Topological Defects Research Papers - Academia.edu (original) (raw)

Topological defects are distinctive signatures of liquid crystals. They profoundly affect the viscoelastic behavior of the fluid by constraining the orientational structure in a way that inevitably requires global changes not achievable with any set of local deformations. In active nematic liquid crystals topological defects not only dictate the global structure of the director, but also act as local sources of motion, behaving as self-propelled particles. In this article we present a detailed analytical and numerical study of the mechanics of topological defects in active nematic liquid crystals.

- by
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- Active Matter, Topological Defects

The equations governing the evolution of quantum vortex defects subject to twist are derived in standard hydrodynamic form. Vortex defects emerge as solutions of the Gross-Pitaevskii equation, that by Madelung transformation admits a hydrodynamic description. Here, we consider a vortex defect subject to superposed twist due to the rotation of the phase of the wave function. We prove that, when twist is present, the corresponding Hamiltonian is non-Hermitian and determine the effect of twist on the energy expectation value of the system. We show how twist diffusion may trigger linear instability, a property directly related to the non-Hermiticity of the Hamiltonian. We derive the correct continuity equation and, by applying defect theory, we obtain the correct momentum equation. Finally, by coupling twist kinematics and vortex dynamics we determine the full set of hydrodynamic equations governing quantum vortex evolution subject to twist.

- by Matteo Foresti and +1
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- Vortex dynamics, Topological Defects, Bose Einstein Condensates
- by Matej Pavsic
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- Theoretical Physics, Gravitation, General Relativity, Dark Matter
- by Carlos Castro Perelman
- •
- Theoretical Physics, Gravitation, General Relativity, Dark Matter

- by Carlos Castro Perelman
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- Theoretical Physics, Gravitation, Particle Physics, General Relativity

We have studied primordial non-Gaussian features from a model of potential driven single field DBI Galileon inflation. We have computed the bispectrum from the three point correlation function considering all possible cross correlation between scalar and tensor modes from the proposed setup. Further, we have computed the trispectrum from four point correlation function considering the contribution from contact interaction, scalar and graviton exchange diagrams in the in-in picture. Finally we have obtained the non-Gaussian consistency conditions from the four point correlator, which results in partial violation of the Suyama-Yamaguchi four-point consistency relation. This further leads to the conclusion that sufficient primordial non-Gaussianities can be obtained from DBI Galileon inflation.

- by Sayantan Choudhury
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- Cosmology (Physics), Gravitation, General Relativity, Observational Cosmology

Para empezar es muy importante asumir que, siguiendo el modelo dinámico estándar visto antes, y de acuerdo a las mediciones efectuadas sobre el fondo de la radiación fósil, el universo observable geométricamente, haciendo abstracción de su estructura capsular exterior, y de su distribución celular general observada hoy, es esencialmente homogéneo e isotrópico, según el modelo propuesto por Gamow. CIFRA DOC CFR#095 -2005 ULT. REV. 06/12/12 -1 M.G. ACOSTA CUADERNOS DE FÍSICA RETRO-ROTATORIA Página 2 de 19 EL BIG-BANG PRIMORDIAL Y LA DINÁMICA RETRO-ROTATORIA

- by Mario G Acosta Alarcon
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- Theoretical Physics, Cosmology (Physics), Gravitation, General Relativity
- by Carlos Castro Perelman
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- Gravitation, General Relativity, Dark Matter, Dark Energy

In this second part of a series of articles, we discuss the fusion of analogue and digital decurring from the Klein Bottle, the Inside/Outside image-schema of Cognitive Semantics and its role in the dualistic organization of knowledge, presenting several examples in biology, astrophysics and chemistry. We present the Möbius strips and Klein Bottle (KB) and HyperKlein Bottles non-orientable surfaces, the non-dual logic and logophysics of the KB, that surmount this dualism, and their elementary harmonics, and the relation with palindromes .We present a corresponding topological protoform of Newton's Third Law surmounting its dualistic character. We discuss Chemical Topology as a paradigm incorporating at its foundations the Klein Bottle ontology and logophysics, and particularly the characterization of life as artifact-making, of molecular complementarity and of semiotic agency as related to self-reference. We discuss the relation between these surfaces and enantiomerism and the existence of a bodyplan for humans related to them and give several examples of its manifestation. We discuss the relations between the Inside/Outside image-schema and its surmountal by the Klein Bottle logophysics in biology, chemistry, astrophysics, holography, metamathematics, and of the location of the real world. We introduce the non-orientable topology of the action/perception cycle and discuss the KB topology of the visual and somatosensory cortical mappings, music perception and of electromagnetic and sound vortices. We discuss the Inside/Outside image-schema and its relations to the topologies of genomes.

The use of moiré pattern of superimposition of linear forked gratings (LFGs) and Fresnel zone
plates (ZPs) has already been reported for study of different physical effects. In spite of a
considerable number of applications, there is no comprehensive formulation for this kind of
moiré pattern. In this work, we introduce a new family of ZPs containing topological defects that
we named defected ZP (DZP) and we present a very simple, uniform, and comprehensive
formulation for the moiré pattern of superimposition of two LFGs, two DZPs, and
superimposition of an LFG on a DZP, using the reciprocal vector approach. For the case of the
two LFGs superimposition, we show that the resulting moiré pattern has a starlike shape or is a
large-scale LFG pattern. In the case in which two DZPs are superimposed, we show that the
resulting moiré pattern has three general forms: large-scale DZP pattern, starlike pattern, and
large-scale LFG pattern. In the superimposition of an LFG on a DZP, in special conditions a new
spiral ZP having a topological defect is produced in which its defect number related to the
superimposed gratings structures. The presented formulation has potential applications in
singular optics measurements.

The main features of how to build a Born's Reciprocal Gravitational theory in curved phase-spaces are developed. The scalar curvature of the 8D cotangent bundle (phase space) is explicitly evaluated and a generalized gravitational action in 8D is constructed that yields the observed value of the cosmological constant and the Brans-Dicke-Jordan Gravity action in 4D as two special cases. It is found that the geometry of the momentum space can be linked to the observed value of the cosmological constant when the curvature in momentum space is very large, namely the small size of P is of the order of (1/R Hubble ). More general 8D actions can be developed that involve sums of 5 distinct types of torsion squared terms and 3 distinct curvature scalars R, P, S. Finally we develop a Born's reciprocal complex gravitational theory as a local gauge theory in 8D of the def ormed Quaplectic group that is given by the semi-direct product of U (1, 3) with the def ormed (noncommutative) Weyl-Heisenberg group involving four noncommutative coordinates and momenta. The metric is complex with symmetric real components and antisymmetric imaginary ones. An action in 8D involving 2 curvature scalars and torsion squared terms is presented.

- by Carlos Castro Perelman
- •
- Theoretical Physics, Gravitation, General Relativity, Dark Matter

We introduce a model of potential driven DBI Galileon inflation in background N=1,D=4 SUGRA. Starting from D4-$\bar{D4}$ brane-antibrane in the bulk N=2,D=5 SUGRA including quadratic Gauss-Bonnet corrections, we derive an effective N=1,D=4 SUGRA by dimensional reduction, that results in a Coleman-Weinberg type Galileon potential. We employ this potential in modeling inflation and in subsequent study of primordial quantum fluctuations for scalar and tensor modes. Further, we estimate the major observable parameters in both de Sitter (DS) and beyond de Sitter (BDS) limits and confront them with recent observational data from WMAP7 by using the publicly available code CAMB.

- by Sayantan Choudhury
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- Mathematical Physics, Gravitation, Particle Physics, General Relativity

Polyvector-valued gauge field theories in Clifford spaces are used to construct a novel Cl(3, 2) gauge theory of gravity that furnishes modif ied curvature and torsion tensors leading to important modif ications of the standard gravitational action with a cosmological constant. Vacuum solutions exist which allow a cancellation of the contributions of a very large cosmological constant term and the extra terms present in the modified field equations. Generalized gravitational actions in Clifford-spaces are provided and some of their physical implications are discussed. It is shown how the 16 fermions and their masses in each family can be accommodated within a Cl(4) gauge field theory. In particular, the Higgs fields admit a natural Clifford-space interpretation that differs from the one in the Chamseddine-Connes spectral action model of Noncommutative geometry. We finalize with a discussion on the relationship with the Pati-Salam color-flavor model group SU (4)C × SU (4)F and its symmetry breaking patterns. An Appendix is included with useful Clifford algebraic relations. * Dedicated to the memory of Gustavo Ponce C-space Relativity naturally incorporates the ideas of an invariant length (Planck scale), maximal acceleration, non-commuting coordinates, supersymmetry, holography, higher derivative gravity with torsion; it permits to study the dynamics of all (closed) p-branes, for different values of p, on a unified footing [1]. It resolves the ordering ambiguities in QFT [2]; the problem of time in Cosmology and admits superluminal propagation (tachyons) without violations of causality [3], [1]. The relativity of signatures of the underlying spacetime results from taking different slices of C-space [4], [1]. Ideas very close to the extended Relativity in Clifford spaces have been considered by [6] and [7]. The conformal group in spacetime emerges as a natural subgroup of the Clifford group and Relativity in C-spaces involves natural scale changes in the sizes of physical objects without the introduction of forces nor Weyl's gauge field of dilations [1]. A generalization of Maxwell theory of Electrodynamics of point charges to a theory in C-spaces involves extended charges coupled to antisymmetric tensor fields of arbitrary rank and where the analog of photons are tensionless p-branes. The Extended Relativity Theory in Born-Clifford Phase Spaces with a Lower and Upper Length Scales and the program behind a Clifford Group Geometric Unification was advanced by [8].

- by Carlos Castro
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- Mathematical Physics, Theoretical Physics, Gravitation, Particle Physics
- by L. García-Tabarés
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- Physics, Theoretical Physics, Gravitation, General Relativity

A family of static solutions of the Einstein field equations with spherical symmetric for a locally anisotropic fluid with homogeneous energy density is obtained. These solutions depend on two adjustable parameters related to degree of anisotropy of the fluid. Some known solutions may be recovered for specific values of these parameters. As a difference to other known solutions it is possible to change the grade of anisotropy of the model, keeping the same functional dependence on the coordinates. By means of a slow adiabatic contraction, the stability of the obtained solutions is studied. Also, it is shown, how it is possible to enhance the stability of the models by adjusting the parameters, and to obtain more compact configurations than those obtained with other similar anisotropic solutions, while the dominant or strong energy condition holds within the sphere.

- by Manuel Malaver de la Fuente
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- Gravitation, General Relativity, Dark Matter, Dark Energy

It is rigorously shown how the static spherically symmetric solutions of Einstein's equations can furnish a null naked singularity associated with a point mass source at r = 0. The construction relies in the possibility of having a metric discontinuity at the location of the point mass. This result should be contrasted with the spacelike singularity described by the textbook black hole solution. It has been argued by some authors why one cannot get any information from the null naked singularity so it will not have any undesirable physical effect to an outside far away observer and cannot cause a breakdown of predictability. In this way one may preserve the essence of the cosmic censorship hypothesis. The field equations due to a deltafunction point-mass source at r = 0 are solved and the Euclidean gravitational action corresponding to those solutions is evaluated explicitly. It is found that it is precisely equal to the black hole entropy (in Planck area units). This result holds in any dimensions D ≥ 3 and may have important consequences to the resolution of the fire wall problem in black holes. We finalize by arguing why the Noncommutative Gravity of the spacetime tangent (co-tangent) bundle is the proper arena to study point masses.

- by Carlos Castro Perelman
- •
- Gravitation, General Relativity, Dark Matter, Dark Energy

In this presentation we explore exactly what General Relativity [GR] is - define the space-time metric, from first principles and derive it from Pythagoras theorem. Then we define the Robertson-Walker metric and how it applies to flat space-time. We look at GR in the context of a large flat space as compared with curved space-time. Then we look at the geometric properties of gravitational lensing. We look at the large scale structure LSS of the universe and see examples of astrophysical observations of gravitational lensing, and examples of Einstein’s Ring. We also see LSS simulations.

- by Estelle Asmodelle
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- Observational Astronomy, Cosmology (Physics), Gravitation, Relativity

Empirically determining the averaged variations of the orbital parameters of the stars orbiting the Supermassive Black Hole (SBH) hosted by the Galactic center (GC) in Sgr A* is, in principle, a valuable tool to test the General Theory of Relativity (GTR), in regimes far stronger than those tested so far, and certain key predictions of it like the “no-hair” theorems. We analytically work out the long-term variations of all the six osculating Keplerian orbital elements of a test particle orbiting a nonspherical, rotating body with quadrupole moment Q2 and angular momentum S for a generic spatial orientation of its spin axis k̂. This choice is motivated by the fact that, basically, we do not know the position in the sky of the spin axis of the SBH in Sgr A* with sufficient accuracy. We apply our results to S2, which is the closest star discovered so far having an orbital period Pb=15.98 yr, and to a hypothetical closer star X with Pb=0.5 yr. Our calculations are quite general, not being related to any specific parameterization of k̂, and can be applied also to astrophysical binary systems, stellar planetary systems, and planetary satellite geodesy in which different reference frames, generally not aligned with the primary’s rotational axis, are routinely used.

- by Lorenzo Iorio
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- Gravitational Astronomy, Gravitation, Space Geodesy, General Relativity
- by Christian Gaser
- •
- Cognitive Science, Algorithms, Magnetic Resonance Imaging, MRI

We study the role of the Gauss-Bonnet corrections and two loop higher genus contribution to the gravity action on the Kaluza-Klien modes and their interactions for different bulk fields which enable one to study various phenomenological implications of string loop corrected Gauss-Bonnet modified warped geometry model in one canvas. We have explicitly derived a phenomenological bound on the Gauss-Bonnet parameter so that the required Planck to TeV scale hierarchy can be achieved through the warp factor in the light of recently discovered Higgs like boson at 125 GeV. Moreover due to the presence of small perturbative Gauss-Bonnet as well as string loop corrections we have shown that the warping solution can be obtained for both de-Sitter and anti-de-Sitter bulk which is quite distinct from Randall-Sundrum scenario. Finally we have evaluated various interactions among these bulk fields and determined the coupling parameters and the Kaluza- Klien mode masses which is crucial to understand the phenomenology of a string two loop corrected Einstein-Gauss-Bonnet warp geometry.

- by Sayantan Choudhury
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- Mathematical Physics, Field Theory, Elementary Particle Physics, Gravitation

We performed first-principle calculations based on density functional theory (DFT) to investigate adsorption of lithium (Li) on graphene with divacancy and Stone–Wales defects. Our results confirm that lithiation is not possible in pristine graphene. However, enhanced Li adsorption is observed on defective graphene because of the increased charge transfer between adatom and underlying defective sheet. Because of increased adsorption, the specific capacity is also increased with the increase in defect densities. For the maximum possible divacancy defect density, Li storage capacities of up to ∼1675 mAh/g can be achieved. While for Stone–Wales defects, we find that a maximum capacity of up to ∼1100 mAh/g is possible. Our results provide deeper understanding of Li-defect interactions and will help to create better high-capacity anode materials for Li-ion batteries.

- by DIBAKAR DATTA
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- Physics, Condensed Matter Physics, Materials Science, Chemistry

Topologi jaringan dalam telekomunikasi adalah suatu cara menghubungkan perangkat telekomunikasi yang satu dengan yang lainnya sehingga membentuk jaringan. Dalam suatu jaringan telekomunikasi, jenis topologi yang dipilih akan mempengaruhi kecepatan komunikasi. Untuk itu maka perlu dicermati kelebihan/keuntungan dan kekurangan/kerugian dari masingmasing topologi berdasarkan karakteristiknya.

- by Fajar Smik
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- JARINGAN, Topological Defects, Topologi Jaringan

Matter engenders a Modified Newtonian Gravitational Potential (MNGP) that has a singularity at a two Normalized Spatial Unit (NSU) distance with a modified gravitational field constant in distance > 2 NSU region, and a saturated potential for distance < 2 NSU region. In Cartesian coordinates, a reference object (RO) resides at origin and a test object (TO) resides on the positive region of the X-axis, the interaction energy between the MNGP of the RO in the X>0 region and the X<0 region with the MNGP of the TO is different; This interaction energy imbalance results an E-space Inter-Domain Interaction potential (EIDIP), a scalar potential. An E-space Inter-Domain Interaction Potential (EIDIP) application models is based on the EIDIP function. Ten EIDIP application models are summarized in this paper with Matlab models simulations and empirical data/figures comparisons. These EIDIP application models cover from elementary particle scale (nuclear binding energy, nuclear charge radius, nucleon-nucleon potential, strong interaction-asymptotic freedom and color confinement, Bohr radius and short range inter-atomic force) to human scale (the Newtonian gravitational interaction and the near earth fly-by anomaly) and astronomical scale (the Pioneer spacecraft 10/11 speed anomaly and the Milky Way rotation curve anomaly). A list of null hypothesis testing node (NHTN), extracted from these EIDIP application model empirical data comparison results, indicates that the EIDIP has 5+ sigma confidence level potential. The EIDIP function, along with the explanatory EIDIP model, could be the missing blocks in completing the Unified theory.

We construct a phenomenological theory of gravitation based on a second order gauge formulation for the Lorentz group. The model presents a long-range modification for the gravitational field leading to a cosmological model provided with an accelerated expansion at recent times. We estimate the model parameters using observational data and verify that our estimative for the age of the Universe is of the same magnitude than the one predicted by the standard model. The transition from the decelerated expansion regime to the accelerated one occurs recently (at sim9.3;Gyr\sim9.3\;Gyrsim9.3;Gyr).

- by Cassius de Melo and +2
- •
- Cosmology (Physics), Gravitation, General Relativity, Dark Matter

One scientifical and technological multiphase flow model is proposed to
predict the behaviour in the Pouring Furnaces (fig.1) and in the Ladle production (fig.2), regarding entrained inclusions in liquid steel, as they enter the orifice of a SMA (Structural Metal Analyzer) sensor for assuring steel quality (fig.3). The SMA method of measurement is based on the UCnF & Vyborcntmat-SMP (VycnT) pseudo-composite technique. Analysis of the liquid metal flow field- used the VycnT – it solving by the three related mechanisms: the Seebeck, Peltier and Thomson mechanisms and effects taking into account the presence of a self induced electromagnetic field. When an entrained non-conducting inclusion passes through the orifice of the probe, in the presence of a direct current, the change in the electrical resistance of the VycnT , due to its presence in the VycnT can register a resistive pulse. Such signals, in turn, can be used to detect the numbers and sizes of entrained inclusions. The trajectories of these entrained inclusions have been modeled using a momentum equation by solving COMSOL Multiphysics models. External forces acting on the particles include those for standard drag (Stokes), added mass, fluid acceleration, buoyancy and, most significantly, electromagnetic. The boundary effects on Stokes drag are also taken into account. Predicted voltage pulse signals are compared with experimental values derived from some based experiments, UCnF & Vyborcntmat-SMP (VycnT) pseudo-composite technique. Keywords: inclusions, multiphase flow, liquid steel, particle motion, trajectory, electromagnetic force

- by Paul OLARU
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- Defect Detection, Defect Classification, Defect Prevention, Topological Defects

An analysis of curvature in woven meshes, through understanding of basic properties of a triaxial or kagome lattice, a traditional basket weaving technique.
Following a finite set of mathematical weaving rules, topologically distinct shapes, from surfaces to curves to solids, may be represented in 3D. Under this unifying framework, a universal and modular system emerges for the design, representation and construction of lightweight, flexible models of polyhedral forms, architectural shapes, high-genus surfaces, knots and links.

- by Alison Grace Martin
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- Morphology, Topology, 3d Weaving, Complex Geometry

Cable joint is used to connect different sections of cable because a cable section is limited to a certain length. The design of a cable joint mainly depends on the cable type, the applied voltage and the cores. These factors contribute to the way of how electric field stress is distributed at the cable joint. If there are defects exist within the cable joint insulation material, the electric field at that region is altered. The alteration may cause electrical discharges to occur within the defects if the electric field magnitude is larger than the breakdown strength at the defect sites. Therefore, this paper investigates the electric field distribution in a medium voltage cable joint in the presence of defects. The investigation was done through modelling a medium voltage (MV) cable joint using finite element analysis (FEA) software. Several parameters such as the defect size and location, insulation material dielectric constant and insulation thickness have been studied of their effects on the electric field distribution at the cable joint. The results obtained may be able to help in the designing of cable joint structures which can reduce the electric field stress.

Présentation de l´éditeur:
En se formant sur un lac, en hiver, la glace montre des petites imperfections en zigzag dues à la congélation indépendante des différentes parties de sa surface. Les physiciens appellent ce type de phénomènes des "défauts topologiques". De façon analogue, l´expansion et le refroidissement de l´Univers primordial, où régnaient des conditions exceptionnelles inaccessibles à nos technologies, n´ont sans doute pas pu se dérouler uniformément et des défauts cosmiques ont dus être générés. Bien sûr, l´approche de ces défauts requiert la compréhension des diverses branches de la physique, mais les connaissances les plus pointues en la matière sont ici exposées en termes clairs et sans équations, et ainsi rendues accessibles, pour la première fois, à un large public. Sont mises en valeur les données les plus récentes obtenues tant par des observations astrophysiques que par des expériences mettant en jeu des matériaux peu ordinaires, à la base des futures technologies, ou encore par des simulations numériques, purement théoriques. Le grand nombre d´illustrations associées au texte permet d´en comprendre les difficultés, jamais techniques mais souvent conceptuelles.
Ces fascinants objets théoriques, fruits de l´union de la physique des particules élémentaires et de la théorie de l´expansion cosmologique, conjonctions entre le monde de l´infiniment petit et celui de l´infiniment grand, peuvent nous permettre de mieux comprendre le comportement de la nature à des énergies extrêmes. Ils pourraient aussi être responsables de la formation des grandes structures (galaxies, amas de galaxies...) présentes dans l´Univers. Pourrons-nous jamais les observer? L´avenir nous le dira..

- by Alejandro Gangui
- •
- Cosmology, Topological Defects

The main features of how to build a Born's Reciprocal Gravitational theory in curved phase-spaces are developed. By recurring to the nonlinear connection formalism of Finsler geometry a generalized gravitational action in the 8D cotangent space (curved phase space) can be constructed involving sums of 5 distinct types of torsion squared terms and 2 distinct curvature scalars R, S which are associated with the curvature in the horizontal and vertical spaces, respectively. A Kaluza-Klein-like approach to the construction of the curvature of the 8D cotangent space and based on the (torsionless) Levi-Civita connection is provided that yields the observed value of the cosmological constant and the Brans-Dicke-Jordan Gravity action in 4D as two special cases. It is found that the geometry of the momentum space can be linked to the observed value of the cosmological constant when the curvature in momentum space is very large, namely the small size of P is of the order of (1/R Hubble ). Finally we develop a Born's reciprocal complex gravitational theory as a local gauge theory in 8D of the deformed Quaplectic group that is given by the semi-direct product of U(1, 3) with the deformed (noncommutative) Weyl-Heisenberg group involving four noncommutative coordinates and momenta. The metric is complex with symmetric real components and antisymmetric imaginary ones. An action in 8D involving 2 curvature scalars and torsion squared terms is presented.

- by Carlos Castro
- •
- Theoretical Physics, Gravitation, General Relativity, Foundations of Physics

Rather generically, multicomponent superconductors and superfluids have intercomponent current-current interaction. We show that in superconductors with substantially strong intercomponent drag interaction, the topological defects which form in external field are characterized by a skyrmionic topological charge. We then demonstrate that they can be distinguished from ordinary vortex matter by a very characteristic magnetization process due to the dipolar nature of interskyrmion forces. The results provide an experimental signature to confirm or rule out the formation p-wave state with reduced spin stiffness in p-wave superconductors. PACS numbers: 74.25.Ha, 12.39.Dc, 74.25.Uv In multicomponent superconductors and superfluids, the intercomponent current-current interaction is rather generic. It usually assumes the form of the scalar product of supercurrents in the two components F d ∝ J 1 · J 2 . This kind of interaction between components can have various microscopic origins. It was discussed in connection with 3 He-4 He mixtures; 1 components of order parameters of spin-triplet superfluids and superconductors; 2-5 hadronic superfluids in neutron stars; 6-10 in metallic hydrogen and deuterium; 11,12 in ultracold atomic mixtures 13,14 and strongly correlated atomic mixtures in optical lattices. 15 In the later case it was shown that it could be tuned to have arbitrary strength (in relative units). 15 This kind of interaction for example affects rotational response of neutron stars 8 and phase transitions, phase diagrams and rotational response of superfluid mixtures. 12,16-21 Despite the generic character of such interaction, much less is known about its effect on the properties of topological excitations and magnetic response, beyond the simplest London approximation. Especially, little is known about collective properties of such defects. Here, we address this problem. We show that beyond a certain interaction threshold, the topological defects in the system acquire a skyrmionic topological charge. This results in long-range interskyrmion forces which alter dramatically the collective behaviour of vortex matter.

- by Egor Babaev and +1
- •
- Theoretical Physics, Condensed Matter Physics, Superconductivity, Condensed Matter Theory

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

- by Mercedes Paniccia
- •
- Physics, Theoretical Physics, Gravitation, General Relativity

This paper presents a new compression technique and image watermarking algorithm based on Contourlet Transform (CT). For image compression, an energy based quantization is used. Scalar quantization is explored for image watermarking. Double filter bank structure is used in CT. The Laplacian Pyramid (LP) is used to capture the point discontinuities, and then followed by a Directional Filter Bank (DFB) to link point
discontinuities. The coefficients of down sampled low pass version of LP decomposed image are re-ordered in a
pre-determined manner and prediction algorithm is used to reduce entropy (bits/pixel). In addition, the coefficients of CT are quantized based on the energy in the particular band. The superiority of proposed algorithm to JPEG is observed in terms of reduced blocking artifacts. The results are also compared with wavelet transform (WT). Superiority of CT to WT is observed when the image contains more contours. The
watermark image is embedded in the low pass image of contourlet decomposition. The watermark can be
extracted with minimum error. In terms of PSNR, the visual quality of the watermarked image is exceptional.
The proposed algorithm is robust to many image attacks and suitable for copyright protection applications.

We introduce a new class of models of Higgs inflation using the superconformal approach to supergravity by modifying the K\"ahler geometry. Using such a mechanism, we construct a phenomenological functional form of a new K\"ahler potential. From this we construct various types of models which are characterized by a superconformal symmetry breaking parameter chi\chichi, and depending on the numerical values of chi\chichi we classify all of the proposed models into three categories. Models with minimal coupling are identified by chi=pmfrac23\chi=\pm\frac{2}{3}chi=pmfrac23 branch which are made up of shift symmetry preserving flat directions. We also propose various other models by introducing a non-minimal coupling of the inflaton field to gravity described by chineqfrac23\chi\neq\frac{2}{3}chineqfrac23 branch. We employ all these proposed models to study the inflationary paradigm by estimating the major cosmological observables and confront them with recent observational data from WMAP9 and other complementary data sets. We also mention an allowed range of non-minimal couplings and the {\it Yukawa} type of couplings appearing in the proposed models used for cosmological parameter estimation.

- by Sayantan Choudhury and +1
- •
- Mathematical Physics, Cosmology (Physics), Gravitation, Particle Physics

We extend the construction of Born's Reciprocal Relativity theory in ordinary phase spaces to an extended phase space based on Quaternions. The invariance symmetry group is the (pseudo) unitary quaternionic group U (N+, N−, H) which is isomorphic to the unitary symplectic group U Sp(2N+, 2N−, C). It is explicitly shown that the quaternionic group U (N+, N−, H) leaves invariant both the quadratic norm (corresponding to the generalized Born-Green interval in the extended phase space) and the tri-symplectic 2-form. The study of Octonionic, Jordan and ternary algebraic structures associated with generalized spacetimes (and their phase spaces) described by Gunaydin and collaborators is reviewed. A brief discussion on n-plectic manifolds whose Lie n-algebra involves multi-brackets and n-ary algebraic structures follows. We conclude with an analysis on the role of higher-order Finsler geometry in the construction of extended relativity theories with an upper and lower bound to the higher order accelerations (associated with the higher order tangent and cotangent spaces).

- by Carlos Castro Perelman
- •
- Mathematics, Mathematical Physics, Theoretical Physics, Gravitation

Spacetimes that include a boundary at infinity have a non-trivial topology. The homology of the background influences gauge fields living on them and lead to topological charges. We investigate the charges and fluxes of fields over a Taub--NUT background in Einstein--Maxwell dilaton--axion gravity, by using the relative homology and de Rham cohomology. It turns out that the electromagnetic sector is devoid of restrictions from a topological viewpoint. There are, however, flux quanta for the axion and dilaton fields. These results are obtained from the absolute homology of the spacetime boundary. The solutions we probe originate in the four dimensional low energy limit of heterotic string theory. So our results are complemented by the stringy coupling present in the fields. The quantization has a bundle theoretic interpretation as the axion's flux corresponds to the topological index of an underlying 2-bundle.

- by Daniel Flores-Alfonso
- •
- Topological Index, Quantization, Topological Defects

We describe the application of superfluid 3 He at very low temperatures as a highly sensitive bolometer for elementary particles detection. Recently we were able to detect the cosmic muon scattering with energy of 45 KeV: The other important property of superfluid 3 He at very low temperatures is its analogy with quantum vacuum of the Universe. At very rapid superfluid transition in 3 He; follows after a reaction with single neutron, the creation of topological defects (vortices) has been demonstrated in accordance with the Kibble-Zurek scenario for the cosmological analogue. We discuss here the extension of the Kibble-Zurek scenario for the case when alternative symmetries may be broken and different states can be nucleated independently. We have calculated the nucleation probability of the various states of superfluid 3 He during a superfluid transition. The new theory of transition from supercooled A phase to the B phase, triggered by nuclear reaction, have been established. Our theory explains the results of Stanford experiments much better, then well known ''Baked Alaska'' scenario. r

- by Yury Bunkov
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- Condensed Matter Physics, Quantum Physics, Quantum Vacuum, Particle detectors

Classical molecular dynamics with the AIREBO potential is used to investigate and compare the thermal conductivity of both zigzag and armchair graphene nanoribbons possessing various densities of Stone-Thrower-Wales (STW) and double vacancy defects, within a temperature range of 100-600 K. Our results indicate that the presence of both kinds of defects can decrease the thermal conductivity by more than 80% as defect densities are increased to 10% coverage, with the decrease at high defect densities being significantly higher in zigzag compared with armchair nanoribbons. Variations of thermal conductivity in armchair nanoribbons were similar for both kinds of defects, whereas double vacancies in the zigzag nanoribbons led to more significant decreases in thermal conductivity than STW defects. The same trends are observed across the entire temperature range tested.

- by Zishun LIU
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- Molecular Dynamics Simulation, Graphene, Nanotechnology, Multidisciplinary

Smectic order on arbitrary curved substrate can be described by a differential form of rank one (1-form), whose geometric meaning is the differential of the local phase field of the density modulation. The exterior derivative of 1-form is the local dislocation density. Elastic deformations are described by superposition of exact differential forms. We use the formalism of differential forms to systematically classify and characterize all low energy smectic states on torus as well as on sphere. A two dimensional smectic order confined on either manifold exhibits many topologically distinct low energy states. Different states are not accessible from each other by local fluctuations. The total number of low energy states scales as the square root of the system area. We also address the energetics of 2D smectic on a curved substrate and calculate the mean field phase diagram of smectic on a thin torus. Finally, we discuss the motion of disclinations for spherical smectics as low energy excitations, and illustrate the interesting connection between spherical smectic and the theory of elliptic functions.

- by Xiangjun Xing
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- Topology, Statistical Physics, Topological order, Degeneracy

Impurities act as in situ probes of nontrivial electronic structure, causing real-space modulations in the density of states detected by scanning tunneling spectroscopy on the sample surface. We show that distinctive topological features of Weyl semimetals can be revealed in the Fourier transform of this map, interpreted in terms of quasiparticle interference (QPI). We develop an exact Green's function formalism and apply it to generalized models of Weyl semimetals with an explicit surface. The type of perturbation lifting the Dirac node degeneracy to produce the three-dimensional bulk Weyl phase determines the specific QPI signatures appearing on the surface. QPI Fermi arcs may or may not appear, depending on the relative surface orientation and quantum interference effects. Line nodes give rise to tube projections of width controlled by the bias voltage. We consider the effect of crystal warping, distinguishing dispersive arclike features from true Fermi arcs. Finally, we demonstrate that the commonly used joint-density-of-states approach fails qualitatively, and cannot describe QPI extinction.

- by Andrew K Mitchell
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- Physics, Theoretical Physics, Condensed Matter Physics, Solid State Physics

We analyze the possible implications of the discreteness of spacetime, which is defined here as the existence of a minimum observable interval of spacetime. First, it is argued that the discreteness of spacetime may result in the existence of a finite invariant speed when combining with the principle of relativity. Next, it is argued that when combining with the uncertainty principle, the discreteness of space may imply that spacetime is curved by matter, and the dynamical relationship between matter and spacetime holds true not only for macroscopic objects but also for microscopic particles. Moreover, the Einstein gravitational constant can also be determined in terms of the minimum size of discrete spacetime. Thirdly, it is argued that the discreteness of time may result in the dynamical collapse of the wave function, and the minimum size of discrete spacetime also yields a plausible collapse criterion consistent with experiments. These heuristic arguments might provide a deeper understanding of the special and general relativity and quantum theory, and also have implications for the solutions to the measurement problem and the problem of quantum gravity.

- by Shan Gao
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- Physics, Theoretical Physics, Quantum Physics, Philosophy of Physics

Modifications of General Relativity usually include extra dynamical degrees of freedom, which to date remain undetected. Here we explore the possibility of modifying Einstein's theory by adding solely nondynamical fields. With the minimal requirement that the theory satisfies the weak equivalence principle and admits a covariant Lagrangian formulation, we show that the field equations generically have to include higher-order derivatives of the matter fields. This has profound consequences for the viability of these theories. We develop a parametrization based on a derivative expansion and show that - to next to leading order - all theories are described by just two parameters. Our approach can be used to put stringent, theory-independent constraints on such theories, as we demonstrate using the Newtonian limit as an example.

- by Daniele Vernieri
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- Gravitation, General Relativity, Dark Matter, Dark Energy

Matter engenders a Modified Newtonian Gravitational Potential (MNGP) that has a singularity at a two Normalized Spatial Unit (NSU) distance with a modified gravitational field constant in distance > 2 NSU region, and a saturated potential for distance < 2 NSU region. In Cartesian coordinates, a reference object (RO) resides at origin and a test object (TO) resides on the positive region of the X-axis, the interaction energy between the MNGP of the RO in the X>0 region and the X<0 region with the MNGP of the TO is different; This interaction energy imbalance results an E-space Inter-Domain Interaction potential (EIDIP), a scalar potential. Between two irrotational objects, the gradient of the scalar EIDIP produces a vector field, EIDIPd; whereas between two rotational objects, the angular EIDIP produces a different vector field, EIDIPr. The EIDIPd is the source of inter-nucleon nuclear force and inter-molecule covalent bonding force; whereas the EIDIPr vector fields engender the strong force in the inter-atomic range and is responsible for the galaxy rotational velocity anomaly at the interstellar distance. A list of null hypothesis testing node (NHTN), extracted from the EIDIP application model empirical data comparison results, indicates that the EIDIP has 5+ sigma confidence level potential. The EIDIP function, along with the explanatory EIDIP model, could be the missing blocks in completing the Unified theory.

- by Michael Y.T. Hwang
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- Field Theory, Elementary Particle Physics, Gravitation, General Relativity
- by Carlos Castro Perelman
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- Physics, Gravitation, General Relativity, Dark Matter