_H(r,d)$ are precisely the irreducible components of the n...

  15. The boundary of the moduli space of stable cubic fivefolds

    OpenAIRE

    Shibata, Yasutaka

    2014-01-01

    By GIT theory due to Mumford, the moduli space of stable cubic fivefolds is compactified by adding non stable semi-stable (i.e. strictly semi-stable) locus. In this paper, we prove that this locus consists of 19 components. Moreover, we give a description of equation and singularity of cubic fivefold corresponding to the generic point in each component.

  16. Pressure Dependency of Young's Moduli of Thermal Sprayed Materials

    Czech Academy of Sciences Publication Activity Database

    Kroupa, František; Dubský, Jiří

    1999-01-01

    Roč. 40, - (1999), s. 1249-1254. ISSN 1359-6462 R&D Projects: GA ČR GA106/01/0094 Institutional research plan: CEZ:AV0Z2043910 Keywords : Young'moduli, thermal sprayed materials Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 0.955, year: 1999

  17. Moduli of Parabolic Higgs Bundles and Atiyah Algebroids

    DEFF Research Database (Denmark)

    Logares, Marina; Martens, Johan

    2010-01-01

    . By considering the case of full flags, we get a Grothendieck–Springer resolution for all other flag types, in particular for the moduli spaces of twisted Higgs bundles, as studied by Markman and Bottacin and used in the recent work of Laumon–Ngô. We discuss the Hitchin system, and demonstrate that...

  18. From Stringy Particle Physics to Moduli Stabilisation and Cosmology

    CERN Document Server

    Honecker, Gabriele

    2015-01-01

    Intersecting D6-branes provide a geometrically intuitive road to stringy particle physics models, where D6-branes stuck at orbifold singularities can lead to the stabilisation of deformation moduli, and the QCD axion can arise from the open string sector in a very constrained way compared to pure field theory. We demonstrate this interplay of different physical features here through an explicit model.

  19. Moduli and (un)attractor black hole thermodynamics

    NARCIS (Netherlands)

    Astefanesei, D.; Goldstein, K.D.; Mahapatra, S.

    2008-01-01

    We investigate four-dimensional spherically symmetric black hole solutions in gravity theories with massless, neutral scalars non-minimally coupled to gauge fields. In the non-extremal case, we explicitly show that, under the variation of the moduli, the scalar charges appear in the first law of bla

  20. The Kontsevich Connection on the Moduli Space of FZZT Liouville

    CERN Document Server

    Giusto, S; Giusto, Stefano; Imbimbo, Camillo

    2005-01-01

    We point out that insertions of matrix fields in (connected amputated) amplitudes of (generalized) Kontsevich models are given by covariant derivatives with respect to the Kontsevich moduli. This implies that correlators are sections of symmetric products of the (holomorphic) tangent bundle on the (complexified) moduli space of FZZT Liouville branes. We discuss the relation of Kontsevich parametrization of moduli space with that provided by either the (p,1) or the (1,p) boundary conformal field theories. It turns out that the Kontsevich connection captures the contribution of contact terms to open string amplitudes of boundary cosmological constant operators in the (1,p) minimal string models. The curvature of the connection is of type (1,1) and has delta-function singularities at the point in moduli space where Kontsevich kinetic term vanishes. We also outline the extention of our formalism to the c=1 string at self-dual radius and discuss the problems that have to be understood to reconciliate first and sec...

  1. Stable Base Locus Decompositions of Kontsevich Moduli Spaces

    OpenAIRE

    Chen, Dawei; Coskun, Izzet

    2009-01-01

    In this paper, we determine the stable base locus decomposition of the Kontsevich moduli spaces of degree two and three stable maps to Grassmannians. This gives new examples of the decomposition for varieties with Picard rank three. We also discuss the birational models that correspond to the chambers in the decomposition.

  2. The global geometry of the moduli space of curves

    OpenAIRE

    Farkas, Gavril

    2006-01-01

    This is a survey written for the Proceedings of the AMS Summer Institute in Algebraic Geometry held in Seattle in 2005. Topics discussed in the survey include the ample and the effective cone of the moduli space of curves, Kodaira dimension, Slope Conjecture, log canonical models etc.

  3. On The Moduli of Surfaces Admitting Genus Two Fibrations Over Elliptic Curves

    OpenAIRE

    Kaya, Gulay

    2006-01-01

    In this paper, we study the structure, deformations and the moduli spaces of complex projective surfaces admitting genus two fibrations over elliptic curves. We observe that, a surface admitting a smooth fibration as above is elliptic and we employ results on the moduli of polarized elliptic surfaces, to construct moduli spaces of these smooth fibrations. In the case of nonsmooth fibrations, we relate the moduli spaces to the Hurwitz schemes ${\\cal H}(1,X(d),n)$ of morphisms of degree $n$ fro...

  4. A flux-scaling scenario for high-scale moduli stabilization in string theory

    OpenAIRE

    Ralph Blumenhagen; Anamaría Font; Michael Fuchs; Daniela Herschmann; Erik Plauschinn; Yuta Sekiguchi; Florian Wolf

    2015-01-01

    Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi-Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms a...

  5. Numerical predictions of viscoelastic properties and dynamic moduli of innovative pothole patching materials

    Science.gov (United States)

    Yuan, K. Y.; Yuan, W.; Ju, J. W.; Yang, J. M.; Kao, W.; Carlson, L.

    2013-04-01

    As asphalt pavements age and deteriorate, recurring pothole repair failures and propagating alligator cracks in the asphalt pavements have become a serious issue to our daily life and resulted in high repairing costs for pavement and vehicles. To solve this urgent issue, pothole repair materials with superior durability and long service life are needed. In the present work, revolutionary pothole patching materials with high toughness, high fatigue resistance that are reinforced with nano-molecular resins have been developed to enhance their resistance to traffic loads and service life of repaired potholes. In particular, DCPD resin (dicyclopentadiene, C10H12) with a Rhuthinium-based catalyst is employed to develop controlled properties that are compatible with aggregates and asphalt binders. In this paper, a multi-level numerical micromechanics-based model is developed to predict the viscoelastic properties and dynamic moduli of these innovative nano-molecular resin reinforced pothole patching materials. Irregular coarse aggregates in the finite element analysis are modeled as randomly-dispersed multi-layers coated particles. The effective properties of asphalt mastic, which consists of fine aggregates, tar, cured DCPD and air voids are theoretically estimated by the homogenization technique of micromechanics in conjunction with the elastic-viscoelastic correspondence principle. Numerical predictions of homogenized viscoelastic properties and dynamic moduli are demonstrated.

  6. Measurements of elastic moduli of silicone gel substrates with a microfluidic device.

    Directory of Open Access Journals (Sweden)

    Edgar Gutierrez

    Full Text Available Thin layers of gels with mechanical properties mimicking animal tissues are widely used to study the rigidity sensing of adherent animal cells and to measure forces applied by cells to their substrate with traction force microscopy. The gels are usually based on polyacrylamide and their elastic modulus is measured with an atomic force microscope (AFM. Here we present a simple microfluidic device that generates high shear stresses in a laminar flow above a gel-coated substrate and apply the device to gels with elastic moduli in a range from 0.4 to 300 kPa that are all prepared by mixing two components of a transparent commercial silicone Sylgard 184. The elastic modulus is measured by tracking beads on the gel surface under a wide-field fluorescence microscope without any other specialized equipment. The measurements have small and simple to estimate errors and their results are confirmed by conventional tensile tests. A master curve is obtained relating the mixing ratios of the two components of Sylgard 184 with the resulting elastic moduli of the gels. The rigidity of the silicone gels is less susceptible to effects from drying, swelling, and aging than polyacrylamide gels and can be easily coated with fluorescent tracer particles and with molecules promoting cellular adhesion. This work can lead to broader use of silicone gels in the cell biology laboratory and to improved repeatability and accuracy of cell traction force microscopy and rigidity sensing experiments.

  7. Measurements of elastic moduli of silicone gel substrates with a microfluidic device.

    Science.gov (United States)

    Gutierrez, Edgar; Groisman, Alex

    2011-01-01

    Thin layers of gels with mechanical properties mimicking animal tissues are widely used to study the rigidity sensing of adherent animal cells and to measure forces applied by cells to their substrate with traction force microscopy. The gels are usually based on polyacrylamide and their elastic modulus is measured with an atomic force microscope (AFM). Here we present a simple microfluidic device that generates high shear stresses in a laminar flow above a gel-coated substrate and apply the device to gels with elastic moduli in a range from 0.4 to 300 kPa that are all prepared by mixing two components of a transparent commercial silicone Sylgard 184. The elastic modulus is measured by tracking beads on the gel surface under a wide-field fluorescence microscope without any other specialized equipment. The measurements have small and simple to estimate errors and their results are confirmed by conventional tensile tests. A master curve is obtained relating the mixing ratios of the two components of Sylgard 184 with the resulting elastic moduli of the gels. The rigidity of the silicone gels is less susceptible to effects from drying, swelling, and aging than polyacrylamide gels and can be easily coated with fluorescent tracer particles and with molecules promoting cellular adhesion. This work can lead to broader use of silicone gels in the cell biology laboratory and to improved repeatability and accuracy of cell traction force microscopy and rigidity sensing experiments. PMID:21980487

  8. No-scale D-term inflation with stabilized moduli

    International Nuclear Information System (INIS)

    We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh–Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains stringent bounds on the gravitino mass. A rough estimate yields 105 GeV≲m3/2≲1010 GeV, contrary to naive expectation.

  9. Quantum moduli spaces of N=1 string theories

    International Nuclear Information System (INIS)

    Generically, string models with N=1 supersymmetry are not expected to have moduli beyond perturbation theory; stringy nonperturbative effects as well as low energy field-theoretic phenomena such as gluino condensation will lift any flat directions. In this work, we describe models where some subspace of the moduli space survives nonperturbatively. Discrete R symmetries forbid any inherently stringy effects, and dynamical considerations control the field-theoretic effects. The surviving subspace is a space of high symmetry; the system is attracted to this subspace by a potential which we compute. Models of this type may be useful for considerations of duality and raise troubling cosmological questions about string theory. Our considerations also suggest a mechanism for fixing the expectation value of the dilaton. copyright 1996 The American Physical Society

  10. Quiver Theories for Moduli Spaces of Classical Group Nilpotent Orbits

    CERN Document Server

    Hanany, Amihay

    2016-01-01

    We approach the topic of Classical group nilpotent orbits from the perspective of their moduli spaces, described in terms of Hilbert series and generating functions. We review the established Higgs and Coulomb branch quiver theory constructions for A series nilpotent orbits. We present systematic constructions for BCD series nilpotent orbits on the Higgs branches of quiver theories defined by canonical partitions; this paper collects earlier work into a systematic framework, filling in gaps and providing a complete treatment. We find new Coulomb branch constructions for above minimal nilpotent orbits, including some based upon twisted affine Dynkin diagrams. We also discuss aspects of 3d mirror symmetry between these Higgs and Coulomb branch constructions and explore dualities and other relationships, such as HyperKahler quotients, between quivers. We analyse all Classical group nilpotent orbit moduli spaces up to rank 4 by giving their unrefined Hilbert series and the Highest Weight Generating functions for ...

  11. No-scale D-term inflation with stabilized moduli

    Energy Technology Data Exchange (ETDEWEB)

    Buchmueller, Wilfried; Domcke, Valerie; Wieck, Clemens

    2013-09-15

    We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh- Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains a stringent bound on the gravitino mass. A rough estimate yields m{sub 3/2}>or similar 10{sup 5} GeV, contrary to naive expectation.

  12. Probing the moduli dependence of refined topological amplitudes

    Directory of Open Access Journals (Sweden)

    I. Antoniadis

    2015-12-01

    Full Text Available With the aim of providing a worldsheet description of the refined topological string, we continue the study of a particular class of higher derivative couplings Fg,n in the type II string effective action compactified on a Calabi–Yau threefold. We analyse first order differential equations in the anti-holomorphic moduli of the theory, which relate the Fg,n to other component couplings. From the point of view of the topological theory, these equations describe the contribution of non-physical states to twisted correlation functions and encode an obstruction for interpreting the Fg,n as the free energy of the refined topological string theory. We investigate possibilities of lifting this obstruction by formulating conditions on the moduli dependence under which the differential equations simplify and take the form of generalised holomorphic anomaly equations. We further test this approach against explicit calculations in the dual heterotic theory.

  13. The Hilbert Series of the One Instanton Moduli Space

    CERN Document Server

    Benvenuti, Sergio; Mekareeya, Noppadol; 10.1007

    2010-01-01

    The moduli space of k G-instantons on R^4 for a classical gauge group G is known to be given by the Higgs branch of a supersymmetric gauge theory that lives on Dp branes probing D(p + 4) branes in Type II theories. For p = 3, these (3 + 1) dimensional gauge theories have N = 2 supersymmetry and can be represented by quiver diagrams. The F and D term equations coincide with the ADHM construction. The Hilbert series of the moduli spaces of one instanton for classical gauge groups is easy to compute and turns out to take a particularly simple form which is previously unknown. This allows for a G invariant character expansion and hence easily generalisable for exceptional gauge groups, where an ADHM construction is not known. The conjectures for exceptional groups are further checked using some new techniques like sewing relations in Hilbert Series. This is applied to Argyres-Seiberg dualities.

  14. Spatial Distributions of Local Elastic Moduli Near the Jamming Transition

    Science.gov (United States)

    Mizuno, Hideyuki; Silbert, Leonardo E.; Sperl, Matthias

    2016-02-01

    Recent progress on studies of the nanoscale mechanical responses in disordered systems has highlighted a strong degree of heterogeneity in the elastic moduli. In this contribution, using computer simulations, we study the elastic heterogeneities in athermal amorphous solids—composed of isotropic static sphere packings—near the jamming transition. We employ techniques based on linear response methods that are amenable to experimentation. We find that the local elastic moduli are randomly distributed in space and are described by Gaussian probability distributions, thereby lacking any significant spatial correlations, that persist all the way down to the transition point. However, the shear modulus fluctuations grow as the jamming threshold is approached, which is characterized by a new power-law scaling. Through this diverging behavior we are able to identify a characteristic length scale, associated with shear modulus heterogeneities, that distinguishes between bulk and local elastic responses.

  15. Von Neuman representations on self-dual Hilbert W* moduli

    International Nuclear Information System (INIS)

    Von Neumann algebras M of bounded operators on self-dual Hilbert W* moduli H possessing a cyclic-separating element x-bar in H are considered. The close relation of them to certain real subspaces of H is established. Under the supposition that the underlying W*-algebra is commutative, a Tomita-Takesaki type theorem is stated. The natural cone in H arising from the pair (M, x-bar) is investigated and its properties are obtained

  16. A Superficial Working Guide to Deformations and Moduli

    OpenAIRE

    Catanese, Fabrizio

    2011-01-01

    This is the first part of a guide to deformations and moduli, especially viewed from the perspective of algebraic surfaces (the simplest higher dimensional varieties). It contains also new results, regarding the question of local homeomorphism between Kuranishi and Teichmueller space, and a survey of new results with Ingrid Bauer, concerning the discrepancy between the deformation of the action of a group G on a minimal models S, respectively the deformation of the action of G on the canonica...

  17. On natural inflation and moduli stabilisation in string theory

    Science.gov (United States)

    Palti, Eran

    2015-10-01

    Natural inflation relies on the existence of an axion decay constant which is super-Planckian. In string theory only sub-Planckian axion decay constants have been found in any controlled regime. However in field theory it is possible to generate an enhanced super-Planckian decay constant by an appropriate aligned mixing between axions with individual sub-Planckian decay constants. We study the possibility of such a mechanism in string theory. In particular we construct a new realisation of an alignment scenario in type IIA string theory compactifications on a Calabi-Yau where the alignment is induced through fluxes. Within field theory the original decay constants are taken to be independent of the parameters which induce the alignment. In string theory however they are moduli dependent quantities and so interact gravitationally with the physics responsible for the mixing. We show that this gravitational effect of the fluxes on the moduli can precisely cancel any enhancement of the effective decay constant. This censorship of an effective super-Planckian decay constant depends on detailed properties of Calabi-Yau moduli spaces and occurs for all the examples and classes that we study. We expand these results to a general superpotential assuming only that the axion superpartners are fixed supersymmetrically and are able to show for a large class of Calabi-Yau manifolds, but not all, that the cancellation effect occurs and is independent of the superpotential. We also study simple models where the moduli are fixed non-supersymmetrically and find that similar cancellation behaviour can emerge. Finally we make some comments on a possible generalisation to axion monodromy inflation models.

  18. Picard Groups of the Moduli Spaces of Semistable Sheaves I

    Indian Academy of Sciences (India)

    Usha N Bhosle

    2004-05-01

    We compute the Picard group of the moduli space ′ of semistable vector bundles of rank and degree on an irreducible nodal curve and show that ′ is locally factorial. We determine the canonical line bundles of ′ and ′L, the subvariety consisting of vector bundles with a fixed determinant. For rank 2, we compute the Picard group of other strata in the compactification of ′.

  19. From stringy particle physics to moduli stabilisation and cosmology

    International Nuclear Information System (INIS)

    Intersecting D6-branes provide a geometrically intuitive road to stringy particle physics models, where D6-branes stuck at orbifold singularities can lead to the stabilisation of deformation moduli, and the QCD axion can arise from the open string sector in a very constrained way compared to pure field theory. We demonstrate this interplay of different physical features here through an explicit model. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Computation of graphene elastic moduli at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zubko, I. Yu., E-mail: zoubko@list.ru; Kochurov, V. I. [Perm National Research Polytechnic University, Perm, 614990 (Russian Federation)

    2015-10-27

    Finding the values of parameters for the simplest Mie’s family potentials is performed in order to estimate elastic moduli of graphene monolayers using lattice statics approach. The coincidence criterion of the experimentally determined Poisson’s ratio with the estimated value is taken in order to select dimensionless power parameters of the Mie-type potential. It allowed obtaining more precise estimation of elastic properties in comparison with variety of other potentials for carbon atoms in graphene monolayer.

  1. Torelli theorem for the Deligne--Hitchin moduli space, II

    CERN Document Server

    Biswas, Indranil; Hoffmann, Norbert

    2012-01-01

    Let X and X' be compact Riemann surfaces of genus at least three. Let G and G' be nontrivial connected semisimple linear algebraic groups over C. If some components $M_{DH}^d(X,G)$ and $M_{DH}^{d'}(X',G')$ of the associated Deligne--Hitchin moduli spaces are biholomorphic, then X' is isomorphic to X or to the conjugate Riemann surface $\\bar{X}$.

  2. Moduli spaces of Dirac operators for finite spectral triples

    CERN Document Server

    Ćaćić, Branimir

    2009-01-01

    The structure theory of finite real spectral triples developed by Krajewski and by Paschke and Sitarz is generalised to allow for arbitrary KO-dimension and the failure of orientability and Poincare duality, and moduli spaces of Dirac operators for such spectral triples are defined and studied. This theory is then applied to recent work by Chamseddine and Connes towards deriving the finite spectral triple of the noncommutative-geometric Standard Model.

  3. Moduli spaces of Dirac operators for finite spectral triples

    OpenAIRE

    Ćaćić, Branimir

    2011-01-01

    The structure theory of finite real spectral triples developed by Krajewski and by Paschke and Sitarz is generalised to allow for arbitrary KO-dimension and the failure of orientability and Poincare duality, and moduli spaces of Dirac operators for such spectral triples are defined and studied. This theory is then applied to recent work by Chamseddine and Connes towards deriving the finite spectral triple of the noncommutative-geometric Standard Model.

  4. Nonlinear N=2 supersymmetry, effective actions and moduli stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Antoniadis, I. [Department of Physics, CERN - Theory Division, CH-1211 Geneva 23 (Switzerland); Centre de Physique Theorique, UMR du CNRS 7644, Ecole Polytechnique, 91128 Palaiseau (France); Derendinger, J.-P. [Physics Institute, Neuchatel University, Breguet 1, CH-2000 Neuchatel (Switzerland); Maillard, T. [Centre de Physique Theorique, UMR du CNRS 7644, Ecole Polytechnique, 91128 Palaiseau (France)], E-mail: maillard@cpht.polytechnique.fr

    2009-02-11

    Nonlinear supersymmetry is used to compute the general form of the effective D-brane action in type I string theory compactified to four dimensions in the presence of internal magnetic fields. In particular, the scalar potential receives three contributions: (1) a nonlinear part of the D-auxiliary component, associated to the Dirac-Born-Infeld action; (2) a Fayet-Iliopoulos (FI) D-term with a moduli-dependent coefficient; (3) a D-auxiliary independent (but moduli dependent) piece from the D-brane tension. Minimization of this potential leads to three general classes of vacua with moduli stabilization: (i) supersymmetric vacua allowing in general FI terms to be cancelled by non-trivial vacuum expectation values (VEV's) of charged scalar fields; (ii) anti-de Sitter vacua of broken supersymmetry in the presence of a non-critical dilaton potential that can be tuned at arbitrarily weak string coupling; (iii) if the dilaton is fixed in a supersymmetric way by three-form fluxes and in the absence of charged scalar VEV's, one obtains non-supersymmetric vacua with positive vacuum energy.

  5. Moduli spaces for point modules on naive blowups

    CERN Document Server

    Nevins, Thomas A

    2010-01-01

    The naive blow-up algebras developed by Keeler-Rogalski-Stafford, after examples of Rogalski, are the first known class of connected graded algebras that are noetherian but not strongly noetherian. This failure of the strong noetherian property is intimately related to the failure of the point modules over such algebras to behave well in families: puzzlingly, there is no fine moduli scheme for such modules, although point modules correspond bijectively with the points of a projective variety X. We give a geometric structure to this bijection and prove that the variety X is a coarse moduli space for point modules. We also describe the natural moduli stack \\tilde{X} for embedded point modules---an analog of a ``Hilbert scheme of one point''---as an infinite blow-up of X and establish good properties of \\tilde{X}. The natural map \\tilde{X} -> X is thus a kind of ``Hilbert-Chow morphism of one point'' for the naive blow-up algebra.

  6. Hilbert Series for Moduli Spaces of Two Instantons

    CERN Document Server

    Hanany, Amihay; Razamat, Shlomo S

    2012-01-01

    The Hilbert Series (HS) of the moduli space of two G instantons on C^2, where G is a simple gauge group, is studied in detail. For a given G, the moduli space is a singular hyperKahler cone with a symmetry group U(2) \\times G, where U(2) is the natural symmetry group of C^2. Holomorphic functions on the moduli space transform in irreducible representations of the symmetry group and hence the Hilbert series admits a character expansion. For cases that G is a classical group (of type A, B, C, or D), there is an ADHM construction which allows us to compute the HS explicitly using a contour integral. For cases that G is of E-type, recent index results allow for an explicit computation of the HS. The character expansion can be expressed as an infinite sum which lives on a Cartesian lattice that is generated by a small number of representations. This structure persists for all G and allows for an explicit expressions of the HS to all simple groups. For cases that G is of type G_2 or F_4, discrete symmetries are eno...

  7. Global structure of moduli space for BPS walls

    International Nuclear Information System (INIS)

    We study the global structure of the moduli space of BPS walls in the Higgs branch of supersymmetric theories with eight supercharges. We examine the structure in the neighborhood of a special Lagrangian submanifold M, and find that the dimension of the moduli space can be larger than that naively suggested by the index theorem, contrary to previous examples of BPS solitons. We investigate BPS wall solutions in an explicit example of M using Abelian gauge theory. Its Higgs branch turns out to contain several special Lagrangian submanifolds including M. We show that the total moduli space of BPS walls is the union of these submanifolds. We also find interesting dynamics between BPS walls as a by-product of the analysis. Namely, mutual repulsion and attraction between BPS walls sometimes forbid a movement of a wall and lock it in a certain position; we also find that a pair of walls can transmute to another pair of walls with different tension after they pass through

  8. Elastic moduli and crosslinking of some tellurite glass systems

    International Nuclear Information System (INIS)

    Tellurite glass systems in the form 80(TeO2)–5(TiO2)–(15 − x)(WO3)–(x)AnOm have been prepared by the melt quenching technique. The AnOm oxide was Nb2O5 or Nd2O3 or Er2O3 and x ≤ 5 mol%. Density and Molar volume have been determined for the prepared glasses. Both longitudinal and shear ultrasonic velocities were measured in different compositions of the glass system by using the pulse-echo method at 5 MHz frequency and at room temperature. Ultrasonic velocity and density data have been used to calculate elastic moduli (longitudinal modulus L, shear modulus G, Young's modulus E, Bulk modulus K), Poisson's ratio σ, and Debye temperature θD. Quantitative analysis of elastic moduli based on the number of bonds per unit volume, average crosslinks and number of vibrating atoms per unit volume has been achieved. - Highlights: • Tellurite glasses. • Elastic moduli, Poisson's ratio, Debye temperature, microhardness. • Number of bonds per unit volume, average crosslinks, number of vibrating atoms per unit volume

  9. Screening corrections to the Coulomb crystal elastic moduli

    CERN Document Server

    Baiko, D A

    2016-01-01

    Corrections to elastic moduli, including the effective shear modulus, of a solid neutron star crust due to electron screening are calculated. At any given mass density, the crust is modelled as a body-centred cubic Coulomb crystal of fully ionized atomic nuclei of a single type with a polarizable charge-compensating electron background. Motion of the nuclei is neglected. The electron polarization is described by a simple Thomas-Fermi model of exponential electron screening. The results of numerical calculations are fitted by convenient analytic formulae. They should be used for precise neutron star oscillation modelling, a rapidly developing branch of stellar seismology.

  10. Aspects of moduli stabilization in type IIB string theory

    OpenAIRE

    Shaaban Khalil; Ahmad Moursy; Ali Nassar

    2015-01-01

    We review moduli stabilization in type IIB string theory compactification with fluxes. We focus on KKLT and Large Volume Scenario (LVS). We show that the predicted soft SUSY breaking terms in KKLT model are not phenomenological viable. In LVS, the following result for scalar mass, gaugino mass, and trilinear term is obtained: m0=m1/2=-A0=m3/2 , which may account for Higgs mass limit if m3/2~O(1.5)  TeV. However, in this case, the relic abundance of the lightest neutralino cannot be consistent...

  11. Sporto prekių internetinis valdymo sistemos diegimo modulis

    OpenAIRE

    Kurilavičius, Artūras

    2008-01-01

    A.Kurilavičius. Sporto prekių internetinis valdymo sistemos diegimo modulis. Savo darbe, bandžiau Jus supažindinti su šių dienų CRM sistemomis. Kaip pateiktieji produktai veikia, kas yra siūloma. Mano tema plėtojosi ties smulkiu ir vidutiniu verslu, o šiuo atveju sporto prekių sfera. Antroje dalyje bandoma įrodyti, kad CRM naudinga ir efektyvi priemonė smulkiajam ir vidutiniam verslui. Pabaigoje, paprasčiausiai parodoma kaip pasinaudoti konkrečiu sporto prekių diegimo moduliu, jį įsidiegti ir...

  12. Electroweak Vacuum Stabilized by Moduli during/after Inflation

    CERN Document Server

    Ema, Yohei; Nakayama, Kazunori

    2016-01-01

    It is known that the present electroweak vacuum is likely to be metastable and it may lead to a serious instability during/after inflation. We propose a simple solution to the problem of vacuum instability during/after inflation. If there is a moduli field which has Planck-suppressed interactions with the standard model fields, the Higgs quartic coupling in the early universe naturally takes a different value from the present one. A slight change of the quartic coupling in the early universe makes the Higgs potential absolutely stable and hence we are free from the vacuum instability during/after inflation.

  13. Veronese geometry and the electroweak vacuum moduli space

    International Nuclear Information System (INIS)

    We explain the origin of the Veronese surface in the vacuum moduli space geometry of the MSSM electroweak sector. While this result appeared many years ago using techniques of computational algebraic geometry, it has never been demonstrated analytically. Here, we present an analytical derivation of the vacuum geometry of the electroweak theory by understanding how the F- and D-term relations lead to the Veronese surface. We moreover give a detailed description of this geometry, realising an extra branch as a zero-dimensional point when quadratic Higgs lifting deformations are incorporated into the superpotential

  14. Veronese geometry and the electroweak vacuum moduli space

    Energy Technology Data Exchange (ETDEWEB)

    He, Yang-Hui, E-mail: hey@maths.ox.ac.uk [Department of Mathematics, City University, London, Northampton Square, London EC1V 0HB (United Kingdom); School of Physics, NanKai University, Tianjin 300071 (China); Merton College, University of Oxford, Oxford OX1 4JD (United Kingdom); Jejjala, Vishnu, E-mail: vishnu@neo.phys.wits.ac.za [Centre for Theoretical Physics, NITheP, and School of Physics, University of the Witwatersrand, Johannesburg, WITS 2050 (South Africa); Matti, Cyril, E-mail: Cyril.Matti.1@city.ac.uk [Department of Mathematics, City University, London, Northampton Square, London EC1V 0HB (United Kingdom); Nelson, Brent D., E-mail: b.nelson@neu.edu [Department of Physics, Northeastern University, Boston, MA 02115 (United States); ICTP, Strada Costiera 11, Trieste 34014 (Italy)

    2014-09-07

    We explain the origin of the Veronese surface in the vacuum moduli space geometry of the MSSM electroweak sector. While this result appeared many years ago using techniques of computational algebraic geometry, it has never been demonstrated analytically. Here, we present an analytical derivation of the vacuum geometry of the electroweak theory by understanding how the F- and D-term relations lead to the Veronese surface. We moreover give a detailed description of this geometry, realising an extra branch as a zero-dimensional point when quadratic Higgs lifting deformations are incorporated into the superpotential.

  15. Non-minimal gauge mediation and moduli stabilization

    International Nuclear Information System (INIS)

    In this Letter we consider U(1)A-gauged Polonyi model with two spurions coupled to a twisted closed string modulus. This offers a consistent setup for metastable SUSY breakdown which allows for moduli stabilization and naturally leads to gauge or hybrid gauge/gravitational mediation mechanism. Due to the presence of the second spurion one can arrange for a solution of the μ and Bμ problems in a version of modified Giudice-Masiero mechanism, which works both in the limit of pure gauge mediation and in the mixed regime of hybrid mediation.

  16. Moduli stabilization and uplifting with dynamically generated F-terms

    CERN Document Server

    Dudas, E; Pokorski, Stefan; Dudas, Emilian; Papineau, Chloe; Pokorski, Stefan

    2007-01-01

    We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector.

  17. Morse functions on the moduli space of $G_2$ structures

    OpenAIRE

    Wang, Sung Ho

    2002-01-01

    Let $ \\mathfrak{M}$ be the moduli space of torsion free $ G_2$ structures on a compact 7-manifold $ M$, and let $ \\mathfrak{M}_1 \\subset \\mathfrak{M}$ be the $ G_2$ structures with volume($M$) $=1$. The cohomology map $ \\pi^3: \\mathfrak{M} \\to H^3(M, R)$ is known to be a local diffeomorphism. It is proved that every nonzero element of $ H^4(M, R) = H^3(M, R)^*$ is a Morse function on $ \\mathfrak{M}_1 $ when composed with $ \\pi^3$. When dim $H^3(M, R) = 2$, the result in particular implies $ \\...

  18. Cohomology of mapping class groups and the abelian moduli space

    DEFF Research Database (Denmark)

    Andersen, Jørgen Ellegaard; Villemoes, Rasmus

    We consider a surface Σ of genus g≥3 , either closed or with exactly one puncture. The mapping class group Γ of Σ acts symplectically on the abelian moduli space M=Hom(π 1 (Σ),U(1))=Hom(H 1 (Σ),U(1)) , and hence both L 2 (M) and C ∞ (M) are modules over Γ . In this paper, we prove that both the c...... cohomology groups H 1 (Γ,L 2 (M)) and H 1 (Γ,C ∞ (M)) vanish....

  19. Homology of the open moduli space of curves

    DEFF Research Database (Denmark)

    Madsen, Ib Henning

    2012-01-01

    This is a survey on the proof of a generalized version of the Mumford conjecture obtained in joint work with M. Weiss stating that a certain map between some classifying spaces which a priori have different natures induces an isomorphism at the level of integral homology. We also discuss our proo...... of the original Mumford conjecture stating that the stable rational cohomology of the moduli space of Riemann surfaces is a certain polynomial algebra generated by the Mumford–Morita–Miller cohomology classes of even degrees....

  20. Roulette Inflation with K\\"ahler Moduli and their Axions

    OpenAIRE

    Bond, J. R.; Kofman, L.; Prokushkin, S.; Vaudrevange, P. M.

    2006-01-01

    We study 2-field inflation models based on the ``large-volume'' flux compactification of type IIB string theory. The role of the inflaton is played by a K\\"ahler modulus \\tau corresponding to a 4-cycle volume and its axionic partner \\theta. The freedom associated with the choice of Calabi Yau manifold and the non-perturbative effects defining the potential V(\\tau, \\theta) and kinetic parameters of the moduli bring an unavoidable statistical element to theory prior probabilities within the low...

  1. Analysis of asphalt pavement structural response from an accelerated loading test

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This study was to compare theoretical calculation and practical measurement structure response of asphalt pavement. Analysis of the pavement layer moduli was determined from a Back-calculation of Falling Weight Deflectometer (FWD) data and the measured stiffness moduli of asphalt layer cores. The pavement response was calculated using a theoretical model and the measured strain response at the bottom different layers.Layered elastic theory was used to back-calculate the layer moduli and three different theory models were used to forward calculate the strain and deflection. The models were: Layered Elastic Theory (LET), the Method of Equivalent Thicknesses (MET) with linear elastic and the Finite Element Method (FEM) where asphalt layer may be viscoelastic. The results showed that the calculation structure response from FEM was consistent with measured results.

  2. On Natural Inflation and Moduli Stabilisation in String Theory

    CERN Document Server

    Palti, Eran

    2015-01-01

    Natural inflation relies on the existence of an axion decay constant which is super-Planckian. In string theory only sub-Planckian axion decay constants have been found in any controlled regime. However in field theory it is possible to generate an enhanced super-Planckian decay constant by an appropriate aligned mixing between axions with individual sub-Planckian decay constants. We study the possibility of such a mechanism in string theory. In particular we construct a new realisation of an alignment scenario in type IIA string theory compactifications on a Calabi-Yau where the alignment is induced through fluxes. Within field theory the original decay constants are taken to be independent of the parameters which induce the alignment. In string theory however they are moduli dependent quantities and so interact gravitationally with the physics responsible for the mixing. We show that this gravitational effect of the fluxes on the moduli can precisely cancel any enhancement of the effective decay constant. T...

  3. Moduli Stabilisation with Nilpotent Goldstino: Vacuum Structure and SUSY Breaking

    CERN Document Server

    Aparicio, Luis; Valandro, Roberto

    2015-01-01

    We study the effective field theory of KKLT and LVS moduli stabilisation scenarios coupled to an anti-D3-brane at the tip of a warped throat. We describe the presence of the anti-brane in terms of a nilpotent goldstino superfield in a supersymmetric effective field theory. The introduction of this superfield produces a term that can lead to a de Sitter minimum. We fix the Kaehler moduli dependence of the nilpotent field couplings by matching this term with the anti-D3-brane uplifting contribution. The main result of this paper is the computation, within this EFT, of the soft supersymmetry breaking terms in both KKLT and LVS for matter living on D3-brane (leaving the D7-brane analysis to an appendix). A handful of distinct phenomenological scenarios emerge that could have low energy implications, most of them having a split spectrum of soft masses. Some cosmological and phenomenological properties of these models are discussed. We also check that the attraction between the D3-brane and the anti-D3-brane does n...

  4. Moduli stabilisation with nilpotent goldstino: vacuum structure and SUSY breaking

    Science.gov (United States)

    Aparicio, Luis; Quevedo, Fernando; Valandro, Roberto

    2016-03-01

    We study the effective field theory of KKLT and LVS moduli stabilisation scenarios coupled to an anti-D3-brane at the tip of a warped throat. We describe the presence of the anti-brane in terms of a nilpotent goldstino superfield in a supersymmetric effective field theory. The introduction of this superfield produces a term that can lead to a de Sitter minimum. We fix the Kähler moduli dependence of the nilpotent field couplings by matching this term with the anti-D3-brane uplifting contribution. The main result of this paper is the computation, within this EFT, of the soft supersymmetry breaking terms in both KKLT and LVS for matter living on D3-brane (leaving the D7-brane analysis to an appendix). A handful of distinct phenomenological scenarios emerge that could have low energy implications, most of them having a split spectrum of soft masses. Some cosmological and phenomenological properties of these models are discussed. We also check that the attraction between the D3-brane and the anti-D3-brane does not affect the leading contribution to the soft masses and does not destabilise the system.

  5. Moduli in General $SU(3)$-Structure Heterotic Compactifications

    CERN Document Server

    Svanes, Eirik Eik

    2014-01-01

    In this thesis, we study moduli in compactifications of ten-dimensional heterotic supergravity. We consider supersymmetric compactifications to four-dimensional maximally symmetric space, commonly referred to as the Strominger system. The compact part of space-time $X$ is a six-dimensional manifold of what we refer to as a heterotic $SU(3)$-structure. We show that this system can be put in terms of a holomorphic operator $\\bar D$ on a bundle $\\mathcal{Q}=T^*X\\oplus\\mathrm{End}(TX)\\oplus\\mathrm{End}(V)\\oplus TX$, defined by a series of extensions. We proceed to compute the infinitesimal deformation space of this structure, given by $T\\mathcal{M}=H^{(0,1)}(\\mathcal{Q})$, which constitutes the infinitesimal spectrum of the four-dimensional theory. In doing so, we find an over counting of moduli by $H^{(0,1)}(\\mathrm{End}(TX))$, which can be reinterpreted as $\\mathcal{O}(\\alpha')$ field redefinitions. We next consider non-maximally symmetric domain wall compactifications of the form $M_{10}=M_3\\times Y$, where $M...

  6. On the permutation combinatorics of worldsheet moduli space

    CERN Document Server

    Freidel, Laurent; Ramgoolam, Sanjaye

    2014-01-01

    Light-cone string diagrams have been used to reproduce the orbifold Euler characteristic of moduli spaces of punctured Riemann surfaces at low genus and with few punctures. Nakamura studied the meromorphic differential introduced by Giddings and Wolpert to characterise light-cone diagrams and introduced a class of graphs related to this differential. These Nakamura graphs were used to parametrise the cells in a light-cone cell decomposition of moduli space. We develop links between Nakamura graphs and realisations of the worldsheet as branched covers. This leads to a development of the combinatorics of Nakamura graphs in terms of permutation tuples. For certain classes of cells, including those of top dimension, there is a simple relation to Belyi maps, which allows us to use results from Hermitian and complex matrix models to give analytic formulae for the counting of cells at arbitrarily high genus. For the most general cells, we develop a new equivalence relation on Hurwitz classes which organises the cell...

  7. The motive of some moduli spaces of vector bundles over a curve

    CERN Document Server

    Del Bano-Rollin, S

    1995-01-01

    We study the motive of the moduli spaces of semistable rank two vector bundles over an algebraic curve. When the degree is odd the moduli space is a smooth projective variety, we obtain the absolute Hodge motive of this, and in particular the Hodge-Poincare polynomial. When the degree is even the moduli space is a singular projective variety, we compute pure Euler characteristics and show that only two weights can occur in each cohomology group, we also see that its cohomology is pure up to a certain degree. As a by-product we obtain the isogeny type of some intermediate jacobians of the moduli spaces.

  8. Non-thermal dark matter and the moduli problem in string frameworks

    International Nuclear Information System (INIS)

    We address the cosmological moduli/gravitino problems and the issue of too little thermal but excessive non-thermal dark matter from the decays of moduli. The main examples we study are the G2-MSSM models arising from M theory compactifications, which allow for a precise calculation of moduli decay rates and widths. We find that the late decaying moduli satisfy both BBN constraints and avoid the gravitino problem. The non-thermal production of Wino LSPs, which is a prediction of G2-MSSM models, gives a relic density of about the right order of magnitude.

  9. The Picard group of the moduli of G-bundles on a curve

    OpenAIRE

    Beauville, Arnaud; Laszlo, Yves; Sorger, Christoph

    1996-01-01

    Let G be a complex semi-simple group, and X a compact Riemann surface. The moduli space of principal G-bundles on X, and in particular the holomorphic line bundles on this space and their global sections, play an important role in the recent applications of Conformal Field Theory to algebraic geometry. In this paper we determine the Picard group of this moduli space when G is of classical or G_2 type (we consider both the coarse moduli space and the moduli stack).

  10. Kahler Moduli Inflation in Type IIB Compactifications: A random tumble through the Calabi-Yau landscape

    CERN Document Server

    Galvez, Richard

    2016-01-01

    In this paper we present an initial exploration of the Calabi-Yau landscape in the context of Kahler moduli inflation. We review how the slow-roll requirement on the scalar potential translates to a geometric constraint on the Kahler geometry of the vacuum. This constraint leads to a hard bound on the moduli space geometry and we consider the effects of this constraint on the string landscape that arises in type IIB string compactifications on an O3/O7 orientifold. Most notably we find that the inflationary constraint is independent of the moduli space dimension and only 6.57% of geometries inspected support high-scale Kahler moduli inflation.

  11. Dynamics of moduli and gaugino condensates in an expanding universe

    Energy Technology Data Exchange (ETDEWEB)

    Papineau, C.; Ramos-Sanchez, S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Postma, M. [NIKHEF, Amsterdam (Netherlands)

    2009-08-15

    We study dynamical moduli stabilization driven by gaugino condensation in supergravity. In the presence of background radiation, there exists a region of initial conditions leading to successful stabilization. We point out that most of the allowed region corresponds to initial Hubble rate H close to the scale of condensation {lambda}, which is the natural cutoff of the effective theory. We first show that including the condensate dynamics sets a strong bound on the initial conditions. We then find that (complete) decoupling of the condensate happens at H about two orders of magnitude below {lambda}. This bound implies that in the usual scenario with the condensate integrated out, only the vicinity of the minimum leads to stabilization. Finally, we discuss the effects of thermal corrections. (orig.)

  12. Explaining the electroweak scale and stabilizing moduli in M theory

    International Nuclear Information System (INIS)

    In a recent paper it was shown that in M theory vacua without fluxes, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results in more detail and generalizes them, finding an essentially unique de Sitter (dS) vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV - 100 TeV range. (author)

  13. A Superficial Working Guide to Deformations and Moduli

    CERN Document Server

    Catanese, Fabrizio

    2011-01-01

    This is the first part of a guide to deformations and moduli, especially viewed from the perspective of algebraic surfaces (the simplest higher dimensional varieties). It contains also new results, regarding the question of local homeomorphism between Kuranishi and Teichmueller space, and a survey of new results with Ingrid Bauer, concerning the discrepancy between the deformation of the action of a group G on a minimal models S, respectively the deformation of the action of G on the canonical model X. Here Def(S) maps properly onto Def(X), but the same does not hold for pairs: Def(S,G) does not map properly onto Def(X,G). Indeed the connected components of Def(S), in the case of tertiary Burniat surfaces, only map to locally closed sets. The last section contains anew result on some surfaces whise Albanese map has generic degree equal to 2.

  14. Graph Complexes and the Moduli Space of Riemann Surfaces

    DEFF Research Database (Denmark)

    Egas Santander, Daniela

    potentially allow to transfer constructions in fat graphs to the black and white model. Moreover, we compare Bödigheimer's radial slit configurations and the space of metric admissible fat graphs, producing an explicit homotopy equivalence using a "critical graph" map. This critical graph map descends...... to a homeomorphism between the Unimodular Harmonic compactification and the space of Sullivan diagrams, which are natural compactifications of the space of radial slit configurations and the space of metric admissible fat graphs, respectively. Finally, we use experimental methods to compute the homology of the chain......In this thesis we compare several combinatorial models for the moduli space of open-closed cobordisms and their compactifications. More precisely, we study Godin's category of admissible fat graphs, Costello's chain complex of black and white graphs, and Bödigheimer's space of radial slit...

  15. Dynamics of moduli and gaugino condensates in an expanding universe

    International Nuclear Information System (INIS)

    We study dynamical moduli stabilization driven by gaugino condensation in supergravity. In the presence of background radiation, there exists a region of initial conditions leading to successful stabilization. We point out that most of the allowed region corresponds to initial Hubble rate H close to the scale of condensation Λ, which is the natural cutoff of the effective theory. We first show that including the condensate dynamics sets a strong bound on the initial conditions. We then find that (complete) decoupling of the condensate happens at H about two orders of magnitude below Λ. This bound implies that in the usual scenario with the condensate integrated out, only the vicinity of the minimum leads to stabilization. Finally, we discuss the effects of thermal corrections. (orig.)

  16. Heavy Tails in Calabi-Yau Moduli Spaces

    CERN Document Server

    Long, Cody; McGuirk, Paul

    2014-01-01

    We study the statistics of the metric on K\\"ahler moduli space in compactifications of string theory on Calabi-Yau hypersurfaces in toric varieties. We find striking hierarchies in the eigenvalues of the metric and of the Riemann curvature contribution to the Hessian matrix: both spectra display heavy tails. The curvature contribution to the Hessian is non-positive, suggesting a reduced probability of metastability compared to cases in which the derivatives of the K\\"ahler potential are uncorrelated. To facilitate our analysis, we have developed a novel triangulation algorithm that allows efficient study of hypersurfaces with $h^{1,1}$ as large as 25, which is difficult using algorithms internal to packages such as Sage. Our results serve as input for statistical studies of the vacuum structure in flux compactifications, and of the distribution of axion decay constants in string theory.

  17. A GIT Construction of Moduli Spaces of Stable Maps in Positive Characteristic

    OpenAIRE

    Baldwin, Elizabeth

    2007-01-01

    In a previous paper, the author and David Swinarski constructed the moduli spaces of stable maps, \\bar M_g,n(P^r,d), via geometric invariant theory (GIT). That paper required the base field to be the complex numbers, a restriction which this paper removes: here the coarse moduli spaces of stable maps are constructed via GIT over a more general base.

  18. Moduli spaces of framed flags of sheaves on the projective plane

    OpenAIRE

    von Flach, Rodrigo A.; Jardim, Marcos

    2016-01-01

    We study the moduli space of framed flags of sheaves on the projective plane via an adaptation of the ADHM construction of framed sheaves. In particular, we prove that, for certain values of the topological invariants, the moduli space of framed flags of sheaves is an irreducible, nonsingular variety carrying a holomorphic pre-symplectic form.

  19. Modification of the Simpson moduli space M_{3m+1}(P_2) by vector bundles (I)

    CERN Document Server

    Iena, Oleksandr

    2010-01-01

    We consider the moduli space of stable vector bundles on curves embedded in P_2 with Hilbert polynomial 3m+1 and construct a compactification of this space by vector bundles. The result is a blow up of the Simpson moduli space M_{3m+1}(P_2).

  20. Moduli of endomorphisms of semistable vector bundles over a compact Riemann surface

    International Nuclear Information System (INIS)

    We consider the moduli problem for endomorphisms of indecomposable semistable vector bundles over a compact convected Riemann surface of genus g greater than two. We develop the 3-dimensional case, which gives an idea of how to solve the moduli problem in general. 13 refs

  1. The Motive of the Moduli Stack of -Bundles over the Universal Curve

    Indian Academy of Sciences (India)

    Donu Arapura; Ajneet Dhillon

    2008-08-01

    We define relative motives in the sense of André. After associating a complex in the derived category of motives to an algebraic stack we study this complex in the case of the moduli of -bundles varying over the moduli of curves.

  2. Geometry of meromorphic functions and intersections on moduli spaces of curves

    OpenAIRE

    Shadrin, Sergei

    2002-01-01

    In this paper we study relations between intersection numbers on moduli spaces of curves and Hurwitz numbers. First, we prove two formulas expressing Hurwitz numbers of (generalized) polynomials via intersections on moduli spaces of curves. Then we show, how intersection numbers can be expressed via Hurwitz numbers. And then we obtain an algorithm expressing intersection numbers $_g$ via correlation functions of primaries.

  3. Bagger-Witten line bundles on moduli spaces of elliptic curves

    CERN Document Server

    Gu, W

    2016-01-01

    In this paper we discuss Bagger-Witten line bundles over moduli spaces of SCFTs. We review how in general they are `fractional' line bundles, not honest line bundles, twisted on triple overlaps. We discuss the special case of moduli spaces of elliptic curves in detail. There, the Bagger-Witten line bundles does not exist as an ordinary line bundle, but rather is necessarily fractional. As a fractional line bundle, it is nontrivial (though torsion) over the uncompactified moduli stack, and its restriction to the interior, excising corners with enhanced stabilizers, is also fractional. We review and compare to results of recent work arguing that well-definedness of the worldsheet metric implies that the Bagger-Witten line bundle is torsion, and give general arguments on the existence of universal structures on moduli spaces of SCFTs, in which superconformal deformation parameters are promoted to nondynamical fields ranging over the SCFT moduli space.

  4. New effective moduli of isotropic viscoelastic composites. Part I. Theoretical justification

    Science.gov (United States)

    Svetashkov, A. A.; Vakurov, A. A.

    2016-04-01

    According to the approach based on the commonality of problems of determining effective moduli of composites and viscoelastic solids, which properties are time-inhomogeneous, it is assumed that a viscoelastic solid is a two-component composite. One component displays temporal properties defined by a pair of Castiglianian-type effective moduli, and the other is defined by a pair of Lagrangian-type effective moduli. The Voigt and Reuss averaging is performed for the obtained two-composite solid with the introduction of a time function of volume fraction. In order to determine closer estimates, a method of iterative transformation of time effective moduli is applied to the viscoelastic Voigt-Reuss model. The physical justification of the method is provided. As a result, new time effective moduli of the viscoelastic solid are obtained which give a closer estimate of temporal properties as compared to the known models.

  5. Back-calculation of source strength and position by a hybrid genetic-Nelder Mead simplex algorithm%基于混合遗传-Nelder Mead单纯形算法的源强及位置反算

    Institute of Scientific and Technical Information of China (English)

    张建文; 王煜薇; 郑小平; 王正

    2011-01-01

    Determination of the locations and strength of the source in a chemical leakage is crucial to crowd evacuation and emergency decision. This paper compares concentrations computed by dispersion model with the measured by receptors and then hybrid genetic-Nelder Mead simplex algorithm model is established. The locations and strength of leakage source are characterized. The feasibility of the algorithm is verified by simulation data. It is indicated that the hybrid genetic-Nelder Mead simplex algorithm is seldom affected by initial values and can get good results even if the initial values are far away from the expected values. This method back-calculates the optimal solution in a smaller errors and a faster pace and is more suitable for the search procedure in multi-dimensional space. Thence, hybrid genetic-Nelder Mead simplex algorithm is able to back-calculate the locations and strength of leakage source quickly and accurately, which will meet the needs of emergency rescue.%确定泄漏源的位置和强度,是进行群体疏散和应急决策的基础.将扩散模型得到的浓度值与传感器观测的浓度值进行比较并建立混合遗传-Nelder Mead单纯形算法模型,反算得到泄露源的位置和强度,进而利用浓度的模拟数据验证该算法的可行性.研究结果表明:混合遗传-Nelder Mead单纯形算法不受初值选取的影响,即使初值远离期望值,也能得到很好的结果,而且能以较小的误差和较快的速度反算出结果,更适合于多维变量的搜索.因此混合遗传-Nelder Mead单纯形算法能够快速准确地反算得到泄漏源的位置和强度,满足应急决策的需要.

  6. Effective moduli of high volume fraction particulate composites

    International Nuclear Information System (INIS)

    Predictions using current micromechanics theories for the effective moduli of particulate-reinforced composites tend to break down at high volume fractions of the reinforcing phase. The predictions are usually well below experimentally measured values of the Young's modulus for volume fractions exceeding about 0.6. In this paper, the concept of contiguity, which is a measure of phase continuity, is applied to Mori-Tanaka micromechanics theory. It is shown that contiguity of the second phase increases with volume fraction, leading eventually to a reversal in the roles of the inclusion and matrix. In powder metallurgy practice, it is well known that at high volume fractions, sintering and consolidation of the reinforcement make it increasingly continuous and more like the matrix phase, while the former matrix tends to become more like the inclusion phase. The concept of contiguity applied to micromechanics theory results in very good agreement between the predicted Young's modulus and experimental data on tungsten carbide particulate-reinforced cobalt

  7. Moduli spaces of discrete gravity; 1, A few points

    CERN Document Server

    Holfter, A

    2002-01-01

    Spectral triples describe and generalize Riemannian spin geometries by converting the geometrical information into algebraic data, which consist of an algebra $A$, a Hilbert space $H$ carrying a representation of $A$ and the Dirac operator $D$ (a selfadjoint operator acting on $H$). The gravitational action is described by the trace of a suitable function of $D$. In this paper we examine the (path-integral-) quantization of such a system given by a finite dimensional commutative algebra. It is then (in concrete examples) possible to construct the moduli space of the theory, i.e. to divide the space of all Dirac operators by the action of the diffeomorphism group, and to construct an invariant measure on this space. We discuss expectation values of various observables and demonstrate some interesting effects such as the effect of coupling the system to Fermions (which renders finite quantities in cases, where the Bosons alone would give infinite quantities) or the striking effect of spontaneous breaking of spe...

  8. Roulette inflation with Kaehler moduli and their axions

    International Nuclear Information System (INIS)

    We study 2-field inflation models based on the 'large-volume' flux compactification of type IIB string theory. The role of the inflaton is played by a Kaehler modulus τ corresponding to a 4-cycle volume and its axionic partner θ. The freedom associated with the choice of Calabi-Yau manifold and the nonperturbative effects defining the potential V(τ,θ) and kinetic parameters of the moduli brings an unavoidable statistical element to theory prior probabilities within the low-energy landscape. The further randomness of (τ,θ) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include 'roulette trajectories', with long-lasting inflations in the direction of the rolling axion, enhanced in the number of e-foldings over those restricted to lie in the τ-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic microwave background and large scale structure data. In particular, the observed scalar tilt with weak or no running can be achieved in spite of a nearly critical de Sitter deceleration parameter and consequently a low gravity wave power relative to the scalar curvature power

  9. Roulette inflation with Kähler moduli and their axions

    Science.gov (United States)

    Bond, J. Richard; Kofman, Lev; Prokushkin, Sergey; Vaudrevange, Pascal M.

    2007-06-01

    We study 2-field inflation models based on the “large-volume” flux compactification of type IIB string theory. The role of the inflaton is played by a Kähler modulus τ corresponding to a 4-cycle volume and its axionic partner θ. The freedom associated with the choice of Calabi-Yau manifold and the nonperturbative effects defining the potential V(τ,θ) and kinetic parameters of the moduli brings an unavoidable statistical element to theory prior probabilities within the low-energy landscape. The further randomness of (τ,θ) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include “roulette trajectories,” with long-lasting inflations in the direction of the rolling axion, enhanced in the number of e-foldings over those restricted to lie in the τ-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic microwave background and large scale structure data. In particular, the observed scalar tilt with weak or no running can be achieved in spite of a nearly critical de Sitter deceleration parameter and consequently a low gravity wave power relative to the scalar curvature power.

  10. Roulette Inflation with K\\"ahler Moduli and their Axions

    CERN Document Server

    Bond, J R; Prokushkin, S F; Vaudrevange, P M

    2006-01-01

    We study 2-field inflation models based on the ``large-volume'' flux compactification of type IIB string theory. The role of the inflaton is played by a K\\"ahler modulus \\tau corresponding to a 4-cycle volume and its axionic partner \\theta. The freedom associated with the choice of Calabi Yau manifold and the non-perturbative effects defining the potential V(\\tau, \\theta) and kinetic parameters of the moduli bring an unavoidable statistical element to theory prior probabilities within the low energy landscape. The further randomness of (\\tau, \\theta) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include ``roulette tractories'', with long-lasting inflations in the direction of the rolling axion, enhanced in number of e-foldings over those restricted to lie in the \\tau-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic mic...

  11. Temperature- and thickness-dependent elastic moduli of polymer thin films

    Directory of Open Access Journals (Sweden)

    Ao Zhimin

    2011-01-01

    Full Text Available Abstract The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk. Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications. However, it is a great challenge to measure their elastic modulus experimentally with in situ heating. In this study, a thermodynamic model for temperature- (T and thickness (h-dependent elastic moduli of polymer thin films Ef(T,h is developed with verification by the reported experimental data on polystyrene (PS thin films. For the PS thin films on a passivated substrate, Ef(T,h decreases with the decreasing film thickness, when h is less than 60 nm at ambient temperature. However, the onset thickness (h*, at which thickness Ef(T,h deviates from the bulk value, can be modulated by T. h* becomes larger at higher T because of the depression of the quenching depth, which determines the thickness of the surface layer δ.

  12. An in situ estimation of anisotropic elastic moduli for a submarine shale

    Science.gov (United States)

    Miller, Douglas E.; Leaney, Scott; Borland, William H.

    1994-11-01

    Direct arrival times and slownesses from wide-aperture walkaway vertical seismic profile data acquired in a layered anisotropic medium can be processed to give direct estimate of the phase slowness surface associated with the medium at the depth of the receivers. This slowness surface can, in turn, be fit by an estimated transversely isotropic medium with a vertical symmetry axis (a 'TIV' medium). While the method requires that the medium between the receivers and the surface be horizontally stratified, no further measurement or knowledge of that medium is required. When applied to data acquired in a compacting shale sequence (here termed the 'Petronas shale') encountered by a well in the South China Sea, the method yields an estimated TIV medium that fits the data extremely well over 180 deg of propagation angles sampled by 201 source positions. The medium is strongly anisotropic. The anisotropy is significantly anelliptic and implies that the quasi-shear mode should be triplicated for off-axis propagation. Estimated density-normalized moduli (in units of sq km/sq s) for the Petronas shale are A(sub 11) = 6.99 +/- 0.21, A(sub 33) = 5.53 +/- 0.17, A(sub 55) = 0.91 +/- 0.05, and A(sub 13) = 2.64 +/- 0.26. Densities in the logged zone just below the survey lie in the range between 2200 and 2400 kg/cu m with an average value close to 2300 kg/cu m.

  13. Universal behavior of changes in elastic moduli of hot compressed oxide glasses

    Science.gov (United States)

    Svenson, Mouritz N.; Guerette, Michael; Huang, Liping; Lönnroth, Nadja; Mauro, John C.; Rzoska, Sylwester J.; Bockowski, Michal; Smedskjaer, Morten M.

    2016-05-01

    The elastic moduli of glasses are important for numerous applications, but predicting them based on their chemical composition and forming history remains a great challenge. In this study, we investigate the relationship between densification and changes in elastic moduli as a result of isostatic compression up to 1 GPa of various oxide compositions at elevated temperature (so-called hot compression). An approximately linear relationship is observed between the relative changes in density and elastic moduli across a variety of glass families, although these glasses exhibit a diverse range of structural responses during compression owing to their dramatically different chemistries.

  14. A Large Deformation Model for the Elastic Moduli of Two-dimensional Cellular Materials

    Institute of Scientific and Technical Information of China (English)

    HU Guoming; WAN Hui; ZHANG Youlin; BAO Wujun

    2006-01-01

    We developed a large deformation model for predicting the elastic moduli of two-dimensional cellular materials. This large deformation model was based on the large deflection of the inclined members of the cells of cellular materials. The deflection of the inclined member, the strain of the representative structure and the elastic moduli of two-dimensional cellular materials were expressed using incomplete elliptic integrals. The experimental results show that these elastic moduli are no longer constant at large deformation, but vary significantly with the strain. A comparison was made between this large deformation model and the small deformation model proposed by Gibson and Ashby.

  15. On the Moduli Space of non-BPS Attractors for N=2 Symmetric Manifolds

    CERN Document Server

    Ferrara, Sergio

    2007-01-01

    We study the ``flat'' directions of non-BPS extremal black hole attractors for N=2, d=4 supergravities whose vector multiplets' scalar manifold is endowed with homogeneous symmetric special Kahler geometry. The non-BPS attractors with non-vanishing central charge have a moduli space described by real special geometry (and thus related to the d=5 parent theory), whereas the moduli spaces of non-BPS attractors with vanishing central charge are certain Kahler homogeneous symmetric manifolds. The moduli spaces of the non-BPS attractors of the corresponding N=2, d=5 theories are also indicated, and shown to be rank-1 homogeneous symmetric manifolds.

  16. Molecular Modeling of the Axial and Circumferential Elastic Moduli of Tubulin

    OpenAIRE

    Zeiger, A. S.; Layton, B. E.

    2008-01-01

    Microtubules play a number of important mechanical roles in almost all cell types in nearly all major phylogenetic trees. We have used a molecular mechanics approach to perform tensile tests on individual tubulin monomers and determined values for the axial and circumferential moduli for all currently known complete sequences. The axial elastic moduli, in vacuo, were found to be 1.25 GPa and 1.34 GPa for α- and β-bovine tubulin monomers. In the circumferential direction, these moduli were 378...

  17. Towards a classification of modular compactifications of the moduli space of curves

    OpenAIRE

    Smyth, David Ishii

    2009-01-01

    The space of smooth curves admits a beautiful compactification by the moduli space of Deligne-Mumford stable curves. In this paper, we undertake a systematic investigation of alternate modular compactifications of the space of smooth curves.

  18. Symplectic geometry of the moduli space of projective structures in homological coordinates

    CERN Document Server

    Bertola, Marco; Norton, Chaya

    2015-01-01

    We introduce a natural symplectic structure on the moduli space of quadratic differentials with simple zeros and describe its Darboux coordinate systems in terms of so-called homological coordinates. We then show that this structure coincides with the canonical Poisson structure on the cotangent bundle of the moduli space of Riemann surfaces, and therefore the homological coordinates provide a new system of Darboux coordinates. We define a natural family of commuting "homological flows" on the moduli space of quadratic differentials and find the corresponding action-angle variables. The space of projective structures over the moduli space can be identified with the cotangent bundle upon selection of a reference projective connection that varies holomorphically and thus can be naturally endowed with a symplectic structure. Different choices of projective connections of this kind (Bergman, Schottky, Wirtinger) give rise to equivalent symplectic structures on the space of projective connections but different sym...

  19. The tautological ring of the moduli space M_{2,n}^rt

    OpenAIRE

    Tavakol, Mehdi

    2011-01-01

    We study the tautological ring of the moduli space of stable n-pointed curves of genus two with rational tails. The algebra is described in terms of explicit generators and relations. It is proven that this algebra is Gorenstein.

  20. Moduli for Decorated Tuples of Sheaves and Representation Spaces for Quivers

    Indian Academy of Sciences (India)

    Alexander Schmitt

    2005-02-01

    We extend the scope of a former paper to vector bundle problems involving more than one vector bundle. As the main application, we obtain the solution of the well-known moduli problems of vector bundles associated with general quivers.

  1. Numerical Weil-Petersson metrics on moduli spaces of Calabi-Yau manifolds

    Science.gov (United States)

    Keller, Julien; Lukic, Sergio

    2015-06-01

    We introduce a simple and very fast algorithm to compute Weil-Petersson metrics on moduli spaces of Calabi-Yau varieties. Additionally, we introduce a second algorithm to approximate the same metric using Donaldson's quantization link between infinite and finite dimensional Geometric Invariant Theoretical (GIT) quotients that describe moduli spaces of varieties. Although this second algorithm is slower and more sophisticated, it can also be used to compute similar metrics on other moduli spaces (e.g. moduli spaces of vector bundles on Calabi-Yau varieties). We study the convergence properties of both algorithms and provide explicit computer implementations using a family of Calabi-Yau quintic hypersurfaces in P4. Also, we include discussions on: the existing methods that are used to compute this class of metrics, the background material that we use to build our algorithms, and how to extend the second algorithm to the vector bundle case.

  2. Multi-centered D1-D5 solutions at finite B-moduli

    International Nuclear Information System (INIS)

    We study the fate of two-centered D1-D5 systems on T4 away from the singular supergravity point in the moduli space. We do this by considering a background D1-D5 black hole with a self-dual B-field moduli turned on and treating the second center in the probe limit in this background. We find that in general marginal bound states at zero moduli become metastable at finite B-moduli, demonstrating a breaking of supersymmetry. However, we also find evidence that when the charges of both centers are comparable, the effects of supersymmetry breaking become negligible. We show that this effect is independent of string coupling and thus it should be possible to reproduce this in the CFT at weak coupling. We comment on the implications for the fuzzball proposal

  3. A flux-scaling scenario for high-scale moduli stabilization in string theory

    Energy Technology Data Exchange (ETDEWEB)

    Blumenhagen, Ralph [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Font, Anamaría [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Arnold Sommerfeld Center for Theoretical Physics, LMU, Theresienstr. 37, 80333 München (Germany); Fuchs, Michael [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Herschmann, Daniela, E-mail: herschma@mpp.mpg.de [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Plauschinn, Erik [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Sekiguchi, Yuta; Wolf, Florian [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Arnold Sommerfeld Center for Theoretical Physics, LMU, Theresienstr. 37, 80333 München (Germany)

    2015-08-15

    Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi–Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms and supersymmetry breaking soft masses on MSSM-like D7-branes are discussed as well. This scenario provides a complete effective framework for realizing the idea of F-term axion monodromy inflation in string theory. It is argued that, with all masses close to the Planck and GUT scales, one is confronted with working at the threshold of controlling all mass hierarchies.

  4. A flux-scaling scenario for high-scale moduli stabilization in string theory

    International Nuclear Information System (INIS)

    Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi–Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms and supersymmetry breaking soft masses on MSSM-like D7-branes are discussed as well. This scenario provides a complete effective framework for realizing the idea of F-term axion monodromy inflation in string theory. It is argued that, with all masses close to the Planck and GUT scales, one is confronted with working at the threshold of controlling all mass hierarchies

  5. A flux-scaling scenario for high-scale moduli stabilization in string theory

    Directory of Open Access Journals (Sweden)

    Ralph Blumenhagen

    2015-08-01

    Full Text Available Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi–Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms and supersymmetry breaking soft masses on MSSM-like D7-branes are discussed as well. This scenario provides a complete effective framework for realizing the idea of F-term axion monodromy inflation in string theory. It is argued that, with all masses close to the Planck and GUT scales, one is confronted with working at the threshold of controlling all mass hierarchies.

  6. Elastic moduli and vibrational modes in jammed particulate packings

    Science.gov (United States)

    Mizuno, Hideyuki; Saitoh, Kuniyasu; Silbert, Leonardo E.

    2016-06-01

    When we elastically impose a homogeneous, affine deformation on amorphous solids, they also undergo an inhomogeneous, nonaffine deformation, which can have a crucial impact on the overall elastic response. To correctly understand the elastic modulus M , it is therefore necessary to take into account not only the affine modulus MA, but also the nonaffine modulus MN that arises from the nonaffine deformation. In the present work, we study the bulk (M =K ) and shear (M =G ) moduli in static jammed particulate packings over a range of packing fractions φ . The affine MA is determined essentially by the static structural arrangement of particles, whereas the nonaffine MN is related to the vibrational eigenmodes. We elucidate the contribution of each vibrational mode to the nonaffine MN through a modal decomposition of the displacement and force fields. In the vicinity of the (un)jamming transition φc, the vibrational density of states g (ω ) shows a plateau in the intermediate-frequency regime above a characteristic frequency ω*. We illustrate that this unusual feature apparent in g (ω ) is reflected in the behavior of MN: As φ →φc , where ω*→0 , those modes for ω ω* approach a constant value which results in MN to approach a critical value MN c, as MN-MN c˜ω* . At φc itself, the bulk modulus attains a finite value Kc=KA c-KN c>0 , such that KN c has a value that remains below KA c. In contrast, for the critical shear modulus Gc, GN c and GA c approach the same value so that the total value becomes exactly zero, Gc=GA c-GN c=0 . We explore what features of the configurational and vibrational properties cause such a distinction between K and G , allowing us to validate analytical expressions for their critical values.

  7. Lectures on moduli of principal G-bundles over algebraic curves

    International Nuclear Information System (INIS)

    These notes are supposed to be an introduction to the moduli of G-bundles on curves. Therefore I will lay stress on ideas in order to make these notes more readable. In the last years the moduli spaces of G-bundles over algebraic curves have attracted some attention from various subjects like from conformal field theory or Beilinson and Drinfeld's geometric Langlands program. In both subjects it turned out that the 'stacky' point of view is more convenient and as the basic motivation of these notes is to introduce to the latter subject our moduli spaces will be moduli stacks (and not coarse moduli spaces). As people may feel uncomfortable with stacks I have included a small introduction to them. Actually there is a forthcoming book of Laumon and Moret-Bailly based on their preprint and my introduction merely does the step -1, i.e. explains why we are forced to use them here and recalls the basic results I need later. So here is the plan of the lectures: after some generalities on G-bundles, I will classify them topologically. Actually the proof is more interesting than the result as it will give a flavor of the basic theorem on G-bundles which describes the moduli stack as a double quotient of loop-groups. This 'uniformization theorem', which goes back to A. Weil as a bijection on sets, will be proved in the section following the topological classification. Then I will introduce two line bundles on the moduli stack: the determinant and the paffian bundle. The first one can be used to describe the canonical bundle on the moduli stack and the second to define a square-root of it. Unless G is simply connected the square root depends on the choice of a theta-characteristic. This square root plays an important role in the geometric Langlands program. Actually, in order to get global differential operators on the moduli stack one has to consider twisted differential operators with values in these square-roots. The rest of the lectures will be dedicated to describe the

  8. Equivalent orthotropic elastic moduli identification method for laminated electrical steel sheets

    Science.gov (United States)

    Saito, Akira; Nishikawa, Yasunari; Yamasaki, Shintaro; Fujita, Kikuo; Kawamoto, Atsushi; Kuroishi, Masakatsu; Nakai, Hideo

    2016-05-01

    In this paper, a combined numerical-experimental methodology for the identification of elastic moduli of orthotropic media is presented. Special attention is given to the laminated electrical steel sheets, which are modeled as orthotropic media with nine independent engineering elastic moduli. The elastic moduli are determined specifically for use with finite element vibration analyses. We propose a three-step methodology based on a conventional nonlinear least squares fit between measured and computed natural frequencies. The methodology consists of: (1) successive augmentations of the objective function by increasing the number of modes, (2) initial condition updates, and (3) appropriate selection of the natural frequencies based on their sensitivities on the elastic moduli. Using the results of numerical experiments, it is shown that the proposed method achieves more accurate converged solution than a conventional approach. Finally, the proposed method is applied to measured natural frequencies and mode shapes of the laminated electrical steel sheets. It is shown that the method can successfully identify the orthotropic elastic moduli that can reproduce the measured natural frequencies and frequency response functions by using finite element analyses with a reasonable accuracy.

  9. Laboratory measurements of a complete set of poroelastic moduli for Berea sandstone and Indiana limestone

    Science.gov (United States)

    Hart, David J.; Wang, Herbert F.

    1995-09-01

    Measurements have been completed for eight different poroelastic moduli of water-saturated Berea sandstone and Indiana limestone as a function of confining pressure and pore pressure. The poroelastic moduli for Indiana limestone are generally consistent to ±10%, which was verified by a formal inversion procedure for independent moduli from the eight measurements. For Indiana limestone, best fit values were drained bulk modulus, 21.2 GPa; the undrained bulk modulus, 31.7 GPa; drained Poisson's ratio, 0.26; undrained Poisson's ratio, 0.33; and pore pressure buildup coefficient, 0.47 at 20-35 MPa effective stress. The poroelastic moduli for Berea sandstone are generally consistent to ±20%. The greater inconsistency is most likely caused by the nonlinear variation of the moduli at different strains. For Berea sandstone, best fit values were drained bulk modulus, 6.6 GPa; undrained bulk modulus, 15.8 GPa; drained Poisson's ratio, 0.17; undrained Poisson's ratio, 0.34; and pore pressure buildup coefficient, 0.75 at 10 MPa effective stress.

  10. Moduli Dark Matter and the Search for Its Decay Line using Suzaku X-Ray Telescope

    Science.gov (United States)

    Kusenko, Alexander; Loewenstein, Michael; Yanagida, Tsutomu T.

    2013-01-01

    Light scalar fields called moduli arise from a variety of different models involving supersymmetry and/or string theory; thus their existence is a generic prediction of leading theories for physics beyond the standard model. They also present a formidable, long-standing problem for cosmology. We argue that an anthropic solution to the moduli problem exists in the case of small moduli masses and that it automatically leads to dark matter in the form of moduli. The recent discovery of the 125 GeV Higgs boson implies a lower bound on the moduli mass of about a keV. This form of dark matter is consistent with the observed properties of structure formation, and it is amenable to detection with the help of x-ray telescopes. We present the results of a search for such dark matter particles using spectra extracted from the first deep x-ray observations of the Draco and Ursa Minor dwarf spheroidal galaxies, which are darkmatter- dominated systems with extreme mass-to-light ratios and low intrinsic backgrounds. No emission line is positively detected, and we set new constraints on the relevant new physics.

  11. Experimentally-based multiscale model of the elastic moduli of bovine trabecular bone and its constituents

    Energy Technology Data Exchange (ETDEWEB)

    Hamed, Elham [University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 1206 West Green Street, Urbana, IL 61801 (United States); Novitskaya, Ekaterina, E-mail: eevdokim@ucsd.edu [University of California, San Diego, Department of Mechanical and Aerospace Engineering, Materials Science and Engineering Program, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Li, Jun; Jasiuk, Iwona [University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 1206 West Green Street, Urbana, IL 61801 (United States); McKittrick, Joanna [University of California, San Diego, Department of Mechanical and Aerospace Engineering, Materials Science and Engineering Program, 9500 Gilman Dr., La Jolla, CA 92093 (United States)

    2015-09-01

    The elastic moduli of trabecular bone were modeled using an analytical multiscale approach. Trabecular bone was represented as a porous nanocomposite material with a hierarchical structure spanning from the collagen–mineral level to the trabecular architecture level. In parallel, compression testing was done on bovine femoral trabecular bone samples in two anatomical directions, parallel to the femoral neck axis and perpendicular to it, and the measured elastic moduli were compared with the corresponding theoretical results. To gain insights on the interaction of collagen and minerals at the nanoscale, bone samples were deproteinized or demineralized. After such processing, the treated samples remained as self-standing structures and were tested in compression. Micro-computed tomography was used to characterize the hierarchical structure of these three bone types and to quantify the amount of bone porosity. The obtained experimental data served as inputs to the multiscale model and guided us to represent bone as an interpenetrating composite material. Good agreement was found between the theory and experiments for the elastic moduli of the untreated, deproteinized, and demineralized trabecular bone. - Highlights: • A multiscale model was used to predict the elastic moduli of trabecular bone. • Samples included demineralized, deproteinized and untreated bone. • The model portrays bone as a porous, interpenetrating two phase composite. • The experimental elastic moduli for trabecular bone fell between theoretical bounds.

  12. Virtual Structure Constants as Intersection Numbers of Moduli Space of Polynomial Maps with Two Marked Points

    Science.gov (United States)

    Jinzenji, Masao

    2008-12-01

    In this paper, we derive the virtual structure constants used in the mirror computation of the degree k hypersurface in CP N-1, by using a localization computation applied to moduli space of polynomial maps from CP 1 to CP N-1 with two marked points. This moduli space corresponds to the GIT quotient of the standard moduli space of instantons of Gauged Linear Sigma Model by the standard torus action. We also apply this technique to the non-nef local geometry {{\\cal O}(1)oplus {\\cal O}(-3)rightarrow CP1} and realize the mirror computation without using Birkhoff factorization. Especially, we obtain a geometrical construction of the expansion coefficients of the mirror maps of these models.

  13. Cusps of the K\\"ahler moduli space and stability conditions on K3 surfaces

    CERN Document Server

    Hartmann, Heinrich

    2010-01-01

    In [Ma1] S. Ma established a bijection between Fourier--Mukai partners of a K3 surface and cusps of the K\\"ahler moduli space. The K\\"ahler moduli space can be described as a quotient of Bridgeland's stability manifold. We study the relation between stability conditions $\\sigma$ near to a cusp and the associated Fourier--Mukai partner Y in the following ways. (1) We compare the heart of $\\sigma$ to the heart of coherent sheaves on Y. (2) We construct Y as moduli space of $\\sigma$-stable objects. An appendix is devoted to the group of auto-equivalences of the derived category which respect the component $Stab^\\dagger(X)$ of the stability manifold.

  14. On moduli stabilisation and de Sitter vacua in MSSM heterotic orbifolds

    International Nuclear Information System (INIS)

    We study the problem of moduli stabilisation in explicit heterotic orbifold compactifications, whose spectra contain the MSSM plus some vector-like exotics that can be decoupled. Considering all the bulk moduli, we obtain the 4D low energy effective action for the compactification, which has contributions from various, computable, perturbative and non-perturbative effects. Hidden sector gaugino condensation and string worldsheet instantons result in a combination of racetrack, KKLT and cusp-form contributions to the superpotential, which lift all the bulk moduli directions. We point out the properties observed in our concrete models, which tend to be missed when only ''generic'' features of a model are assumed. We search for interesting vacua and find several de Sitter solutions, but so far, they all turn out to be unstable. (orig.)

  15. On moduli stabilisation and de Sitter vacua in MSSM heterotic orbifolds

    Energy Technology Data Exchange (ETDEWEB)

    Parameswaran, Susha L. [Uppsala Univ. (Sweden). Dept. of Physics and Astronomy; Ramos-Sanchez, Saul [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zavala, Ivonne [Bonn Univ. (Germany). Bethe Center for Theoretical Physics and Physikalisches Inst.

    2010-09-15

    We study the problem of moduli stabilisation in explicit heterotic orbifold compactifications, whose spectra contain the MSSM plus some vector-like exotics that can be decoupled. Considering all the bulk moduli, we obtain the 4D low energy effective action for the compactification, which has contributions from various, computable, perturbative and non-perturbative effects. Hidden sector gaugino condensation and string worldsheet instantons result in a combination of racetrack, KKLT and cusp-form contributions to the superpotential, which lift all the bulk moduli directions. We point out the properties observed in our concrete models, which tend to be missed when only ''generic'' features of a model are assumed. We search for interesting vacua and find several de Sitter solutions, but so far, they all turn out to be unstable. (orig.)

  16. Temperature and time-dependence of the elastic moduli of Pu and Pu-Ga alloys

    Energy Technology Data Exchange (ETDEWEB)

    Migliori, Albert [Los Alamos National Laboratory, Los Alamos, NM (United States); Mihut, I. [Los Alamos National Laboratory, Los Alamos, NM (United States)], E-mail: izabela@lanl.gov; Betts, J.B.; Ramos, M.; Mielke, C.; Pantea, C.; Miller, D. [Los Alamos National Laboratory, Los Alamos, NM (United States)

    2007-10-11

    In previous work, on cooling from 300 K to 10 K the elastic moduli for both {alpha}- and {delta}-Pu dropped 30%. This large change may reflect effects of 5f-electron localization. In this work, the elastic moduli at ambient temperature of several Pu-Ga alloys were measured using resonant ultrasound spectroscopy (RUS). The strong temperature dependence of the bulk and shear modulus and the temperature independence of Poisson's ratio was confirmed and the upper temperature limit for {alpha}-Pu was extended to 360 K. Measurements of the time dependence of the shear moduli of Pu and Pu-2.36 at.% Ga were determined with high precision as a function of time and temperature. Using a model for time dependence of point defects, we determined the exponential time constant at ambient temperature for such variations. The low temperature results are consistent with Fluss.

  17. Temperature and time-dependence of the elastic moduli of Pu and Pu-Ga alloys

    International Nuclear Information System (INIS)

    In previous work, on cooling from 300 K to 10 K the elastic moduli for both α- and δ-Pu dropped 30%. This large change may reflect effects of 5f-electron localization. In this work, the elastic moduli at ambient temperature of several Pu-Ga alloys were measured using resonant ultrasound spectroscopy (RUS). The strong temperature dependence of the bulk and shear modulus and the temperature independence of Poisson's ratio was confirmed and the upper temperature limit for α-Pu was extended to 360 K. Measurements of the time dependence of the shear moduli of Pu and Pu-2.36 at.% Ga were determined with high precision as a function of time and temperature. Using a model for time dependence of point defects, we determined the exponential time constant at ambient temperature for such variations. The low temperature results are consistent with Fluss

  18. World-sheet instanton superpotentials in heterotic string theory and their moduli dependence

    International Nuclear Information System (INIS)

    To understand in detail the contribution of a world-sheet instanton to the superpotential in a heterotic string compactification, one has to understand the moduli dependence (bundle and complex structure moduli) of the one-loop determinants from the fluctuations, which accompany the classical exponential contribution (involving Kaehler moduli) when evaluating the world-volume partition function. Here we use techniques to describe geometrically these Pfaffians for spectral bundles over rational base curves in elliptically fibered Calabi-Yau threefolds, and provide a (partially exhaustive) list of cases involving factorising (or vanishing) superpotential. This gives a conceptual explanation and generalisation of the few previously known cases which were obtained just experimentally by a numerical computation.

  19. Probing asthenospheric density, temperature, and elastic moduli below the western United States.

    Science.gov (United States)

    Ito, Takeo; Simons, Mark

    2011-05-20

    Periodic ocean tides continually provide a cyclic load on Earth's surface, the response to which can be exploited to provide new insights into Earth's interior structure. We used geodetic observations of surface displacements induced by ocean tidal loads to constrain a depth-dependent model for the crust and uppermost mantle that provides independent estimates of density and elastic moduli below the western United States and nearby offshore regions. Our observations require strong gradients in both density and elastic shear moduli at the top and bottom of the asthenosphere but no discrete structural discontinuity at a depth of 220 kilometers. The model indicates that the asthenosphere has a low-density anomaly of ~50 kilograms per cubic meter; a temperature anomaly of ~300°C can simultaneously explain this density anomaly and inferred colocated minima in elastic moduli. PMID:21493821

  20. The permeability and elastic moduli of tuff from Campi Flegrei, Italy: implications for ground deformation modelling

    Science.gov (United States)

    Heap, M. J.; Baud, P.; Meredith, P. G.; Vinciguerra, S.; Reuschlé, T.

    2014-01-01

    The accuracy of ground deformation modelling at active volcanoes is a principal requirement in volcanic hazard mitigation. However, the reliability of such models relies on the accuracy of the rock physical property (permeability and elastic moduli) input parameters. Unfortunately, laboratory-derived values on representative rocks are usually rare. To this end we have performed a systematic laboratory study on the influence of pressure and temperature on the permeability and elastic moduli of samples from the two most widespread lithified pyroclastic deposits at the Campi Flegrei volcanic district, Italy. Our data show that the water permeability of Neapolitan Yellow Tuff and a tuff from the Campanian Ignimbrite differ by about 1.5 orders of magnitude. As pressure (depth) increases beyond the critical point for inelastic pore collapse (at an effective pressure of 10-15 MPa, or a depth of about 750 m), permeability and porosity decrease significantly, and ultrasonic wave velocities and dynamic elastic moduli increase significantly. Increasing the thermal stressing temperature increases the permeability and decreases the ultrasonic wave velocities and dynamic elastic moduli of the Neapolitan Yellow Tuff; whereas the tuff from the Campanian Ignimbrite remains unaffected. This difference is due to the presence of thermally unstable zeolites within the Neapolitan Yellow Tuff. For both rocks we also find, under the same pressure conditions, that the dynamic (calculated from ultrasonic wave velocities) and static (calculated from triaxial stress-strain data) elastic moduli differ significantly. The choice of elastic moduli in ground deformation modelling is therefore an important consideration. While we urge that these new laboratory data should be considered in routine ground deformation modelling, we highlight the challenges for ground deformation modelling based on the heterogeneous nature (vertically and laterally) of the rocks that comprise the caldera at Campi

  1. The geometry of the light-cone cell decomposition of moduli space

    CERN Document Server

    Garner, David

    2015-01-01

    The moduli space of Riemann surfaces with at least two punctures can be decomposed into a cell complex by using a particular family of ribbon graphs called Nakamura graphs. We distinguish the moduli space with all punctures labelled from that with a single labelled puncture. In both cases, we describe a cell decomposition where the cells are parametrised by graphs or equivalence classes of finite sequences (tuples) of permutations. Each cell is a convex polytope defined by a system of linear equations and inequalities relating light-cone string parameters, quotiented by the automorphism group of the graph. We give explicit examples of the cell decomposition at low genus with few punctures.

  2. The Determinant Bundle on the Moduli Space of Stable Triples over a Curve

    Indian Academy of Sciences (India)

    Indranil Biswas; N Raghavendra

    2002-08-01

    We construct a holomorphic Hermitian line bundle over the moduli space of stable triples of the form (1, 2, ), where 1 and 2 are holomorphic vector bundles over a fixed compact Riemann surface , and : 2 → 1 is a holomorphic vector bundle homomorphism. The curvature of the Chern connection of this holomorphic Hermitian line bundle is computed. The curvature is shown to coincide with a constant scalar multiple of the natural Kähler form on the moduli space. The construction is based on a result of Quillen on the determinant line bundle over the space of Dolbeault operators on a fixed ∞ Hermitian vector bundle over a compact Riemann surface.

  3. Poincaré Polynomial of the Moduli Spaces of Parabolic Bundles

    Indian Academy of Sciences (India)

    Yogish I Holla

    2000-08-01

    In this paper we use Weil conjectures (Deligne's theorem) to calculate the Betti numbers of the moduli spaces of semi-stable parabolic bundles on a curve. The quasi parabolic analogue of the Siegel formula, together with the method of Harder-Narasimhan filtration gives us a recursive formula for the Poincaré polynomials of the moduli. We solve the recursive formula by the method of Zagier, to give the Poincaré polynomial in a closed form. We also give explicit tables of Betti numbers in small rank, and genera.

  4. The Picard group of the moduli space of r-Spin Riemann surfaces

    DEFF Research Database (Denmark)

    Randal-Williams, Oscar

    2012-01-01

    An r-Spin Riemann surface is a Riemann surface equipped with a choice of rth root of the (co)tangent bundle. We give a careful construction of the moduli space (orbifold) of r-Spin Riemann surfaces, and explain how to establish a Madsen–Weiss theorem for it. This allows us to prove the “Mumford c...... conjecture” for these moduli spaces, but more interestingly allows us to compute their algebraic Picard groups (for g≥10, or g≥9 in the 2-Spin case). We give a complete description of these Picard groups, in terms of explicitly constructed line bundles....

  5. The information metric on the moduli space of instantons with global symmetries

    Directory of Open Access Journals (Sweden)

    Emanuel Malek

    2016-02-01

    Full Text Available In this note we revisit Hitchin's prescription [1] of the Fisher metric as a natural measure on the moduli space of instantons that encodes the space–time symmetries of a classical field theory. Motivated by the idea of the moduli space of supersymmetric instantons as an emergent space in the sense of the gauge/gravity duality, we extend the prescription to encode also global symmetries of the underlying theory. We exemplify our construction with the instanton solution of the CPN sigma model on R2.

  6. The homology groups of moduli spaces on non-classical Klein surfaces

    International Nuclear Information System (INIS)

    We describe the moduli space M-vector±(g,c) of non-classical directed Klein surfaces of genus g=h-c-1 with c≥0 distinguished points as a configuration space B±(h,c) of classes h-slit pairs in C. Based on this model, we prove that M-vector±(g,c) is non-orientable for any g and c and we compute the homology groups of the moduli spaces M-vector±(g,c) for g≤2. (author)

  7. The geometry of the light-cone cell decomposition of moduli space

    Energy Technology Data Exchange (ETDEWEB)

    Garner, David, E-mail: d.p.r.garner@qmul.ac.uk; Ramgoolam, Sanjaye, E-mail: s.ramgoolam@qmul.ac.uk [Centre for Research in String Theory, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2015-11-15

    The moduli space of Riemann surfaces with at least two punctures can be decomposed into a cell complex by using a particular family of ribbon graphs called Nakamura graphs. We distinguish the moduli space with all punctures labelled from that with a single labelled puncture. In both cases, we describe a cell decomposition where the cells are parametrised by graphs or equivalence classes of finite sequences (tuples) of permutations. Each cell is a convex polytope defined by a system of linear equations and inequalities relating light-cone string parameters, quotiented by the automorphism group of the graph. We give explicit examples of the cell decomposition at low genus with few punctures.

  8. Impacts of non-geometric moduli on effective theory of 5D supergravity

    CERN Document Server

    Sakamura, Yutaka

    2013-01-01

    5D supergravity generically has non-geometric moduli other than the radion that belong to 5D vector multiplets. We summarize the impacts of such moduli on 4D effective theory of 5D supergravity on S^1/Z_2. We mainly discuss the structure of the effective Kahler potential including the one-loop quantum corrections. As an illustrative example, we construct a model in which the size of the extra dimension is stabilized at an exponentially large value compared to the Planck length, which is similar to the LARGE volume scenario in string theory.

  9. The geometry of the light-cone cell decomposition of moduli space

    Science.gov (United States)

    Garner, David; Ramgoolam, Sanjaye

    2015-11-01

    The moduli space of Riemann surfaces with at least two punctures can be decomposed into a cell complex by using a particular family of ribbon graphs called Nakamura graphs. We distinguish the moduli space with all punctures labelled from that with a single labelled puncture. In both cases, we describe a cell decomposition where the cells are parametrised by graphs or equivalence classes of finite sequences (tuples) of permutations. Each cell is a convex polytope defined by a system of linear equations and inequalities relating light-cone string parameters, quotiented by the automorphism group of the graph. We give explicit examples of the cell decomposition at low genus with few punctures.

  10. On the moduli space of semi-stable plane sheaves with Hilbert polynomial P(m)=6m+2

    CERN Document Server

    Maican, Mario

    2011-01-01

    We study the Simpson moduli space of semi-stable sheaves on the complex projective plane that have dimension 1, multiplicity 6 and Euler characteristic 2. We describe concretely these sheaves as cokernels of morphisms of locally free sheaves and we stratify the moduli space according to the types of sheaves that occur.

  11. Moduli spaces for linear differential equations and the Painlev'e equations

    NARCIS (Netherlands)

    Put, Marius van der; Saito, Masa-Hiko

    2009-01-01

    In this paper, we give a systematic construction of ten isomonodromic families of connections of rank two on P1 inducing Painlev´e equations. The classification of ten families is given by considering the Riemann-Hilbert morphism from a moduli space of connections with certain type of regular and ir

  12. On Rationality of Moduli Spaces of Vector Bundles on Real Hirzebruch Surfaces

    Indian Academy of Sciences (India)

    Indranil Biswas; Ronnie Sebastian

    2013-05-01

    Let be a real form of a Hirzebruch surface. Let $M_H(r,c_1,c_2)$ be the moduli space of vector bundles on . Under some numerical conditions on $r,c_1$ and $c_2$, we identify those $M_H(r,c_1,c_2)$ that are rational.

  13. BPS/CFT correspondence II: Instantons at crossroads, Moduli and Compactness Theorem

    CERN Document Server

    Nekrasov, Nikita

    2016-01-01

    Gieseker-Nakajima moduli spaces $M_{k}(n)$ parametrize the charge $k$ noncommutative $U(n)$ instantons on ${\\bf R}^{4}$ and framed rank $n$ torsion free sheaves $\\mathcal{E}$ on ${\\bf C\\bf P}^{2}$ with ${\\rm ch}_{2}({\\mathcal{E}}) = k$. They also serve as local models of the moduli spaces of instantons on general four-manifolds. We study the generalization of gauge theory in which the four dimensional spacetime is a stratified space $X$ immersed into a Calabi-Yau fourfold $Z$. The local model ${\\bf M}_{k}({\\vec n})$ of the corresponding instanton moduli space is the moduli space of charge $k$ (noncommutative) instantons on origami spacetimes. There, $X$ is modelled on a union of (up to six) coordinate complex planes ${\\bf C}^{2}$ intersecting in $Z$ modelled on ${\\bf C}^{4}$. The instantons are shared by the collection of four dimensional gauge theories sewn along two dimensional defect surfaces and defect points. We also define several quiver versions ${\\bf M}_{\\bf k}^{\\gamma}({\\vec{\\bf n}})$ of ${\\bf M}_{k}...

  14. D-branes at del Pezzo singularities: global embedding and moduli stabilisation

    Science.gov (United States)

    Cicoli, Michele; Krippendorf, Sven; Mayrhofer, Christoph; Quevedo, Fernando; Valandro, Roberto

    2012-09-01

    In the context of type IIB string theory we combine moduli stabilisation and model building on branes at del Pezzo singularities in a fully consistent global compactification. By means of toric geometry, we classify all the Calabi-Yau manifolds with 3 K-theory charges and Freed-Witten anomaly cancellation. We briefly discuss phenomenological and cosmological implications of our models.

  15. Refined Estimates for the Equivalence Between Ditzian-Totik Moduli of Smoothness and K-Functionals

    Directory of Open Access Journals (Sweden)

    Gancho T. Tachev

    2012-11-01

    Full Text Available The aim of this note is to study the magnitude of the constants in the equivalence between the first and second order Ditzian-Totik moduli of smoothness and related K-functionals. Applications to some classic approximation operators are given.

  16. Analytic solution for bending-compression/tension members with different moduli

    International Nuclear Information System (INIS)

    In this paper, based on elastic theory of different tension-compression moduli, formulas for calculation of stress and displacement are obtained for bending-compression/tension members under complex stress and subject to combined loadings. An example is given and the obtained analytical solution is compared with numerical results, showing high accuracy of the obtained analytic solution

  17. Hilbert Series for Moduli Spaces of Instantons on C^2/Z_n

    CERN Document Server

    Dey, Anindya; Mekareeya, Noppadol; Rodríguez-Gómez, Diego; Seong, Rak-Kyeong

    2014-01-01

    We study chiral gauge-invariant operators on moduli spaces of G instantons for any classical group G on A-type ALE spaces using Hilbert Series (HS). Moduli spaces of instantons on an ALE space can be realized as Higgs branches of certain quiver gauge theories which appear as world-volume theories on Dp branes in a Dp-D(p+4) system with the D(p+4) branes (with or without O(p+4) planes) wrapping the ALE space. We study in detail a list of quiver gauge theories which are related to G-instantons of arbitrary ranks and instanton numbers on a generic A_{n-1} ALE space and discuss the corresponding brane configurations. For a large class of theories, we explicitly compute the Higgs branch HS which reveals various algebraic/geometric aspects of the moduli space such as the dimension of the space, generators of the moduli space and relations connecting them. In a large number of examples involving lower rank instantons, we demonstrate that HS for equivalent instantons of isomorphic gauge groups but very different quiv...

  18. A stringy mechanism for a small cosmological constant — multi-moduli cases

    International Nuclear Information System (INIS)

    Based on the properties of probability distributions of functions of random variables, we proposed earlier a simple stringy mechanism that prefers the meta-stable vacua with a small cosmological constant Λ. As an illustration of this approach, we study in this paper particularly simple but non-trivial models of the Kähler uplift in the large volume flux compactification scenario in Type IIB string theory, where all parameters introduced in the model are treated either as fixed constants motivated by physics, or as random variables with some given uniform probability distributions. We determine the value w0 of the superpotential W0 at the supersymmetric minima, and find that the resulting probability distribution P(w0) peaks at w0 = 0; furthermore, this peaking behavior strengthens as the number of complex structure moduli increases. The resulting probability distribution P(Λ) for meta-stable vacua also peaks as Λ → 0, for both positive and negative Λ. This peaking/divergent behavior of P(Λ) strengthens as the number of moduli increases. In some scenarios for Λ > 0, the likely value of Λ decreases exponentially as the number of moduli increases. The light cosmological moduli issue accompanying a very small Λ is also mentioned

  19. Quantum states to brane geometries via fuzzy moduli spaces of giant gravitons

    CERN Document Server

    Pasukonis, Jurgis

    2012-01-01

    Eighth-BPS local operators in N=4 SYM are dual to quantum states arising from the quantization of a moduli space of giant gravitons in AdS5xS5. Earlier results on the quantization of this moduli space give a Hilbert space of multiple harmonic oscillators in 3 dimensions. We use these results, along with techniques from fuzzy geometry, to develop a map between quantum states and brane geometries. In particular there is a map between the oscillator states and points in a discretization of the base space in the toric fibration of the moduli space. We obtain a geometrical decomposition of the space of BPS states with labels consisting of U(3) representations along with U(N) Young diagrams and associated group theoretic multiplicities. Factorization properties in the counting of BPS states lead to predictions for BPS world-volume excitations of specific brane geometries. Some of our results suggest an intriguing complementarity between localisation in the moduli space of branes and localisation in space-time.

  20. An Approach to Calculate Mineralś Bulk Moduli KS from Chemical Composition and Density ρ

    Science.gov (United States)

    Breuer, S.; Schilling, F. R.; Mueller, B.; Drüppel, K.

    2015-12-01

    The elastic properties of minerals are fundamental parameters for technical and geotechnical applications and an important research topic towards a better understanding of the Eart&hacute;s interior. Published elastic properties, chemical composition, and density data of 86 minerals (total of 258 data including properties of minerals at various p, T conditions) were collected into a database. It was used to test different hypotheses about relationships between these properties (e.g. water content in minerals and their Poisson's ratio). Furthermore, a scheme to model the average elastic properties, i.e. the bulk modulus KS, based on mineral density and composition was developed. Birc&hacute;s law, a linearity between density ρ and wave velocity (e.g. vp.), is frequently used in seismic and seismology to derive density of the Eart&hacute;s interior from seismic velocities. Applying the compiled mineral data contradicts the use of a simple velocity-density relation (e.g. Gardneŕs relation, 1974). The presented model-approach to estimate the mineralś bulk moduli Ks (as Voigt-Reuss-Hill average) is based on the idea of pressure-temperature (p-T) dependent ionś bulk moduli. Using a multi-exponential regression to ascertain the ionś bulk moduli and by applying an exponential scaling with density ρ, their bulk moduli could be modelled. As a result, > 88 % of the 258 bulk moduli data are predicted with an uncertainty of < 20 % compared to published values. Compared to other models (e.g. Anderson et al. 1970 and Anderson & Nafe 1965), the here presented approach to model the bulk moduli only requires the density ρ and chemical composition of the mineral and is not limited to a specific group of minerals, composition, or structure. In addition to this, by using the pressure and temperature dependent density ρ(p, T), it is possible to predict bulk moduli for varying p-T conditions. References:Gardner, G.H.F, Gardner, L.W. and Gregory, A.R. (1974). Geophysics, 39, No. 6

  1. Fiber/collagen composites for ligament tissue engineering: influence of elastic moduli of sparse aligned fibers on mesenchymal stem cells.

    Science.gov (United States)

    Thayer, Patrick S; Verbridge, Scott S; Dahlgren, Linda A; Kakar, Sanjeev; Guelcher, Scott A; Goldstein, Aaron S

    2016-08-01

    Electrospun microfibers are attractive for the engineering of oriented tissues because they present instructive topographic and mechanical cues to cells. However, high-density microfiber networks are too cell-impermeable for most tissue applications. Alternatively, the distribution of sparse microfibers within a three-dimensional hydrogel could present instructive cues to guide cell organization while not inhibiting cell behavior. In this study, thin (∼5 fibers thick) layers of aligned microfibers (0.7 μm) were embedded within collagen hydrogels containing mesenchymal stem cells (MSCs), cultured for up to 14 days, and assayed for expression of ligament markers and imaged for cell organization. These microfibers were generated through the electrospinning of polycaprolactone (PCL), poly(ester-urethane) (PEUR), or a 75/25 PEUR/PCL blend to produce microfiber networks with elastic moduli of 31, 15, and 5.6 MPa, respectively. MSCs in composites containing 5.6 MPa fibers exhibited increased expression of the ligament marker scleraxis and the contractile phenotype marker α-smooth muscle actin versus the stiffer fiber composites. Additionally, cells within the 5.6 MPa microfiber composites were more oriented compared to cells within the 15 and 31 MPa microfiber composites. Together, these data indicate that the mechanical properties of microfiber/collagen composites can be tuned for the engineering of ligament and other target tissues. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1894-1901, 2016. PMID:27037972

  2. Foliations on the moduli space of curves, vanishing in cohomology, and Calogero-Moser curves

    CERN Document Server

    Grushevsky, Samuel

    2011-01-01

    Using meromorphic differentials with real periods, we show that a certain tautological homology class on the moduli space of smooth algebraic curves of genus g vanishes. The vanishing of the entire tautological ring for degree g-1 and higher, part of Faber's conjecture, is known in both homology and Chow --- it was proven by Looijenga, Ionel, and Graber-Vakil, and the class that we show vanishes is just one such tautological class. However, our approach, motivated by the Whitham perturbation theory of soliton equations, is completely new, elementary in the sense that no techniques beyond elementary complex analysis are used, and also leads to a natural non-speciality conjecture, which would imply many more vanishing results and relations among tautological classes. In the course of the proof we define and study foliations of the moduli space of curves constructed using periods of meromorphic differentials, in a way providing for meromorphic differentials a theory similar to that developed for abelian differen...

  3. Determination of Elastic Moduli of Fiber-Resin Composites Using an Impulse Excitation Technique

    Science.gov (United States)

    Viens, Michael J.; Johnson, Jeffrey J.

    1996-01-01

    The elastic moduli of graphite/epoxy and graphite/cyanate ester composite specimens with various laminate lay-ups was determined using an impulse excitation/acoustic resonance technique and compared to those determined using traditional strain gauge and extensometer techniques. The stiffness results were also compared to those predicted from laminate theory using uniaxial properties. The specimen stiffnesses interrogated ranged from 12 to 30 Msi. The impulse excitation technique was found to be a relatively quick and accurate method for determining elastic moduli with minimal specimen preparation and no requirement for mechanical loading frames. The results of this investigation showed good correlation between the elastic modulus determined using the impulse excitation technique, strain gauge and extensometer techniques, and modulus predicted from laminate theory. The flexural stiffness determined using the impulse excitation was in good agreement with that predicted from laminate theory. The impulse excitation/acoustic resonance interrogation technique has potential as a quality control test.

  4. Mathematical Models for in-Plane Moduli of Honeycomb Structures-A Review

    Directory of Open Access Journals (Sweden)

    Imran Ali

    2014-01-01

    Full Text Available Honeycomb structures are light weight cellular structures having high strength to weight ratio with enormous applications in aerospace industry, high speed automobiles, computers and other electronics equipment bodies and recently as flexible structures and mechanisms. In this paper a review of mathematical models for stress strain behaviour of two dimensional honeycomb structures is presented. As proposed by different authors, expressions for in-plane Elastic Moduli and shear Modulus are presented and compared on same scale dimensions. In addition to that, effects of number of unit cells on effective in plane and out of plane Moduli of the testing specimen for regular honeycombs and open and closed cell foams, are also reviewed.

  5. Cosmological moduli and the post-inflationary universe: A critical review

    Science.gov (United States)

    Kane, Gordon; Sinha, Kuver; Watson, Scott

    2015-06-01

    We critically review the role of cosmological moduli in determining the post-inflationary history of the universe. Moduli are ubiquitous in string and M-theory constructions of beyond the Standard Model physics, where they parametrize the geometry of the compactification manifold. For those with masses determined by supersymmetry (SUSY) breaking this leads to their eventual decay slightly before Big Bang nucleosynthesis (BBN) (without spoiling its predictions). This results in a matter dominated phase shortly after inflation ends, which can influence baryon and dark matter genesis, as well as observations of the cosmic microwave background (CMB) and the growth of large-scale structure. Given progress within fundamental theory, and guidance from dark matter and collider experiments, nonthermal histories have emerged as a robust and theoretically well-motivated alternative to a strictly thermal one. We review this approach to the early universe and discuss both the theoretical challenges and the observational implications.

  6. A measurement of elastic moduli for tungsten films on polymer substrate using wrinkling analysis

    International Nuclear Information System (INIS)

    The elastic moduli of ultra thin tungsten (W) films on polymers were assessed with wrinkling analysis. Thin W films with a range of thickness between 17 and 100 nm were deposited on compliant polymers and Si strips using DC magnetron sputtering method, causing the tensile stress in a few GPa scale with respect to the thickness of W films. By applying lateral compression on polymer, wrinkle patterns were developed in the W thin film with well-defined amplitude and wavelength. Using a simple equation on wrinkle analysis, the range of elastic moduli was estimated with increasing the thickness. It was found that the elastic modulus and the tensile stress decreased with increasing the film thickness.

  7. Intersection theory on moduli of disks, open KdV and Virasoro

    CERN Document Server

    Pandharipande, Rahul; Tessler, Ran J

    2014-01-01

    We define a theory of descendent integration on the moduli spaces of stable pointed disks. The descendent integrals are proved to be coefficients of the $\\tau$-function of an open KdV heirarchy. A relation between the integrals and a representation of half the Virasoro algebra is also proved. The construction of the theory requires an in depth study of homotopy classes of multivalued boundary conditions. Geometric recursions based on the combined structure of the boundary conditions and the moduli space are used to compute the integrals. We also provide a detailed analysis of orientations. Our open KdV and Virasoro constraints uniquely specify a theory of higher genus open descendent integrals. As a result, we obtain an open analog (governing all genera) of Witten's conjectures concerning descendent integrals on the Deligne-Mumford space of stable curves.

  8. Cosmological Moduli and the Post-Inflationary Universe: A Critical Review

    CERN Document Server

    Kane, Gordon; Watson, Scott

    2015-01-01

    We critically review the role of cosmological moduli in determining the post-inflationary history of the universe. Moduli are ubiquitous in string and M-theory constructions of beyond the Standard Model physics, where they parametrize the geometry of the compactification manifold. For those with masses determined by supersymmetry breaking this leads to their eventual decay slightly before Big Bang Nucleosynthesis (without spoiling its predictions). This results in a matter dominated phase shortly after inflation ends, which can influence baryon and dark matter genesis, as well as observations of the Cosmic Microwave Background and the growth of large-scale structure. Given progress within fundamental theory, and guidance from dark matter and collider experiments, non-thermal histories have emerged as a robust and theoretically well-motivated alternative to a strictly thermal one. We review this approach to the early universe and discuss both the theoretical challenges and the observational implications.

  9. Moduli backreaction and supersymmetry breaking in string-inspired inflation models

    International Nuclear Information System (INIS)

    We emphasize the importance of effects from heavy fields on supergravity models of inflation. We study, in particular, the backreaction of stabilizer fields and geometric moduli in the presence of supersymmetry breaking. Many effects do not decouple even if those fields are much heavier than the inflaton field. We apply our results to successful models of Starobinsky-like inflation and natural inflation. In most scenarios producing a plateau potential it proves difficult to retain the flatness of the potential after backreactions are taken into account. Some of them are incompatible with non-perturbative moduli stabilization. In natural inflation there exist a number of models which are not constrained by backreactions at all. In those cases the correction terms from heavy fields have the same inflaton-dependence as the uncorrected potential, so that inflation may be possible even for very large gravitino masses.

  10. Prediction of the overall moduli of a cylindrical short-fiber reinforced composite

    Science.gov (United States)

    Shanyi, Du; Linzhi, Wu

    1993-02-01

    With respect to obtaining the effective elastic moduli of the composite, the present theory differs from both Eshelby's equivalent inclusion method and Hill's self-consistent one, both of which only consider the mechanical properties of the matrix and inclusions (fibers). In fact, the inclusion-inclusion interaction is more pronounced when the volume fraction of inclusions of the composite increases. Hence, in this paper the effective elastic moduli of the composite are derived by taking into account the shapes, sizes and distribution of inclusions, and the interactions between inclusions. In addition, it is more convincing to assume short-fibers as cylindrical inclusions as in the present paper than as ellipsoidal ones as in others[7,8]. Finally, numerical results are given.

  11. Realistic D-Brane Models on Warped Throats: Fluxes, Hierarchies and Moduli Stabilization

    CERN Document Server

    Cascales, J F G; Quevedo, Fernando; Uranga, Angel M

    2004-01-01

    We describe the construction of string theory models with semirealistic spectrum in a sector of (anti) D3-branes located at an orbifold singularity at the bottom of a highly warped throat geometry, which is a generalisation of the Klebanov-Strassler deformed conifold. These models realise the Randall-Sundrum proposal to naturally generate the Planck/electroweak hierarchy in a concrete string theory embedding, and yielding interesting chiral open string spectra. We describe examples with Standard Model gauge group (or left-right symmetric extensions) and three families of SM fermions, with correct quantum numbers including hypercharge. The dilaton and complex structure moduli of the geometry are stabilised by the 3-form fluxes required to build the throat. We describe diverse issues concerning the stabilisation of geometric Kahler moduli, like blow-up modes of the orbifold singularities, via D term potentials and gauge theory non-perturbative effects, like gaugino condensation. This local geometry, once embedd...

  12. Gauge/Bethe correspondence on $S^1 \\times \\Sigma_h$ and index over moduli space

    CERN Document Server

    Okuda, Satoshi

    2015-01-01

    We introduce two-types of topologically twisted Chern-Simons-matter theories on the direct product of circle and genus-h Riemann surface (S^1 \\times \\Sigma_h). The partition functions of first model agrees with the partition functions of a generalizations of G/G gauged WZW model. We also find that correlation functions of Wilson loops in first type Chern-Simons-matter theory coincide with correlation functions of G elements in the generalization of G/G gauged WZW model. The partition function of this model also has nice interpretations as norms of eigen states of Hamiltonian in the quantum integrable model (q-boson hopping model) and also as a geometric index over a particular moduli space. In the second-type Chern-Simons-matter theory, the partition function is related to integration over moduli space of Hitchin equation on Riemann surface.

  13. Gravitational moduli forces in small nuclei and analytical computation of the Newton constant

    OpenAIRE

    Vayenas, Constantinos G.; Giannareli, Stamatia; Souentie, Stamatios

    2007-01-01

    The magnitude of gravity at subatomic distances was investigated in the nuclear size range by examining the vibrational kinetic energy of baryons and quarks, treated as waveparticles and strings, in the 4He and 2H nuclei. Due to the relativistic increase in mass and concomitant wave particle confinement at high vibrational energies, it is found that gravitational moduli forces are significant and comparable in size with the strong interaction forces exerted between color quarks. This leads to...

  14. Global D-brane models with stabilised moduli and light axions

    CERN Document Server

    Cicoli, Michele

    2012-01-01

    We review recent attempts to try to combine global issues of string compactifications, like moduli stabilisation, with local issues, like semi-realistic D-brane constructions. We list the main problems encountered, and outline a possible solution which allows globally consistent embeddings of chiral models. We also argue that this stabilisation mechanism leads to an axiverse. We finally illustrate our general claims in a concrete example where the Calabi-Yau manifold is explicitly described by toric geometry.

  15. Obstruction bundles over moduli spaces with boundary and the action filtration in symplectic field theory

    OpenAIRE

    Fabert, Oliver

    2007-01-01

    Branched covers of orbit cylinders are the basic examples of holomorphic curves studied in symplectic field theory. Since all curves with Fredholm index one can never be regular for any choice of cylindrical almost complex structure, we generalize the obstruction bundle technique of Taubes for determining multiple cover contributions from Gromov-Witten theory to the case of moduli spaces with boundary. Our result proves that the differential in rational symplectic field theory and contact hom...

  16. MPL - a program for computations with iterated integrals on moduli spaces of curves of genus zero

    CERN Document Server

    Bogner, Christian

    2015-01-01

    We introduce the computer program MPL for computations with homotopy invariant iterated integrals on moduli spaces $\\mathcal{M}_{0,n}$ of curves of genus 0 with $n$ ordered marked points. The program is an implementation of the algorithms presented in [13], based on Maple. It includes the symbol map and procedures for the analytic computation of period integrals on $\\mathcal{M}_{0,n}.$ It supports the automated computation of a certain class of Feynman integrals.

  17. PRIMERJAVA ENERGETSKE UČINKOVITOSTI MED STIRLINGOVIM MOTORJEM IN FOTONAPETOSTNIMI MODULI

    OpenAIRE

    Skok, Jure

    2014-01-01

    V diplomski nalogi sem primerjal Stirlingov motor alfa izvedbe, ki pridobi toploto preko solarnih kolektorjev z fotonapetostnimi moduli. Obe izvedbi sta postavljeni namerno na isti lokaciji, ki bi bila zanimiva za komercialen namen. Prav tako sta oba sistema cenovno namenjena komercialni uporabi in prodaji. V diplomski nalogi sem prišel do zaključka, da se uporabniku, ki kupuje sistem za sedaj bolj izplača postaviti fotovoltaične sisteme.

  18. Algebraic cohomology of the moduli space of rank 2 vector bundles on a curve

    CERN Document Server

    Balaji, V; Newstead, P E; Balaji, V; King, A D; Newstead, P E

    1995-01-01

    Let \\MC be the moduli space of stable holomorphic vector bundles of rank 2 and fixed determinant of odd degree, over a smooth projective curve C. This paper identifies the algebraic cohomology ring \\HA^*(\\MC), i.e. the subring of the rational cohomology ring H^*(\\MC;\\QQ) spanned by the fundamental classes of algebraic cycles, in terms of the algebraic cohomology ring of the Jacobian \\JC.

  19. Tangent moduli of the Hencky material model derived from the stored energy function at finite strains

    Czech Academy of Sciences Publication Activity Database

    Poživilová, Alena; Plešek, Jiří

    2005-01-01

    Roč. 482, č. 482 (2005), s. 327-330. ISSN 0255-5476 R&D Projects: GA ČR(CZ) GA101/03/0331; GA ČR(CZ) GP106/03/D038 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustoelasticity * large strains * third order elastic moduli Subject RIV: JG - Metallurgy Impact factor: 0.399, year: 2005

  20. Virtual Structure Constants as Intersection Numbers of Moduli Space of Polynomial Maps with Two Marked Points

    OpenAIRE

    Jinzenji, Masao

    2007-01-01

    In this paper, we derive the virtual structure constants used in mirror computation of degree k hypersurface in CP^{N-1}, by using localization computation applied to moduli space of polynomial maps from CP^{1} to CP^{N-1} with two marked points. We also apply this technique to non-nef local geometry O(1)+O(-3)->CP^{1} and realize mirror computation without using Birkhoff factorization.

  1. Functional Apparent Moduli (FAMs) as Predictors of Oral Implant Osseointegration Dynamics

    OpenAIRE

    Chang, Po-Chun; Seol, Yang-Jo; Kikuchi, Noboru; Goldstein, Steven A.; Giannobile, William V.

    2010-01-01

    At present, limited functional data exists regarding the application and use of biomechanical and imaging technologies for oral implant osseointegration assessment. The objective of this investigation was to determine the functional apparent moduli (FAMs) that could predict the dynamics of oral implant osseointegration. Using an in vivo dental implant osseous healing model, two FAMs, functional bone apparent modulus (FBAM) and composite tissue apparent modulus (FCAM), of the selected peri-imp...

  2. Pre-Stressed Viscoelastic Composites: Effective Incremental Moduli and Band-Gap Tuning

    International Nuclear Information System (INIS)

    We study viscoelastic wave propagation along pre-stressed nonlinear elastic composite bars. In the pre-stressed state we derive explicit forms for the effective incremental storage and loss moduli with dependence on the pre-stress. We also derive a dispersion relation for the effective wavenumber in the case of arbitrary frequency, hence permitting a study of viscoelastic band-gap tuning via pre-stress.

  3. Simultaneous measurement of field-dependence elastic moduli by laser interferometry

    OpenAIRE

    Bayón Rojo, A.; Chicharro Higuera, José Manuel; Salazar Bloise, F.

    2000-01-01

    A methodology is applied which allows the simultaneous determination of the Youngs modulus and the shear modulus to evaluate elastic moduli variations with the magnetic field ($Delta E$ and $Delta G$). The methodology followed is based on the simultaneous detection of the transverse and torsional natural frequencies of a slender magnetic bar found inside a solenoid. The resultant vibration is detected via a heterodyne interferometric optical system with a broad bandwidth....

  4. Moduli Space of IIB Superstring and SUYM in AdS5xS5

    International Nuclear Information System (INIS)

    This paper consists of two parts. In part I, we interpret the hidden symmetry of the moduli space of IIB superstring on AdS5xS5 in terms of the chiral embedding in AdS5, which turns out to be the CP3 conformal affine Toda model. We review how the position μ of poles in the Riemann-Hilbert formulation of dressing transformation and the value of loop parameter μ in the vertex operator of affine algebra determine the moduli space of the soliton solutions, which describes the moduli space of the Green-Schwarz superstring. We show also how this affine SU(4) symmetry affinizes the conformal symmetry in the twistor space, and how a soliton string corresponds to a Robinson congruence with twist and dilation spin coefficients μ of twistor. In part II, by extending the dressing symmetric action of IIB string in AdS5xS5 to the D3 brane, we find a gauged WZW action of Higgs Yang-Mills field including the 2-cocycle of axially anomaly. The left and right twistor structures of left and right α-planes glue into an ambitwistor. The symmetry group of Nahm equations is centrally extended to an affine group, thus we explain why the spectral curve is given by affine Toda.

  5. Experimentally-based multiscale model of the elastic moduli of bovine trabecular bone and its constituents.

    Science.gov (United States)

    Hamed, Elham; Novitskaya, Ekaterina; Li, Jun; Jasiuk, Iwona; McKittrick, Joanna

    2015-09-01

    The elastic moduli of trabecular bone were modeled using an analytical multiscale approach. Trabecular bone was represented as a porous nanocomposite material with a hierarchical structure spanning from the collagen-mineral level to the trabecular architecture level. In parallel, compression testing was done on bovine femoral trabecular bone samples in two anatomical directions, parallel to the femoral neck axis and perpendicular to it, and the measured elastic moduli were compared with the corresponding theoretical results. To gain insights on the interaction of collagen and minerals at the nanoscale, bone samples were deproteinized or demineralized. After such processing, the treated samples remained as self-standing structures and were tested in compression. Micro-computed tomography was used to characterize the hierarchical structure of these three bone types and to quantify the amount of bone porosity. The obtained experimental data served as inputs to the multiscale model and guided us to represent bone as an interpenetrating composite material. Good agreement was found between the theory and experiments for the elastic moduli of the untreated, deproteinized, and demineralized trabecular bone. PMID:26046284

  6. Models of discretized moduli spaces, cohomological field theories, and Gaussian means

    Science.gov (United States)

    Andersen, Jørgen Ellegaard; Chekhov, Leonid O.; Norbury, Paul; Penner, Robert C.

    2015-12-01

    We prove combinatorially the explicit relation between genus filtrated s-loop means of the Gaussian matrix model and terms of the genus expansion of the Kontsevich-Penner matrix model (KPMM). The latter is the generating function for volumes of discretized (open) moduli spaces Mg,sdisc given by Ng,s(P1, …, Ps) for (P1, …, Ps) ∈ Z+s. This generating function therefore enjoys the topological recursion, and we prove that it is simultaneously the generating function for ancestor invariants of a cohomological field theory thus enjoying the Givental decomposition. We use another Givental-type decomposition obtained for this model by the second authors in 1995 in terms of special times related to the discretization of moduli spaces thus representing its asymptotic expansion terms (and therefore those of the Gaussian means) as finite sums over graphs weighted by lower-order monomials in times thus giving another proof of (quasi)polynomiality of the discrete volumes. As an application, we find the coefficients in the first subleading order for Mg,1 in two ways: by using the refined Harer-Zagier recursion and by exploiting the above Givental-type transformation. We put forward the conjecture that the above graph expansions can be used for probing the reduction structure of the Deligne-Mumford compactification M bar g, s of moduli spaces of punctured Riemann surfaces.

  7. Scattering and Sequestering of Blow-Up Moduli in Local String Models

    CERN Document Server

    Conlon, Joseph P

    2011-01-01

    We study the scattering and sequestering of blow-up fields - either local to or distant from a visible matter sector - through a CFT computation of the dependence of physical Yukawa couplings on the blow-up moduli. For a visible sector of D3-branes on orbifold singularities we compute the disk correlator between orbifold blow-up moduli and matter Yukawa couplings. For n = 1 we determine the full quantum and classical correlator. This result has the correct factorisation onto lower 3-point functions and also passes numerous other consistency checks. For n > 1 we show that the structure of picture-changing applied to the twist operators establishes the sequestering of distant blow-up moduli at disk level to all orders in \\alpha'. We explain how these results are relevant to suppressing soft terms to scales parametrically below the gravitino mass. By giving vevs to the blow-up fields we can move into the smooth limit and thereby derive CFT results for the smooth Swiss-cheese Calabi-Yaus that appear in the Large...

  8. Stability of Picard Bundle Over Moduli Space of Stable Vector Bundles of Rank Two Over a Curve

    Indian Academy of Sciences (India)

    Indranil Biswas; Tomás L Gómez

    2001-08-01

    Answering a question of [BV] it is proved that the Picard bundle on the moduli space of stable vector bundles of rank two, on a Riemann surface of genus at least three, with fixed determinant of odd degree is stable.

  9. Uncoupling shear and uniaxial elastic moduli of semiflexible biopolymer networks: compression-softening and stretch-stiffening

    Science.gov (United States)

    van Oosten, Anne S. G.; Vahabi, Mahsa; Licup, Albert J.; Sharma, Abhinav; Galie, Peter A.; Mackintosh, Fred C.; Janmey, Paul A.

    2016-01-01

    Gels formed by semiflexible filaments such as most biopolymers exhibit non-linear behavior in their response to shear deformation, e.g., with a pronounced strain stiffening and negative normal stress. These negative normal stresses suggest that networks would collapse axially when subject to shear stress. This coupling of axial and shear deformations can have particularly important consequences for extracellular matrices and collagenous tissues. Although measurements of uniaxial moduli have been made on biopolymer gels, these have not directly been related to the shear response. Here, we report measurements and simulations of axial and shear stresses exerted by a range of hydrogels subjected to simultaneous uniaxial and shear strains. These studies show that, in contrast to volume-conserving linearly elastic hydrogels, the Young’s moduli of networks formed by the biopolymers are not proportional to their shear moduli and both shear and uniaxial moduli are strongly affected by even modest degrees of uniaxial strain.

  10. Investigation of the influence of fraction of SiC particles on the elastic moduli of SiCp/aluminum

    International Nuclear Information System (INIS)

    We investigate the influence of the volume fraction of silicon carbide particles (SiCp) in an Al matrix composite on the elastic moduli of composites by using laser ultrasonic method. A series of SiCp/Al composites with six volume fractions of reinforcement SiCp are used as samples. The results show that the value of the elastic moduli Change linearly with the increasing of the volume fraction of the SiCp. The relative elastic moduli changes can be reached to 86.42% for shear modulus and to 95.25% for Young's modulus. We also calculate the elastic moduli of composite based on the elastic theory for two phase system. The detailed results and discussions are presented in this paper

  11. Estimating elastic moduli of rocks from thin sections: Digital rock study of 3D properties from 2D images

    Science.gov (United States)

    Saxena, Nishank; Mavko, Gary

    2016-03-01

    Estimation of elastic rock moduli using 2D plane strain computations from thin sections has several numerical and analytical advantages over using 3D rock images, including faster computation, smaller memory requirements, and the availability of cheap thin sections. These advantages, however, must be weighed against the estimation accuracy of 3D rock properties from thin sections. We present a new method for predicting elastic properties of natural rocks using thin sections. Our method is based on a simple power-law transform that correlates computed 2D thin section moduli and the corresponding 3D rock moduli. The validity of this transform is established using a dataset comprised of FEM-computed elastic moduli of rock samples from various geologic formations, including Fontainebleau sandstone, Berea sandstone, Bituminous sand, and Grossmont carbonate. We note that using the power-law transform with a power-law coefficient between 0.4-0.6 contains 2D moduli to 3D moduli transformations for all rocks that are considered in this study. We also find that reliable estimates of P-wave (Vp) and S-wave velocity (Vs) trends can be obtained using 2D thin sections.

  12. Stress relaxation and creep on living cells with the atomic force microscope: a means to calculate elastic moduli and viscosities of cell components

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Flores, Susana; Toca-Herrera, Jose Luis [Biosurfaces Unit, CIC BiomaGUNE, Paseo Miramon 182, E-20009 San Sebastian-Donostia (Spain); Benitez, Rafael [Departamento Matematicas, Centro Universitario de Plasencia, Universidad de Extremadura, Avenida Virgen del Puerto 2, E-10600 Plasencia (Spain); Vivanco, Maria dM, E-mail: jltocaherrera@cicbiomagune.es, E-mail: jose.toca-herrera@boku.ac.at [Cell Biology and Stem Cells Unit, CIC BioGUNE, Parque tecnologico de Bizkaia, Ed. 801A, E-48160 Derio (Spain)

    2010-11-05

    In this work we present a unified method to study the mechanical properties of cells using the atomic force microscope. Stress relaxation and creep compliance measurements permitted us to determine, the relaxation times, the Young moduli and the viscosity of breast cancer cells (MCF-7). The results show that the mechanical behaviour of MCF-7 cells responds to a two-layered model of similar elasticity but differing viscosity. Treatment of MCF-7 cells with an actin-depolymerising agent results in an overall decrease in both cell elasticity and viscosity, however to a different extent for each layer. The layer that undergoes the smaller decrease (36-38%) is assigned to the cell membrane/cortex while the layer that experiences the larger decrease (70-80%) is attributed to the cell cytoplasm. The combination of the method presented in this work, together with the approach based on stress relaxation microscopy (Moreno-Flores et al 2010 J. Biomech. 43 349-54), constitutes a unique AFM-based experimental framework to study cell mechanics. This methodology can also be extended to study the mechanical properties of biomaterials in general.

  13. In vitro behaviors of rat mesenchymal stem cells on bacterial celluloses with different moduli

    International Nuclear Information System (INIS)

    Compressive moduli of bacteria-synthesized cellulose (BC) were altered by two drying techniques: ambient-air drying and freeze drying. While no significant differences in dry weight were found, their cross-sectional structures and thickness varied greatly. Freeze dried BCs had loose cross-sectional structures and a thickness of ∼ 4.7 mm, whereas air dried BCs had more compacted cross-sectional structures and a thickness of ∼ 0.1 mm. The compressive moduli of the rehydrated freeze dried and rehydrated air dried BCs were measured to be 21.06 ± 0.22 kPa and 90.09 ± 21.07 kPa, respectively. When rat mesenchymal stem cells (rMSCs) were seeded on these BCs, they maintained a round morphology in the first 3 days of cultivation. More spread-out morphology and considerable proliferation on freeze dried BCs were observed in 7 days, but not on air-dried BCs. The cells were further grown for 3 weeks in the absence and presence of differentiation agents. Without using any differentiation agents, no detectable differentiation was noticed for rMSCs further cultivated on both types of BC. With differentiation inducing agents, chondrogenic differentiation, visualized by histological staining, was observed in some area of the rehydrated freeze dried BCs; while osteogenic differentiation was noticed on the stiffer rehydrated air dried BCs. - Graphical abstract: In the presence of induction agents, rat mesenchymal stem cells (rMSCs) preferentially differentiated into osteocytes on stiffer air dried BC films. - Highlights: • Bacterial cellulose (BC) sheets with different moduli generated by drying differently • Air-dried BC exhibited a modulus similar to that of bone. • Freeze-dried BC showed a modulus in the range of that of muscle. • Air-dried BC promoted the differentiation of rMSCs into osteocytes. • Freeze-dried BC promoted the differentiation of rMSCs into chondrocytes

  14. GUT scale extra dimensions and light moduli in supergravity and cosmology

    International Nuclear Information System (INIS)

    We study the dynamical properties of geometric moduli in five- and six-dimensional supergravity compactified on flat orbifolds, focusing on the impact of the Kaehler potential. In both cases, the Kaehler potential exhibits no-scale structure at tree level. In five dimensions, the volume modulus (radion) can be stabilized by means of perturbative Kaehler corrections. In six dimensions, the same holds for size and shape of the extra dimensions, only if the dilaton can be stabilized in a Minkowski vacuum by nonperturbative effects. We develop a systematic description of almost no-scale models and derive a model independent formula for the radion mass. The radion mass is suppressed compared to the gravitino mass. The supression factor reflects the hierarchy between the Planck and the compactification scale. We analyze a specific example, where the compactification scale is determined by Fayet-Iliopoulos terms of a locally anomalous Abelian gauge group, which are O(MGUT). In a scenario with gravitino dark matter, this leads to a radion mass of 1-10 MeV. In this mass range, the radion is cosmologically stable and contributes to the dark matter density. Based on galactic gamma ray data, we derive a tight bound on the initial displacement of the field value from its low energy vacuum. We also investigate implications of typical moduli Kaehler potentials on the cosmological evolution of the scalar fields. In particular, we discuss a class of models with steep exponential potentials and non-canonical kinetic terms, motivated by our radion example. We consider the overshooting problem of cosmological moduli dynamics, and the possibility of slow-roll solutions despite the steepness of the scalar potential. (orig.)

  15. In vitro behaviors of rat mesenchymal stem cells on bacterial celluloses with different moduli

    Energy Technology Data Exchange (ETDEWEB)

    Taokaew, Siriporn [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906 (United States); Phisalaphong, Muenduen [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Zhang Newby, Bi-min, E-mail: bimin@uakron.edu [Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906 (United States)

    2014-05-01

    Compressive moduli of bacteria-synthesized cellulose (BC) were altered by two drying techniques: ambient-air drying and freeze drying. While no significant differences in dry weight were found, their cross-sectional structures and thickness varied greatly. Freeze dried BCs had loose cross-sectional structures and a thickness of ∼ 4.7 mm, whereas air dried BCs had more compacted cross-sectional structures and a thickness of ∼ 0.1 mm. The compressive moduli of the rehydrated freeze dried and rehydrated air dried BCs were measured to be 21.06 ± 0.22 kPa and 90.09 ± 21.07 kPa, respectively. When rat mesenchymal stem cells (rMSCs) were seeded on these BCs, they maintained a round morphology in the first 3 days of cultivation. More spread-out morphology and considerable proliferation on freeze dried BCs were observed in 7 days, but not on air-dried BCs. The cells were further grown for 3 weeks in the absence and presence of differentiation agents. Without using any differentiation agents, no detectable differentiation was noticed for rMSCs further cultivated on both types of BC. With differentiation inducing agents, chondrogenic differentiation, visualized by histological staining, was observed in some area of the rehydrated freeze dried BCs; while osteogenic differentiation was noticed on the stiffer rehydrated air dried BCs. - Graphical abstract: In the presence of induction agents, rat mesenchymal stem cells (rMSCs) preferentially differentiated into osteocytes on stiffer air dried BC films. - Highlights: • Bacterial cellulose (BC) sheets with different moduli generated by drying differently • Air-dried BC exhibited a modulus similar to that of bone. • Freeze-dried BC showed a modulus in the range of that of muscle. • Air-dried BC promoted the differentiation of rMSCs into osteocytes. • Freeze-dried BC promoted the differentiation of rMSCs into chondrocytes.

  16. GUT scale extra dimensions and light moduli in supergravity and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, Jan

    2010-05-15

    We study the dynamical properties of geometric moduli in five- and six-dimensional supergravity compactified on flat orbifolds, focusing on the impact of the Kaehler potential. In both cases, the Kaehler potential exhibits no-scale structure at tree level. In five dimensions, the volume modulus (radion) can be stabilized by means of perturbative Kaehler corrections. In six dimensions, the same holds for size and shape of the extra dimensions, only if the dilaton can be stabilized in a Minkowski vacuum by nonperturbative effects. We develop a systematic description of almost no-scale models and derive a model independent formula for the radion mass. The radion mass is suppressed compared to the gravitino mass. The supression factor reflects the hierarchy between the Planck and the compactification scale. We analyze a specific example, where the compactification scale is determined by Fayet-Iliopoulos terms of a locally anomalous Abelian gauge group, which are O(M{sub GUT}). In a scenario with gravitino dark matter, this leads to a radion mass of 1-10 MeV. In this mass range, the radion is cosmologically stable and contributes to the dark matter density. Based on galactic gamma ray data, we derive a tight bound on the initial displacement of the field value from its low energy vacuum. We also investigate implications of typical moduli Kaehler potentials on the cosmological evolution of the scalar fields. In particular, we discuss a class of models with steep exponential potentials and non-canonical kinetic terms, motivated by our radion example. We consider the overshooting problem of cosmological moduli dynamics, and the possibility of slow-roll solutions despite the steepness of the scalar potential. (orig.)

  17. Simultaneous measurement of field dependence of elastic moduli by laser interferometry

    International Nuclear Information System (INIS)

    A methodology is applied which allows the simultaneous determination of Young's modulus and the shear modulus to evaluate elastic moduli variations with the magnetic field (ΔE and ΔG). The method employed is based on the simultaneous detection of the transverse and torsional natural frequencies of a slender magnetic bar located within a solenoid. The resultant vibration is detected via a heterodyne interferometric optical system with a broad bandwidth. The vibration detection and excitation systems do not interact with the sample. The applicability of the method is demonstrated by characterizing 10-mm-diameter nickel bars. The results are compared with those obtained from longitudinal vibrations

  18. Biomedical titanium alloys with Young’s moduli close to that of cortical bone

    OpenAIRE

    Niinomi, Mitsuo; Liu, Yi; Nakai, Masaki; Liu, Huihong; Li, Hua

    2016-01-01

    Biomedical titanium alloys with Young’s moduli close to that of cortical bone, i.e., low Young’s modulus titanium alloys, are receiving extensive attentions because of their potential in preventing stress shielding, which usually leads to bone resorption and poor bone remodeling, when implants made of their alloys are used. They are generally β-type titanium alloys composed of non-toxic and allergy-free elements such as Ti–29Nb–13Ta–4.6Zr referred to as TNTZ, which is highly expected to be us...

  19. Irreducible cycles and points in special position in moduli spaces for tropical curves

    OpenAIRE

    Gathmann, Andreas; Schroeter, Franziska

    2011-01-01

    In the first part of this paper, we discuss the notion of irreducibility of cycles in the moduli spaces of n-marked rational tropical curves. We prove that Psi-classes and vital divisors are irreducible, and that locally irreducible divisors are also globally irreducible for n \\leq 6. In the second part of the paper, we show that the locus of point configurations in (\\R^2)^n in special position for counting rational plane curves (defined in two different ways) can be given the structure a tro...

  20. Irreducible cycles and points in special position in moduli spaces for tropical curves

    CERN Document Server

    Gathmann, Andreas

    2011-01-01

    In the first part of this paper, we discuss the notion of irreducibility of cycles in the moduli spaces of $n$-marked rational tropical curves. We prove that Psi-classes and vital divisors are irreducible, and that locally irreducible divisors are also globally irreducible for $ n \\le 6 $. In the second part of the paper, we show that the locus of point configurations in $ (\\R^2)^n $ in special position for counting rational plane curves (defined in two different ways) can be given the structure a tropical cycle of codimension 1. In addition, we compute explicitly the weights of this cycle.

  1. Moduli of $G_2$ structures and the Strominger system in dimension 7

    CERN Document Server

    Clarke, Andrew; Tipler, Carl

    2016-01-01

    We consider $G_2$ structures with torsion coupled with $G_2$-instantons, on a compact $7$-dimensional manifold. The coupling is via an equation for $4$-forms which appears in supergravity and generalized geometry, known as the Bianchi identity. The resulting system of partial differential equations can be regarded as an analogue of the Strominger system in $7$-dimensions. We initiate the study of the moduli space of solutions and show that it is finite dimensional using elliptic operator theory. We also relate the associated geometric structures to generalized geometry.

  2. Fluxes, moduli fixing and MSSM-like vacua in Type IIA String Theory

    CERN Document Server

    Camara, P G

    2006-01-01

    We review some of the features of Type IIA compactifications in the presence of fluxes. In particular, the case of $T^6/(\\Omega (-1)^{F_L} \\sigma)$ orientifolds with RR, NS and metric fluxes is considered. This has revealed to possess remarkable properties such as vacua with all the closed string moduli stabilized, null or negative contributions to the RR tadpoles or supersymmetry on the branes enforced by the closed string background. In this way, Type IIA compactifications with non trivial fluxes seem to constitute a new window into the building of semi-realistic models in String Theory.

  3. Feeding strategies as revealed by the section moduli of the humerus bones in bipedal theropod dinosaurs

    Science.gov (United States)

    Lee, Scott; Richards, Zachary

    2015-03-01

    The section modulus of a bone is a measure of its ability to resist bending torques. Carnivorous dinosaurs presumably had strong arm bones to hold struggling prey during hunting. Some theropods are believed to have become herbivorous and such animals would not have needed such strong arms. In this work, the section moduli of the humerus bones of bipedal theropod dinosaurs (from Microvenator celer to Tyrannosaurus rex) are studied to determine the maximum bending loads their arms could withstand. The results show that bending strength is not of uniform importance to these magnificent animals. The predatory theropods had strong arms for use in hunting. In contrast, the herbivorous dinosaurs had weaker arms.

  4. Simultaneous measurement of field dependence of elastic moduli by laser interferometry

    CERN Document Server

    Bayon, A; Salazar, F

    2000-01-01

    A methodology is applied which allows the simultaneous determination of Young's modulus and the shear modulus to evaluate elastic moduli variations with the magnetic field (DELTA E and DELTA G). The method employed is based on the simultaneous detection of the transverse and torsional natural frequencies of a slender magnetic bar located within a solenoid. The resultant vibration is detected via a heterodyne interferometric optical system with a broad bandwidth. The vibration detection and excitation systems do not interact with the sample. The applicability of the method is demonstrated by characterizing 10-mm-diameter nickel bars. The results are compared with those obtained from longitudinal vibrations.

  5. ON DISTORTION OF THE MODULI OF RINGS UNDER LOCALLY QUASICONFORMAL MAPPINGS IN R^n

    Directory of Open Access Journals (Sweden)

    S. Yu. Graf

    2015-12-01

    Full Text Available Some of the earlier results of author concerning distortion of the moduli of ring domains under planar locally quasiconformal mappings are generalized on the case of locally quasiconformal mappings in Rn, n ≥ 2. The main result of the article represents the sharp double-sided estimation of modulus M(D of the image D of the concentric spherical ring K(r, R = {x ∈ ∈ Rn : r < |x| < R} under locally quasiconformal homeomorphism f: Z R r P1/(1−n f (t dt t ≤ Mod(D ≤ Z R r P1/(n−1 f (t dt t . Here the function Pf is the majorant of dilatation of mapping f and Pf is well defined as Pf (t = limε→0+ essup{pf (x : t − ε ≤ |x| ≤ t + ε}. As the consequence of the main inequalities the sharp estimations of the derivative f0 (0 of the normalized locally quasiconformal automorphisms f of the unit ball in the terms of majorant of the dilatation of function f are proved. The sharpness of the results is demonstrated by examples of non-trivial locally quasiconformal mappings with unbounded dilatation that provide the equalities in estimations. The main theorems were obtained by means of method of moduli of families of curves and hypersurfaces in Rn.

  6. Beauty is more attractive: particle production and moduli trapping with higher dimensional interaction

    International Nuclear Information System (INIS)

    We study quantum effects on moduli dynamics arising from particle production near the enhanced symmetry point (ESP). We focus on non-renormalizable couplings between the moduli field and the field that becomes light at the ESP. Considering higher dimensional interaction, we find that particle production is significant in a large area, which is even larger than the area that is expected from a renormalizable interaction. It is possible to find this possibility from a trivial adiabatic condition; however the quantitative estimation of particle production and trapping of the field in motion are far from trivial. In this paper we study particle production and trapping in detail, using both the analytical and numerical calculations, to find a clear and intuitive result that supports trapping in a vast variety of theories. Our study shows that trapping driven by a non-renormalizable interaction is possible. This possibility has not been considered in previous works. Some phenomenological models of particle physics will be mentioned to complement discussion

  7. General analysis of LARGE Volume Scenarios with string loop moduli stabilisation

    International Nuclear Information System (INIS)

    We study the topological conditions for general Calabi-Yaus to get a non-supersymmetric AdS exponentially large volume minimum of the scalar potential in flux compactifications of IIB string theory. We show that negative Euler number and the existence of at least one blow-up mode resolving point-like singularities are necessary and sufficient conditions for moduli stabilisation with exponentially large volumes. We also analyse the general effects of string loop corrections on this scenario. While the combination of α' and nonperturbative corrections are sufficient to stabilise blow-up modes and the overall volume, quantum corrections are needed to stabilise other directions transverse to the overall volume. This allows exponentially large volume minima to be realised for fibration Calabi-Yaus, with the various moduli of the fibration all being stabilised at exponentially large values. String loop corrections may also play a role in stabilising 4-cycles which support chiral matter and cannot enter directly into the non-perturbative superpotential. We illustrate these ideas by studying the scalar potential for various Calabi-Yau three-folds including K3 fibrations and briefly discuss the potential phenomenological and cosmological implications of our results.

  8. Moduli stabilization in type II Calabi-Yau compactifications at finite temperature

    CERN Document Server

    Liu, Lihui

    2011-01-01

    We consider the type II superstring compactified on Calabi-Yau threefolds at finite temperature. The latter is implemented at the string level by a free action on the Euclidean time circle. We show that all Kahler and complex structure moduli involved in the gauge theories geometrically engineered in the vicinity of singular loci are lifted by the stringy thermal effective potential. The analysis is based on the effective gauged supergravity at low energy, without integrating out the BPS states becoming massless at the singular loci. The universal form of the action in the weak coupling regime at low enough temperature is determined in two cases. Namely the conifold locus, as well as a locus where the internal space develops a genus-g curve of A{N-1} singularities, realizing an SU(N) gauge theory coupled to g hypermultiplets in the adjoint. In general, the favored points of stabilization sit at the intersection of several singular loci. Thus the entire vector multiplet moduli space can be lifted, together wit...

  9. Beauty is more attractive: particle production and moduli trapping with higher dimensional interaction

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, Seishi [Kobayashi Maskawa Institute, Nagoya University,Nagoya 464-8602 (Japan); Institute of Theoretical Physics, Faculty of Physics,University of Warsaw, Hoa 69, 00-681 Warsaw (Poland); Iida, Satoshi [Department of Physics, Nagoya University,Nagoya 464-8602 (Japan); Maekawa, Nobuhiro [Kobayashi Maskawa Institute, Nagoya University,Nagoya 464-8602 (Japan); Department of Physics, Nagoya University,Nagoya 464-8602 (Japan); Matsuda, Tomohiro [Laboratory of Physics, Saitama Institute of Technology,Saitama 369-0293 (Japan)

    2014-01-24

    We study quantum effects on moduli dynamics arising from particle production near the enhanced symmetry point (ESP). We focus on non-renormalizable couplings between the moduli field and the field that becomes light at the ESP. Considering higher dimensional interaction, we find that particle production is significant in a large area, which is even larger than the area that is expected from a renormalizable interaction. It is possible to find this possibility from a trivial adiabatic condition; however the quantitative estimation of particle production and trapping of the field in motion are far from trivial. In this paper we study particle production and trapping in detail, using both the analytical and numerical calculations, to find a clear and intuitive result that supports trapping in a vast variety of theories. Our study shows that trapping driven by a non-renormalizable interaction is possible. This possibility has not been considered in previous works. Some phenomenological models of particle physics will be mentioned to complement discussion.

  10. Moduli of curve families and (quasi-)conformality of power-law entropies

    Science.gov (United States)

    Kalogeropoulos, Nikos

    2016-03-01

    We present aspects of the moduli of curve families on a metric measure space which may prove useful in calculating, or in providing bounds to, non-additive entropies having a power-law functional form. We use as paradigmatic cases the calculations of the moduli of curve families for a cylinder and for an annulus in ℝn. The underlying motivation for these studies is that the definitions and some properties of the modulus of a curve family resembles those of the Tsallis entropy, when the latter is seen from a micro-canonical viewpoint. We comment on the origin of the conjectured invariance of the Tsallis entropy under Möbius transformations of the non-extensive (entropic) parameter. Needing techniques applicable to both locally Euclidean and fractal classes of spaces, we examine the behavior of the Tsallis functional, via the modulus, under quasi-conformal maps. We comment on properties of such maps and their possible significance for the dynamical foundations of power-law entropies.

  11. The moduli space of heterotic line bundle models: a case study for the tetra-quadric

    Energy Technology Data Exchange (ETDEWEB)

    Buchbinder, Evgeny I. [The University of Western Australia,35 Stirling Highway, Crawley WA 6009 (Australia); Constantin, Andrei; Lukas, Andre [Rudolf Peierls Centre for Theoretical Physics, Oxford University,1 Keble Road, Oxford, OX1 3NP (United Kingdom)

    2014-03-05

    It has recently been realised that polystable, holomorphic sums of line bundles over smooth Calabi-Yau three-folds provide a fertile ground for heterotic model building. Large numbers of phenomenologically promising such models have been constructed for various classes of Calabi-Yau manifolds. In this paper we focus on a case study for the tetra-quadric — a Calabi-Yau hypersurface embedded in a product of four ℂℙ{sup 1} spaces. We address the question of finiteness of the class of consistent and physically viable line bundle models constructed on this manifold. Further, for a specific semi-realistic example, we explore the embedding of the line bundle sum into the larger moduli space of non-Abelian bundles, both by means of constructing specific polystable non-Abelian bundles and by turning on VEVs in the associated low-energy theory. In this context, we explore the fate of the Higgs doublets as we move in bundle moduli space. The non-Abelian compactifications thus constructed lead to SU(5) GUT models with an additional global B−L symmetry. The non-Abelian compactifications inherit many of the appealing phenomenological features of the Abelian model, such as the absence of dimension four and dimension five operators triggering fast proton decay.

  12. Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure

    Energy Technology Data Exchange (ETDEWEB)

    Ray, U., E-mail: ray_ugrasen@yahoo.co [Department of Physics, Bhaktapur Multiple Campus, Tribhuvan University, Kathmandu (Nepal)

    2010-08-01

    The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born-Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C{sub 123}) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson-Grueneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.

  13. Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure

    International Nuclear Information System (INIS)

    The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born-Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C123) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson-Grueneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.

  14. The Moduli Space of Heterotic Line Bundle Models: a Case Study for the Tetra-Quadric

    CERN Document Server

    Buchbinder, Evgeny I; Lukas, Andre

    2014-01-01

    It has recently been realised that polystable, holomorphic sums of line bundles over smooth Calabi-Yau three-folds provide a fertile ground for heterotic model building. Large numbers of phenomenologically promising such models have been constructed for various classes of Calabi-Yau manifolds. In this paper we focus on a case study for the tetra-quadric - a Calabi-Yau hypersurface embedded in a product of four CP1 spaces. We address the question of finiteness of the class of consistent and physically viable line bundle models constructed on this manifold. Further, for a specific semi-realistic example, we explore the embedding of the line bundle sum into the larger moduli space of non-Abelian bundles, both by means of constructing specific polystable non-Abelian bundles and by turning on VEVs in the associated low-energy theory. In this context, we explore the fate of the Higgs doublets as we move in bundle moduli space. The non-Abelian compactifications thus constructed lead to SU(5) GUT models with an addit...

  15. Fluxes, moduli fixing and MSSM-like vacua in a simple IIA orientifold

    CERN Document Server

    Camara, P G; Ibáñez, L E

    2005-01-01

    We study the effects of adding RR, NS and metric fluxes on a T^6/(\\Omega (-1)^{F_L} I_3) Type IIA orientifold. By using the effective flux-induced superpotential we obtain Minkowski or AdS vacua with broken or unbroken supersymmetry. In the Minkowski case some combinations of real moduli remain undetermined, whereas all can be stabilized in the AdS solutions. Many flux parameters are available which are unconstrained by RR tadpole cancellation conditions allowing to locate the minima at large volume and small dilaton. We also find that in AdS supersymmetric vacua with metric fluxes, the overall flux contribution to RR tadpoles can vanish or have opposite sign to that of D6-branes, allowing for new model-building possibilities. In particular, we construct the first N=1 supersymmetric intersecting D6-brane models with MSSM-like spectrum and with all closed string moduli stabilized. Some axion-like fields remain undetermined but they are precisely required to give St\\"uckelberg masses to (potentially anomalous) ...

  16. Models of discretized moduli spaces, cohomological field theories, and Gaussian means

    CERN Document Server

    Andersen, Jørgen Ellegaard; Norbury, Paul; Penner, Robert C

    2015-01-01

    We prove combinatorially the explicit relation between genus filtrated $s$-loop means of the Gaussian matrix model and terms of the genus expansion of the Kontsevich--Penner matrix model (KPMM). The latter is the generating function for volumes of discretized (open) moduli spaces $M_{g,s}^{\\mathrm{disc}}$ given by $N_{g,s}(P_1,\\dots,P_s)$ for $(P_1,\\dots,P_s)\\in{\\mathbb Z}_+^s$. This generating function therefore enjoys the topological recursion, and we prove that it is simultaneously the generating function for ancestor invariants of a cohomological field theory thus enjoying the Givental decomposition. We use another Givental-type decomposition obtained for this model by the second authors in 1995 in terms of special times related to the discretisation of moduli spaces thus representing its asymptotic expansion terms (and therefore those of the Gaussian means) as finite sums over graphs weighted by lower-order monomials in times thus giving another proof of (quasi)polynomiality of the discrete volumes. As a...

  17. Moduli Thermalization and Finite Temperature Effects in "Big" Divisor Large Volume D3/D7 Swiss-Cheese Compactification

    CERN Document Server

    Shukla, Pramod

    2010-01-01

    In the context of Type IIB compactified on a large volume Swiss-Cheese orientifold in the presence of a mobile space-time filling $D3$-brane and stacks of fluxed D7-branes wrapping the "big" divisor \\Sigma_B of a Swiss-Cheese Calabi Yau in {\\bf WCP}^4[1,1,1,6,9], we explore on various implications of moduli dynamics and discuss their couplings and decay into MSSM (-like) matter fields early in the history of universe to reach thermal equilibrium. Like finite temperature effects in O'KKLT, we observe that the local minimum of zero-temperature effective scalar potential is stable against any finite temperature corrections (up to two-loops) in large volume scenarios as well. Also we find that moduli are heavy enough to avoid any cosmological moduli problem.

  18. PREDICTION OF THE VISCOELASTIC PROPERTIES OF THE EQUIVALENT PARTICLE FOR THE INTERCALATED MULTI-LAYER STACK OF NANOPLASTICS

    Institute of Scientific and Technical Information of China (English)

    Weimin Zhang; Ping Zhang; Xuhui Deng; Chunyuan Zhang

    2007-01-01

    The aim of this paper is to apply the asymptotic homogenization method to determining analytically and numerically the transversely isotropic viscoelastic relaxation moduli of the equivalent particle for the intercalated multi-layer stack of intercalated type nanoplastics. A two-phase multilayered material containing n layers is considered. The matrix is assumed to be an isotropic viscoelastic standard linear body and the reinforcement is assumed to be an isotropic elastic body. Final explicit analytical formulae for the effective elastic moduli of the multilayered material are derived first; and then the correspondence principle is employed to obtain the homogenized relaxation moduli of the equivalent intercalated particle. A numerical example is given. Final explicit analytical formulae in the time domain derived here make it convenient to estimate the influence of all the particle parameters of micro-structural details on the effective properties of the equivalent intercalated particle. The results of this paper can also be applied to multi-layer composites.

  19. Moduli stabilization with F-term uplifting in heterotic string theory

    CERN Document Server

    Jeong, Kwang Sik

    2008-01-01

    We discuss the role of F-term uplifting in stabilizing moduli within the framework of heterotic string theory. It turns out that the uplifting sector plays an important role in fixing the volume modulus at one of the self-dual points of a modular invariant potential. For the volume modulus stabilized at a self-dual point, the F-term uplifting leads to the dilation stabilization which can naturally yield the mirage mediation pattern of soft supersymmetry breaking terms. Generalizing to the case with anomalous U(1) gauge symmetry, we also find that the U(1) sector generically gives a contribution to sfermion masses comparable to the dilaton mediated one while maintaining the mirage mediation pattern.

  20. Flavor and CP conserving moduli mediated SUSY breaking in flux compactification

    CERN Document Server

    Choi, Kiwoon; Okumura, Ken-Ichi

    2008-01-01

    In certain class of flux compactification, moduli mediated supersymmetry (SUSY) breaking preserves flavor and CP at leading order in the perturbative expansion controlled by the vacuum expectation value of the messenger modulus. Nevertheless there still might be dangerous flavor or CP violation induced by higher order K\\"ahler potential. We examine the constraints on such SUSY breaking scheme imposed by low energy flavor and/or CP violating observables. It is found that all phenomenological constraints can be satisfied even for generic form of higher order K\\"ahler potential and sparticle spectra in the sub-TeV range, under plausible assumptions on the size of higher order correction and flavor mixing angles. This implies for instance that mirage mediation scheme of SUSY breaking, which involves such modulus mediation together with an anomaly mediation of comparable size, and also the modulus-dominated mediation realized in flux compactification can be free from the SUSY flavor and CP problems, while giving g...

  1. Exploring Lovelock theory moduli space for Schrödinger solutions

    Science.gov (United States)

    Jatkar, Dileep P.; Kundu, Nilay

    2016-09-01

    We look for Schrödinger solutions in Lovelock gravity in D > 4. We span the entire parameter space and determine parametric relations under which the Schrödinger solution exists. We find that in arbitrary dimensions pure Lovelock theories have Schrödinger solutions of arbitrary radius, on a co-dimension one locus in the Lovelock parameter space. This co-dimension one locus contains the subspace over which the Lovelock gravity can be written in the Chern-Simons form. Schrödinger solutions do not exist outside this locus and on this locus they exist for arbitrary dynamical exponent z. This freedom in z is due to the degeneracy in the configuration space. We show that this degeneracy survives certain deformation away from the Lovelock moduli space.

  2. Topological recursion for chord diagrams, RNA complexes, and cells in moduli spaces

    CERN Document Server

    Andersen, Jørgen E; Penner, R C; Reidys, Christian M; Sułkowski, Piotr

    2012-01-01

    We introduce and study the Hermitian matrix model with potential V(x)=x^2/2-stx/(1-tx), which enumerates the number of linear chord diagrams of fixed genus with specified numbers of backbones generated by s and chords generated by t. For the one-cut solution, the partition function, correlators and free energies are convergent for small t and all s as a perturbation of the Gaussian potential, which arises for st=0. This perturbation is computed using the formalism of the topological recursion. The corresponding enumeration of chord diagrams gives at once the number of RNA complexes of a given topology as well as the number of cells in Riemann's moduli spaces for bordered surfaces. The free energies are computed here in principle for all genera and explicitly for genera less than four.

  3. Topological recursion for chord diagrams, RNA complexes, and cells in moduli spaces

    International Nuclear Information System (INIS)

    We introduce and study the Hermitian matrix model with potential Vs,t(x)=x2/2−stx/(1−tx), which enumerates the number of linear chord diagrams with no isolated vertices of fixed genus with specified numbers of backbones generated by s and chords generated by t. For the one-cut solution, the partition function, correlators and free energies are convergent for small t and all s as a perturbation of the Gaussian potential, which arises for st=0. This perturbation is computed using the formalism of the topological recursion. The corresponding enumeration of chord diagrams gives at once the number of RNA complexes of a given topology as well as the number of cells in Riemann's moduli spaces for bordered surfaces. The free energies are computed here in principle for all genera and explicitly in genus less than four.

  4. Symmetry-surfing the moduli space of Kummer K3s

    CERN Document Server

    Taormina, Anne

    2013-01-01

    A maximal subgroup of the Mathieu group M24 arises as the combined holomorphic symplectic automorphism group of all Kummer surfaces whose K\\"ahler class is induced from the underlying complex torus. As a subgroup of M24, this group is the stabilizer group of an octad in the Golay code. To meaningfully combine the symmetry groups of distinct Kummer surfaces, we introduce the concepts of Niemeier markings and overarching maps between pairs of Kummer surfaces. The latter induce a prescription for symmetry-surfing the moduli space, while the former can be seen as a first step towards constructing a vertex algebra that governs the elliptic genus of K3 in an M24-compatible fashion. We thus argue that a geometric approach from K3 to Mathieu Moonshine may bear fruit.

  5. More about structures localized on domain walls: strings, skyrmions, analytic solutions for orientational moduli, symmetry analysis

    CERN Document Server

    Bychkov, Vladimir; Kurianovych, Evgeniy

    2016-01-01

    We further discuss properties of a simple model, which allows existence of domain walls with orientational moduli, localized on them. We review an analytic solution of such a model and discuss properties of that solution in a context of previous results. We discuss an existence of one-dimensional domain walls, localized on two-dimensional ones, and construct a corresponding effective action. Then in low-energy limit, which is $O(3)$ sigma-model, we discuss existence of skyrmions, localized on domain walls, and provide a solution for a skyrmion configuration, based on the analogy with instantons. We perform a symmetry analysis of the initial model and low-energy theory on the domain wall world volume.

  6. Application of Monte Carlo simulations to the prediction of the effective elastic moduli of hydrated Nafion

    Science.gov (United States)

    Weiland, Lisa Mauck; Lada, Emily K.; Smith, Ralph C.; Leo, Donald J.

    2005-05-01

    Application of Rotational Isomeric State (RIS) theory to the prediction of Young's modulus of a solvated ionomer is considered. RIS theory directly addresses polymer chain conformation as it relates to mechanical response trends. Successful adaptation of this methodology to the prediction of elastic moduli would thus provide a powerful tool for guiding ionomer fabrication. The Mark-Curro Monte Carlo methodology is applied to generate a statistically valid number of end-to-end chain lengths via RIS theory for a solvated Nafion case. The distribution of chain lengths is then fitted to a Probability Density Function by the Johnson Bounded distribution method. The fitting parameters, as they relate to the model predictions and physical structure of the polymer, are studied so that a means to extend RIS theory to the reliable prediction of ionomer stiffness may be identified.

  7. The Moduli of Flat U(p,1) Structures on Riemann Surfaces

    OpenAIRE

    Xia, Eugene Z.

    1999-01-01

    For a compact Riemann surface $X$ of genus $g > 1$, $\\Hom(\\pi_1(X), U(p,1))/U(p,1)$ is the moduli space of flat $\\U(p,1)$-connections on $X$. There is an integer invariant, $\\tau$, the Toledo invariant associated with each element in $\\Hom(\\pi_1(X), U(p,1))/U(p,1)$. If $q = 1$, then $-2(g-1) \\le \\tau \\le 2(g-1)$. This paper shows that $\\Hom(\\pi_1(X), U(p,1))/U(p,1)$ has one connected component corresponding to each $\\tau \\in 2Z$ with $-2(g-1) \\le \\tau \\le 2(g-1)$. Therefore the total number o...

  8. Effect of neutron irradiation on the third order elasticity moduli in Al

    International Nuclear Information System (INIS)

    Investigations were conducted into the effect of neutron irradiation and subsequent isochronous annealing on the third order elasticity moduli (TOEM) in Al of commercial purity. The results show that irradiation greatly reduces (approximately halves) the absolute value of TOEM. In subsequent isochronous annealing in the temperature range 300-450 K TOEM returns to the initial value and the dependence of TOEM on annealing temperature contains a number of maxima and minima. The assumptions on the pinning of the dislocations by complexes of inherent interstitial atoms (IIA) and on the effect of dislocations of TOEM were used to estimate the migration energy of the vacancies in the volume of the crystal and the bonding energy of IIA with the solute atoms in the volume. (author)

  9. Influence of Young's moduli in 3D fluid-structure coupled models of the human cochlea

    Science.gov (United States)

    Böhnke, Frank; Semmelbauer, Sebastian; Marquardt, Torsten

    2015-12-01

    The acoustic wave propagation in the human cochlea was studied using a tapered box-model with linear assumptions respective to all mechanical parameters. The discretisation and evaluation is conducted by a commercial finite element package (ANSYS). The main difference to former models of the cochlea was the representation of the basilar membrane by a 3D elastic solid. The Young's moduli of this solid were modified to study their influence on the travelling wave. The lymph in the scala vestibuli and scala tympani was represented by a viscous and nearly incompressible fluid finite element approach. Our results show the maximum displacement for f = 2kHz at half of the length of the cochlea in accordance with former experiments. For low frequencies f <200 Hz nearly zero phase shifts were found, whereas for f =1 kHz it reaches values up to -12 cycles depending on the degree of orthotropy.

  10. Deformations on tilted tori and moduli stabilisation at the orbifold point

    Science.gov (United States)

    Blaszczyk, Michael; Honecker, Gabriele; Koltermann, Isabel

    2015-11-01

    We discuss deformations of orbifold singularities on tilted tori in the context of Type IIA orientifold model building with D6-branes on special Lagrangian cycles. Starting from {T}^6/({{Z}}_2× {{Z}}_2) , we mod out an additional {{Z}}_3 symmetry to describe phenomenologically appealing backgrounds and reduce to {{Z}}_3 and Ω R invariant orbits of deformations. While D6-branes carrying SO(2 N) or USp(2 N) gauge groups do not constrain deformations, D6-branes with U( N) gauge groups develop non-vanishing D-terms if they couple to previously singular, now deformed cycles. We present examples for both types of D6-branes, and in a three-generation Pati-Salam model on {T}^6/({{Z}}_2× {{Z}}_6^') we find that ten out of 15 twisted complex structure moduli are indeed stabilised at the orbifold point by the existence of the brane stacks.

  11. Beauty is more attractive: Particle Production and Moduli trapping with Higher Dimensional Interaction

    CERN Document Server

    Enomoto, Seishi; Maekawa, Nobuhiro; Matsuda, Tomohiro

    2013-01-01

    We study quantum effects on moduli dynamics arising from the particle production near the enhanced symmetry point (ESP). We paid special attention to the non-conventional interactions, which are suppressed by the cutoff scale of the effective action but the power of the field is larger. This kind of interaction is sometimes called the "higher dimensional" interaction. Considering the higher dimensional interaction, we find that the particle production is significant in a large area, which is even larger than the area that is expected from the conventional interaction. It is possible to find this possibility from the trivial adiabatic condition; however the quantitative estimation of the particle production and the trapping of the field in motion are far from trivial. In this paper we study the particle production and the trapping in detail, using both the analytical and the numerical calculations, to find a clear and intuitive result that supports trapping in a vast variety of theories. Our study shows that t...

  12. N=1/2 gauge theory and its instanton moduli space from open strings in R-R background

    OpenAIRE

    Billo', Marco; Frau, Marialuisa; Pesando, Igor(Dipartimento di Fisica, Università di Torino, and I.N.F.N. – sezione di Torino, Via P. Giuria 1, I-10125 Torino, Italy); Lerda, Alberto

    2004-01-01

    We derive the four dimensional N=1/2 super Yang-Mills theory from tree-level computations in RNS open string theory with insertions of closed string Ramond-Ramond vertices. We also study instanton configurations in this gauge theory and their ADHM moduli space, using systems of D3 and D(-1) branes in a R-R background.

  13. Laser ultrasonic assessment of the effects of porosity and microcracking on the elastic moduli of nuclear graphites

    Science.gov (United States)

    Spicer, James B.; Olasov, Lauren R.; Zeng, Fan W.; Han, Karen; Gallego, Nidia C.; Contescu, Cristian I.

    2016-04-01

    Laser ultrasonic methods have been used to measure the elastic moduli of various nuclear graphites. Measurements were made to assess wavespeeds for longitudinal and shear waves in different propagation directions and these were used along with density measurements to compute the longitudinal and shear moduli as well as Young's modulus. All moduli decreased with increasing graphite porosity and these variations could be interpreted using models describing the effect of porosity on material stiffness. Extrapolations for these models to zero porosity were used to infer the moduli for theoretically dense graphite; the results were far below predicted values reported in the literature for fully dense, polycrystalline, isotropic graphite. Differences can be attributed to microcracking in the graphite microstructure. Using models for the effects of microcracking on modulus, estimates for microcrack populations indicate that the number of cracks per unit volume must be much greater than the number of pores per unit volume. Experimental results reported in the literature for irradiated graphites as well as for the stress dependence of graphite modulus are consistent with the influence of microcracking on elastic behavior and could be interpreted using concepts developed here. Results in this work for graphite structure-property relationships should allow for more sophisticated characterization of nuclear graphites using ultrasonic methods.

  14. The relationship between 3D bone architectural parameters and elastic moduli of three orthogonal directions predicted from finite elements analysis

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kwan Soo; Lee, Sam Sun; Huh, Kyung Hoe; Yi, Wan Jin; Heo, Min Suk; Choi, Soon Chul [Department of Oral and Maxillofacial Radiology, School of Dentistry, Seoul National University, Seoul (Korea, Republic of)

    2008-06-15

    To investigate the relationship between 3D bone architectural parameters and direction-related elastic moduli of cancellous bone of mandibular condyle. Two micro-pigs (Micro-pigR, PWG Genetics Korea) were used. Each pig was about 12 months old and weighing around 44 kg. 31 cylindrical bone specimen were obtained from cancellous bone of condyles for 3D analysis and measured by micro-computed tomography. Six parameters were trabecular thickness (Tb.Th), bone specific surface (BS/BV), percent bone volume (BV/TV), structure model index (SMI), degree of anisotropy (DA) and 3-dimensional fractal dimension (3DFD). Elastic moduli of three orthogonal directions (superiorinferior (SI), medial-lateral (ML), andterior-posterior (AP) direction) were calculated through finite element analysis. Elastic modulus of superior-inferior direction was higher than those of other directions. Elastic moduli of 3 orthogonal directions showed different correlation with 3D architectural parameters. Elastic moduli of SI and ML directions showed significant strong to moderate correlation with BV/TV, SMI and 3DFD. Elastic modulus of cancellous bone of pig mandibular condyle was highest in the SI direction and it was supposed that the change into plate-like structure of trabeculae was mainly affected by increase of trabeculae of SI and ML directions.

  15. Speed limit in internal space of domain walls via all-order effective action of moduli motion

    CERN Document Server

    Eto, Minoru

    2015-01-01

    We find that motion in internal moduli spaces of generic domain walls has an upper bound for its velocity. Our finding is based on our generic formula for all-order effective actions of internal moduli parameter of domain wall solitons. It is known that the Nambu-Goldstone mode $Z$ associated with spontaneous breaking of translation symmetry obeys a Nambu-Goto effective Lagrangian $\\sqrt{1 - (\\partial_0 Z)^2}$ detecting the speed of light ($|\\partial_0 Z|=1$) in the target spacetime. Solitons can have internal moduli parameters as well, associated with a breaking of internal symmetries such as a phase rotation acting on a field. We obtain, for generic domain walls, an effective Lagrangian of the internal moduli $\\epsilon$ to all order in $(\\partial \\epsilon)$. The Lagrangian is given by a function of the Nambu-Goto Lagrangian: $L = g(\\sqrt{1 + (\\partial_\\mu \\epsilon)^2})$. This shows generically the existence of an upper bound on $\\partial_0 \\epsilon$, i.e. a speed limit in the internal space. The speed limit...

  16. Speed limit in internal space of domain walls via all-order effective action of moduli motion

    Science.gov (United States)

    Eto, Minoru; Hashimoto, Koji

    2016-03-01

    We find that motion in internal moduli spaces of generic domain walls has an upper bound for its velocity. Our finding is based on our generic formula for all-order effective actions of internal moduli parameter of domain wall solitons. It is known that the Nambu-Goldstone mode Z associated with spontaneous breaking of translation symmetry obeys a Nambu-Goto effective Lagrangian √{1 -(∂0Z )2 } detecting the speed of light (|∂0Z |=1 ) in the target spacetime. Solitons can have internal moduli parameters as well, associated with a breaking of internal symmetries such as a phase rotation acting on a field. We obtain, for generic domain walls, an effective Lagrangian of the internal moduli ɛ to all orders in (∂ɛ ). The Lagrangian is given by a function of the Nambu-Goto Lagrangian: L =g (√{1 +(∂μɛ )2 }). This shows generically the existence of an upper bound on ∂0ɛ , i.e., a speed limit in the internal space. The speed limit exists even for solitons in some nonrelativistic field theories, where we find that ɛ is a type I Nambu-Goldstone mode that also obeys a nonlinear dispersion to reach the speed limit. This offers a possibility of detecting the speed limit in condensed matter experiments.

  17. Upper bounds for the essential dimension of the moduli stack of ${\\sl_{n}}$-bundles over a curve

    OpenAIRE

    Dhillon, Ajneet; Lemire, Nicole

    2009-01-01

    We find upper bounds for the essential dimension of various moduli stacks of $\\sln$-bundles over a curve. When $n$ is a prime power, our calculation computes the essential dimension of the stack of stable bundles exactly and the essential dimension is not equal to the dimension in this case.

  18. Acoustic cloaking using layered pentamode materials.

    Science.gov (United States)

    Scandrett, Clyde L; Boisvert, Jeffrey E; Howarth, Thomas R

    2010-05-01

    While receiving less attention in the literature than electromagnetic cloaking, theoretical efforts to define and create acoustic cloaks based upon mimicking coordinate transformations through use of metamaterials is of interest. The present work extends recent analysis of Norris [Proc. R. Soc. London, Ser. A 464, 2411-2434 (2008)] by considering a range of cloaks, from those comprised of fluid layers which are isotropic in bulk moduli with anisotropic density to those having anisotropic bulk moduli and isotropic density. In all but pure inertial varieties, fluid layers comprising the cloaks are pentamode materials governed by a special scalar acoustic equation for pseudopressure derived by Norris. In most cases presented, material properties of the fluid/pentamode layers are based upon target values specified by continuously varying properties resulting from theoretical coordinate transformations geared to minimize scattered pressure limited by realistic goals. The present work analyzes such cloaks for the specific case of plane wave scattering from an acoustically hard sphere. An initial exploration of the parameter space defining such cloaks (for example, material properties of its constituent layers, and operating frequency) is undertaken with a view toward "optimal" design. PMID:21117736

  19. An Asymptotic Model of Seismic Reflection from a Permeable Layer

    OpenAIRE

    Silin, Dmitriy; Goloshubin, Gennady

    2010-01-01

    Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot’s model of poroelasticity. A review of t...

  20. Evaluation of accelerated deterioration in NAPTF flexible test pavements

    Institute of Scientific and Technical Information of China (English)

    Kasthurirangan GOPALAKRISHNAN

    2008-01-01

    Previous research studies have successfully demonstrated the use of artificial neural network(ANN)models for predicting critical structural responses and layer moduli of highway flexible pavements.The primary objective of this study was to develop an ANN-based approach for backcalculation of pavement moduli based on heavy weight deflectometer(HWD)test data,especially in the analysis of airport flexible pavements subjected to new generation aircraft(NGA).Two medium-strength subgrade flexible test sections,at the National Airport Pavement Test Facility(NAPTF),were modeled using a finite element(FE) based pavement analysis program,which can consider the non-linear stress-dependent behavior of pavement geomaterials.A multi-layer,feed-forward network which uses an error-backpropagation algorithm was trained to approximate the HWD backcalculation function using the FE program generated synthetic database.At the NAPTF,test sections were subjected to Boeing 777 (B777)trafficking on one lane and Boeing 747(B747)trafficking on the other lane using a test machine.To monitor the effect of traffic and climatic variations on pavement structural responses.HWD tests were conducted on the traffieked lanes and on the untraffieked centerline of test sections as trafficking progressed.The trained ANN models were successfully applied on the actual HWD test data acquired at the NAPTF to predict the asphalt concrete moduli and non-1inear subgrade moduli of the medium-strength subgrade flexible test sections.

  1. Multi-Regge kinematics and the moduli space of Riemann spheres with marked points

    CERN Document Server

    Del Duca, Vittorio; Drummond, James; Duhr, Claude; Dulat, Falko; Marzucca, Robin; Papathanasiou, Georgios; Verbeek, Bram

    2016-01-01

    We show that scattering amplitudes in planar N = 4 Super Yang-Mills in multi-Regge kinematics can naturally be expressed in terms of single-valued iterated integrals on the moduli space of Riemann spheres with marked points. As a consequence, scattering amplitudes in this limit can be expressed as convolutions that can easily be computed using Stokes' theorem. We apply this framework to MHV amplitudes to leading-logarithmic accuracy (LLA), and we prove that at L loops all MHV amplitudes are determined by amplitudes with up to L + 4 external legs. We also investigate non-MHV amplitudes, and we show that they can be obtained by convoluting the MHV results with a certain helicity flip kernel. We classify all leading singularities that appear at LLA in the Regge limit for arbitrary helicity configurations and any number of external legs. Finally, we use our new framework to obtain explicit analytic results at LLA for all MHV amplitudes up to five loops and all non-MHV amplitudes with up to eight external legs and...

  2. Biomedical titanium alloys with Young's moduli close to that of cortical bone.

    Science.gov (United States)

    Niinomi, Mitsuo; Liu, Yi; Nakai, Masaki; Liu, Huihong; Li, Hua

    2016-09-01

    Biomedical titanium alloys with Young's moduli close to that of cortical bone, i.e., low Young's modulus titanium alloys, are receiving extensive attentions because of their potential in preventing stress shielding, which usually leads to bone resorption and poor bone remodeling, when implants made of their alloys are used. They are generally β-type titanium alloys composed of non-toxic and allergy-free elements such as Ti-29Nb-13Ta-4.6Zr referred to as TNTZ, which is highly expected to be used as a biomaterial for implants replacing failed hard tissue. Furthermore, to satisfy the demands from both patients and surgeons, i.e., a low Young's modulus of the whole implant and a high Young's modulus of the deformed part of implant, titanium alloys with changeable Young's modulus, which are also β-type titanium alloys, for instance Ti-12Cr, have been developed. In this review article, by focusing on TNTZ and Ti-12Cr, the biological and mechanical properties of the titanium alloys with low Young's modulus and changeable Young's modulus are described. In addition, the titanium alloys with shape memory and superelastic properties were briefly addressed. Surface modifications for tailoring the biological and anti-wear/corrosion performances of the alloys have also been briefly introduced. PMID:27252887

  3. Deformations on Tilted Tori and Moduli Stabilisation at the Orbifold Point

    CERN Document Server

    Blaszczyk, Michael; Koltermann, Isabel

    2015-01-01

    We discuss deformations of orbifold singularities on tilted tori in the context of Type IIA orientifold model building with D6-branes on special Lagrangian cycles. Starting from $T^6/(\\mathbb{Z}_2 \\times \\mathbb{Z}_2)$, we mod out an additional $\\mathbb{Z}_3$ symmetry to describe phenomenologically appealing backgrounds and reduce to $\\mathbb{Z}_3$ and $\\Omega\\mathcal{R}$ invariant orbits of deformations. While D6-branes carrying SO(2N) or USp(2N) gauge groups do not constrain deformations, D6-branes with U(N) gauge groups develop non-vanishing D-terms if they couple to previously singular, now deformed cycles. We present examples for both types of D6-branes, and in a three-generation Pati-Salam model on $T^6/(\\mathbb{Z}_2 \\times \\mathbb{Z}_6')$ we find that ten out of 15 twisted complex structure moduli are indeed stabilised at the orbifold point by the existence of the brane stacks.

  4. Local structure controls the nonaffine shear and bulk moduli of disordered solids

    Science.gov (United States)

    Schlegel, M.; Brujic, J.; Terentjev, E. M.; Zaccone, A.

    2016-01-01

    Paradigmatic model systems, which are used to study the mechanical response of matter, are random networks of point-atoms, random sphere packings, or simple crystal lattices; all of these models assume central-force interactions between particles/atoms. Each of these models differs in the spatial arrangement and the correlations among particles. In turn, this is reflected in the widely different behaviours of the shear (G) and compression (K) elastic moduli. The relation between the macroscopic elasticity as encoded in G, K and their ratio, and the microscopic lattice structure/order, is not understood. We provide a quantitative analytical connection between the local orientational order and the elasticity in model amorphous solids with different internal microstructure, focusing on the two opposite limits of packings (strong excluded-volume) and networks (no excluded-volume). The theory predicts that, in packings, the local orientational order due to excluded-volume causes less nonaffinity (less softness or larger stiffness) under compression than under shear. This leads to lower values of G/K, a well-documented phenomenon which was lacking a microscopic explanation. The theory also provides an excellent one-parameter description of the elasticity of compressed emulsions in comparison with experimental data over a broad range of packing fractions.

  5. Galois coverings of moduli spaces of curves and loci of curves with symmetry

    CERN Document Server

    Boggi, Marco

    2011-01-01

    Let $\\ccM_{g,[n]}$, for $2g-2+n>0$, be the stack of genus $g$, stable algebraic curves, endowed with $n$ unordered marked points. Looijenga introduced the notion of Prym level structures in order to construct smooth projective Galois coverings of the stack $\\ccM_{g}$. In \\S 2 of this paper, we introduce the notion of Looijenga level structure which generalizes Looijenga construction and provides a tower of Galois coverings of $\\ccM_{g,[n]}$ equivalent to the tower of all geometric level structures over $\\ccM_{g,[n]}$. In \\S 3, Looijenga level structures are interpreted geometrically in terms of moduli of curves with symmetry. A byproduct of this characterization is a simple criterion for their smoothness. As a consequence of this criterion, it is shown that Looijenga level structures are smooth under very mild hypotheses. The second part of the paper, from \\S 4, deals with the problem of describing the D-M boundary of level structures. In \\S 6, a description is given of the nerve of the D-M boundary of abelia...

  6. Bending moduli for wormlike micelles determined using SANS. The role of counterion specificity

    International Nuclear Information System (INIS)

    Complete text of publication follows. Microstructures in aqueous micellar solutions of cationic surfactants such as cetyltrimethylammonium (CTA+, X-) or cetylpyridinium (Cpy+, X-) surfactants can be elegantly manipulated by changing the counterions, X-. Some counterions that penetrate the micellar interface, especially substituted chloro- and hydroxybenzoates, produce viscoelastic aqueous micellar solutions containing giant semi-flexible wormlike micelles that overlap and entangle. CTA26ClBz/Cl is an ideal model system for tuning micellar morphology from spheres to short cylinders to giant wormlike micelles and back to spheres, by manipulating the counterion molar ratio and the concentration of added salt. SANS is used to study the changing micellar structure and interactions on multiple length scales, including contour lengths, persistence lengths (bending moduli), cross-sectional radii and areas per head group at the micellar surface. The micellar form factors employed take into account both micellar flexibility and excluded volume effects (Pedersen, Schurtenberger). Results are also presented for micelles of CPySal, CPyBr and sodium dodecylsulfate (SDS), and the role of counterions on micellar packing parameters, surface charge densities and hence on transitions in aggregate morphology will be discussed. (author)

  7. Biomedical titanium alloys with Young’s moduli close to that of cortical bone

    Science.gov (United States)

    Niinomi, Mitsuo; Liu, Yi; Nakai, Masaki; Liu, Huihong; Li, Hua

    2016-01-01

    Biomedical titanium alloys with Young’s moduli close to that of cortical bone, i.e., low Young’s modulus titanium alloys, are receiving extensive attentions because of their potential in preventing stress shielding, which usually leads to bone resorption and poor bone remodeling, when implants made of their alloys are used. They are generally β-type titanium alloys composed of non-toxic and allergy-free elements such as Ti–29Nb–13Ta–4.6Zr referred to as TNTZ, which is highly expected to be used as a biomaterial for implants replacing failed hard tissue. Furthermore, to satisfy the demands from both patients and surgeons, i.e., a low Young’s modulus of the whole implant and a high Young’s modulus of the deformed part of implant, titanium alloys with changeable Young’s modulus, which are also β-type titanium alloys, for instance Ti–12Cr, have been developed. In this review article, by focusing on TNTZ and Ti–12Cr, the biological and mechanical properties of the titanium alloys with low Young’s modulus and changeable Young’s modulus are described. In addition, the titanium alloys with shape memory and superelastic properties were briefly addressed. Surface modifications for tailoring the biological and anti-wear/corrosion performances of the alloys have also been briefly introduced. PMID:27252887

  8. A Stringy Mechanism for A Small Cosmological Constant -- Multi-Moduli Cases

    CERN Document Server

    Sumitomo, Yoske

    2012-01-01

    Based on the properties of probability distributions of functions of random variables, we proposed earlier a simple stringy mechanism that prefers the meta-stable vacua with a small cosmological constant \\Lambda. As an illustration of this approach, we study in this paper particularly simple but non-trivial models of the K\\"ahler uplift in the large volume flux compactification scenario in Type IIB string theory, where all parameters introduced in the model are treated either as fixed constants motivated by physics, or as random variables with some given probability distributions. We determine the value w_0 of the superpotential W_0 at the supersymmetric minima, and find that the resulting probability distribution P(w_0) peaks at w_0=0; furthermore, this peaking behavior strengthens as the number of complex structure moduli increases. The resulting probability distribution P(\\Lambda) for meta-stable vacua also peaks as \\Lambda -> 0, for both positive and negative \\Lambda. This peaking/divergent behavior of P(...

  9. Experimental verification of tearing moduli as the material resistance against ductile crack growth

    International Nuclear Information System (INIS)

    There is the stage of stable crack propagation prior to the final unstable break-down in the large structures made of the materials with high toughness such as reactor pressure vessel steel. The transient phenomenon from the stable crack propagation to the unstable break-down is divided into ductile cleavage transition and tearing unstable break-down. Such unstable break-down is caused by the unbalance in the give and take of energy between materials and loading systems, and in order to analyze the tearing unstable break-down, it is important to determine the resistance to break-down peculiar to materials in the process of stable crack propagation. In this study, the fracture toughness test pieces with side grooves of A533 B-1 steel were used, and the tearing moduli for J-integral resistance curves, the change of plastic work and crack opening angle were comparatively examined. Also, the simple method for evaluating the resistance to ductile crack propagation peculiar to materials was proposed. The experimental method, the observation of fractured surfaces, and the effect of the dimensions and side grooves of test pieces on crack propagation resistance are reported. (Kako, I.)

  10. Area Expansivity Moduli of Regenerating Plant Protoplast Cell Walls Exposed to Shear Flows

    Science.gov (United States)

    Fujimura, Yuu; Iino, Masaaki; Watanabe, Ugai

    2005-05-01

    To control the elasticity of the plant cell wall, protoplasts isolated from cultured Catharanthus roseus cells were regenerated in shear flows of 115 s-1 (high shear) and 19.2 s-1 (low shear, as a control). The surface area expansivity modulus and the surface breaking strength of these regenerating protoplasts were measured by a micropipette aspiration technique. Cell wall synthesis was also measured using a cell wall-specific fluorescent dye. High shear exposure for 3 h doubled both the surface area modulus and breaking strength observed under low shear, significantly decreased cell wall synthesis, and roughly quadrupled the moduli of the cell wall. Based on the cell wall synthesis data, we estimated the three-dimensional modulus of the cell wall to be 4.1± 1.2 GPa for the high shear, and 0.35± 0.2 GPa for the low shear condition, using the surface area expansivity modulus divided by the cell wall thickness, which is identical with the Young’s modulus divided by 2(1-σ), where σ is Poisson's ratio. We concluded that high shear exposure considerably strengthens the newly synthesized cell wall.

  11. 合数模上的伪随机二进制数列%Pseudorandom Binary Sequences with Composite Moduli

    Institute of Scientific and Technical Information of China (English)

    刘华宁; 高静

    2012-01-01

    Let m be a modulus of "RSA type", i.e., it is the product of two primes not far apart, say, m = pq, p, q are primes, p 〈 q 〈 2p. Rivat and Sarkozy gave two families of pseudorandom binary sequences with composite moduli. In this paper we present two new families of binary sequences with composite moduli, and show that they are pseudorandom.%设m为"RSA"类型的模,即m为两个大小差不多的素数的乘积:m=pqp,q为素数,p〈q〈2p.Rivat与Sarkozy提出了两种合数模上的伪随机二进制数列本文将提出两种新的合数模上的二进制数列,并证明其具有很好的伪随机性.

  12. Measurement of Elastic Moduli of the Arterial Wall at Multiple Frequencies by Remote Actuation for Assessment of Viscoelasticity

    Science.gov (United States)

    Hasegawa, Hideyuki; Kanai, Hiroshi

    2004-05-01

    To characterize tissues in atherosclerotic plaques, we have developed a method, the phased tracking method, for measuring the strain (change in wall thickness) and elasticity of the arterial wall. However, some types of tissue, such as lipids and blood clots, cannot be discriminated from each other based only on elasticity due to the small difference in their elasticity. For more precise tissue characterization, we have measured the regional viscoelasticity. To obtain the viscoelasticity, in this study, elastic moduli at multiple frequencies were measured with ultrasound by generating the change in internal pressure due to remote cyclic actuation. Furthermore, the viscoelasticity of the arterial wall was estimated from the measured elastic moduli at multiple actuation frequencies.

  13. MPL-A program for computations with iterated integrals on moduli spaces of curves of genus zero

    Science.gov (United States)

    Bogner, Christian

    2016-06-01

    We introduce the Maple program MPL for computations with multiple polylogarithms. The program is based on homotopy invariant iterated integrals on moduli spaces M0,n of curves of genus 0 with n ordered marked points. It includes the symbol map and procedures for the analytic computation of period integrals on M0,n. It supports the automated computation of a certain class of Feynman integrals.

  14. ANALYTICAL EXPRESSIONS FOR BULK MODULI AND FREQUENCIES OF VOLUMETRICAL VIBRATIONS OF FULLERENES C20 AND C60

    OpenAIRE

    KOVALEV OLEG; KUZKIN VITALY

    2011-01-01

    In the present paper simple analytical expressions connecting bulk moduli for fullerenes C20 and C60 with stiffness of interatomic bond and geometrical characteristics of the fullerenes are derived. Ambiguities related to definition of the bulk modulus are discussed. Nonlinear volumetrical deformation of the fullerenes is considered. Pressure-volume dependence for the fullerenes under volumetrical compression are derived. Simple analytical model for volumetrical vibrations of the fullerenes i...

  15. Identification of couple-stress moduli of vertebral trabecular bone based on the 3D internal architectures.

    Science.gov (United States)

    Goda, Ibrahim; Ganghoffer, Jean-François

    2015-11-01

    The purpose of this paper is to develop a homogeneous, orthotropic couple-stress continuum model as a substitute of the 3D periodic heterogeneous cellular solid model of vertebral trabecular bone. Vertebral trabecular bone is modeled as a porous material with an idealized periodic structure made of 3D open cubic cells, which is effectively orthotropic. The chosen architecture is based on studies of samples taken from the central part of vertebral bodies. The effective properties are obtained based on the response of the representative volume element under prescribed boundary conditions. Mixed boundary conditions comprising both traction and displacement boundary conditions are applied on the structure boundaries. In this contribution, the effective mechanical constants of the effective couple-stress continuum are deduced by an equivalent strain energy method. The characteristic lengths for bending and torsion are identified from the resulting homogenized orthotropic moduli. We conduct this study computationally using a finite element approach. Vertebral trabecular bone is modeled either as a cellular solid or as a two-phase material consisting of bone tissue (stiff phase) forming a trabecular network, and a surrounding soft tissue referring to the bone marrow present in the pores. Both the bone tissue forming the network and the pores are assumed to be homogeneous linear elastic, and isotropic media. The scale effects on the predicted couple stress moduli of these networks are investigated by varying the size of the bone specimens over which the boundary conditions are applied. The analysis using mixed boundary conditions gives results that are independent of unit cell size when computing the first couple stress tensor, while it is dependent on the cell size as to the second couple stress tensor moduli. This study provides overall guidance on how the size of the trabecular specimen influence couple stresses elastic moduli of cellular materials, with focus on bones

  16. Ellipticity loss analysis for tangent moduli deduced from a large strain elastic–plastic self-consistent model

    OpenAIRE

    FRANZ, Gérald; ABED-MERAIM, Farid; Lorrain, Jean-Paul; BEN ZINEB, Tarak; LEMOINE, Xavier; Berveiller, Marcel

    2009-01-01

    In order to investigate the impact of microstructures and deformation mechanisms on the ductility of materials, the criterion first proposed by Rice is applied to elastic–plastic tangent moduli derived from a large strain micromechanical model combined with a self-consistent scale-transition technique. This approach takes into account several microstructural aspects for polycrystalline aggregates: initial and induced textures, dislocation densities as well as softening mechanisms such that th...

  17. A Database of Cepheid Distance Moduli and TRGB, GCLF, PNLF and SBF Data Useful for Distance Determinations

    OpenAIRE

    Ferrarese, Laura; Ford, Holland C.; Huchra, John,; Kennicutt, Jr., Robert C.; Mould, Jeremy R.; Sakai, Shoko; Freedman, Wendy L.; Peter B. Stetson; Madore, Barry F.; Gibson, Brad K.; Graham, John A.; Hughes, Shaun M.; Illingworth, Garth D.; Kelson, Daniel D.; Macri, Lucas

    1999-01-01

    We present a compilation of Cepheid distance moduli and data for four secondary distance indicators that employ stars in the old stellar populations: the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), the tip of the red giant branch (TRGB), and the surface brightness fluctuation (SBF) method. The database includes all data published as of July 15, 1999. The main strength of this compilation resides in all data being on a consistent and homogeneou...

  18. Field measurements of the linear and nonlinear shear moduli of cemented alluvium using dynamically loaded surface footings

    Science.gov (United States)

    Park, Kwangsoo

    In this dissertation, a research effort aimed at development and implementation of a direct field test method to evaluate the linear and nonlinear shear modulus of soil is presented. The field method utilizes a surface footing that is dynamically loaded horizontally. The test procedure involves applying static and dynamic loads to the surface footing and measuring the soil response beneath the loaded area using embedded geophones. A wide range in dynamic loads under a constant static load permits measurements of linear and nonlinear shear wave propagation from which shear moduli and associated shearing strains are evaluated. Shear wave velocities in the linear and nonlinear strain ranges are calculated from time delays in waveforms monitored by geophone pairs. Shear moduli are then obtained using the shear wave velocities and the mass density of a soil. Shear strains are determined using particle displacements calculated from particle velocities measured at the geophones by assuming a linear variation between geophone pairs. The field test method was validated by conducting an initial field experiment at sandy site in Austin, Texas. Then, field experiments were performed on cemented alluvium, a complex, hard-to-sample material. Three separate locations at Yucca Mountain, Nevada were tested. The tests successfully measured: (1) the effect of confining pressure on shear and compression moduli in the linear strain range and (2) the effect of strain on shear moduli at various states of stress in the field. The field measurements were first compared with empirical relationships for uncemented gravel. This comparison showed that the alluvium was clearly cemented. The field measurements were then compared to other independent measurements including laboratory resonant column tests and field seismic tests using the spectral-analysis-of-surface-waves method. The results from the field tests were generally in good agreement with the other independent test results, indicating

  19. The Moduli Space and M(Atrix) Theory of 9d N=1 Backgrounds of M/String Theory

    Energy Technology Data Exchange (ETDEWEB)

    Aharony, Ofer; /Weizmann Inst. /Stanford U., ITP /SLAC; Komargodski, Zohar; Patir, Assaf; /Weizmann Inst.

    2007-03-21

    We discuss the moduli space of nine dimensional N = 1 supersymmetric compactifications of M theory/string theory with reduced rank (rank 10 or rank 2), exhibiting how all the different theories (including M theory compactified on a Klein bottle and on a Moebius strip, the Dabholkar-Park background, CHL strings and asymmetric orbifolds of type II strings on a circle) fit together, and what are the weakly coupled descriptions in different regions of the moduli space. We argue that there are two disconnected components in the moduli space of theories with rank 2. We analyze in detail the limits of the M theory compactifications on a Klein bottle and on a Moebius strip which naively give type IIA string theory with an uncharged orientifold 8-plane carrying discrete RR flux. In order to consistently describe these limits we conjecture that this orientifold non-perturbatively splits into a D8-brane and an orientifold plane of charge (-1) which sits at infinite coupling. We construct the M(atrix) theory for M theory on a Klein bottle (and the theories related to it), which is given by a 2 + 1 dimensional gauge theory with a varying gauge coupling compactified on a cylinder with specific boundary conditions. We also clarify the construction of the M(atrix) theory for backgrounds of rank 18, including the heterotic string on a circle.

  20. The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

    Institute of Scientific and Technical Information of China (English)

    WANG Bo; WANG RongXiu; WU Yong

    2009-01-01

    The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite ele-ment models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be ac-ceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforce-ment.

  1. The Young’s moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young’s modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young’s moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be acceptable to predict the Young’s moduli of the grafted closed-cell PP foams with short-fiber reinforcement.

  2. A new calibration of seismic velocities, anisotropy, fabrics, and elastic moduli of amphibole-rich rocks

    Science.gov (United States)

    Ji, Shaocheng; Shao, Tongbin; Michibayashi, Katsuyoshi; Long, Changxing; Wang, Qian; Kondo, Yosuke; Zhao, Weihua; Wang, Hongcai; Salisbury, Matthew H.

    2013-09-01

    large portion of the middle to lower crust beneath the continents and oceanic island arcs consists of amphibolites dominated by hornblende and plagioclase. We have measured P and S wave velocities (Vp and Vs) and anisotropy of 17 amphibole-rich rock samples containing 34-80 vol % amphibole at hydrostatic pressures (P) up to 650 MPa. Combined petrophysical and geochemical analyses provide a new calibration for mean density, average major element contents, mean Vp-P and Vs-P coefficients, intrinsic Vp and Vs anisotropy, Poisson's ratios, the logarithmic ratio Rs/p, and elastic moduli of amphibole-rich rocks. The Vp values decrease with increasing SiO2 and Na2O + K2O contents but increase with increasing MgO and CaO contents. The maximum (≤0.38-0.40 km/s) and minimum S wave birefringence values occur generally in the propagation direction parallel to Y and normal to foliation, respectively. Amphibole plays a critical role in the formation of seismic anisotropy, whereas the presence of plagioclase, quartz, pyroxene, and garnet diminishes the anisotropy induced by amphibole crystallographic preferred orientations (CPOs). The CPO variations cause different anisotropy patterns illustrated in the Flinn diagram of Vp(X)/Vp(Y)-Vp(Y)/Vp(Z) plots. The results make it possible to distinguish, in terms of seismic properties, the amphibolites from other categories of lithology such as granite-granodiorite, diorite, gabbro-diabase, felsic gneiss, mafic gneiss, eclogite, and peridotite within the Earth's crust. Hence, amphibole, aligned by dislocation creep, anisotropic growth, or rigid-body rotation, is the most important contributor to the seismic anisotropy of the deep crust beneath the continents and oceanic island arcs, which contains rather little phyllosilicates such as mica or chlorite.

  3. On the elastic moduli of two-dimensional assemblies of disks: Relevance and modeling of fluctuations in particle displacements and rotations

    OpenAIRE

    Agnolin, I.; Kruyt, N.P.;  

    2007-01-01

    We determine the elastic moduli of two-dimensional assemblies of disks by computer simulations. The disks interact through elastic contact forces, that oppose the relative displacement at the contact points by means of a normal and a tangential stiffness, both taken constant. Our simulations confirm that the uniform strain assumption results in inaccurate predictions of the elastic moduli, since large fluctuations in particle displacements and rotations occur. We phrase their contribution in ...

  4. Measurement of the dynamic shear modulus of surface layers I. Theory

    OpenAIRE

    Waterman, Herman A.

    1984-01-01

    In measuring the dynamic surface-shear modulus of a surface layer on a liquid, conditions may occur—low-shear modulus and/or high frequencies—which promote wave-propagation effects to play a predominant role. A theory is presented with the help of which the (complex) wave number of the wave in the layer can be expressed in the densities and shear moduli of both the surface layer and the liquid. The theory can also be applied to an interfacial layer between two liquids. It predicts that in pra...

  5. NASA/University JOint VEnture (JOVE) Program: Transverse Shear Moduli Using the Torsional Responses of Rectangular Laminates

    Science.gov (United States)

    Bogan, Sam

    2001-01-01

    The first year included a study of the non-visible damage of composite overwrapped pressure vessels with B. Poe of the Materials Branch of Nasa-Langley. Early determinations showed a clear reduction in non-visible damage for thin COPVs when partially pressurized rather than unpressurized. Literature searches on Thicker-wall COPVs revealed surface damage but clearly visible. Analysis of current Analytic modeling indicated that that current COPV models lacked sufficient thickness corrections to predict impact damage. After a comprehensive study of available published data and numerous numerical studies based on observed data from Langley, the analytic framework for modeling the behavior was determined lacking and both Poe and Bogan suggested any short term (3yr) result for Jove would be overly ambitious and emphasis should be placed on transverse shear moduli studies. Transverse shear moduli determination is relevant to the study of fatigue, fracture and aging effects in composite structures. Based on the techniques developed by Daniel & Tsai, Bogan and Gates determined to verify the results for K3B and 8320. A detailed analytic and experimental plan was established and carried out that included variations in layup, width, thickness, and length. As well as loading rate variations to determine effects and relaxation moduli. The additional axial loads during the torsion testing were studied as was the placement of gages along the composite specimen. Of the proposed tasks, all of tasks I and 2 were completed with presentations given at Langley, SEM conferences and ASME/AIAA conferences. Sensitivity issues with the technique associated with the use of servohydraulic test systems for applying the torsional load to the composite specimen limited the torsion range for predictable and repeatable transverse shear properties. Bogan and Gates determined to diverge on research efforts with Gates continuing the experimental testing at Langley and Bogan modeling the apparent non

  6. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    OpenAIRE

    Cantrell, John H.

    2015-01-01

    The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds) formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS) of the composite. The H-bond contributions τ to the ILSS and magnitudes KN of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites,...

  7. Marginal and relevant deformations of N=4 field theories and non-commutative moduli spaces of vacua

    International Nuclear Information System (INIS)

    We study marginal and relevant supersymmetric deformations of the N=4 super Yang-Mills theory in four dimensions. Our primary innovation is the interpretation of the moduli spaces of vacua of these theories as non-commutative spaces. The construction of these spaces relies on the representation theory of the related quantum algebras, which are obtained from F-term constraints. These field theories are dual to superstring theories propagating on deformations of the AdS5xS5 geometry. We study D-branes propagating in these vacua and introduce the appropriate notion of algebraic geometry for non-commutative spaces. The resulting moduli spaces of D-branes have several novel features. In particular, they may be interpreted as symmetric products of non-commutative spaces. We show how mirror symmetry between these deformed geometries and orbifold theories follows from T-duality. Many features of the dual closed string theory may be identified within the non-commutative algebra. In particular, we make progress towards understanding the K-theory necessary for backgrounds where the Neveu-Schwarz antisymmetric tensor of the string is turned on, and we shed light on some aspects of discrete anomalies based on the non-commutative geometry

  8. Measurements of Elastic Moduli of Silicone Gel Substrates with a Microfluidic Device

    OpenAIRE

    Gutierrez, Edgar; Groisman, Alex

    2011-01-01

    Thin layers of gels with mechanical properties mimicking animal tissues are widely used to study the rigidity sensing of adherent animal cells and to measure forces applied by cells to their substrate with traction force microscopy. The gels are usually based on polyacrylamide and their elastic modulus is measured with an atomic force microscope (AFM). Here we present a simple microfluidic device that generates high shear stresses in a laminar flow above a gel-coated substrate and apply the d...

  9. Elastic moduli of η-Ta2N3, a tough self-healing material, via laser ultrasonics

    International Nuclear Information System (INIS)

    The elastic moduli of the dense polycrystalline oxygen-bearing η-Ta2N3, a novel hard and tough high-pressure (HP) material, were measured using the laser ultrasonic technique. The bulk modulus was determined to be B0 = 281(15) GPa which is only ∝11% below that from HP compression measurements. Our value of the shear modulus G0 = 123(2) GPa is below those ones predicted theoretically for model structures. The discrepancies in G0 could be due to a substitution of an- ions and the formation of cation vacancies in η-Ta2N3. Self-healing behaviour of η-Ta2N3 by mechanical polishing was observed and confirmed by two independent experimental methods. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Effect of pore pressure on the elastic moduli, porosity and permeability of Berea sandstone and Leuders limestone

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, T.W.; Kelkar, S.M.; Gray, K.E.

    1983-02-01

    The behavior of Berea sandstone and Leuders limestone under atmospheric and elevated pore pressures is reported. The porosity and the permeability changes, along with the static and dynamic moduli for these rocks have been determined under various conditions. The existing theoretical background pertinent to the study is reviewed along with the previous experimental work. The detailed descriptions and the discussions on the experimental procedure involved and the equipment utilized are presented. A discussion on the sources of experimental errors is included. It also includes the error propagation equations and relevant discussions on the data acquisition and analysis. The findings are summarized together with a discussion of the results. The conclusions drawn from these results are included. The bulk of the data acquired and the results computed from it are presented.

  11. Six-dimensional supersymmetric gauge theories, quantum cohomology of instanton moduli spaces and gl( N) Quantum Intermediate Long Wave Hydrodynamics

    Science.gov (United States)

    Bonelli, Giulio; Sciarappa, Antonio; Tanzini, Alessandro; Vasko, Petr

    2014-07-01

    We show that the exact partition function of U( N) six-dimensional gauge theory with eight supercharges on ℂ2 × S 2 provides the quantization of the integrable system of hydrodynamic type known as gl( N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S 2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl( N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl( N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W N algebrae, thus providing a gauge theoretical proof of AGT correspondence.

  12. Influence of C concentration on elastic moduli of α‧-Fe1-xCx alloys

    Science.gov (United States)

    Janßen, Jan; Gunkelmann, Nina; Urbassek, Herbert M.

    2016-05-01

    The elastic constants of tetragonally distorted ?-? crystallites are calculated for several available interatomic interaction potentials. Besides embedded-atom-method-type potentials also a simple pair potential, modified embedded-atom-method and bond-order potentials are investigated. Care is taken to minimise the crystal structure properly in the presence of the C interstitials; we verify that the influence of statistics, i.e. the randomness of the C positions in the lattice, affects the elastic properties only little, as long as C is not allowed to cluster. We find that both sign and order of magnitude of the tetragonal elastic constants vary strongly between the predictions of the available potentials. Recent experimental data are available for the orientation-averaged elastic moduli; in contrast to the tetragonal constants, they feature only a mild dependence on C content. The experimental data are well reproduced by several of the potentials studied here. Existing deviations between experiment and predictions are discussed.

  13. Asteroseismic study on cluster distance moduli for red giant branch stars in NGC 6791 and NGC 6819

    International Nuclear Information System (INIS)

    Stellar distance is an important basic parameter in stellar astrophysics. Stars in a cluster are thought to be formed coevally from the same interstellar cloud of gas and dust; therefore, they are expected to have common properties. These common properties strengthen our ability to constrain theoretical models and/or to determine fundamental parameters, such as stellar mass, metal fraction, and distance, when tested against an ensemble of cluster stars. Here we derive a new relation based on solar-like oscillations, photometric observations, and the theory of stellar structure and evolution of red giant branch stars to determine cluster distance moduli through the global oscillation parameters Δν and νmax and photometric data V. The values of Δν and νmax are derived from Kepler observations. At the same time, it is used to interpret the trends between V and Δν. From the analyses of this newly derived relation and observational data of NGC 6791 and NGC 6819, we devise a method in which all stars in a cluster are regarded as one entity to determine the cluster distance modulus. This approach fully reflects the characteristic of member stars in a cluster as a natural sample. From this method we derive true distance moduli of 13.09 ± 0.10 mag for NGC 6791 and 11.88 ± 0.14 mag for NGC 6819. Additionally, we find that the distance modulus only slightly depends on the metallicity [Fe/H] in the new relation. A change of 0.1 dex in [Fe/H] will lead to a change of 0.06 mag in the distance modulus.

  14. The first cohomology of the mapping class group with coefficients in algebraic functions on the SL2(C) moduli space

    DEFF Research Database (Denmark)

    Andersen, Jørgen Ellegaard; Villemoes, Rasmus

    2009-01-01

    Consider a compact surface of genus at least two. We prove that the first cohomology group of the mapping class group with coefficients in the space of algebraic functions on the SL2(C) moduli space vanishes. In the genus one case, this cohomology group is infinite dimensional....

  15. Monte Carlo calculations of the elastic moduli and pressure-volume-temperature equation of state for hexahydro-1,3,5-trinitro-1,3,5-triazine

    International Nuclear Information System (INIS)

    Isothermal-isobaric Monte Carlo calculations were used to obtain predictions of the elastic coefficients and derived engineering moduli and Poisson ratios for crystalline hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The elastic coefficients were computed using the strain fluctuation formula due to Rahman and Parrinello [J. Chem. Phys. 76, 2662 (1982)]. Calculations were performed as a function of temperature (218 K≤T≤333 K) and hydrostatic pressure (0 GPa≤p≤4 GPa). The predicted values of the moduli and Poisson ratios under ambient conditions are in accord with general expectations for molecular crystals and with a very recent, unpublished determination for RDX. The moduli exhibit a sensitive pressure dependence whereas the Poisson ratios are relatively independent of pressure. The temperature dependence of the moduli is comparable to the precision of the results. However, the crystal does exhibit thermal softening for most pressures. An additional product of the calculations is information about the pressure-volume-temperature (pVT) equation of state. We obtain near-quantitative agreement with experiment for the case of hydrostatic compression and reasonable, but not quantitative, correspondence for thermal expansion. The results indicate a significant dependence of the thermal expansion coefficients on hydrostatic pressure. (c) 2000 American Institute of Physics

  16. Tangent moduli of the Green-Lagrange and left Hencky material descriptions derived from the stored energy function at finite strains

    Czech Academy of Sciences Publication Activity Database

    Poživilová, Alena; Plešek, Jiří

    Brno : VUTIUM Brno, 2004 - (Šandera, P.), s. 55 [Materials Structure and Micromechanics of Fracture. Brno (CZ), 23.06.2004-25.06.2004] Institutional research plan: CEZ:AV0Z2076919 Keywords : acoustoelasticity * large strains * third order elastic moduli Subject RIV: JJ - Other Materials

  17. Boundary Layer

    Science.gov (United States)

    Loitsianskii. L. G.

    1956-01-01

    The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the boundary layer. The presence of a boundary layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of boundary layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work "On the Form of Ships" published as early as 1890. In his book "Theoretical Foundations of Air Navigation," Joukowsky gave an account of the most important properties of the boundary layer and pointed out the part played by it in the production of the resistance of bodies to motion. The fundamental differential equations of the motion of a fluid in a laminar boundary layer were given by Prandtl in 1904; the first solutions of these equations date from 1907 to 1910. As regards the turbulent boundary layer, there does not exist even to this day any rigorous formulation of this problem because there is no closed system of equations for the turbulent motion of a fluid. Soviet scientists have done much toward developing a general theory of the boundary layer, and in that branch of the theory which is of greatest practical importance at the present time, namely the study of the boundary layer at large velocities of the body in a compressed gas, the efforts of the scientists of our country have borne fruit in the creation of a new theory which leaves far behind all that has been done previously in this direction. We shall herein enumerate the most important results by Soviet scientists in the development of the theory of the boundary layer.

  18. Microemulsions: Structures, surfactant layer properties and wetting transitions

    Science.gov (United States)

    Abillon, O.; Lee, L. T.; Langevin, D.; Wong, K.

    1991-03-01

    We review briefly the basic known features of microemulsion structures, emphasizing the importance of the surfactant layer bending elasticity. The results for water-alkane-nonionic-surfactant systems, confirming the close relationship between the maximum characteristic size in the microemulsion and the persistence length of the surfactant layer, are presented. We show that microemulsions are formed when the surfactant layer bending moduli are in a well defined range: if the bending modulus is too large, ordered lamellar phases are obtained, while if it is too small, the surfactant film cannot form, and the medium is a structureless molecular mixture. The evolution between microemulsions and molecular mixtures is continuous; its relationship with the wetting transition between the microemulsion and the two excess phases is discussed.

  19. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junhua, E-mail: junhua.zhao@uni-weimar.de [Jiangsu Province Key Laboratory of Advanced Manufacturing Equipment and Technology of Food, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Jiang, Jin-Wu, E-mail: jwjiang5918@hotmail.com [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Rabczuk, Timon, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); School of Civil, Environmental and Architectural Engineering, Korea University, 136-701 Seoul (Korea, Republic of)

    2013-12-02

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  20. Moduli spaces of framed symplectic and orthogonal bundles on P2 and the K-theoretic Nekrasov partition functions

    Science.gov (United States)

    Choy, Jaeyoo

    2016-08-01

    Let K be the compact Lie group USp(N / 2) or SO(N , R) . Let MnK be the moduli space of framed K-instantons over S4 with the instanton number n. By Donaldson (1984), MnK is endowed with a natural scheme structure. It is a Zariski open subset of a GIT quotient of μ-1(0) , where μ is a holomorphic moment map such that μ-1(0) consists of the ADHM data. The purpose of the paper is to study the geometric properties of μ-1(0) and its GIT quotient, such as complete intersection, irreducibility, reducedness and normality. If K = USp(N / 2) then μ is flat and μ-1(0) is an irreducible normal variety for any n and even N. If K = SO(N , R) the similar results are proven for low n and N. As an application one can obtain a mathematical interpretation of the K-theoretic Nekrasov partition function of Nekrasov and Shadchin (2004).

  1. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, John H., E-mail: john.h.cantrell@nasa.gov [Research Directorate, NASA Langley Research Center, Hampton, Virginia 23681 (United States)

    2015-03-15

    The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds) formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS) of the composite. The H-bond contributions τ to the ILSS and magnitudes K{sub N} of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The K{sub N} calculations fall in the range (2.01 – 4.67) ×10{sup 17} N m{sup −3}. The average ratio K{sub N}/|τ| is calculated to be (2.59 ± 0.043) × 10{sup 10} m{sup −1} for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of K{sub N} via a technique such as angle beam ultrasonic spectroscopy.

  2. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    International Nuclear Information System (INIS)

    The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds) formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS) of the composite. The H-bond contributions τ to the ILSS and magnitudes KN of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The KN calculations fall in the range (2.01 – 4.67) ×1017 N m−3. The average ratio KN/|τ| is calculated to be (2.59 ± 0.043) × 1010 m−1 for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of KN via a technique such as angle beam ultrasonic spectroscopy

  3. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    Directory of Open Access Journals (Sweden)

    John H. Cantrell

    2015-03-01

    Full Text Available The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS of the composite. The H-bond contributions τ to the ILSS and magnitudes KN of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The KN calculations fall in the range (2.01 – 4.67 ×1017 N m−3. The average ratio KN/|τ| is calculated to be (2.59 ± 0.043 × 1010 m−1 for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of KN via a technique such as angle beam ultrasonic spectroscopy.

  4. Gradient moduli lens models: how material properties and application of forces can affect deformation and distributions of stress

    Science.gov (United States)

    Wang, Kehao; Venetsanos, Demetrios; Wang, Jian; Pierscionek, Barbara K.

    2016-01-01

    The human lens provides one-third of the ocular focussing power and is responsible for altering focus over a range of distances. This ability, termed accommodation, defines the process by which the lens alters shape to increase or decrease ocular refractive power; this is mediated by the ciliary muscle through the zonule. This ability decreases with age such that around the sixth decade of life it is lost rendering the eye unable to focus on near objects. There are two opponent theories that provide an explanation for the mechanism of accommodation; definitive support for either of these requires investigation. This work aims to elucidate how material properties can affect accommodation using Finite Element models based on interferometric measurements of refractive index. Gradients of moduli are created in three models from representative lenses, aged 16, 35 and 48 years. Different forms of zonular attachments are studied to determine which may most closely mimic the physiological form by comparing stress and displacement fields with simulated shape changes to accommodation in living lenses. The results indicate that for models to mimic accommodation in living eyes, the anterior and posterior parts of the zonule need independent force directions. Choice of material properties affects which theory of accommodation is supported. PMID:27507665

  5. Complete determination of the elastic moduli of α-quartz under hydrostatic pressure up to 1 GPa: an ultrasonic study

    International Nuclear Information System (INIS)

    Using the ultrasonic pulse-echo technique and a newly developed method to treat the data, all the elastic compliances of α-quartz have been obtained as a function of hydrostatic pressure up to 1 GPa with great accuracy. Fifteen independent measurements were performed in five directions of high symmetry (X, Y, Z, Y' and Z'). The pressure dependence of the six second-order elastic and two piezoelectric constants were deduced. The pressure derivatives of c14 and c44 are positive, whereas that of c66 is negative, in contradiction to previously published results. Under ambient conditions, the linear and bulk moduli Ba0 = 103.4(0.5) GPa, Bc0 137.0(0.5) GPa and B0 = 37.5(0.2) GPa calculated from our determination of the elastic tensor are in good agreement with the published values. However, we find a clear discrepancy with published values for the pressure derivative of the bulk modulus B' = 4.7(0.5). From these results, the Born stability criteria have been calculated as a function of pressure and compared with previous results. Their behavior can help to explain the structural instability of α-quartz at around 18 GPa

  6. Elastic wave speeds and moduli in polycrystalline ice Ih, si methane hydrate, and sll methane-ethane hydrate

    Science.gov (United States)

    Helgerud, M.B.; Waite, W.F.; Kirby, S.H.; Nur, A.

    2009-01-01

    We used ultrasonic pulse transmission to measure compressional, P, and shear, S, wave speeds in laboratory-formed polycrystalline ice Ih, si methane hydrate, and sll methane-ethane hydrate. From the wave speed's linear dependence on temperature and pressure and from the sample's calculated density, we derived expressions for bulk, shear, and compressional wave moduli and Poisson's ratio from -20 to 15??C and 22.4 to 32.8 MPa for ice Ih, -20 to 15??C and 30.5 to 97.7 MPa for si methane hydrate, and -20 to 10??C and 30.5 to 91.6 MPa for sll methane-ethane hydrate. All three materials had comparable P and S wave speeds and decreasing shear wave speeds with increasing applied pressure. Each material also showed evidence of rapid intergranular bonding, with a corresponding increase in wave speed, in response to pauses in sample deformation. There were also key differences. Resistance to uniaxial compaction, indicated by the pressure required to compact initially porous samples, was significantly lower for ice Ih than for either hydrate. The ice Ih shear modulus decreased with increasing pressure, in contrast to the increase measured in both hydrates ?? 2009.

  7. Line operators in theories of class S, quantized moduli space of flat connections, and Toda field theory

    International Nuclear Information System (INIS)

    Non-perturbative aspects of N=2 supersymmetric gauge theories of class S are deeply encoded in the algebra of functions on the moduli space Mflat of at SL(N)-connections on Riemann surfaces. Expectation values of Wilson and 't Hooft line operators are related to holonomies of flat connections, and expectation values of line operators in the low-energy effective theory are related to Fock-Goncharov coordinates on Mflat. Via the decomposition of UV line operators into IR line operators, we determine their noncommutative algebra from the quantization of Fock-Goncharov Laurent polynomials, and find that it coincides with the skein algebra studied in the context of Chern-Simons theory. Another realization of the skein algebra is generated by Verlinde network operators in Toda field theory. Comparing the spectra of these two realizations provides non-trivial support for their equivalence. Our results can be viewed as evidence for the generalization of the AGT correspondence to higher-rank class S theories.

  8. Determination and validation of the elastic moduli of small and complex biological samples: bone and keratin in bird beaks.

    Science.gov (United States)

    Soons, Joris; Herrel, Anthony; Aerts, Peter; Dirckx, Joris

    2012-06-01

    In recent years, there has been a surge in the development of finite-element (FE) models aimed at testing biological hypotheses. For example, recent modelling efforts suggested that the beak in Darwin's finches probably evolved in response to fracture avoidance. However, knowledge of the material properties of the structures involved is crucial for any model. For many biological structures, these data are not available and may be difficult to obtain experimentally given the complex nature of biological structures. Beaks are interesting as they appear to be highly optimized in some cases. In order to understand the biomechanics of this small and complex structure, we have been developing FE models that take into account the bilayered structure of the beak consisting of bone and keratin. Here, we present the results of efforts related to the determination and validation of the elastic modulus of bone and keratin in bird beaks. The elastic moduli of fresh and dried samples were obtained using a novel double-indentation technique and through an inverse analysis. A bending experiment is used for the inverse analysis and the validation of the measurements. The out-of-plane displacements during loading are measured using digital speckle pattern interferometry. PMID:22090286

  9. Layered materials

    Science.gov (United States)

    Johnson, David; Clarke, Simon; Wiley, John; Koumoto, Kunihito

    2014-06-01

    Layered compounds, materials with a large anisotropy to their bonding, electrical and/or magnetic properties, have been important in the development of solid state chemistry, physics and engineering applications. Layered materials were the initial test bed where chemists developed intercalation chemistry that evolved into the field of topochemical reactions where researchers are able to perform sequential steps to arrive at kinetically stable products that cannot be directly prepared by other approaches. Physicists have used layered compounds to discover and understand novel phenomena made more apparent through reduced dimensionality. The discovery of charge and spin density waves and more recently the remarkable discovery in condensed matter physics of the two-dimensional topological insulating state were discovered in two-dimensional materials. The understanding developed in two-dimensional materials enabled subsequent extension of these and other phenomena into three-dimensional materials. Layered compounds have also been used in many technologies as engineers and scientists used their unique properties to solve challenging technical problems (low temperature ion conduction for batteries, easy shear planes for lubrication in vacuum, edge decorated catalyst sites for catalytic removal of sulfur from oil, etc). The articles that are published in this issue provide an excellent overview of the spectrum of activities that are being pursued, as well as an introduction to some of the most established achievements in the field. Clusters of papers discussing thermoelectric properties, electronic structure and transport properties, growth of single two-dimensional layers, intercalation and more extensive topochemical reactions and the interleaving of two structures to form new materials highlight the breadth of current research in this area. These papers will hopefully serve as a useful guideline for the interested reader to different important aspects in this field and

  10. Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22 pct CaF2 eutectic salt

    Science.gov (United States)

    Wolfenden, A.; Lastrapes, G.; Duggan, M. B.; Raj, S. V.

    1991-01-01

    Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-(22 mol pct)CaF2 eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique. The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF2 single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young modulus values, where this disagreement increases with increasing temperature.

  11. Elastic moduli of advanced orthorhombic binary and ternary metal (V, Ta, Nb) nitrides with the U{sub 2}S{sub 3} structure

    Energy Technology Data Exchange (ETDEWEB)

    Orisakwe, Esther Nkiruka; Sharma, Vinit; Lowther, John E. [School of Physics and DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg (South Africa)

    2012-05-15

    The elastic constants and isotropic moduli of a recently synthesized orthorhombic ternary metal nitride are examined using first-principles calculations. Tantalum nitride has the largest moduli but other metals such as vanadium or niobium are shown to affect the elastic constants. It is suggested that such metals could be incorporated into the Ta-N material and play a critical role in engineering its properties. Low concentrations of V seem especially significant leading to a stabilized metallic material with possible enhancement of hardness relative to Ta{sub 2}N{sub 3}. There are significant results between various computational approaches. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. A first-principles study of cementite (Fe3C and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Directory of Open Access Journals (Sweden)

    G. Ghosh

    2015-08-01

    Full Text Available A comprehensive computational study of elastic properties of cementite (Fe3C and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT, all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA. Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i single-crystal elastic constants, Cij, of above M3Cs; (ii anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated Cijs, demonstrating their extreme anisotropies; (iii isotropic (polycrystalline elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio of M3Cs by homogenization of calculated Cijs; and (iv acoustic Debye temperature, θD, of M3Cs based on calculated Cijs. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  13. A first-principles study of cementite (Fe3C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Science.gov (United States)

    Ghosh, G.

    2015-08-01

    A comprehensive computational study of elastic properties of cementite (Fe3C) and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C) having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, Cij, of above M3Cs; (ii) anisotropies of bulk, Young's and shear moduli, and Poisson's ratio based on calculated Cijs, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young's moduli and Poisson's ratio) of M3Cs by homogenization of calculated Cijs; and (iv) acoustic Debye temperature, θD, of M3Cs based on calculated Cijs. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  14. Computational efficiency of numerical approximations of tangent moduli for finite element implementation of a fiber-reinforced hyperelastic material model.

    Science.gov (United States)

    Liu, Haofei; Sun, Wei

    2016-08-01

    In this study, we evaluated computational efficiency of finite element (FE) simulations when a numerical approximation method was used to obtain the tangent moduli. A fiber-reinforced hyperelastic material model for nearly incompressible soft tissues was implemented for 3D solid elements using both the approximation method and the closed-form analytical method, and validated by comparing the components of the tangent modulus tensor (also referred to as the material Jacobian) between the two methods. The computational efficiency of the approximation method was evaluated with different perturbation parameters and approximation schemes, and quantified by the number of iteration steps and CPU time required to complete these simulations. From the simulation results, it can be seen that the overall accuracy of the approximation method is improved by adopting the central difference approximation scheme compared to the forward Euler approximation scheme. For small-scale simulations with about 10,000 DOFs, the approximation schemes could reduce the CPU time substantially compared to the closed-form solution, due to the fact that fewer calculation steps are needed at each integration point. However, for a large-scale simulation with about 300,000 DOFs, the advantages of the approximation schemes diminish because the factorization of the stiffness matrix will dominate the solution time. Overall, as it is material model independent, the approximation method simplifies the FE implementation of a complex constitutive model with comparable accuracy and computational efficiency to the closed-form solution, which makes it attractive in FE simulations with complex material models. PMID:26692168

  15. DAQ USB moduly

    OpenAIRE

    Kaderka, Tomasz

    2009-01-01

    Bakalářská práce se zabývá problematikou sběru a zpracování dat. V první části je okrajově rozebrán vývoj měřící techniky, virtuální instrumentace a rozhraní pro komunikaci. Druhá část práce obsahuje srovnání USB měřicích modulů z hlediska hardwarových vlastností i dostupného softwaru v cenové kategorii do 10.000Kč. Třetí část práce popisuje postup vytvoření uživatelsky jednoduchého obslužného programu pro měřicí modul NI USB-6008, který je doplněn o uživatelský manuál. The aim of this bac...

  16. Dynamic bulk and shear moduli due to grain-scale local fluid flow in fluid-saturated cracked poroelastic rocks: Theoretical model

    Science.gov (United States)

    Song, Yongjia; Hu, Hengshan; Rudnicki, John W.

    2016-07-01

    Grain-scale local fluid flow is an important loss mechanism for attenuating waves in cracked fluid-saturated poroelastic rocks. In this study, a dynamic elastic modulus model is developed to quantify local flow effect on wave attenuation and velocity dispersion in porous isotropic rocks. The Eshelby transform technique, inclusion-based effective medium model (the Mori-Tanaka scheme), fluid dynamics and mass conservation principle are combined to analyze pore-fluid pressure relaxation and its influences on overall elastic properties. The derivation gives fully analytic, frequency-dependent effective bulk and shear moduli of a fluid-saturated porous rock. It is shown that the derived bulk and shear moduli rigorously satisfy the Biot-Gassmann relationship of poroelasticity in the low-frequency limit, while they are consistent with isolated-pore effective medium theory in the high-frequency limit. In particular, a simplified model is proposed to quantify the squirt-flow dispersion for frequencies lower than stiff-pore relaxation frequency. The main advantage of the proposed model over previous models is its ability to predict the dispersion due to squirt flow between pores and cracks with distributed aspect ratio instead of flow in a simply conceptual double-porosity structure. Independent input parameters include pore aspect ratio distribution, fluid bulk modulus and viscosity, and bulk and shear moduli of the solid grain. Physical assumptions made in this model include (1) pores are inter-connected and (2) crack thickness is smaller than the viscous skin depth. This study is restricted to linear elastic, well-consolidated granular rocks.

  17. A first-principles study of cementite (Fe{sub 3}C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, G., E-mail: g-ghosh@northwestern.edu [Department of Materials Science and Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)

    2015-08-15

    A comprehensive computational study of elastic properties of cementite (Fe{sub 3}C) and its alloyed counterparts (M{sub 3}C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr{sub 2}FeC and CrFe{sub 2}C) having the crystal structure of Fe{sub 3}C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, C{sub ij}, of above M{sub 3}Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated C{sub ij}s, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M{sub 3}Cs by homogenization of calculated C{sub ij}s; and (iv) acoustic Debye temperature, θ{sub D}, of M{sub 3}Cs based on calculated C{sub ij}s. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  18. Comment on 'Parametrization of Stillinger-Weber potential based on a valence force field model: application to single-layer MoS2 and black phosphorus'.

    Science.gov (United States)

    Midtvedt, Daniel; Croy, Alexander

    2016-06-10

    We compare the simplified valence-force model for single-layer black phosphorus with the original model and recent ab initio results. Using an analytic approach and numerical calculations we find that the simplified model yields Young's moduli that are smaller compared to the original model and are almost a factor of two smaller than ab initio results. Moreover, the Poisson ratios are an order of magnitude smaller than values found in the literature. PMID:27121075

  19. Parametrization of U(N)-Monopoles on Black Holes by the Moduli Space of Holomorphic Vector Bundles Over Two-Sphere and Black Hole Entropy

    Science.gov (United States)

    Goncharov, Yu. P.

    We discuss how to describe U(N) monopoles on the Schwarzschild and Reissner-Nordström black holes by the parameters of the moduli space of holomorphic vector bundles over S2. For N = 2,3 we obtain such a description in an explicit form as well as the expressions for the corresponding monopole masses. This gives a possibility of adducing some reasonings in favor of existence of both a fine structure for black holes and the statistical ensemble tied with it which might generate the black hole entropy. Also, there arises an analogy with the famous K-theory in topology.

  20. Parametrization of U(N)-monopoles on black holes by the moduli space of holomorphic vector bundles over two-sphere and black hole entropy

    CERN Document Server

    Goncharov, Yu P

    1996-01-01

    We discuss how to describe U(N)-monopoles on the Schwarzschild and Reissner-Nordström black holes by the parameters of the moduli space of holomorphic vector bundles over S^2. For N = 2,3 we obtain such a description in an explicit form as well as the expressions for the corresponding monopole masses. This gives a possibility to adduce some reasonings in favour of existence of both a `fine structure' for black holes and the statistical ensemble tied with it which might generate the black hole entropy. Also there arises some analogy with the famous K-theory in topology.

  1. Mechanical analysis of poly-layer reinforcement schemes for pulse magnets

    International Nuclear Information System (INIS)

    The major philosophies of pulse magnet design are discussed. Two of these are compared in terms of the von Mises stress generated within the winding at equal fields. The shortcomings of the use of fiber reinforcement in magnets is described and a method for utilizing it more effectively by the fabrication of multiple layers of composite of different moduli is suggested. A number of examples are given of the stress reduction effects on particular magnet designs that can be obtained by using this method

  2. An efficient RNS parity checker for moduli set {2n-1,2n+1,22n+1} and its applications

    Institute of Scientific and Technical Information of China (English)

    MA Shang; HU JianHao; ZHANG Lin; LING Xiang

    2008-01-01

    Residue number system (RNS) has received considerable attention since decades before,because it has inherent carry-free and parallel properties in addition,subtraction,and multiplication operations.For an odd moduli set,the fundamental problems in RNS,such as number comparison,sign determination,and overflow detection,can be solved based on parity checking.The paper proposes a parity checking algorithm along with related propositions and the certification based on the celebrated Chinese remainder theory (CRT) and mixed radix conversion (MRC) for the moduli set {2n-1,2n+1,22n+1}.The parity checker consists of two modular adders and a carry-look-ahead chain.The hardware implementation requires less area and path delay.Besides,the implementations of number comparison,sign determination,and overflow detection,which are based on this parity checker,are also performed in this paper.And this kind of parity checker can be used as a basic element to design ALUs and DSP module in RNS.

  3. High Elastic Moduli of a 54Al2O3-46Ta2O5 Glass Fabricated via Containerless Processing

    Science.gov (United States)

    Rosales-Sosa, Gustavo A.; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki; Yanaba, Yutaka; Mizoguchi, Teruyasu; Umada, Takumi; Okamura, Kohei; Kato, Katsuyoshi; Watanabe, Yasuhiro

    2015-10-01

    Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region, and its refractive index nd was as high as 1.94. The measured Young’s modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta5+ ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.

  4. A method for measuring single-crystal elastic moduli using high-energy X-ray diffraction and a crystal-based finite element model

    International Nuclear Information System (INIS)

    This paper presents a method - based on high-energy synchrotron X-ray diffraction data and a crystal-based finite element simulation formulation - for understanding grain scale deformation behavior within a polycrystalline aggregate. We illustrate this method by using it to determine the single-crystal elastic moduli of β21s, a body-centered cubic titanium alloy. We employed a polycrystalline sample. Using in situ loading and high-energy X-rays at the Advanced Photon Source beamline 1-ID-C, we measured components of the lattice strain tensor from four individual grains embedded within a polycrystalline specimen. We implemented an optimization routine that minimized the difference between the experiment and simulation lattice strains. Sensitivity coefficients needed in the optimization routine are generated numerically using the finite element model. The elastic moduli that we computed for the β21s are C11 = 110 GPa, C12 = 74 GPa and C44 = 89 GPa. The resulting Zener anisotropic ratio is A = 5.

  5. Design of bending multi-layer electroactive polymer actuators

    Science.gov (United States)

    Balakrisnan, Bavani; Nacev, Alek; Smela, Elisabeth

    2015-04-01

    The effects of layer thickness and stiffness on multilayer bending actuator performance were investigated with an analytical mechanical model. Performance was evaluated in terms of curvature, blocked force, and work. Multilayer device designs corresponding to dielectric elastomer actuator, ionic polymer metal composite, and conjugated polymer structures were examined. Normalized plots of the performance metrics as functions of relative layer thickness and stiffness are presented that should allow initial, starting-point estimates for designs for particular applications. The results show that to achieve high curvature, layer thickness and stiffness may need to be set above or below particular bounds, or varied together, depending on the device configuration; often there is a broad plateau of combinations that work equally well. There is a conflict between achieving high bending and high force: the former requires the device to behave as much as possible like a simple bilayer with optimal ratios of thickness and modulus, while the latter requires thicker layers and shows little dependence on their moduli. Finally, to maximize work there are areas in the thickness-modulus plane that should be avoided, these areas varying with the configuration in sometimes surprising ways.

  6. Acoustically-induced slip in sheared granular layers: application to dynamic earthquake triggering

    CERN Document Server

    Ferdowsi, Behrooz; Guyer, Robert A; Johnson, Paul A; Marone, Chris; Carmeliet, Jan

    2015-01-01

    A fundamental mystery in earthquake physics is "how can an earthquake be triggered by distant seismic sources?" A possible explanation is suggested by results found in discrete element method simulations of a granular layer, during stick-slip, that is subject to transient vibrational excitation. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance, i.e., transient vibration and earthquake are simultaneous. The critical strain is of order 10^{-6}, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic increase in the number of slipping contacts and decrease in the coordination number. Associated with this frictional weakening is a pronounced decrease in the elastic moduli of the layer.

  7. Role of an encapsulating layer for reducing resistance drift in phase change random access memory

    Directory of Open Access Journals (Sweden)

    Bo Jin

    2014-12-01

    Full Text Available Phase change random access memory (PCRAM devices exhibit a steady increase in resistance in the amorphous phase upon aging and this resistance drift phenomenon directly affects the device reliability. A stress relaxation model is used here to study the effect of a device encapsulating layer material in addressing the resistance drift phenomenon in PCRAM. The resistance drift can be increased or decreased depending on the biaxial moduli of the phase change material (YPCM and the encapsulating layer material (YELM according to the stress relationship between them in the drift regime. The proposed model suggests that the resistance drift can be effectively reduced by selecting a proper material as an encapsulating layer. Moreover, our model explains that reducing the size of the phase change material (PCM while fully reset and reducing the amorphous/crystalline ratio in PCM help to improve the resistance drift, and thus opens an avenue for highly reliable multilevel PCRAM applications.

  8. On the Moduli Space of Non-Primary Hopf Surfaces%关于非主Hopf曲面的模空间

    Institute of Scientific and Technical Information of China (English)

    李庆忠; 张锦豪

    2000-01-01

    The authorsconstructed in this paper the fine moduli space ofall complex structures on S3 / H-bundle over S1 whose transitionfunction u : S3/H→S3/H is an involution of S3/H, where H U(2) is a finite gronp whose action is properly discontinuousand free on S3.%构造了S1上S3 / H-丛的所有复结构的模空间, 其中丛的转换函数u: S3/H→S3/H是S3/H的一个对合, H U(2), H为有限群且在S3 / H上的作用是自由的.真不连续的.

  9. Comment on ‘Parametrization of Stillinger–Weber potential based on a valence force field model: application to single-layer MoS2 and black phosphorus’

    Science.gov (United States)

    Midtvedt, Daniel; Croy, Alexander

    2016-06-01

    We compare the simplified valence-force model for single-layer black phosphorus with the original model and recent ab initio results. Using an analytic approach and numerical calculations we find that the simplified model yields Young's moduli that are smaller compared to the original model and are almost a factor of two smaller than ab initio results. Moreover, the Poisson ratios are an order of magnitude smaller than values found in the literature.

  10. Evidence for multiple pulses of crystal-bearing magma during emplacement of the Doros layered intrusion, Namibia

    Science.gov (United States)

    Owen-Smith, T. M.; Ashwal, L. D.

    2015-12-01

    The Doros Complex is a relatively small (maximum 3.5 km × 7.5 km) shallow-level, lopolithic, layered mafic intrusion in the early Cretaceous Paraná-Etendeka Large Igneous Province. The stratigraphy broadly comprises a minor, fine-grained gabbroic sill and a sequence of primitive olivine-cumulate melagabbros, with a basal chilled margin, an intermediate plagioclase-cumulate olivine gabbro, and a sequence of mineralogically and texturally variable, intermediate, strongly foliated, plagioclase-, olivine- or magnetite-cumulate gabbros. An evolved syenitic (bostonite) phase occurs as cross-cutting dykes or as enclaves within the foliated gabbros. Major element modelling of the liquid line of descent shows that the spectrum of rock types, including the bostonite, is consistent with the fractionation of a basaltic parental magma that crystallised olivine, clinopyroxene, plagioclase, magnetite, K-feldspar and apatite. However, the stratigraphic succession does not correspond to a simple progressive differentiation trend but instead shows a series of punctuated trends, each defined by a compositional reversal or hiatus. Incompatible trace element concentrations do not increase upwards though the body of the intrusion. The major units show similar, mildly enriched rare earth element patterns, with minimal Eu anomalies. Back-calculation of the rare earth element concentrations of these cumulate rocks produces relatively evolved original liquid compositions, indicating fractionation of this liquid from a more primitive precursor. Based on combined field, petrographic, geochemical and geophysical evidence, we propose an origin for the Doros Complex by a minimum of seven closely spaced influxes of crystal-bearing magmas, each with phenocryst contents between 5% and 55%. These findings represent a departure from the traditional single-pulse liquid model for the formation of layered mafic intrusions and suggest the presence of an underlying magmatic mush column, i.e., a large

  11. Ozone layer tragedy

    International Nuclear Information System (INIS)

    A brief introduction is given on how the ozone layer formed and about the factors depleted ozone layer such as chloro bromo compounds and so on; then, it follows the processes which destroy the troposphere. The damaging effect of ultraviolet radiation is described. Finally,the action taken to reduce the depletion of ozone layer is presented

  12. An asymptotic model of seismic reflection from a permeable layer

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Goloshubin, G.

    2009-10-15

    Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot's model of poroelasticity. A review of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and Darcy's law suggests an alternative new physical interpretation of some coefficients of the classical poroelasticity. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The absolute value of this parameter is equal to the product of the kinematic reservoir fluid mobility and the wave frequency. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). Practical applications of the obtained asymptotic formulae are seismic modeling, inversion, and at-tribute analysis.

  13. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli.

    Science.gov (United States)

    Holten-Andersen, Niels; Harrington, Matthew J; Birkedal, Henrik; Lee, Bruce P; Messersmith, Phillip B; Lee, Ka Yee C; Waite, J Herbert

    2011-02-15

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75-133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216-220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe(3+) interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe(3+) cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G') that approach covalently cross-linked gels as well as self-healing properties. PMID:21278337

  14. Six-dimensional supersymmetric gauge theories, quantum cohomology of instanton moduli spaces and gl(N) Quantum Intermediate Long Wave Hydrodynamics

    CERN Document Server

    Bonelli, Giulio; Tanzini, Alessandro; Vasko, Petr

    2014-01-01

    We show that the exact partition function of U(N) six-dimensional gauge theory with eight supercharges on C^2 x S^2 provides the quantization of the integrable system of hydrodynamic type known as gl(N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S^2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl(N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl(N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W_N algebrae, thus providing a gauge theoretical proof of AGT correspondence.

  15. Inter-layer FEC decoded multi-layer video streaming

    OpenAIRE

    Huo, Yongkai; Zuo, Xin; Robert G. Maunder; Hanzo, L

    2012-01-01

    Layered video coding creates multiple layers of unequal importance, where the enhancement layers will be affected when the base layer is corrupted. In this treatise, a novel inter-layer FEC scheme is investigated, where the information of the base layer1 is incorporated into the systematic bits of the enhancement layers with the aid of an exclusive-OR operation. When the base layer can be recovered independently, the soft information of the enhancement layers can be deduced by flipping the si...

  16. Boosting Water Oxidation Layer-by-Layer

    OpenAIRE

    Hidalgo Acosta, Jonnathan Cesar; Scanlon, Micheal; Mendez, Manuel A.; Amstutz, Véronique; Vrubel, Heron; Opallo, Marcin; Girault, Hubert

    2016-01-01

    Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2 NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and ...

  17. Building biomedical materials layer-by-layer

    Directory of Open Access Journals (Sweden)

    Paula T. Hammond

    2012-05-01

    Full Text Available In this materials perspective, the promise of water based layer-by-layer (LbL assembly as a means of generating drug-releasing surfaces for biomedical applications, from small molecule therapeutics to biologic drugs and nucleic acids, is examined. Specific advantages of the use of LbL assembly versus traditional polymeric blend encapsulation are discussed. Examples are provided to present potential new directions. Translational opportunities are discussed to examine the impact and potential for true biomedical translation using rapid assembly methods, and applications are discussed with high need and medical return.

  18. Layer Formation in Semiconvection

    OpenAIRE

    Biello, Joseph A.

    2001-01-01

    Layer formation in a thermally destabilized fluid with stable density gradient has been observed in laboratory experiments and has been proposed as a mechanism for mixing molecular weight in late stages of stellar evolution in regions which are unstable to semiconvection. It is not yet known whether such layers can exist in a very low viscosity fluid: this work undertakes to address that question. Layering is simulated numerically both at high Prandtl number (relevant to the laboratory) in or...

  19. Layering in Provenance Systems

    OpenAIRE

    Seltzer, Margo I.; Muniswamy-Reddy, Kiran-Kumar; Braun, Uri Jacob; Holland, David A.; MACKO Peter; Maclean, Diana; Margo, Daniel Wyatt; Smogor, Robin

    2009-01-01

    Digital provenance describes the ancestry or history of a digital object. Most existing provenance systems, however, operate at only one level of abstraction: the sys- tem call layer, a workflow specification, or the high-level constructs of a particular application. The provenance collectable in each of these layers is different, and all of it can be important. Single-layer systems fail to account for the different levels of abstraction at which users need to reason about their data and proc...

  20. Non-contact evaluation of mechanical properties of electroplated wear resistant Ni-P layer from the velocity dispersion of laser SAW; Laser reiki Rayleigh ha no sokudo bunsan wo mochiita taimamo Ni-P mekkiso tokusei no hisesshoku hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Morikawa, Y.; Cho, H.; Takemoto, M. [Aoyama Gakuin University, Tokyo (Japan). Faculty of Science and Engineering; Nakayama, T. [Kobe Steel Ltd., Kobe (Japan)

    1996-11-01

    We developed a new laser surface acoustic wave (SAW) system and applied this to estimate the mechanical properties of the wear-resistant Ni-P layer electroplated on a stainless steel. The velocity dispersions of Rayleigh wave of the as -plated and heat-treated Ni-P layer were obtained by the one point time domain signal processing. The Ni-P layers with excellent wear resistance produced by the heated treatment higher than 725K were found to show higher Rayleigh velocities than that of the substrate steel, while the Ni-P layer with poor wear resistance showed lower velocities. Young`s moduli of the Ni-P layer, estimated so as the computed velocity dispersion agreed with the measured one, increased with the increase of wear resistance. 10 refs., 9 figs., 2 tabs.

  1. Improved electron transport layer

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides: a method of preparing a coating ink for forming a zinc oxide electron transport layer, comprising mixing zinc acetate and a wetting agent in water or methanol; a coating ink comprising zinc acetate and a wetting agent in aqueous solution or methanolic solution; a...... method of preparing a zinc oxide electron transporting layer, which method comprises: i) coating a substrate with the coating ink of the present invention to form a film; ii) drying the film; and iii) heating the dry film to convert the zinc acetate substantially to ZnO; a method of preparing an organic...... photovoltaic device or an organic LED having a zinc oxide electron transport layer, the method comprising, in this order: a) providing a substrate bearing a first electrode layer; b) forming an electron transport layer according to the following method: i) coating a coating ink comprising an ink according to...

  2. Thin-Layer Hydroxyapatite Deposition on a Nanofiber Surface Stimulates Mesenchymal Stem Cell Proliferation and Their Differentiation into Osteoblasts

    Directory of Open Access Journals (Sweden)

    Eva Prosecká

    2012-01-01

    Full Text Available Pulsed laser deposition was proved as a suitable method for hydroxyapatite (HA coating of coaxial poly-ɛ-caprolactone/polyvinylalcohol (PCL/PVA nanofibers. The fibrous morphology of PCL/PVA nanofibers was preserved, if the nanofiber scaffold was coated with thin layers of HA (200 nm and 400 nm. Increasing thickness of HA, however, resulted in a gradual loss of fibrous character. In addition, biomechanical properties were improved after HA deposition on PCL/PVA nanofibers as the value of Young's moduli of elasticity significantly increased. Clearly, thin-layer hydroxyapatite deposition on a nanofiber surface stimulated mesenchymal stem cell viability and their differentiation into osteoblasts. The optimal depth of HA was 800 nm.

  3. Moduli of relatively nilpotent extensions

    OpenAIRE

    Fried, Michael d.

    2009-01-01

    Gives the most precise available description of the p-Frattini module for any p-perfect finite group G=G_0 (Thm. 2.8), and therefore of the groups G_{k,ab}, k \\ge 0, from which we form the abelianized M(odular) T(ower). \\S 4 includes a classification of Schur multiplier quotients, from which we figure two points (see the html file http://www.math.uci.edu/~mfried/paplist-mt/rims-rev.html): 1. Whether there is a non-empty MT over a given Hurwitz space component at level 0; and 2. whether all cu...

  4. Probleminis mokymasis: Mikrobiologija. Modulis: Infekcija

    OpenAIRE

    Janulaitytė-Günther, Daiva; Holton, John; Pavilonis, Alvydas

    2011-01-01

    Probleminis mokymasis yra specifine mokymosi technika pagrįstas metodas, labiausiai atitinkantis modernaus medicininio ugdymo tikslus. Tai metodas, skatinantis nepriklausomą mokymąsi, gilesnį medžiagos supratimą ir suteikiantis studentams praktinių įgūdžių spręsti painias klinikines situacijas. Įdiegus probleminio mokymosi metodą Lietuvos sveikatos mokslų universitete (LSMU), studentai susidūrė su iki tol nepatirtais iššūkiais – valdyti savo mokymosi procesą, pasirinkti metodus, planuoti s...

  5. Consistent Orientation of Moduli Spaces

    Science.gov (United States)

    Freed, Daniel S.; Hopkins, Michael J.; Teleman, Constantin

    In a series of papers by Freed, Hopkins, and Teleman (2003, 2005, 2007a) the relationship between positive energy representations of the loop group of a compact Lie group G and the twisted equivariant K-theory Kτ+dimGG (G) was developed. Here G acts on itself by conjugation. The loop group representations depend on a choice of ‘level’, and the twisting τ is derived from the level. For all levels the main theorem is an isomorphism of abelian groups, and for special transgressed levels it is an isomorphism of rings: the fusion ring of the loop group andKτ+dimGG (G) as a ring. For G connected with π1G torsionfree, it has been proven that the ring Kτ+dimGG (G) is a quotient of the representation ring of G and can be calculated explicitly. In these cases it agrees with the fusion ring of the corresponding centrally extended loop group. This chapter explicates the multiplication on the twisted equivariant K-theory for an arbitrary compact Lie group G. It constructs a Frobenius ring structure on Kτ+dimGG (G). This is best expressed in the language of topological quantum field theory: a two-dimensional topological quantum field theory (TQFT) is constructed over the integers in which the abelian group attached to the circle is Kτ+dimGG (G).

  6. Dilational Viscoelasticity of Adsorption Layers Measured by Drop and Bubble Profile Analysis: Reason for Different Results.

    Science.gov (United States)

    Fainerman, V B; Kovalchuk, V I; Aksenenko, E V; Miller, R

    2016-06-01

    The dilational viscoelasticity of adsorption layer was measured at different frequencies of drop and bubble surface area oscillations for aqueous C12EO5 solutions. The modulus values obtained by the two experimental protocols are the same for Π surface pressures the values from drop experiments exceed those from bubble profile analysis. The nature of this phenomenon was studied using stress deformation experiments. At high surfactant concentrations the magnitude of surface tension variations is essentially higher for drops as compared with bubbles, leading to an increased viscoelasticity modulus for oscillating drops. The observed effects are analyzed quantitatively using a diffusion controlled exchange of matter model. The viscoelasticity moduli for a number of surfactants (different CnEOm and Tritons, C13DMPO, and SDS) are reported, and it is shown that the discrepancies between the data obtained by the two methods for many surfactants agree well with the predictions made here. PMID:27164467

  7. Boosting water oxidation layer-by-layer.

    Science.gov (United States)

    Hidalgo-Acosta, Jonnathan C; Scanlon, Micheál D; Méndez, Manuel A; Amstutz, Véronique; Vrubel, Heron; Opallo, Marcin; Girault, Hubert H

    2016-04-01

    Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2 NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and sizes. UV/vis spectroscopic and spectro-electrochemical studies confirmed that the total surface coverage and electrochemically addressable surface coverage of IrO2 NPs increased linearly with the number of bilayers up to 10 bilayers. The voltammetry of the modified electrode was that of hydrous iridium oxide films (HIROFs) with an observed super-Nernstian pH response of the Ir(iii)/Ir(iv) and Ir(iv)-Ir(iv)/Ir(iv)-Ir(v) redox transitions and Nernstian shift of the oxygen evolution onset potential. The overpotential of the oxygen evolution reaction (OER) was essentially pH independent, varying only from 0.22 V to 0.28 V (at a current density of 0.1 mA cm(-2)), moving from acidic to alkaline conditions. Bulk electrolysis experiments revealed that the IrO2/PDDA films were stable and adherent under acidic and neutral conditions but degraded in alkaline solutions. Oxygen was evolved with Faradaic efficiencies approaching 100% under acidic (pH 1) and neutral (pH 7) conditions, and 88% in alkaline solutions (pH 13). This layer-by-layer approach forms the basis of future large-scale OER electrode development using ink-jet printing technology. PMID:26977761

  8. The Equatorial Ekman Layer

    CERN Document Server

    Marcotte, Florence; Soward, Andrew

    2016-01-01

    The steady incompressible viscous flow in the wide gap between spheres rotating about a common axis at slightly different rates (small Ekman number E) has a long and celebrated history. The problem is relevant to the dynamics of geophysical and planetary core flows, for which, in the case of electrically conducting fluids, the possible operation of a dynamo is of considerable interest. A comprehensive asymptotic study, in the limit E<<1, was undertaken by Stewartson (J. Fluid Mech. 1966, vol. 26, pp. 131-144). The mainstream flow, exterior to the E^{1/2} Ekman layers on the inner/outer boundaries and the shear layer on the inner sphere tangent cylinder C, is geostrophic. Stewartson identified a complicated nested layer structure on C, which comprises relatively thick quasi-geostrophic E^{2/7} (inside C) and E^{1/4} (outside C) layers. They embed a thinner E^{1/3} ageostrophic shear layer (on C), which merges with the inner sphere Ekman layer to form the E^{2/5} Equatorial Ekman layer of axial length E^{...

  9. Multi-layer coatings

    Energy Technology Data Exchange (ETDEWEB)

    Maghsoodi, Sina; Brophy, Brenor L.; Abrams, Ze' ev R.; Gonsalves, Peter R.

    2016-06-28

    Disclosed herein are coating materials and methods for applying a top-layer coating that is durable, abrasion resistant, highly transparent, hydrophobic, low-friction, moisture-sealing, anti-soiling, and self-cleaning to an existing conventional high temperature anti-reflective coating. The top coat imparts superior durability performance and new properties to the under-laying conventional high temperature anti-reflective coating without reducing the anti-reflectiveness of the coating. Methods and data for optimizing the relative thickness of the under-layer high temperature anti-reflective coating and the top-layer thickness for optimizing optical performance are also disclosed.

  10. The Application of Layer Theory to Design: The Control Layer

    Science.gov (United States)

    Gibbons, Andrew S.; Langton, Matthew B.

    2016-01-01

    A theory of design layers proposed by Gibbons ("An Architectural Approach to Instructional Design." Routledge, New York, 2014) asserts that each layer of an instructional design is related to a body of theory closely associated with the concerns of that particular layer. This study focuses on one layer, the control layer, examining…

  11. Elastic moduli, thermal expansion, and inferred permeability of Climax quartz monzonite and Sudbury gabbro to 500/sup 0/C and 55 MPa

    Energy Technology Data Exchange (ETDEWEB)

    Page, L.; Heard, H.C.

    1981-03-17

    Young's modulus (E), bulk modulus (K), and the coefficient of thermal linear expansion (..cap alpha..) have been determined for Climax quartz monzonite to 500/sup 0/C and pressures (P) to 55 MPa and for Sudbury gabbro to 300/sup 0/C and 55 MPa. For each rock, both E and K decreased with T and increased with P in a nonlinear manner. In the monzonite, E and K decreased by up to 60% as P decreased from 55.2 to 6.9 MPa isothermally, while the gabbro indicated a decrease up to 70% over the same pressure range. As T increased isobarically, E and K for the monzonite decreased by up to a factor of approx. 80% from 19 to 500/sup 0/C. The moduli of the gabbro decreased by as much as 70% from 19 to 300/sup 0/C. ..cap alpha.. for the monzonite increased with T and decreased with P in a nonmonotonic fashion, with most measured values for ..cap alpha.. greater than values calculated for the crack-free aggregate. Depending on P, ..cap alpha.. in the monzonite increased from 8 to 11.10/sup -6/ /sup 0/C/sup -1/ at 40/sup 0/C to 22 to 25.10/sup -6/C/sup -1/ at 475/sup 0/C. For the gabbro, ..cap alpha.. also generally decreased with increasing P. Values ranged from 6 to 11.10/sup -6/ /sup 0/C/sup -1/, showing a nonlinear trend and very little net increas over the T range from 19 to 300/sup 0/C. Calculated permeability of these rocks based on the ..cap alpha.. determinations indicated that permeabilities may increase by up to a factor of 3 over the temperature interval 19 to 300/sup 0/C, and the permeability of the monzonite is inferred to increase by up to a factor of 8 by 500/sup 0/C. In both rocks, most measurements are consistent with microcracks controlling the thermoelastic response by opening with T and closing with sigma and P.

  12. Polyamide-layered silicate nanocomposites by melt processing

    Science.gov (United States)

    Fornes, Timothy Dean

    Polyamide-layered silicate nanocomposites based on nylon 6, 11, and 12 and organically modified montmorillonites (organoclay) were prepared by twin screw extrusion. Carefully designed component structure-nanocomposite morphology and property investigations on these materials were executed to understand why nylon 6 readily exfoliates organoclay. The polyamide structure strongly influences the extent of clay platelet delamination and level of property enhancement, as determined by X-ray, transmission electron microscopy and stress-strain analyses. High molecular weight nylon 6 materials lead to better organoclay exfoliation and greater nanocomposite moduli and yield strengths than lower molecular weight materials; this is attributed to higher levels of shear stress imparted on the clay by the higher viscosity polymer. The ratio of amide to methylene units in the repeat structure of nylon 6 appears to affect the polymer-organoclay affinity since a large increase in aliphatic content, i.e., nylon 6 versus nylon 12, results in less organoclay dispersion and lower reinforcing efficiency. The structure of the organoclay is also critical for producing well-exfoliated nylon 6 nanocomposites. Alkyl ammonium surfactants that cover less montmorillonite surface in the organoclay are more effective at exfoliating clay and generating improved nanocomposite stiffness and strength; such surfactants facilitate more desirable polyamide-silicate interactions, yet maintain sufficient organoclay gallery spacings needed both to overcome the cohesive forces between neighboring platelets and to facilitate polymer intercalation. The source of sodium montmorillonite used to form the organoclay is also important. The superior properties observed in nylon 6 nanocomposites may be explained by conventional ideas of reinforcement as predicted by composite theories like those of Halpin-Tsai or Mori-Tanaka. Based on good agreement between experimental nanocomposite moduli and model predictions it

  13. Layers of the Skin

    Science.gov (United States)

    ... Review Abstracting, Coding, & Staging ICD-O Site Codes Morphology & Grade Extent of Disease Evaluation Physical Exam Lab ... the majority of the structure of the skin, hair, and nails. The squamous cell layer is the ...

  14. Layered inorganic solids

    Czech Academy of Sciences Publication Activity Database

    Čejka, Jiří; Morris, R. E.; Nachtigall, P.; Roth, Wieslaw Jerzy

    2014-01-01

    Roč. 43, č. 27 (2014), s. 10274-10275. ISSN 1477-9226 Institutional support: RVO:61388955 Keywords : layered inorganic solids * physical chemistry * catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.197, year: 2014

  15. Stratosphere and ozone layer

    International Nuclear Information System (INIS)

    Human activities disturb natural balance of earth atmosphere, in short time in comparison with time of great climatic evolutions of the past. Rapid destruction of ozone layer, modifications of chemical balances in Arctic by similar processes to which observed in Antarctic, first experimental views of ozone decreasing in stratosphere and increasing in troposphere, are indications of human perturbation in ozone layer balance which protect us from solar radiation. 17 figs., 6 tabs., 27 refs

  16. Structured luminescence conversion layer

    Science.gov (United States)

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  17. Layered volume splatting

    OpenAIRE

    Schlegel, P.; Pajarola, R.

    2009-01-01

    We present a new layered, hardware-accelerated splatting algorithm for volume rendering. Layered volume splatting features the speed benefits of fast axis-aligned pre-classified sheet-buffer splatting while at the same time exhibiting display quality comparable to high-quality post-classified view-aligned sheet-buffer splatting. Additionally, we enhance the quality by using a more accurate approximation of the volume rendering integral. Commonly, the extinction coefficient of the volume r...

  18. Field studies and numerical models of hydrofracture propagation in layered fractured reservoirs

    Science.gov (United States)

    Philipp, S. L.; Gudmundsson, A.; Meier, S.; Reyer, D.

    2009-04-01

    Hydrofractures are formed, at least partly, as a result of internal fluid overpressure. They may be formed by magma (dykes, sheets, sills), geothermal water (mineral veins), or oil, gas and water (many joints) and also include the man-made hydraulic fractures used to increase the permeability of reservoirs. Theoretical models show that any hydrofracture with a significant fluid overpressure (fluid pressure in excess of the fracture-normal stress) develops such high tensile stresses at the fracture tips that it should continue its propagation upwards and eventually reach the earth surface, provided the crust was homogeneous and isotropic. Rocks, however, are normally heterogeneous and anisotropic; in particular, they are layered. For many layered rocks, the mechanical properties, particularly their Young's moduli, change between layers, that is, the rocks are mechanically layered. Mechanical layering may coincide with changes in grain size, mineral content, fracture frequencies, or facies. For example, in sedimentary rocks, stiff (high Young's modulus) limestone or sandstone layers commonly alternate with soft (low Young's modulus) shale layers. Here we present results of studies of fracture systems in mechanically layered rocks. These include joints in the Middle Triassic Muschelkalk in Southwest Germany, and joints and veins in the Lower Jurassic Blue Lias Formation in South Wales. In both field areas, limestone is interlayered with marl. These field studies show that most hydrofractures become arrested at layer contacts, particularly at contacts between layers with contrasting mechanical properties. To understand the mechanics of hydrofracture propagation we explore the stress fields affecting fracture propagation using numerical models (finite-element and boundary-element methods). The models focus on the effects of mechanical layering and show that stresses commonly concentrate in stiff layers. Also, at the contacts between soft and stiff layers, the stress

  19. Interference layer metallography

    International Nuclear Information System (INIS)

    Refractory metallic materials for application in Gas Cooled High Temperature Reactors are age-hardened nickel or iron base alloys. To control their behaviour and to adapt it to realistic load conditions, these materials have to be subjected to suitable informing tests and characterized. In the past few years, interference layer metallography has proved to be a highly flexible characterization procedure, suitable as an independent investigation method as well as an outstanding way of sample preparation for application of automatic quantitative image analysis to refractory alloys. This paper reports the problems of characterization of the Ni and Fe base alloys to be solved by interference layer metallography and the physical background of this method. The procedure of chromatic contrasting is discussed. From these considerations arises the result that for technical applications the optimum layer material for each special sample should be selected a priori. For that purpose it is necessary to measure the optical constants of the respective structural elements of the alloys as well as those of the candidate layer materials. The measuring procedures are discussed in detail. A routine procedure is deduced which allows to determine a priori the layer material and thickness fitting best to a given problem. (orig.)

  20. Quark Neutron Layer Stars

    CERN Document Server

    Carinhas, P A

    1993-01-01

    Typical nuclear equations of state and a quark bag model, surprisingly, allow compact stars with alternate layers of neutrons and quarks. One can determine on the basis of the Gibbs free energy which phase, nuclear or quark, is energetically favorable. Using the nuclear equation of state of Wiringa, and a quark equation of state given by Freedman and McLerran, the allowed quark parameter space for such layer stars is searched. This paper differs from past work in that configurations are found in which quark matter is located exterior and interior to shells of nuclear matter, i.e., dependent on quark parameters, a star may contain several alternating layers of quark and nuclear matter. Given the uncertainty in the quark parameter space, one can estimate the probability for finding pure neutron stars, pure quark stars (strange stars), stars with a quark core and a nucleon exterior, or layer stars. Several layer models are presented. The physical characteristics, stability, and results of a thorough search of th...

  1. Interaction of angiogenically stimulated intermediate CD163+ monocytes/macrophages with soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli matched to that of human arteries.

    Science.gov (United States)

    Mayer, Anke; Kratz, Karl; Hiebl, Bernhard; Lendlein, Andreas; Jung, Friedrich

    2012-03-01

    mRNA expression profile of the aMO2 was not influenced by the substrate elasticity. In the supernatant of aMO2 on cPnBA0250, significantly less VEGF-A(165) product was found than expected based on the mRNA level measured (P < 0.01). Tests with recombinant VEGF-A(165) then demonstrated that significantly more VEGF-A(165) was adhered on cPnBA0250 than on cPnBA1100 (P < 0.01). Seeded on cPnBA, aMO2-unaffected by the elastic moduli of both substrates-seemed to remain in their subset status and secreted VEGF-A(165) without release of proinflammatory cytokines. These in vitro results might indicate that this MO subset can be used as cellular delivery system for proangiogenic and noninflammatory mediators to support the endothelialization of cPnBA. PMID:22360779

  2. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  3. Computation of the lamina stacking sequence effect on elastic moduli of a plain-weave Nicalon/SiC laminated composite with a [0/30/60] lay-up

    International Nuclear Information System (INIS)

    Estimation of the elastic modulus is important in engineering design. One difference between CFCCs (continuous fiber-reinforced ceramic-matrix composites), and CMCs (whisker, particulate, or short fiber-reinforced ceramic-matrix composites), is that the anisotropic behavior of CFCCs plays an important role in affecting their mechanical behavior. This feature may also contribute to the variation of elastic properties and strengths of CFCC. In this paper, a Fortran program is developed to quantify the lamina stacking sequence effect on the effective elastic moduli of the laminated CFCCs. The material for modeling is a plain-weave Nicalon fiber-reinforced silicon carbide (Nicalon/SiC) CFCCs. Results show that various stacking sequences within the CFCC (a [0/30/60] lay-up) will give different effective elastic moduli of the CFCCs. This trend leads to a variation of the slope of the linear portion on the flexural stress-strain curve, i.e., changing the position of the starting point of the non-linear portion, and the shape of the whole curve, which gives a different value of the peak stress in the curve. (orig.)

  4. Mechanical properties of layers of corrosion products at steel / concrete interface

    International Nuclear Information System (INIS)

    To take account of the development of corrosion products layers in residual lifetime calculations of reinforced concrete structures requires a good knowledge of the mechanical properties of these products. Our study aims to determine the mechanical properties of layers of corrosion products. The approach consists of an identification of the microstructure properties complemented by homogenization calculations to calculate a mesoscopic behavior in linear elasticity of layers of corrosion products. The study includes a series of experimental campaigns at the microscopic scale. Vickers micro indentation tests analyzed by a Gaussian mixture model approach allowed the acquisition of hardness and elastic moduli at the microscale. An identification of the microstructure products is performed by Raman microspectrometry. The microstructure's characterization brings valuable information for homogenization calculations. The first approach has consisted of calculations of random media homogenization by self-consistent and generalized self-consistent schemes. In the second approach, effective modulus calculations were performed using numerical microstructures resulting from 2D images taken with an optical microscope. The corpus is composed of samples of different ages and origins, their microstructures were compared. (author)

  5. A method to measure mechanical properties of pulmonary epithelial cell layers.

    Science.gov (United States)

    Dassow, Constanze; Armbruster, Caroline; Friedrich, Christian; Smudde, Eva; Guttmann, Josef; Schumann, Stefan

    2013-10-01

    The lung has a huge inner alveolar surface composed of epithelial cell layers. The knowledge about mechanical properties of lung epithelia is helpful to understand the complex lung mechanics and biomechanical interactions. Methods have been developed to determine mechanical indices (e.g., tissue elasticity) which are both very complex and in need of costly equipment. Therefore, in this study, a mechanostimulator is presented to dynamically stimulate lung epithelial cell monolayers in order to determine their mechanical properties based on a simple mathematical model. First, the method was evaluated by comparison to classical tensile testing using silicone membranes as substitute for biological tissue. Second, human pulmonary epithelial cells (A549 cell line) were grown on flexible silicone membranes and stretched at a defined magnitude. Equal secant moduli were determined in the mechanostimulator and in a conventional tension testing machine (0.49 ± 0.05 MPa and 0.51 ± 0.03 MPa, respectively). The elasticity of the cell monolayer could be calculated by the volume-pressure relationship resulting from inflation of the membrane-cell construct. The secant modulus of the A549 cell layer was calculated as 0.04 ± 0.008 MPa. These findings suggest that the mechanostimulator may represent an adequate device to determine mechanical properties of cell layers. PMID:23564730

  6. Oxygen-implanted induced formation of oxide layer enhances blood compatibility on titanium for biomedical applications.

    Science.gov (United States)

    Hung, Wei-Chiang; Chang, Fang-Mo; Yang, Tzu-Sen; Ou, Keng-Liang; Lin, Che-Tong; Peng, Pei-Wen

    2016-11-01

    Titanium dioxide (TiO2) layers were prepared on a Ti substrate by using oxygen plasma immersion ion implantation (oxygen PIII). The surface chemical states, structure, and morphology of the layers were studied using X-ray photoelectron spectroscopy, X-ray diffraction, Raman microscopy, atomic force microscopy and scanning electron microscope. The mechanical properties, such as the Young's modulus and hardness, of the layers were investigated using nanoindentation testing. The Ti(4+) chemical state was determined to be present on oxygen-PIII-treated surfaces, which consisted of nanocrystalline TiO2 with a rutile structure. Compared with Ti substrates, the oxygen-PIII-treated surfaces exhibited decreased Young's moduli and hardness. Parameters indicating the blood compatibility of the oxygen-PIII-treated surfaces, including the clotting time and platelet adhesion and activation, were studied in vitro. Clotting time assays indicated that the clotting time of oxygen-PIII-treated surfaces was longer than that of the Ti substrate, which was associated with decreased fibrinogen adsorption. In conclusion, the surface characteristics and the blood compatibility of Ti implants can be modified and improved using oxygen PIII. PMID:27524050

  7. Reinforcement of Mono- and Bi-layer Poly(Ethylene Glycol) Hydrogels with a Fibrous Collagen Scaffold.

    Science.gov (United States)

    Kinneberg, K R C; Nelson, A; Stender, M E; Aziz, A H; Mozdzen, L C; Harley, B A C; Bryant, S J; Ferguson, V L

    2015-11-01

    Biomaterial-based tissue engineering strategies hold great promise for osteochondral tissue repair. Yet significant challenges remain in joining highly dissimilar materials to achieve a biomimetic, mechanically robust design for repairing interfaces between soft tissue and bone. This study sought to improve interfacial properties and function in a bi-layer hydrogel interpenetrated with a fibrous collagen scaffold. 'Soft' 10% (w/w) and 'stiff' 30% (w/w) PEGDM was formed into mono- or bi-layer hydrogels possessing a sharp diffusional interface. Hydrogels were evaluated as single-(hydrogel only) or multi-phase (hydrogel + fibrous scaffold penetrating throughout the stiff layer and extending >500 μm into the soft layer). Including a fibrous scaffold into both soft and stiff mono-layer hydrogels significantly increased tangent modulus and toughness and decreased lateral expansion under compressive loading. Finite element simulations predicted substantially reduced stress and strain gradients across the soft-stiff hydrogel interface in multi-phase, bilayer hydrogels. When combining two low moduli constituent materials, composites theory poorly predicts the observed, large modulus increases. These results suggest material structure associated with the fibrous scaffold penetrating within the PEG hydrogel as the major contributor to improved properties and function-the hydrogel bore compressive loads and the 3D fibrous scaffold was loaded in tension thus resisting lateral expansion. PMID:26001970

  8. Moduli stabilization, large-volume dS minimum without D3-bar -branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi-Yau's

    International Nuclear Information System (INIS)

    We consider two sets of issues in this paper. The first has to do with moduli stabilization, existence of 'area codes' [A. Giryavets, New attractors and area codes, JHEP 0603 (2006) 020, (hep-th/0511215)] and the possibility of getting a non-supersymmetric dS minimum without the addition of D3-bar-branes as in KKLT for type II flux compactifications. The second has to do with the 'inverse problem' [K. Saraikin, C. Vafa, Non-supersymmetric black holes and topological strings, (hep-th/0703214)] and 'fake superpotentials' [A. Ceresole, G. Dall'Agata, Flow equations for non-BPS extremal black holes, JHEP 0703 (2007) 110, (hep-th/0702088)] for extremal (non-)supersymmetric black holes in type II compactifications. We use (orientifold of) a 'Swiss cheese' Calabi-Yau [J.P. Conlon, F. Quevedo, K. Suruliz, Large-volume flux compactifications: Moduli spectrum and D3/D7 soft supersymmetry breaking, JHEP 0508 (2005) 007, (hep-th/0505076)] expressed as a degree-18 hypersurface in WCP4[1,1,1,6,9] in the 'large-volume-scenario' limit [V. Balasubramanian, P. Berglund, J.P. Conlon, F. Quevedo, Systematics of moduli stabilisation in Calabi-Yau flux compactifications, JHEP 0503 (2005) 007, (hep-th/0502058)]. The main result of our paper is that we show that by including non-perturbative α' and instanton corrections in the Kaehler potential and superpotential [T.W. Grimm, Non-perturbative corrections and modularity in N=1 type IIB compactifications, (arXiv: 0705.3253 [hep-th])], it may be possible to obtain a large-volume non-supersymmetric dS minimum without the addition of anti-D3 branes a la KKLT. The chosen Calabi-Yau has been of relevance also from the point of other studies of Kaehler moduli stabilization via non-perturbative instanton contributions [F. Denef, M.R. Douglas, B. Florea, Building a better racetrack, JHEP 0406 (2004) 034, (hep-th/0404257)] and non-supersymmetric AdS vacua (and their subsequent dS-uplifts) using (α')3 corrections to the Kaehler potential [V

  9. Layer-Cake Earth

    Science.gov (United States)

    Tedford, Rebecca; Warny, Sophie

    2006-01-01

    In this article, the authors offer a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes. This activity introduces the concepts and challenges that geologists face and at the same time strengthens students' inferential, observational, and problem-solving skills. It also addresses…

  10. MITRE sensor layer prototype

    Science.gov (United States)

    Duff, Francis; McGarry, Donald; Zasada, David; Foote, Scott

    2009-05-01

    The MITRE Sensor Layer Prototype is an initial design effort to enable every sensor to help create new capabilities through collaborative data sharing. By making both upstream (raw) and downstream (processed) sensor data visible, users can access the specific level, type, and quantities of data needed to create new data products that were never anticipated by the original designers of the individual sensors. The major characteristic that sets sensor data services apart from typical enterprise services is the volume (on the order of multiple terabytes) of raw data that can be generated by most sensors. Traditional tightly coupled processing approaches extract pre-determined information from the incoming raw sensor data, format it, and send it to predetermined users. The community is rapidly reaching the conclusion that tightly coupled sensor processing loses too much potentially critical information.1 Hence upstream (raw and partially processed) data must be extracted, rapidly archived, and advertised to the enterprise for unanticipated uses. The authors believe layered sensing net-centric integration can be achieved through a standardize-encapsulate-syndicateaggregate- manipulate-process paradigm. The Sensor Layer Prototype's technical approach focuses on implementing this proof of concept framework to make sensor data visible, accessible and useful to the enterprise. To achieve this, a "raw" data tap between physical transducers associated with sensor arrays and the embedded sensor signal processing hardware and software has been exploited. Second, we encapsulate and expose both raw and partially processed data to the enterprise within the context of a service-oriented architecture. Third, we advertise the presence of multiple types, and multiple layers of data through geographic-enabled Really Simple Syndication (GeoRSS) services. These GeoRSS feeds are aggregated, manipulated, and filtered by a feed aggregator. After filtering these feeds to bring just the type

  11. Peeling Back the Layers

    Science.gov (United States)

    2004-01-01

    NASA's Mars Exploration Rover Spirit took this panoramic camera image of the rock target named 'Mazatzal' on sol 77 (March 22, 2004). It is a close-up look at the rock face and the targets that will be brushed and ground by the rock abrasion tool in upcoming sols. Mazatzal, like most rocks on Earth and Mars, has layers of material near its surface that provide clues about the history of the rock. Scientists believe that the top layer of Mazatzal is actually a coating of dust and possibly even salts. Under this light coating may be a more solid portion of the rock that has been chemically altered by weathering. Past this layer is the unaltered rock, which may give scientists the best information about how Mazatzal was formed. Because each layer reveals information about the formation and subsequent history of Mazatzal, it is important that scientists get a look at each of them. For this reason, they have developed a multi-part strategy to use the rock abrasion tool to systematically peel back Mazatzal's layers and analyze what's underneath with the rover's microscopic imager, and its Moessbauer and alpha particle X-ray spectrometers. The strategy began on sol 77 when scientists used the microscopic imager to get a closer look at targets on Mazatzal named 'New York,' 'Illinois' and 'Arizona.' These rock areas were targeted because they posed the best opportunity for successfully using the rock abrasion tool; Arizona also allowed for a close-up look at a range of tones. On sol 78, Spirit's rock abrasion tool will do a light brushing on the Illinois target to preserve some of the surface layers. Then, a brushing of the New York target should remove the top coating of any dust and salts and perhaps reveal the chemically altered rock underneath. Finally, on sol 79, the rock abrasion tool will be commanded to grind into the New York target, which will give scientists the best chance of observing Mazatzal's interior. The Mazatzal targets were named after the home states of

  12. Layered Composite Analysis Capability

    Science.gov (United States)

    Narayanaswami, R.; Cole, J. G.

    1985-01-01

    Laminated composite material construction is gaining popularity within industry as an attractive alternative to metallic designs where high strength at reduced weights is of prime consideration. This has necessitated the development of an effective analysis capability for the static, dynamic and buckling analyses of structural components constructed of layered composites. Theoretical and user aspects of layered composite analysis and its incorporation into CSA/NASTRAN are discussed. The availability of stress and strain based failure criteria is described which aids the user in reviewing the voluminous output normally produced in such analyses. Simple strategies to obtain minimum weight designs of composite structures are discussed. Several example problems are presented to demonstrate the accuracy and user convenient features of the capability.

  13. Crack layer theory

    Science.gov (United States)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  14. Physical Layer Network Coding

    DEFF Research Database (Denmark)

    Fukui, Hironori; Yomo, Hironori; Popovski, Petar

    2013-01-01

    Physical layer network coding (PLNC) has the potential to improve throughput of multi-hop networks. However, most of the works are focused on the simple, three-node model with two-way relaying, not taking into account the fact that there can be other neighboring nodes that can cause....../receive interference. The way to deal with this problem in distributed wireless networks is usage of MAC-layer mechanisms that make a spatial reservation of the shared wireless medium, similar to the well-known RTS/CTS in IEEE 802.11 wireless networks. In this paper, we investigate two-way relaying in presence...... be vanishing when the two-way relaying is considered in a broader context of a larger wireless network....

  15. Layered seal for turbomachinery

    Science.gov (United States)

    Sarawate, Neelesh Nandkumar; Morgan, Victor John; Weber, David Wayne

    2015-11-20

    The present application provides seal assemblies for reducing leakages between adjacent components of turbomachinery. The seal assemblies may include outer shims, and at least a portion of the outer shims may be substantially impervious. At least one of the outer shims may be configured for sealing engagement with seal slots of the adjacent components. The seal assemblies may also include at least one of an inner shim and a filler layer positioned between the outer shims. The at least one inner shim may be substantially solid and the at least one filler layer may be relatively porous. The seal assemblies may be sufficiently flexible to account for misalignment between the adjacent components, sufficiently stiff to meet assembly requirements, and sufficiently robust to operating meet requirements associated with turbomachinery.

  16. Multifunctional layered magnetic composites

    Directory of Open Access Journals (Sweden)

    Maria Siglreitmeier

    2015-01-01

    Full Text Available A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material.

  17. Seismic Waves in Finely Layered VTI Media: Poroelasticity, Thomsen Parameters, and Fluid Effects on Shear Waves

    Energy Technology Data Exchange (ETDEWEB)

    Berryman, J G

    2004-02-24

    Layered earth models are well justified by experience, and provide a simple means of studying fairly general behavior of the elastic and poroelastic characteristics of seismic waves in the earth. Thomsen's anisotropy parameters for weak elastic and poroelastic anisotropy are now commonly used in exploration, and can be conveniently expressed in terms of the layer averages of Backus. Since our main interest is usually in the fluids underground, it would be helpful to have a set of general equations relating the Thomsen parameters as directly as possible to the fluid properties. This end can be achieved in a rather straightforward fashion for these layered earth models, and the present paper develops and then discusses these relations. Furthermore, it is found that, although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves in VTI media. The effects of the pore fluids on this effective shear modulus can be substantial - an increase of shear wave speed on the order of 10% is shown to be possible when circumstances are favorable -when the medium behaves in an undrained fashion, and the shear modulus fluctuations are large (resulting in strong anisotropy). These effects are expected to be seen at higher frequencies such as sonic and ultrasonic waves for well-logging or laboratory experiments, or at seismic wave frequencies for low permeability regions of reservoirs, prior to hydrofracing. Results presented are strictly for velocity analysis.

  18. Optical properties and weakening of elastic moduli with increasing glass transition temperature (Tg) in (80-x)TeO2-xBaO-20ZnO glasses

    International Nuclear Information System (INIS)

    BaO addition to ternary (80-x)TeO2-20ZnO-xBaO (x = 0-20 mol.%) glasses resulted in a decrease in ultrasonic velocities and independent elastic moduli; this result indicated that the rigidity of the glass network weakened possibly because non-bridging oxygen increased. Thermal analysis results showed that glass transition temperature increased as BaO content increased because of the stabilizing effect of Ba2+ on the glass network. Additional analyses using bulk compression and ring deformation models revealed that the ratio between theoretical bulk modulus and experimental bulk modulus increased; this result indicated that the compression mechanism mainly involved isotropic ring compression. Furthermore, the increase in non-bridging oxygen formation with BaO addition caused a decrease in optical energy gap and an increase in refractive index. An increase in Urbach energy indicated that the degree of disorder in the glass system also increased.

  19. Earth's ozone layer

    International Nuclear Information System (INIS)

    The paper contain the actual results of investigations of the influence of the human activity on the Earth's ozone layer. History of the ozone measurements and of the changes in its concentrations within the last few years are given. The influence of the trace gases on both local and global ozone concentrations are discussed. The probable changes of the ozone concentrations are presented on the basis of the modelling investigations. The effect of a decrease in global ozone concentration on human health and on biosphere are also presented. (author). 33 refs, 36 figs, 5 tabs

  20. Physical layer network coding

    DEFF Research Database (Denmark)

    Fukui, Hironori; Popovski, Petar; Yomo, Hiroyuki

    2014-01-01

    Physical layer network coding (PLNC) has been proposed to improve throughput of the two-way relay channel, where two nodes communicate with each other, being assisted by a relay node. Most of the works related to PLNC are focused on a simple three-node model and they do not take into account...... the impact of interference from other transmissions. Unlike these conventional studies, in this paper, we apply PLNC to a large-scale cellular network in the presence of intercell interference (ICI). In cellular networks, a terminal and a Base Station (BS) have different transmission power, which causes...

  1. Layered titanium diphosphonates

    Czech Academy of Sciences Publication Activity Database

    Melánová, Klára; Beneš, L.; Svoboda, Jan; Zima, Vítězslav; Vlček, Milan

    Strasbourg: European Materials Research Society, 2012. P1 6-P1 6. ISBN -. [E- MRS Spring Meeating 2012 – Symposium P Advanced Hybrid Materials II: design and applications. 14.05.2012-18.05.2012, Strasbourg] R&D Projects: GA ČR GA203/08/0208 Institutional support: RVO:61389013 Keywords : titanium diphosphonate * layered compounds * powder x-ray difraction Subject RIV: CA - Inorganic Chemistry http://www.emrs-strasbourg.com/index.php?option=com_content&task=view&Itemid=132&id=479

  2. Collapse of grafted polyelectrolyte layer

    OpenAIRE

    Borisov, O.; Birshtein, T.; Zhulina, E.

    1991-01-01

    The theory describing chain conformation in a planar layer of grafted polyelectrolyte (polyampholyte) molecules and the conformational transition related to the collapse of this layer caused by the decrease in solvent strenght is developed. Depending on the values of the layer parameters (grafting and charge densities) this transition may occur as a continuous (cooperative) or as a first order phase transition.

  3. Atomic layer epitaxy

    Science.gov (United States)

    Goodman, Colin H. L.; Pessa, Markus V.

    1986-08-01

    Atomic layer epitaxy (ALE) is not so much a new technique for the preparation of thin films as a novel modification to existing methods of vapor-phase epitaxy, whether physical [e.g., evaporation, at one limit molecular-beam epitaxy (MBE)] or chemical [e.g., chloride epitaxy or metalorganic chemical vapor deposition (MOCVD)]. It is a self-regulatory process which, in its simplest form, produces one complete molecular layer of a compound per operational cycle, with a greater thickness being obtained by repeated cycling. There is no growth rate in ALE as in other crystal growth processes. So far ALE has been applied to rather few materials, but, in principle, it could have a quite general application. It has been used to prepare single-crystal overlayers of CdTe, (Cd,Mn)Te, GaAs and AlAs, a number of polycrystalline films and highly efficient electroluminescent thin-film displays based on ZnS:Mn. It could also offer particular advantages for the preparation of ultrathin films of precisely controlled thickness in the nanometer range and thus may have a special value for growing low-dimensional structures.

  4. Physical Layer Network Coding

    CERN Document Server

    Shengli, Zhang; Lam, Patrick P K

    2007-01-01

    A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). This paper shows that the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to straightforward network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. And in doing so, PNC can potentially achieve 100% and 50% throughput increase...

  5. A low-frequency asymptotic model of seismic reflection from a high-permeability layer

    Energy Technology Data Exchange (ETDEWEB)

    Silin, Dmitriy; Goloshubin, Gennady

    2009-03-01

    Analysis of compression wave propagation through a high-permeability layer in a homogeneous poroelastic medium predicts a peak of reflection in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of the Biot's model of poroelasticity. A new physical interpretation of some coefficients of the classical poroelasticity is a result of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and the Darcy's law. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The latter is equal to the product of the kinematic reservoir fluid mobility, an imaginary unit, and the frequency of the signal. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). The practical implications of the theory developed here are seismic modeling, inversion, and attribute analysis.

  6. Metal deposition using seed layers

    Science.gov (United States)

    Feng, Hsein-Ping; Chen, Gang; Bo, Yu; Ren, Zhifeng; Chen, Shuo; Poudel, Bed

    2013-11-12

    Methods of forming a conductive metal layers on substrates are disclosed which employ a seed layer to enhance bonding, especially to smooth, low-roughness or hydrophobic substrates. In one aspect of the invention, the seed layer can be formed by applying nanoparticles onto a surface of the substrate; and the metallization is achieved by electroplating an electrically conducting metal onto the seed layer, whereby the nanoparticles serve as nucleation sites for metal deposition. In another approach, the seed layer can be formed by a self-assembling linker material, such as a sulfur-containing silane material.

  7. Analysis of turbulent boundary layers

    CERN Document Server

    Cebeci, Tuncer

    2012-01-01

    Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculati

  8. Layer-by-layer growth of superparamagnetic, fluorescent barcode nanospheres

    International Nuclear Information System (INIS)

    We report a novel stepwise layer-by-layer synthesis strategy to achieve multi-component barcode nanospheres that contain magnetic nanoparticles (MNPs) as the core and quantum dots (QDs) of different emission colors in spatially separated silica layers as the shells, with QD-free silica layers as the insulation layers. This strategy offers the following unique features: (1) the location of the MNPs and the QDs in the silica spheres are separated spatially, so that no interference of the QD photoluminescence (PL) by the magnetic particles is observed; (2) the PL spectra of barcode nanospheres can be easily tuned through the ratio of different QDs loaded in each layer; (3) the size of the silica nanospheres can range from submicron (∼100 nm) to micrometers depending on the number of layers and the thickness of each layer; (4) QD stability is preserved by embedding the QDs covalently in the silica matrix; (5) fluorescence resonance energy transfer (FRET) between different colored QDs is avoided by isolating them into separated layers with a silica spacer layer

  9. Layer-by-layer growth of superparamagnetic, fluorescent barcode nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qiangbin [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Liu Yan [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Lin Chenxiang [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287 (United States); Yan Hao [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States)

    2007-10-10

    We report a novel stepwise layer-by-layer synthesis strategy to achieve multi-component barcode nanospheres that contain magnetic nanoparticles (MNPs) as the core and quantum dots (QDs) of different emission colors in spatially separated silica layers as the shells, with QD-free silica layers as the insulation layers. This strategy offers the following unique features: (1) the location of the MNPs and the QDs in the silica spheres are separated spatially, so that no interference of the QD photoluminescence (PL) by the magnetic particles is observed; (2) the PL spectra of barcode nanospheres can be easily tuned through the ratio of different QDs loaded in each layer; (3) the size of the silica nanospheres can range from submicron ({approx}100 nm) to micrometers depending on the number of layers and the thickness of each layer; (4) QD stability is preserved by embedding the QDs covalently in the silica matrix; (5) fluorescence resonance energy transfer (FRET) between different colored QDs is avoided by isolating them into separated layers with a silica spacer layer.

  10. Ozone Layer Observations

    Science.gov (United States)

    McPeters, Richard; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    The US National Aeronautics and Space Administration (NASA) has been monitoring the ozone layer from space using optical remote sensing techniques since 1970. With concern over catalytic destruction of ozone (mid-1970s) and the development of the Antarctic ozone hole (mid-1980s), long term ozone monitoring has become the primary focus of NASA's series of ozone measuring instruments. A series of TOMS (Total Ozone Mapping Spectrometer) and SBUV (Solar Backscatter Ultraviolet) instruments has produced a nearly continuous record of global ozone from 1979 to the present. These instruments infer ozone by measuring sunlight backscattered from the atmosphere in the ultraviolet through differential absorption. These measurements have documented a 15 Dobson Unit drop in global average ozone since 1980, and the declines in ozone in the antarctic each October have been far more dramatic. Instruments that measure the ozone vertical distribution, the SBUV and SAGE (Stratospheric Aerosol and Gas Experiment) instruments for example, show that the largest changes are occurring in the lower stratosphere and upper troposphere. The goal of ozone measurement in the next decades will be to document the predicted recovery of the ozone layer as CFC (chlorofluorocarbon) levels decline. This will require a continuation of global measurements of total column ozone on a global basis, but using data from successor instruments to TOMS. Hyperspectral instruments capable of measuring in the UV will be needed for this purpose. Establishing the relative roles of chemistry and dynamics will require instruments to measure ozone in the troposphere and in the stratosphere with good vertical resolution. Instruments that can measure other chemicals important to ozone formation and destruction will also be needed.

  11. Magnetism in layered Ruthenates

    International Nuclear Information System (INIS)

    In this thesis, the magnetism of the layered Ruthenates has been studied by means of different neutron scattering techniques. Magnetic correlations in the single-layer Ruthenates of the series Ca2-xSrxRuO4 have been investigated as function of Sr-concentration (x=0.2 and 0.62), temperature and magnetic field. These inelastic neutron scattering studies demonstrate the coexistence of ferromagnetic paramagnon scattering with antiferromagnetic fluctuations at incommensurate wave vectors. The temperature dependence of the amplitudes and energies of both types of excitations indicate the proximity to magnetic instabilities; their competition seems to determine the complex behavior of these materials. In Ca1.8Sr0.2RuO4, which shows a metamagnetic transition, the ferromagnetic fluctuations are strongly suppressed at low temperature, but appear at higher temperature or application of a magnetic field. In the high-field phase of Ca1.8Sr0.2RuO4 above the metamagnetic transition, a ferromagnetic magnon dominates the excitation spectrum. Polarized neutron scattering revealed the existence of a very broad signal around the zone centre, in addition to the well-known incommensurate excitations at Q=(0.3,0.3,0) in the unconventional superconductor Sr2RuO4. With this additional contribution, it is possible to set up a general model for the Q-dependent magnetic susceptibility, which is well consistent with the results of other measurement methods that do not resolve the Q-dependence. Upon doping with Ti, the incommensurate fluctuations are enhanced, in particular near the critical concentration for the onset of magnetic order, but no divergence down to very low temperature is observed. In the bilayer Ti-doped Ca3Ru2O7, the existence of magnetic order with a propagation vector of about ((1)/(4),(1)/(4),0) has been discovered and characterized in detail. Above and below TN, excitations at this wave vector and another one, related to Sr3Ru2O7, have been observed. Furthermore, in a

  12. Boundary-Layer & health

    Science.gov (United States)

    Costigliola, V.

    2010-09-01

    It has long been known that specific atmospheric processes, such as weather and longer-term climatic fluctuations, affect human health. The biometeorological literature refers to this relationship as meteorotropism, defined as a change in an organism that is correlated with a change in atmospheric conditions. Plenty of (patho)physiological functions are affected by those conditions - like the respiratory diseases - and currently it is difficult to put any limits for pathologies developed in reply. Nowadays the importance of atmospheric boundary layer and health is increasingly recognised. A number of epidemiologic studies have reported associations between ambient concentrations of air pollution, specifically particulate pollution, and adverse health effects, even at the relatively low concentrations of pollution found. Since 1995 there have been over twenty-one studies from four continents that have explicitly examined the association between ambient air pollutant mixes and daily mortality. Statistically significant and positive associations have been reported in data from various locations around the world, all with varying air pollutant concentrations, weather conditions, population characteristics and public health policies. Particular role has been given to atmospheric boundary layer processes, the impact of which for specific patient-cohort is, however, not well understood till now. Assessing and monitoring air quality are thus fundamental to improve Europe's welfare. One of current projects run by the "European Medical Association" - PASODOBLE will develop and demonstrate user-driven downstream information services for the regional and local air quality sectors by combining space-based and in-situ data with models in 4 thematic service lines: - Health community support for hospitals, pharmacies, doctors and people at risk - Public information for regions, cities, tourist industry and sporting event organizers - Compliance monitoring support on particulate

  13. Magnetism in layered Ruthenates

    Energy Technology Data Exchange (ETDEWEB)

    Steffens, Paul C.

    2008-07-01

    In this thesis, the magnetism of the layered Ruthenates has been studied by means of different neutron scattering techniques. Magnetic correlations in the single-layer Ruthenates of the series Ca{sub 2-x}Sr{sub x}RuO{sub 4} have been investigated as function of Sr-concentration (x=0.2 and 0.62), temperature and magnetic field. These inelastic neutron scattering studies demonstrate the coexistence of ferromagnetic paramagnon scattering with antiferromagnetic fluctuations at incommensurate wave vectors. The temperature dependence of the amplitudes and energies of both types of excitations indicate the proximity to magnetic instabilities; their competition seems to determine the complex behavior of these materials. In Ca{sub 1.8}Sr{sub 0.2}RuO{sub 4}, which shows a metamagnetic transition, the ferromagnetic fluctuations are strongly suppressed at low temperature, but appear at higher temperature or application of a magnetic field. In the high-field phase of Ca{sub 1.8}Sr{sub 0.2}RuO{sub 4} above the metamagnetic transition, a ferromagnetic magnon dominates the excitation spectrum. Polarized neutron scattering revealed the existence of a very broad signal around the zone centre, in addition to the well-known incommensurate excitations at Q=(0.3,0.3,0) in the unconventional superconductor Sr{sub 2}RuO{sub 4}. With this additional contribution, it is possible to set up a general model for the Q-dependent magnetic susceptibility, which is well consistent with the results of other measurement methods that do not resolve the Q-dependence. Upon doping with Ti, the incommensurate fluctuations are enhanced, in particular near the critical concentration for the onset of magnetic order, but no divergence down to very low temperature is observed. In the bilayer Ti-doped Ca{sub 3}Ru{sub 2}O{sub 7}, the existence of magnetic order with a propagation vector of about ((1)/(4),(1)/(4),0) has been discovered and characterized in detail. Above and below T{sub N}, excitations at this

  14. Neocortical layer 6, a review

    Directory of Open Access Journals (Sweden)

    Alex M Thomson

    2010-03-01

    Full Text Available This review attempts to summarise some of the major areas of neocortical research as it pertains to layer 6. After a brief summary of the development of this intriguing layer, the major pyramidal cell classes to be found in layer 6 are described and compared. The connections made and received by these different classes of neurones are then discussed and the possible functions of these connections, with particular reference to the shaping of responses in visual cortex and thalamus. Inhibition in layer 6 is discussed where appropriate, but not in great detail. Many types of interneurones are to be found in each cortical layer and layer 6 is no exception, but the functions of each type remain to be elucidated.

  15. Oxygen-reducing catalyst layer

    Science.gov (United States)

    O'Brien, Dennis P.; Schmoeckel, Alison K.; Vernstrom, George D.; Atanasoski, Radoslav; Wood, Thomas E.; Yang, Ruizhi; Easton, E. Bradley; Dahn, Jeffrey R.; O'Neill, David G.

    2011-03-22

    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  16. Six layers Architecture Model for Object Oriented Database

    OpenAIRE

    Mansaf Alam

    2011-01-01

    In this paper, a six layered architecture for object oriented database from access and management point of view is proposed. This architecture model consist of six layers: Interaction layer, Application layer, Administration layer, Security layer, Paging layer, and Virtual layer.

  17. Superradiance in spherical layered nanostructures

    Science.gov (United States)

    Goupalov, S. V.

    2016-06-01

    We propose a design of a spherically symmetric nanostructure consisting of alternate concentric semiconductor and dielectric layers. The exciton states in different semiconductor layers of such a structure interact via the common electromagnetic field of light. We show that, if the exciton states in N semiconductor layers are in resonance with one another, then a superradiant state emerges under optical excitation of such a structure. We discuss the conditions under which superradiance can be observed and show that they strongly depend on the valence-band structure of the semiconductor layers.

  18. Plasma boundary layer and magnetopause layer of the earth's magnetosphere

    International Nuclear Information System (INIS)

    IMP 6 observations of the plasma boundary layer (PBL) and magnetopause layer (MPL) of the earth's magnetosphere indicate that plasma in the low-latitude portion of the PBL is supplied primarily by direct transport of magnetosheath plasma across the MPL and that this transport process is relatively widespread over the entire sunward magnetospheric boundary

  19. Layer-by-Layer Proteomic Analysis of Mytilus galloprovincialis Shell.

    Directory of Open Access Journals (Sweden)

    Peng Gao

    Full Text Available Bivalve shell is a biomineralized tissue with various layers/microstructures and excellent mechanical properties. Shell matrix proteins (SMPs pervade and envelop the mineral crystals and play essential roles in biomineralization. Despite that Mytilus is an economically important bivalve, only few proteomic studies have been performed for the shell, and current knowledge of the SMP set responsible for different shell layers of Mytilus remains largely patchy. In this study, we observed that Mytilus galloprovincialis shell contained three layers, including nacre, fibrous prism, and myostracum that is involved in shell-muscle attachment. A parallel proteomic analysis was performed for these three layers. By combining LC-MS/MS analysis with Mytilus EST database interrogations, a whole set of 113 proteins was identified, and the distribution of these proteins in different shell layers followed a mosaic pattern. For each layer, about a half of identified proteins are unique and the others are shared by two or all of three layers. This is the first description of the protein set exclusive to nacre, myostracum, and fibrous prism in Mytilus shell. Moreover, most of identified proteins in the present study are novel SMPs, which greatly extended biomineralization-related protein data of Mytilus. These results are useful, on one hand, for understanding the roles of SMPs in the deposition of different shell layers. On the other hand, the identified protein set of myostracum provides candidates for further exploring the mechanism of adductor muscle-shell attachment.

  20. Layer-layer competition in multiplex complex networks

    CERN Document Server

    Gómez-Gardeñes, Jesús; Gutiérrez, Gerardo; Arenas, Alex; Gómez, Sergio

    2015-01-01

    The coexistence of multiple types of interactions within social, technological and biological networks has moved the focus of the physics of complex systems towards a multiplex description of the interactions between their constituents. This novel approach has unveiled that the multiplex nature of complex systems has strong influence in the emergence of collective states and their critical properties. Here we address an important issue that is intrinsic to the coexistence of multiple means of interactions within a network: their competition. To this aim, we study a two-layer multiplex in which the activity of users can be localized in each of the layer or shared between them, favoring that neighboring nodes within a layer focus their activity on the same layer. This framework mimics the coexistence and competition of multiple communication channels, in a way that the prevalence of a particular communication platform emerges as a result of the localization of users activity in one single interaction layer. Our...

  1. Natural melanin composites by layer-by-layer assembly

    Science.gov (United States)

    Eom, Taesik; Shim, Bong Sub

    2015-04-01

    Melanin is an electrically conductive and biocompatible material, because their conjugated backbone structures provide conducting pathways from human skin, eyes, brain, and beyond. So there is a potential of using as materials for the neural interfaces and the implantable devices. Extracted from Sepia officinalis ink, our natural melanin was uniformly dispersed in mostly polar solvents such as water and alcohols. Then, the dispersed melanin was further fabricated to nano-thin layered composites by the layer-by-layer (LBL) assembly technique. Combined with polyvinyl alcohol (PVA), the melanin nanoparticles behave as an LBL counterpart to from finely tuned nanostructured films. The LBL process can adjust the smart performances of the composites by varying the layering conditions and sandwich thickness. We further demonstrated the melanin loading degree of stacked layers, combination nanostructures, electrical properties, and biocompatibility of the resulting composites by UV-vis spectrophotometer, scanning electron microscope (SEM), multimeter, and in-vitro cell test of PC12, respectively.

  2. A tribo-mechanical analysis of PVA-based building-blocks for implementation in a 2-layered skin model.

    Science.gov (United States)

    Morales Hurtado, M; de Vries, E G; Zeng, X; van der Heide, E

    2016-09-01

    Poly(vinyl) alcohol hydrogel (PVA) is a well-known polymer widely used in the medical field due to its biocompatibility properties and easy manufacturing. In this work, the tribo-mechanical properties of PVA-based blocks are studied to evaluate their suitability as a part of a structure simulating the length scale dependence of human skin. Thus, blocks of pure PVA and PVA mixed with Cellulose (PVA-Cel) were synthesised via freezing/thawing cycles and their mechanical properties were determined by Dynamic Mechanical Analysis (DMA) and creep tests. The dynamic tests addressed to elastic moduli between 38 and 50kPa for the PVA and PVA-Cel, respectively. The fitting of the creep compliance tests in the SLS model confirmed the viscoelastic behaviour of the samples with retardation times of 23 and 16 seconds for the PVA and PVA-Cel, respectively. Micro indentation tests were also achieved and the results indicated elastic moduli in the same range of the dynamic tests. Specifically, values between 45-55 and 56-81kPa were obtained for the PVA and PVA-Cel samples, respectively. The tribological results indicated values of 0.55 at low forces for the PVA decreasing to 0.13 at higher forces. The PVA-Cel blocks showed lower friction even at low forces with values between 0.2 and 0.07. The implementation of these building blocks in the design of a 2-layered skin model (2LSM) is also presented in this work. The 2LSM was stamped with four different textures and their surface properties were evaluated. The hydration of the 2LSM was also evaluated with a corneometer and the results indicated a gradient of hydration comparable to the human skin. PMID:27236420

  3. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...

  4. Decorative layers on tin bronzes

    Directory of Open Access Journals (Sweden)

    Z. Konopka

    2010-10-01

    Full Text Available Decorative layers are decisive for aesthetic value of castings, therefore significant demands are raised towards such layers, e.g. pleasant durable colour, gloss, and smoothness. The work discusses the influence of the type of mechanical working applied to the surfaces of CuSn10 tin bronze castings on the quality and durability of a decorative coating. The scope of the work has included designing and manufacturing of cast samples of tin bronze, mechanical working of the surfaces in order to prepare them for applying coating layers,generating decorative layers as a result of chemical reactions, and the quality assessment and comparison of the obtained coating. Theassessment of thickness and continuity of the obtained decorative layers based on metallographic examinations has been presented.

  5. Stability of weak double layers

    International Nuclear Information System (INIS)

    The transverse stability of weak double-layers in plasmas with a two-temperature electron component is investigated. The double layers appear as shocklike solutions of the modified Korteweg-de Vries (mKdV) equation with a negative coefficient of the cubic nonlinear term. The investigations are performed both for an unmagnetized and a magnetized plasma. In the former case the two-dimensional evolution of the double layer is governed by a modified Kadomtsev-Petviashvili (mKP) equation and the double layer is unstable. In a magnetized plasma the two-dimensional evolution is governed by a modified Zakharov-Kuznetsov (mZK) equation and the double layer is found to be stable. (au)

  6. Large-scale simulations of layered double hydroxide nanocomposite materials

    Science.gov (United States)

    Thyveetil, Mary-Ann

    Layered double hydroxides (LDHs) have the ability to intercalate a multitude of anionic species. Atomistic simulation techniques such as molecular dynamics have provided considerable insight into the behaviour of these materials. We review these techniques and recent algorithmic advances which considerably improve the performance of MD applications. In particular, we discuss how the advent of high performance computing and computational grids has allowed us to explore large scale models with considerable ease. Our simulations have been heavily reliant on computational resources on the UK's NGS (National Grid Service), the US TeraGrid and the Distributed European Infrastructure for Supercomputing Applications (DEISA). In order to utilise computational grids we rely on grid middleware to launch, computationally steer and visualise our simulations. We have integrated the RealityGrid steering library into the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) 1 . which has enabled us to perform re mote computational steering and visualisation of molecular dynamics simulations on grid infrastruc tures. We also use the Application Hosting Environment (AHE) 2 in order to launch simulations on remote supercomputing resources and we show that data transfer rates between local clusters and super- computing resources can be considerably enhanced by using optically switched networks. We perform large scale molecular dynamics simulations of MgiAl-LDHs intercalated with either chloride ions or a mixture of DNA and chloride ions. The systems exhibit undulatory modes, which are suppressed in smaller scale simulations, caused by the collective thermal motion of atoms in the LDH layers. Thermal undulations provide elastic properties of the system including the bending modulus, Young's moduli and Poisson's ratios. To explore the interaction between LDHs and DNA. we use molecular dynamics techniques to per form simulations of double stranded, linear and plasmid DNA up

  7. Layer-by-layer pattern propagtion and pulsed laser deposition

    OpenAIRE

    Westerhoff, F.; Brendel, L.; Wolf, D. E.

    2001-01-01

    In this article kinetic Monte Carlo simulations for molecular beam epitaxy (MBE) and pulsed laser depositon (PLD) are compared. It will be shown that an optimal pattern conservation during MBE is achieved for a specific ratio of diffusion to deposition rate. Further on pulsed laser deposition is presented as an alternative way to control layer by layer growth. First results concerning the island density in the submonolayer regime are shown.

  8. On Multiple-Layered Vortices

    Science.gov (United States)

    Rossow, Vernon J.

    2011-01-01

    As part of an ongoing effort to find ways to make vortex flow fields decompose more quickly, photographs and observations are presented of vortex flow fields that indicate the presence of multiple layers of fluid rotating about a common axis. A survey of the literature indicates that multiple-layered vortices form in waterspouts, tornadoes and lift-generated vortices of aircraft. An explanation for the appearance of multiple-layered structures in vortices is suggested. The observations and data presented are intended to improve the understanding of the formation and persistence of vortex flow fields.

  9. Ultrasonic classification of thin layers within multi-layered materials

    International Nuclear Information System (INIS)

    Methods for non-destructive inspection of layered materials are becoming more and more popular as a way of assuring product integrity and quality. In this paper, we present a model-based technique using ultrasonic measurements for classification of thin bonding layers within three-layered materials. This could be, for example, an adhesive bond between two thin plates, where the integrity of the bonding layer needs to be evaluated. The method is based on a model of the wave propagation of pulse-echo ultrasound that first reduces the measured data to a few parameters for each measured point. The model parameters are then fed into a statistical classifier that assigns the bonding layer to one of a set of predefined classes. In this paper, two glass plates are bonded together with construction silicone, and the classifiers are trained to determine if the bonding layer is intact or if it contains regions of air or water. Two different classification methods are evaluated: nominal logistic regression and discriminant analysis. The former is slightly more computationally demanding but, as the results show, it performs better when the model parameters cannot be assumed to belong to a multivariate Gaussian distribution. The performance of the classifiers is evaluated using both simulations and real measurements

  10. On the origin of rhythmic layering in layered gabbros

    Science.gov (United States)

    Wang, Z.; Zhang, J.

    2015-12-01

    Rhythmic layering of silicates (plagioclase, pyroxene and olivine), ilmenite and magnitite is a common feature in mafic-ultramafic intrusions. The origin of rhythmic layering has been hotly debated in the literatures. Proposed mechanisms include gravity differentiation, double-diffusive convection, oscillatory crystallization of magma, repeated injection and supplement of magma, etc. Here we provide detailed FTIR and EBSD studies on the water content and deformation microstructure of gabbros from the Panzhihua intrusion and experimentally deformed synthetic gabrros and magnetite aggregates with a volume ratio of 6:4. The FTIR analyses revealed a significant amount of hydroxyls in both clinopyroxene (411-775 ppm) and plagioclase (328-716 ppm), suggesting a high water content mantle plume source. The EBSD analyses show similar fabrics in constitutent minerals of natural and experimental specimens: a weak clinopyroxene fabric of (100) parallel to foliation and [001] parallel to lineation; a strong plagioclase fabric of (010) parallel to foliation and [100] parallel to lineation, a weak ilmenite fabric of (001) parallel to foliation and [hk0] parallel to lieantion; and a near random magnitite fabric. There is an obvious rhythmic layering in sheared gabrros and magnetite aggregates similar to natural observations. Our results revealed strong layer-parallel shearing deformation during the formation of the Panxi layered intructions. There is a significant strength contrast between gabbro and Fe-Ti oxides. We propose that the formation of the rhythmic layering in mafic-ultramafic intrusions is caused mainly by rheological stratification of Fe-Ti oxides and gabbros.

  11. National Flood Hazard Layer (NFHL)

    Data.gov (United States)

    Federal Emergency Management Agency, Department of Homeland Security — The National Flood Hazard Layer (NFHL) is a compilation of GIS data that comprises a nationwide digital Flood Insurance Rate Map. The GIS data and services are...

  12. Sub-Transport Layer Coding

    DEFF Research Database (Denmark)

    Hansen, Jonas; Krigslund, Jeppe; Roetter, Daniel Enrique Lucani;

    2014-01-01

    Packet losses in wireless networks dramatically curbs the performance of TCP. This paper introduces a simple coding shim that aids IP-layer traffic in lossy environments while being transparent to transport layer protocols. The proposed coding approach enables erasure correction while being...... oblivious to the congestion control algorithms of the utilised transport layer protocol. Although our coding shim is indifferent towards the transport layer protocol, we focus on the performance of TCP when ran on top of our proposed coding mechanism due to its widespread use. The coding shim provides gains...... in throughput that exceed 10x for TCP traffic while requiring a limited sacrifice in terms of fairness towards other flows on the channel....

  13. Magnetic microscopy of layered structures

    CERN Document Server

    Kuch, Wolfgang; Fischer, Peter; Hillebrecht, Franz Ulrich

    2015-01-01

    This book presents the important analytical technique of magnetic microscopy. This method is applied to analyze layered structures with high resolution. This book presents a number of layer-resolving magnetic imaging techniques that have evolved recently. Many exciting new developments in magnetism rely on the ability to independently control the magnetization in two or more magnetic layers in micro- or nanostructures. This in turn requires techniques with the appropriate spatial resolution and magnetic sensitivity. The book begins with an introductory overview, explains then the principles of the various techniques and gives guidance to their use. Selected examples demonstrate the specific strengths of each method. Thus the book is a valuable resource for all scientists and practitioners investigating and applying magnetic layered structures.

  14. Boundary Layer under Oscillatory Wave

    OpenAIRE

    Mohammad Bagus Adityawan; Hitoshi Tanaka

    2011-01-01

    Turbulence due to wave motion and propagation is a very important aspect in sediment transport modeling. The boundary layer characteristic during the process will highly influence the sediment transport mechanism at the bottom. 1D model approach has been widely used to assess the turbulent boundary layer. However, the need for a more detailed model leads to the development of a more sophisticated models. This study presents a 2D turbulent model using k-ω equation to approach the turbulent bou...

  15. Transport kinetics of wetting layers

    OpenAIRE

    Herminghaus, Stephan; Paatzsch, Thomas; Häcker, T.; Leiderer, Paul

    1995-01-01

    The transport kinetics of wetting layers of ethanol and propane on silver substrates is investigated by monitoring the temporal decay of pulsed-laser-induced spatial thickness modulations. Our method allows to distinguish between different transport mechanisms, such as direct exchange with the vapour phase, viscous flow within the wetting layer, or surface diffusion. In either ease, the activation energy found for the lateral transport points to viscous flow as the dominant mechanism in the i...

  16. Modeling the urban boundary layer

    Science.gov (United States)

    Bergstrom, R. W., Jr.

    1976-01-01

    A summary and evaluation is given of the Workshop on Modeling the Urban Boundary Layer; held in Las Vegas on May 5, 1975. Edited summaries from each of the session chairpersons are also given. The sessions were: (1) formulation and solution techniques, (2) K-theory versus higher order closure, (3) surface heat and moisture balance, (4) initialization and boundary problems, (5) nocturnal boundary layer, and (6) verification of models.

  17. Hybrid window layer for photovoltaic cells

    Science.gov (United States)

    Deng, Xunming

    2010-02-23

    A novel photovoltaic solar cell and method of making the same are disclosed. The solar cell includes: at least one absorber layer which could either be a lightly doped layer or an undoped layer, and at least a doped window-layers which comprise at least two sub-window-layers. The first sub-window-layer, which is next to the absorber-layer, is deposited to form desirable junction with the absorber-layer. The second sub-window-layer, which is next to the first sub-window-layer, but not in direct contact with the absorber-layer, is deposited in order to have transmission higher than the first-sub-window-layer.

  18. Layer-by-layer films for biomedical applications

    CERN Document Server

    Picart, Catherine; Voegel, Jean-Claude

    2015-01-01

    The layer-by-layer (LbL) deposition technique is a versatile approach for preparing nanoscale multimaterial films: the fabrication of multicomposite films by the LbL procedure allows the combination of literally hundreds of different materials with nanometer thickness in a single device to obtain novel or superior performance. In the last 15 years the LbL technique has seen considerable developments and has now reached a point where it is beginning to find applications in bioengineering and biomedical engineering. The book gives a thorough overview of applications of the LbL technique in the c

  19. DAR Assisted Layer-by-Layer Assembly of Aromatic Compounds

    Institute of Scientific and Technical Information of China (English)

    姜思光; 陈晓东; 张莉; 刘鸣华

    2003-01-01

    A facile DAR (diphenylamine-4-diazonium-formaldehyde resin)assisted layer-by-layer (LbL) assembly of uitrathin organic film of aromatic compounds has been investigated. The muitilayer of pyrene or anthracene was fabricated through simple dipping of the glass slide into the mixed solution of DAR with the target compounds. In this method, DAR acted as an assistant compound to help the assembling of the aromatic compounds. Such a convenient deposition method not only reserves the advantages of the traditional LbL technique but also simplifies the technique and extends the effectiveness of LbL technique to small molecules without any charge.

  20. Layer By Layer Assembly with Sol-Gel Materials and Its Electrochemical Application

    OpenAIRE

    Kim, Jun Ho

    2015-01-01

    Layer by layer assembly, a coating method that uses two opposite charged solutions, has led to functional coating field due to its advantages [1]. Charged polyelectrolytes are widely used as glue in layer by layer assembly, because they provide opposite charge between the solutions, thus avoiding an agglomerate form of coating. However, only a few instance of layer by layer assembly without polyelectrolyte are studied. In this study, layer by layer assembly using the sol-gel oxides instead of...