The Gravitational Field of a Twisted Skyrmion
Hadi, Miftachul; Husein, Andri
2015-01-01
We study nonlinear sigma model, especially Skyrme model without twist and Skyrme model with twist: twisted Skyrme model. Twist term, $mkz$, is indicated in vortex solution. We are interested to construct a space-time containing a string with Lagrangian plus a twist. To add gravity, we replace $\\eta^{\\mu\
Magnetic Field Twisting by Intergranular Downdrafts
Taroyan, Youra; Williams, Thomas
2016-10-01
The interaction of an intergranular downdraft with an embedded vertical magnetic field is examined. It is demonstrated that the downdraft may couple to small magnetic twists leading to an instability. The descending plasma exponentially amplifies the magnetic twists when it decelerates with depth due to increasing density. Most efficient amplification is found in the vicinity of the level, where the kinetic energy density of the downdraft reaches equipartition with the magnetic energy density. Continual extraction of energy from the decelerating plasma and growth in the total azimuthal energy occurs as a consequence of the wave-flow coupling along the downdraft. The presented mechanism may drive vortices and torsional motions that have been detected between granules and in simulations of magnetoconvection.
Twisted boundary states in c=1 coset conformal field theories
Ishikawa, H; Ishikawa, Hiroshi; Yamaguchi, Atsushi
2003-01-01
We study the mutual consistency of twisted boundary conditions in the coset conformal field theory G/H. We calculate the overlap of the twisted boundary states of G/H with the untwisted ones, and show that the twisted boundary states are consistently defined in the diagonal modular invariant. The overlap of the twisted boundary states is expressed by the branching functions of a twisted affine Lie algebra. As a check of our argument, we study the diagonal coset theory so(2n)_1 \\oplus so(2n)_1/so(2n)_2, which is equivalent with the orbifold S^1/\\Z_2. We construct the boundary states twisted by the automorphisms of the unextended Dynkin diagram of so(2n), and show their mutual consistency by identifying their counterpart in the orbifold. For the triality of so(8), the twisted states of the coset theory correspond to neither the Neumann nor the Dirichlet boundary states of the orbifold and yield the conformal boundary states that preserve only the Virasoro algebra.
Noncommutative fields and actions of twisted Poincaré algebra
Chaichian, M.; Kulish, P. P.; Tureanu, A.; Zhang, R. B.; Zhang, Xiao
2008-04-01
Within the context of the twisted Poincaré algebra, there exists no noncommutative analog of the Minkowski space interpreted as the homogeneous space of the Poincaré group quotiented by the Lorentz group. The usual definition of commutative classical fields as sections of associated vector bundles on the homogeneous space does not generalize to the noncommutative setting, and the twisted Poincaré algebra does not act on noncommutative fields in a canonical way. We make a tentative proposal for the definition of noncommutative classical fields of any spin over the Moyal space, which has the desired representation theoretical properties. We also suggest a way to search for noncommutative Minkowski spaces suitable for studying noncommutative field theory with deformed Poincaré symmetries.
Noncommutative fields and actions of twisted Poincare algebra
Chaichian, M; Tureanu, A; Zhang, R B; Zhang, Xiao
2007-01-01
Within the context of the twisted Poincar\\'e algebra, there exists no noncommutative analogue of the Minkowski space interpreted as the homogeneous space of the Poincar\\'e group quotiented by the Lorentz group. The usual definition of commutative classical fields as sections of associated vector bundles on the homogeneous space does not generalise to the noncommutative setting, and the twisted Poincar\\'e algebra does not act on noncommutative fields in a canonical way. We make a tentative proposal for the definition of noncommutative classical fields of any spin over the Moyal space, which has the desired representation theoretical properties. We also suggest a way to search for noncommutative Minkowski spaces suitable for studying noncommutative field theory with deformed Poincar\\'e symmetries.
Twist Field as Three String Interaction Vertex in Light Cone String Field Theory
Kishimoto, Isao; Moriyama, Sanefumi; Teraguchi, Shunsuke
2006-01-01
It has been suggested that matrix string theory and light-cone string field theory are closely related. In this paper, we investigate the relation between the twist field, which represents string interactions in matrix string theory, and the three-string interaction vertex in light-cone string field theory carefully. We find that the three-string interaction vertex can reproduce some of the most important OPEs satisfied by the twist field.
Twist Field as Three String Interaction Vertex in Light Cone String Field Theory
Kishimoto, Isao; Moriyama, Sanefumi; Teraguchi, Shunsuke
2006-01-01
It has been suggested that matrix string theory and light-cone string field theory are closely related. In this paper, we investigate the relation between the twist field, which represents string interactions in matrix string theory, and the three-string interaction vertex in light-cone string field theory carefully. We find that the three-string interaction vertex can reproduce some of the most important OPEs satisfied by the twist field.
Supersymmetric gauged Double Field Theory: Systematic derivation by virtue of \\textit{Twist}
Cho, Wonyoung; Jeon, Imtak; Park, Jeong-Hyuck
2015-01-01
In a completely systematic and geometric way, we derive maximal and half-maximal supersymmetric gauged double field theories in lower than ten dimensions. To this end, we apply a simple twisting ansatz to the $D=10$ ungauged maximal and half-maximal supersymmetric double field theories constructed previously within the so-called semi-covariant formalism. The twisting ansatz may not satisfy the section condition. Nonetheless, all the features of the semi-covariant formalism, including its complete covariantizability, are still valid after the twist under alternative consistency conditions. The twist allows gaugings as supersymmetry preserving deformations of the $D=10$ untwisted theories after Scherk-Schwarz-type dimensional reductions. The maximal supersymmetric twist requires an extra condition to ensure both the Ramond-Ramond gauge symmetry and the $32$ supersymmetries unbroken.
Particle image velocimetry measurements of 2-dimensional velocity field around twisted tape
Energy Technology Data Exchange (ETDEWEB)
Song, Min Seop; Park, So Hyun; Kim, Eung Soo, E-mail: kes7741@snu.ac.kr
2016-11-01
Highlights: • Measurements of the flow field in a pipe with twisted tape were conducted by particle image velocimetry (PIV). • A novel matching index of refraction technique utilizing 3D printing and oil mixture was adopted to make the test section transparent. • Undistorted particle images were clearly captured in the presence of twisted tape. • 2D flow field in the pipe with twisted tape revealed the characteristic two-peak velocity profile. - Abstract: Twisted tape is a passive component used to enhance heat exchange in various devices. It induces swirl flow that increases the mixing of fluid. Thus, ITER selected the twisted tape as one of the candidates for turbulence promoting in the divertor cooling. Previous study was mainly focused on the thermohydraulic performance of the twisted tape. As detailed data on the velocity field around the twisted tape was insufficient, flow visualization study was performed to provide fundamental data on velocity field. To visualize the flow in a complex structure, novel matching index of refraction technique was used with 3-D printing and mixture of anise and mineral oil. This technique enables the camera to capture undistorted particle image for velocity field measurement. Velocity fields at Reynolds number 1370–9591 for 3 different measurement plane were obtained through particle image velocimetry. The 2-dimensional averaged velocity field data were obtained from 177 pair of instantaneous velocity fields. It reveals the characteristic two-peak flow motion in axial direction. In addition, the normalized velocity profiles were converged with increase of Reynolds numbers. Finally, the uncertainty of the result data was analyzed.
Slow twists of solar magnetic flux tubes and the polar magnetic field of the sun
Hollweg, Joseph V.; Lee, Martin A.
1989-01-01
The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric magnetic field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). Magnetic-field components transverse to r do not in general grow to dominate the radial component at large r. The analysis also yields expressions for the Poynting flux associated with the steady twists.
Heavy Pseudoscalar Twist-3 Distribution Amplitudes within QCD Theory in Background Fields
Zhong, Tao; Huang, Tao; Fu, Hai-Bing
2016-01-01
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudo-scalars such as $\\eta_c$, $B_c$ and $\\eta_b$. New sum rules for the twist-3 DA moments $\\left_{\\rm HP}$ and $\\left_{\\rm HP}$ up to sixth orders and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudo-scalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the $B_c\\to\\eta_c$ transition form factor ($f^{B_c\\to\\eta_c}_+(q^2)$) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs $\\phi^P_{3;\\eta_c}$ and $\\phi^\\sigma_{3;\\eta_c}$ are important for a reliable prediction of $f^{B_c\\to\\eta_c}_+(q^2)$. For example, at the maximum recoil region, we have $f^{B_c\\to\\eta_c}_+(0) = 0.674 \\pm 0.066$, in which those two twist-3 terms provide $\\sim3...
Correlation functions of twist fields from Ward identities in the massive Dirac theory
Doyon, Benjamin; Silk, James
2011-07-01
We derive non-linear differential equations for correlation functions of U(1) twist fields in the two-dimensional massive Dirac theory. Primary U(1) twist fields correspond to exponential fields in the sine-Gordon model at the free-fermion point, and it is well-known that their vacuum two-point functions are determined by integrable differential equations. We extend part of this result to more general quantum states (pure or mixed) and to certain descendents, showing that some two-point functions are determined by the sinh-Gordon differential equations whenever there is translation and parity invariance, and the density matrix is the exponential of a bilinear expression in fermions. We use methods involving Ward identities associated to the copy-rotation symmetry in a model with two independent, anti-commuting copies. Such methods were used in the context of the thermally perturbed Ising quantum field theory model. We show that they are applicable to the Dirac theory as well, and we suggest that they are likely to have a much wider applicability to free fermion models in general. Finally, we note that our form-factor study of descendents twist fields combined with a CFT analysis provides a new way of evaluating vacuum expectation values of primary U(1) twist fields: by deriving and solving a recursion relation.
Correlation functions of twist fields from Ward identities in the massive Dirac theory
Energy Technology Data Exchange (ETDEWEB)
Doyon, Benjamin [Department of Mathematics, King' s College London, Strand WC2R 2LS (United Kingdom); Silk, James [Department of Mathematical Sciences, Durham University, Science Laboratories, South Road, Durham DH1 3LE (United Kingdom)
2011-07-22
We derive non-linear differential equations for correlation functions of U(1) twist fields in the two-dimensional massive Dirac theory. Primary U(1) twist fields correspond to exponential fields in the sine-Gordon model at the free-fermion point, and it is well-known that their vacuum two-point functions are determined by integrable differential equations. We extend part of this result to more general quantum states (pure or mixed) and to certain descendents, showing that some two-point functions are determined by the sinh-Gordon differential equations whenever there is translation and parity invariance, and the density matrix is the exponential of a bilinear expression in fermions. We use methods involving Ward identities associated to the copy-rotation symmetry in a model with two independent, anti-commuting copies. Such methods were used in the context of the thermally perturbed Ising quantum field theory model. We show that they are applicable to the Dirac theory as well, and we suggest that they are likely to have a much wider applicability to free fermion models in general. Finally, we note that our form-factor study of descendents twist fields combined with a CFT analysis provides a new way of evaluating vacuum expectation values of primary U(1) twist fields: by deriving and solving a recursion relation.
Branch point twist field correlators in the massive free Boson theory
Bianchini, Davide; Castro-Alvaredo, Olalla A.
2016-12-01
Well-known measures of entanglement in one-dimensional many body quantum systems, such as the entanglement entropy and the logarithmic negativity, may be expressed in terms of the correlation functions of local fields known as branch point twist fields in a replica quantum field theory. In this "replica" approach the computation of measures of entanglement generally involves a mathematically non-trivial analytic continuation in the number of replicas. In this paper we consider two-point functions of twist fields and their analytic continuation in the 1 + 1 dimensional massive (non-compactified) free Boson theory. This is one of the few theories for which all matrix elements of twist fields are known so that we may hope to compute correlation functions very precisely. We study two particular two-point functions which are related to the logarithmic negativity of semi-infinite disjoint intervals and to the entanglement entropy of one interval. We show that our prescription for the analytic continuation yields results which are in full agreement with conformal field theory predictions in the short-distance limit. We provide numerical estimates of universal quantities and their ratios, both in the massless (twist field structure constants) and the massive (expectation values of twist fields) theory. We find that particular ratios are given by divergent form factor expansions. We propose such divergences stem from the presence of logarithmic factors in addition to the expected power-law behaviour of two-point functions at short-distances. Surprisingly, at criticality these corrections give rise to a log (log ℓ) correction to the entanglement entropy of one interval of length ℓ. This hitherto overlooked result is in agreement with results by Calabrese, Cardy and Tonni and has been independently derived by Blondeau-Fournier and Doyon [25].
Mixed-state form factors of U(1) twist fields in the Dirac theory
Chen, Yixiong
2016-08-01
Using the ‘Liouville space’ (the space of operators) of the massive Dirac theory, we define mixed-state form factors of U(1) twist fields. We consider mixed states with density matrices diagonal in the asymptotic particle basis. This includes the thermal Gibbs state as well as all generalized Gibbs ensembles of the Dirac theory. When the mixed state is specialized to a thermal Gibbs state, using a Riemann-Hilbert problem and low-temperature expansion, we obtain finite-temperature form factors of U(1) twist fields. We then propose the expression for form factors of U(1) twist fields in general diagonal mixed states. We verify that these form factors satisfy a system of nonlinear functional differential equations, which is derived from the trace definition of mixed-state form factors. At last, under weak analytic conditions on the eigenvalues of the density matrix, we write down the large distance form factor expansions of two-point correlation functions of these twist fields. Using the relation between the Dirac and Ising models, this provides the large-distance expansion of the Rényi entropy (for integer Rényi parameter) in the Ising model in diagonal mixed states.
Revisiting the Twist-3 Distribution Amplitudes of K Meson Within the QCD Background Field Approach
Institute of Scientific and Technical Information of China (English)
钟涛; 吴兴刚; 韩华勇; 廖其力; 付海斌; 方祯云
2012-01-01
In the present paper, we investigate the kaon twist-3 distribution amplitudes （DAs）Cp within the QCD background field approach. The SUf （3）-breaking effects are studied in detail under a systematical way, especiaJ1y the sum rules for the moments of are obtained by keeping all the mass terms in the s-quark propagator consistently. After adding all the uncertainties in quadrature, the first two Gegenbauler moments of are a GeV. A detailed discussion on the properties tion parameters moments shows that the higher-order s-quark mass terms can indeed provide sizable contributions. Fhrthermore, based on the newly obtained moments, a model for the kaon twist-3 wavefunction with a better end-point behavior is constructed, which shall be useful for perturbative QCD calculations. As a byproduct, we make a discussion on the properties of the pion twist-3 DAs.
Heavy pseudoscalar twist-3 distribution amplitudes within QCD theory in background fields
Energy Technology Data Exchange (ETDEWEB)
Zhong, Tao [Henan Normal University, College of Physics and Materials Science, Xinxiang (China); Wu, Xing-Gang [Chongqing University, Department of Physics, Chongqing (China); Huang, Tao [Chinese Academy of Sciences, Institute of High Energy Physics and Theoretical Physics Center for Science Facilities, Beijing (China); Fu, Hai-Bing [Guizhou Minzu University, School of Science, Guiyang (China)
2016-09-15
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudoscalars such as η{sub c}, B{sub c}, and η{sub b}. New sum rules for the twist-3 DA moments left angle ξ{sup n}{sub P} right angle {sub HP} and left angle ξ{sup n}{sub σ} right angle {sub HP} up to sixth order and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudoscalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the B{sub c} → η{sub c} transition form factor (f{sub +}{sup B{sub c}→η{sub c}}(q{sup 2})) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs φ{sup P}{sub 3;η{sub c}} and φ{sup σ}{sub 3;η{sub c}} are important for a reliable prediction of f{sub +}{sup B{sub c}→η{sub c}}(q{sup 2}). For example, at the maximum recoil region, we have f{sub +}{sup B{sub c}→η{sub c}}(0) = 0.674 ± 0.066, in which those two twist-3 terms provide ∝33 and ∝22% contributions. Also we calculate the branching ratio of the semi-leptonic decay B{sub c} → η{sub c}lν Br(B{sub c} → η{sub c}lν) = (9.31{sup +2.27}{sub -2.01}) x 10{sup -3}. (orig.)
Twisted self-duality for higher spin gauge fields and prepotentials
Henneaux, Marc; Leonard, Amaury
2016-01-01
We show that the equations of motion for (free) integer higher spin gauge fields can be formulated as twisted self-duality conditions on the higher spin curvatures of the spin-$s$ field and its dual. We focus on the case of four spacetime dimensions, but formulate our results in a manner applicable to higher spacetime dimensions. The twisted self-duality conditions are redundant and we exhibit a non-redundant subset of conditions, which have the remarkable property to involve only first-order derivatives with respect to time. This non-redundant subset equates the electric field of the spin-$s$ field (which we define) to the magnetic field of its dual (which we also define), and vice versa. The non-redundant subset of twisted self-duality conditions involve the purely spatial components of the spin-$s$ field and its dual, and also the components of the fields with one zero index. One can get rid of these gauge components by taking the curl of the equations, which does not change their physical content. In this...
Branch Point Twist Field Correlators in the Massive Free Boson Theory
Bianchini, Davide
2016-01-01
Well-known measures of entanglement in one-dimensional many body quantum systems, such as the entanglement entropy and the logarithmic negativity, may be expressed in terms of the correlation functions of local fields known as branch point twist fields in a replica quantum field theory. In this "replica" approach the computation of measures of entanglement generally involves a mathematically non-trivial analytic continuation in the number of replicas. In this paper we consider two-point functions of twist fields and their analytic continuation in the 1+1 dimensional massive (non-compactified) free Boson theory. This is one of the few theories for which all matrix elements of twist fields are known so that we may hope to compute correlation functions very precisely. We study two particular two-point functions which are related to the logarithmic negativity of semi-infinite disjoint intervals and to the entanglement entropy of one interval. We show that our prescription for the analytic continuation yields resu...
Some exact computations on the twisted butterfly state in string field theory
Okawa, Y
2004-01-01
The twisted butterfly state solves the equation of motion of vacuum string field theory in the singular limit. The finiteness of the energy density of the solution is an important issue, but possible conformal anomaly resulting from the twisting has prevented us from addressing this problem. We present a description of the twisted regulated butterfly state in terms of a conformal field theory with a vanishing central charge which consists of the ordinary bc ghosts and a matter system with c=26. Various quantities relevant to vacuum string field theory are computed exactly using this description. We find that the energy density of the solution can be finite in the limit, but the finiteness depends on the subleading structure of vacuum string field theory. We further argue, contrary to our previous expectation, that contributions from subleading terms in the kinetic term to the energy density can be of the same order as the contribution from the leading term which consists of the midpoint ghost insertion.
Twisted Backgrounds, PP-Waves and Nonlocal Field Theories
Alishahiha, M; Alishahiha, Mohsen; Ganor, Ori J.
2003-01-01
We study partially supersymmetric plane-wave like deformations of string theories and M-theory on brane backgrounds. These deformations are dual to nonlocal field theories. We calculate various expectation values of configurations of closed as well as open Wilson loops and Wilson surfaces in those theories. We also discuss the manifestation of the nonlocality structure in the supergravity backgrounds. A plane-wave like deformation of little string theory has also been studied.
Effect of Twisted Fiber Anisotropy in Cardiac Tissue on Ablation with Pulsed Electric Fields
Xie, Fei; Zemlin, Christian W.
2016-01-01
Background Ablation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart. Methods We developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium (“penetrating needles” configuration) and one circular electrode each on epi- and endocardium, opposing each other (“epi-endo” configuration). Results For thick tissues (10 mm) and moderate anisotropy ratio (a = 2), we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10) leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration. For thinner tissues (4 mm, typical for human atria) and higher anisotropy ratio (a = 10), the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist. Conclusions These results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the
Correlation functions of twist fields from Ward identities in the massive Dirac theory
Doyon, Benjamin
2011-01-01
We derive non-linear differential equations for correlation functions of U(1) twist fields in the two-dimensional massive Dirac theory. Primary U(1) twist fields correspond to exponential fields in the sine-Gordon model at the free-fermion point, and it is well-known that their vacuum two-point functions are determined by integrable differential equations. We extend part of this result to more general quantum states (pure or mixed) and to certain descendents, showing that some two-point functions are determined by the sinh-Gordon differential equations whenever there is translation and parity invariance, and the density matrix is the exponential of a bilinear expression in fermions. We use methods involving Ward identities associated to the copy-rotation symmetry in a model with two independent, anti-commuting copies. Such methods were used in the context of the thermally perturbed Ising quantum field theory model. We show that they are applicable to the Dirac theory as well, and we suggest that they are like...
On closed-string twist-field correlators and their open-string descendants
Anastasopoulos, Pascal; Richter, Robert
2011-01-01
In a recent paper we have proposed the possibility that the lightest massive string states could be identified with open strings living at intersections of D-branes forming small angles. In this note, we reconsider the relevant twist-field correlation functions and perform the analysis of the sub-dominant physical poles in the various channels. Our derivation is new in that it is based on the algebraic procedure for the construction of open string models starting from their closed-string `parents' rather than on the stress-tensor method. We also indicate possible generalizations and diverse applications of our approach.
Relativistic models of magnetars: the twisted-torus magnetic field configuration
Ciolfi, R; Gualtieri, L; Pons, J A
2009-01-01
We find general relativistic solutions of equilibrium magnetic field configurations in magnetars, extending previous results of Colaiuda et al. (2008). Our method is based on the solution of the relativistic Grad-Shafranov equation, to which Maxwell's equations can be reduced in some limit. We obtain equilibrium solutions with the toroidal magnetic field component confined into a finite region inside the star, and the poloidal component extending to the exterior. These so-called twisted-torus configurations have been found to be the final outcome of dynamical simulations in the framework of Newtonian gravity, and appear to be more stable than other configurations. The solutions include higher order multipoles, which are coupled to the dominant dipolar field. We use arguments of minimal energy to constrain the ratio of the toroidal to the poloidal field.
Do the Legs of Magnetic Clouds Contain Twisted Flux-rope Magnetic Fields?
Owens, M. J.
2016-02-01
Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.
DO THE LEGS OF MAGNETIC CLOUDS CONTAIN TWISTED FLUX-ROPE MAGNETIC FIELDS?
Energy Technology Data Exchange (ETDEWEB)
Owens, M. J. [Space and Atmospheric Electricity Group, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB (United Kingdom)
2016-02-20
Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
Zhong, Tao; Wang, Zhi-Gang; Huang, Tao; Fu, Hai-Bing; Han, Hua-Yong
2014-01-01
We study the pion leading-twist distribution amplitude (DA) within the framework of SVZ sum rules under the background field theory. To improve the accuracy of the sum rules, we expand both the quark propagator and the vertex $(z\\cdot \\tensor{D})^n$ of the correlator up to dimension-six operators in the background field theory. The sum rules for the pion DA moments are obtained, in which all condensates up to dimension-six have been taken into consideration. Using the sum rules, we obtain $\\left|_{\\rm 1\\;GeV} = 0.338 \\pm 0.032$, $\\left|_{\\rm 1\\;GeV} = 0.211 \\pm 0.030$ and $\\left|_{\\rm 1\\;GeV} = 0.163 \\pm 0.030$. It is shown that the dimension-six condensates shall provide sizable contributions to the pion DA moments. We show that the first Gegenbauer moment of the pion leading-twist DA is $a^\\pi_2|_{\\rm 1\\;GeV} = 0.403 \\pm 0.093$, which is consistent with those obtained in the literature within errors but prefers a larger central value as indicated by lattice QCD predictions.
Fu, Hai-Bing; Cheng, Wei; Zhong, Tao
2016-01-01
We revisit the $\\rho$-meson longitudinal leading-twist distribution amplitude (DA) $\\phi_{2;\\rho}^\\|$ by using the QCD sum rules approach within the background field theory. To improve the accuracy of the sum rules for its moments $\\langle\\xi_{n;\\rho}^\\|\\rangle$, we include the next-to-leading order QCD correction to the perturbative part and keep all non-perturbative condensates up to dimension-six consistently within the background field theory. The first two moments read $\\langle \\xi_{2;\\rho}^\\| \\rangle|_{1{\\rm GeV}} = 0.241(28)$ and $\\langle \\xi_{4;\\rho}^\\| \\rangle|_{1{\\rm GeV}} = 0.108(27)$, indicating a double humped behavior for $\\phi_{2;\\rho}^\\|$ at low $q^2$-region. As an application, we apply them to the $B\\to \\rho $ transition form factors within the QCD light-cone sum rules, which are key components for the decay width $\\Gamma(B\\to \\rho \\ell \
Vacuum Structure of Twisted Scalar Field Theories on $M^{D-1} \\otimes S^{1}$
Hatanaka, H; Ohnishi, K; Sakamoto, M
2001-01-01
We study scalar field theories on M^{D-1} \\otimes S^1, which allow to impose twisted boundary conditions for the S^1 direction, in detail and report several interesting properties overlooked so far. One of characteristic features is the appearance of critical radii of the circle S^1. A phase transition can occur at the classical level or can be caused by quantum effects. Radiative corrections can restore broken symmetries or can break symmetries for small radius. A surprising feature is that the translational invariance for the S^1 direction can spontaneously be broken. A particular class of coordinate-dependent vacuum configurations is clarified and the O(N) \\phi^4 model on M^{D-1}\\otimes S^1 is extensively studied, as an illustrative example.
Emergence of non-twisted magnetic fields in the Sun: Jets and atmospheric response
Syntelis, Petros; Gontikakis, Costis; Tsinganos, Kanaris
2015-01-01
Aims. We study the emergence of a non-twisted flux tube from the solar interior into the solar atmosphere. We investigate whether the length of the buoyant part of the flux tube (i.e. {\\lambda}) affects the emergence of the field and the dynamics of the evolving magnetic flux system. Methods. We perform three-dimensional (3D), time-dependent, resistive, compressible MHD simulations using the Lare3D code. Results. We find that there are considerable differences in the dynamics of the emergence of a magnetic flux tube when {\\lambda} is varied. In the solar interior, for larger values of {\\lambda}, the rising magnetic field emerges faster and expands more due to its lower magnetic tension. As a result, its field strength decreases and its emergence above the photosphere occurs later than in the smaller {\\lambda} case. However, in both cases, the emerging field at the photosphere becomes unstable in two places, forming two magnetic bipoles that interact dynamically during the evolution of the system. Most of the ...
Exact Zero Vacuum Energy in twisted SU(N) Principal Chiral Field
Leurent, Sebastien
2015-01-01
We present a finite set of equations for twisted PCF model. At the special twist in the root of unity we demonstrate that the vacuum energy is exactly zero at any size L. Also in SU(2) case we numerically calculate the energy of the single particle state with zero rapidity, as a function of L.
Exact zero vacuum energy in twisted SU(N) principal chiral field
Energy Technology Data Exchange (ETDEWEB)
Leurent, Sebastien [Univ. de Bourgogne Franche-Comte, Dijon (France). Inst. de Mathematique de Bourgogne; Sobko, Evgeny [DESY, Hamburg (Germany). Theory Group
2015-11-15
We present a finite set of equations for twisted PCF model. At the special twist in the root of unity we demonstrate that the vacuum energy is exactly zero at any size L. Also in SU(2) case we numerically calculate the energy of the single particle state with zero rapidity, as a function of L.
On gl((⌒)2｜2)(2)k Current Superalgebra and Twisted Conformal Field Theory
Institute of Scientific and Technical Information of China (English)
DING Xiang-Mao; WANG Gui-Dong; WANG Shi-Kun
2007-01-01
Motivated by the recently discovered hidden symmetry of the type ∏B Green-Schwarz superstring on certain background, the non-semisimple Kac-Moody twisted superalgebra gl((⌒)2|2)(2)k is investigated by means of the vector coherent state method and boson-fermion realization. The free field realization of the twisted current superalgebra at general level k is constructed. The corresponding Conformal Field Theory (CFT) has zero central charge. According to the classification theory, this CFT is a nonunitary field theory. After projecting out a U(1) factor and an outer automorphism operator, we get the free field representation of psl((⌒)2|2)(2)k, which is the algebra of gl((⌒)2|2)(2)k modulo the Z4-outer automorphism, the CFT has central charge -2.
Generalised twisted partition functions
Petkova, V B
2001-01-01
We consider the set of partition functions that result from the insertion of twist operators compatible with conformal invariance in a given 2D Conformal Field Theory (CFT). A consistency equation, which gives a classification of twists, is written and solved in particular cases. This generalises old results on twisted torus boundary conditions, gives a physical interpretation of Ocneanu's algebraic construction, and might offer a new route to the study of properties of CFT.
ρ -meson longitudinal leading-twist distribution amplitude within QCD background field theory
Fu, Hai-Bing; Wu, Xing-Gang; Cheng, Wei; Zhong, Tao
2016-10-01
We revisit the ρ -meson longitudinal leading-twist distribution amplitude (DA) ϕ2;ρ ∥ by using the QCD sum rules approach within the background field theory. To improve the accuracy of the sum rules for its moments ⟨ξn;ρ ∥⟩ , we include the next-to-leading order QCD correction to the perturbative part and keep all nonperturbative condensates up to dimension-six consistently within the background field theory. The first two moments read ⟨ξ2;ρ ∥⟩|1 GeV=0.241 (28 ) and ⟨ξ4;ρ ∥⟩|1 GeV=0.109 (10 ) , indicating a double humped behavior for ϕ2;ρ ∥ at small energy scale. As an application, we apply them to the B →ρ transition form factors within the QCD light-cone sum rules, which are key components for the decay width Γ (B →ρ ℓνℓ) . To compare with the world average of Γ (B →ρ ℓνℓ) issued by Particle Data Group, we predict |Vub|=3.1 9-0.62+0.65 , which agrees with the BABAR and Omnès parametrization prediction within errors.
Energy Technology Data Exchange (ETDEWEB)
Karami, K. [Department of Physics, University of Kurdistan, Pasdaran Street, Sanandaj (Iran, Islamic Republic of); Bahari, K., E-mail: KKarami@uok.ac.ir, E-mail: K.Bahari@razi.ac.ir [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)
2012-10-01
We consider nonaxisymmetric magnetohydrodynamic (MHD) modes in a zero-beta cylindrical compressible thin magnetic flux tube modeled as a twisted core surrounded by a magnetically twisted annulus, with both embedded in a straight ambient external field. The dispersion relation is derived and solved analytically and numerically to obtain the frequencies of the nonaxisymmetric MHD waves. The main result is that the twisted magnetic annulus does affect the period ratio P{sub 1}/P{sub 2} of the kink modes. For the kink modes, the magnetic twist in the annulus region can achieve deviations from P{sub 1}/P{sub 2} = 2 of the same order of magnitude as in the observations. Furthermore, the effect of the internal twist on the fluting modes is investigated.
CSIR Research Space (South Africa)
Forbes, A
2010-12-01
Full Text Available Research at the Mathematical Optics Group uses "twisted" light to study new quatum-based information security systems. In order to understand the structure of "twisted" light, it is useful to start with an ordinary light beam with zero twist, namely...
Heavy pseudoscalar twist-3 distribution amplitudes within QCD theory in background fields
Zhong, Tao; Wu, Xing-Gang; Huang, Tao; Fu, Hai-Bing
2016-09-01
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudoscalars such as η _c, B_c, and η _b. New sum rules for the twist-3 DA moments Huang-Lepage prescription. Furthermore, we apply them to the B_c→ η _c transition form factor (f^{B_c→ η _c}_+(q^2)) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs φ ^P_{3;η _c} and φ ^σ _{3;η _c} are important for a reliable prediction of f^{B_c→ η _c}_+(q^2). For example, at the maximum recoil region, we have f^{B_c→ η _c}_+(0) = 0.674 ± 0.066, in which those two twist-3 terms provide {˜ }33 and {˜ }22 % contributions. Also we calculate the branching ratio of the semi-leptonic decay B_c → η _c lν as Br(B_c → η _c lν ) = ( 9.31^{+2.27}_{-2.01} ) × 10^{-3}.
Nibbelink, Stefan Groot
2016-01-01
Inspired by the tachyon-free non-supersymmetric heterotic SO(16)xSO(16) string we consider a special class of non-supersymmetric field theories: Those that can be obtained from supersymmetric field theories by supersymmetry breaking twists. We argue that such theories, like their supersymmetric counter parts, may still possess some fermionic symmetries as left-overs of the super gauge transformations and have special one-loop non-renormalization properties due to holomorphicity. In addition, we extend the supergraph techniques to these theories to calculate some explicit supersymmetry-breaking corrections.
Groot Nibbelink, Stefan; Parr, Erik
2016-08-01
Inspired by the tachyon-free nonsupersymmetric heterotic SO (16 )×SO (16 ) string we consider a special class of nonsupersymmetric field theories: those that can be obtained from supersymmetric field theories by supersymmetry-breaking twists. We argue that such theories, like their supersymmetric counterparts, may still possess some fermionic symmetries as leftovers of the supergauge transformations and have special one-loop nonrenormalization properties due to holomorphicity. In addition, we extend the supergraph techniques to these theories to calculate some explicit supersymmetry-breaking corrections.
The $\\epsilon$-expansion of the codimension two twist defect from conformal field theory
Yamaguchi, Satoshi
2016-01-01
We apply the framework of Rychkov-Tan arXiv:1505.00963 to the codimension two twist defect at the Wilson-Fisher fixed point in $4-\\epsilon$ dimensions. We obtain the scaling dimensions of the operators on the defect up to the lowest nontrivial order in the $\\epsilon$-expansion without using Feynman diagram computation. Our results agree with the known results.
The ɛ-expansion of the codimension two twist defect from conformal field theory
Yamaguchi, Satoshi
2016-09-01
We apply the framework of Rychkov and Tan [S. Rychkov and Z. M. Tan, J. Phys. A 48, 29FT01 (2015)] to the codimension two twist defect at the Wilson-Fisher fixed point in 4-ɛ dimensions. We obtain the scaling dimensions of the operators on the defect up to the lowest nontrivial order in the ɛ-expansion without using Feynman diagram computation. Our results agree with the known results.
Force-free Field Modeling of Twist and Braiding-induced Magnetic Energy in an Active-region Corona
Thalmann, J. K.; Tiwari, S. K.; Wiegelmann, T.
2014-01-01
The theoretical concept that braided magnetic field lines in the solar corona may dissipate a sufficient amount of energy to account for the brightening observed in the active-region (AR) corona has only recently been substantiated by high-resolution observations. From the analysis of coronal images obtained with the High Resolution Coronal Imager, first observational evidence of the braiding of magnetic field lines was reported by Cirtain et al. (hereafter CG13). We present nonlinear force-free reconstructions of the associated coronal magnetic field based on Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetograms. We deliver estimates of the free magnetic energy associated with a braided coronal structure. Our model results suggest (~100 times) more free energy at the braiding site than analytically estimated by CG13, strengthening the possibility of the AR corona being heated by field line braiding. We were able to appropriately assess the coronal free energy by using vector field measurements and we attribute the lower energy estimate of CG13 to the underestimated (by a factor of 10) azimuthal field strength. We also quantify the increase in the overall twist of a flare-related flux rope that was noted by CG13. From our models we find that the overall twist of the flux rope increased by about half a turn within 12 minutes. Unlike another method to which we compare our results, we evaluate the winding of the flux rope's constituent field lines around each other purely based on their modeled coronal three-dimensional field line geometry. To our knowledge, this is done for the first time here.
Force-free field modeling of twist and braiding-induced magnetic energy in an active-region corona
Energy Technology Data Exchange (ETDEWEB)
Thalmann, J. K. [Institute of Physics/IGAM, University of Graz, Universitätsplatz 5, A-8010 Graz (Austria); Tiwari, S. K.; Wiegelmann, T., E-mail: julia.thalmann@uni-graz.at [Max Plank Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)
2014-01-01
The theoretical concept that braided magnetic field lines in the solar corona may dissipate a sufficient amount of energy to account for the brightening observed in the active-region (AR) corona has only recently been substantiated by high-resolution observations. From the analysis of coronal images obtained with the High Resolution Coronal Imager, first observational evidence of the braiding of magnetic field lines was reported by Cirtain et al. (hereafter CG13). We present nonlinear force-free reconstructions of the associated coronal magnetic field based on Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetograms. We deliver estimates of the free magnetic energy associated with a braided coronal structure. Our model results suggest (∼100 times) more free energy at the braiding site than analytically estimated by CG13, strengthening the possibility of the AR corona being heated by field line braiding. We were able to appropriately assess the coronal free energy by using vector field measurements and we attribute the lower energy estimate of CG13 to the underestimated (by a factor of 10) azimuthal field strength. We also quantify the increase in the overall twist of a flare-related flux rope that was noted by CG13. From our models we find that the overall twist of the flux rope increased by about half a turn within 12 minutes. Unlike another method to which we compare our results, we evaluate the winding of the flux rope's constituent field lines around each other purely based on their modeled coronal three-dimensional field line geometry. To our knowledge, this is done for the first time here.
Nandy, Dibyendu; Calhoun, A.; Windschitl, J.; Canfield, R. C.; Linton, M. G.
2007-05-01
The twist component of magnetic helicity in solar active regions is known to be an important indicator of sub-photospheric flux tube dynamics and solar eruptive activity. Traditionally, estimates of the parameter alpha -- appearing in the force-free-field equation -- has been used to infer the twist of photospheric active regions. However, the photosphere is not force-free and this has lead to recent concerns on the validity of using the alpha parameter for determining photospheric active region twist. We have devised a new flux-tube-fitting technique for determining the twist of active regions without recourse to the force-free-field equation. This method assumes that the underlying active region flux system is cylindrically symmetric and uniformly twisted. By using this new technique, on a statistically compelling number of photospheric active region vector magnetograms, we re-confirm the hemispheric helicity rule independent of the force-free-field assumption. This research has been supported in parts by a NASA Living With a Star grant NNG05GE47G. A.C. and J.W. were supported by a NSF Research Experience for Undergraduates grant ATM-0243923 to Montana State University. M.G.L. acknowledges support from NASA and the Office of Naval Research.
Twisted radio waves and twisted thermodynamics.
Kish, Laszlo B; Nevels, Robert D
2013-01-01
We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta 'twisted wave' mode, to the far field in free space is therefore not possible.
Dowker, J. S.
2016-04-01
I compute the conformal weights of the twist operators of free scalar fields for charged Rényi entropy in both odd and even dimensions. Explicit expressions can be found, in odd dimensions as a function of the chemical potential in the absence of a conical singularity and thence by images for all integer coverings. This method, developed some time ago, is equivalent, in results, to the replica technique. A review is given. The same method applies for even dimensions but a general form is more immediately available. For no chemical potential, the closed form in the covering order is written in an alternative way related to old trigonometric sums. Some derivatives are obtained. An analytical proof is given of a conjecture made by Bueno, Myers and Witczak-Krempa regarding the relation between the conformal weights and a corner coefficient (a universal quantity) in the Rényi entropy.
Twisted supergravity and its quantization
Costello, Kevin
2016-01-01
Twisted supergravity is supergravity in a background where the bosonic ghost field takes a non-zero value. This is the supergravity counterpart of the familiar concept of twisting supersymmetric field theories. In this paper, we give conjectural descriptions of type IIA and IIB supergravity in $10$ dimensions. Our conjectural descriptions are in terms of the closed-string field theories associated to certain topological string theories, and we conjecture that these topological string theories are twists of the physical string theories. For type IIB, the results of arXiv:1505.6703 show that our candidate twisted supergravity theory admits a unique quantization in perturbation theory. This is despite the fact that the theories, like the original physical theories, are non-renormalizable. Although we do not prove our conjectures, we amass considerable evidence. We find that our candidates for the twisted supergravity theories contain the residual supersymmetry one would expect. We also prove (using heavily a res...
Twisting formula of epsilon factors
Indian Academy of Sciences (India)
SAZZAD ALI BISWAS
2017-09-01
For characters of a non-Archimedean local field we have explicit formula for epsilon factors. But in general, we do not have any generalized twisting formula of epsilon factors. In this paper, we give a generalized twisting formula of epsilon factorsvia local Jacobi sums.
Quinteiro, G F; Kuhn, T
2016-01-01
The formulation of the interaction of matter with singular light fields needs special care. In a recent article [Phys.~Rev.~A {\\bf 91}, 033808 (2015)] we have shown that the Hamiltonian describing the interaction of a twisted light beam having parallel orbital and spin angular momenta with a small object located close to the phase singularity can be expressed only in terms of the electric field of the beam. Here, we complement our studies by providing an interaction Hamiltonian for beams having antiparallel orbital and spin angular momenta. Such beams may exhibit unusually strong magnetic effects. We further extend our formulation to radially and azimuthally polarized beams. The advantages of our formulation are that for all beams the Hamiltonian is written solely in terms of the electric and magnetic fields of the beam and as such it is manifestly gauge-invariant. Furthermore it is intuitive by resembling the well-known expressions in the dipole-electric and dipole-magnetic moment approximations.
Dullin, Holger R
2015-01-01
A complete description of twisting somersaults is given using a reduction to a time-dependent Euler equation for non-rigid body dynamics. The central idea is that after reduction the twisting motion is apparent in a body frame, while the somersaulting (rotation about the fixed angular momentum vector in space) is recovered by a combination of dynamic and geometric phase. In the simplest "kick-model" the number of somersaults $m$ and the number of twists $n$ are obtained through a rational rotation number $W = m/n$ of a (rigid) Euler top. This rotation number is obtained by a slight modification of Montgomery's formula [9] for how much the rigid body has rotated. Using the full model with shape changes that take a realistic time we then derive the master twisting-somersault formula: An exact formula that relates the airborne time of the diver, the time spent in various stages of the dive, the numbers $m$ and $n$, the energy in the stages, and the angular momentum by extending a geometric phase formula due to C...
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and explo
Third and higher order NFPA twisted constructions of conformal field theories from lattices
Energy Technology Data Exchange (ETDEWEB)
Montague, P.S. [Cambridge Univ. (United Kingdom). Dept. of Applied Mathematics and Theoretical Physics (DAMTP)
1995-05-08
We investigate orbifold constructions of conformal field theories from lattices by no-fixed-point automorphisms (NFPAs) Z{sub p} for p prime, p>2, concentrating on the case p=3. Explicit expressions are given for most of the relevant vertex operators, and we consider the locality relations necessary for these to define a consistent conformal field theory. A relation to constructions of lattices from codes, analogous to that found in earlier work in the p=2 case which led to a generalisation of the triality structure of the Monster module, is also demonstrated. ((orig.)).
Third and higher order NFPA twisted constructions of conformal field theories from lattices
Montague, P S
1995-01-01
We investigate orbifold constructions of conformal field theories from lattices by no-fixed-point automorphisms (NFPA's) Z_p for p prime, p>2 concentrating on the case p=3. Explicit expressions are given for most of the relevant vertex operators, and we consider the locality relations necessary for these to define a consistent conformal field theory. A relation to constructions of lattices from codes, analogous to that found in earlier work in the p=2 case which led to a generalisation of the triality structure of the Monster module, is also demonstrated.
Hermann, Keith; Pratumyot, Yaowalak; Polen, Shane; Hardin, Alex M; Dalkilic, Erdin; Dastan, Arif; Badjić, Jovica D
2015-02-23
A preparative procedure for obtaining a pair of twisted molecular baskets, each comprising a chiral framework with either right ((P)-1syn) or left ((M)-1syn) sense of twist and six ester groups at the rim has been developed and optimized. The racemic (P/M)-1syn can be obtained in three synthetic steps from accessible starting materials. The resolution of (P/M)-1syn is accomplished by its transesterification with (1R,2S,5R)-(-)-menthol in the presence of a Ti(IV) catalyst to give diastereomeric 8(P) and 8(M). It was found that dendritic-like cavitands 8(P) and 8(M), in CD2Cl2, undergo self-inclusion ((1)H NMR spectroscopy) with a menthol moiety occupying the cavity of each host. Importantly, the degree of inclusion of the menthol group was ((1)H NMR spectroscopy) found to be greater in the case of 8(P) than 8(M). Accordingly, it is suggested that different folding characteristic of 8(P) and 8(M) ought to affect the physicochemical characteristics of the hosts to permit their effective separation by column chromatography. The absolute configuration of 8(P)/8(M), encompassing right- and left-handed "cups", was determined with the exciton chirality method and also verified in silico (DFT: B3LYP/TZVP). Finally, the twisted baskets are strongly fluorescent due to three naphthalene chromophores, having a high fluorescence quantum yield within the rigid framework of 8(P)/8(M).
Do the legs of magnetic clouds contain twisted flux-rope magnetic fields?
Owens, Mathew
2016-01-01
Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterised primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The tim...
Global Twist of Sunspot Magnetic Fields Obtained from High Resolution Vector Magnetograms
Tiwari, Sanjiv Kumar; Sankarasubramanian, K
2009-01-01
The presence of fine structures in the sunspot vector magnetic fields has been confirmed from Hinode as well as other earlier observations. We studied 43 sunspots based on the data sets taken from ASP/DLSP, Hinode (SOT/SP) and SVM (USO). In this \\emph{Letter}, (i) We introduce the concept of signed shear angle (SSA) for sunspots and establish its importance for non force-free fields. (ii) We find that the sign of global $\\alpha$ (force-free parameter) is well correlated with the global SSA and the photospheric chirality of sunspots. (iii) Local $\\alpha$ patches of opposite signs are present in the umbra of each sunspot. The amplitude of the spatial variation of local $\\alpha$ in the umbra is typically of the order of the global $\\alpha$ of the sunspot. (iv) We find that the local $\\alpha$ is distributed as alternately positive and negative filaments in the penumbra. The amplitude of azimuthal variation of the local $\\alpha$ in the penumbra is approximately an order of magnitude larger than that in the umbra. ...
Twists and turns--How we stepped into and had fun in the "boring" lipid field.
Han, Min
2015-11-01
Compared to proteins and RNAs, functional specificities associated with structural variations in fatty acids and lipids have been greatly underexplored. This review describes how our lab naively started to work on lipids 14 years ago, and how we have gradually overcome obstacles to address some interesting biological questions by combining genetics with biochemical methods on the nematode Caenorhabditis elegans. Our studies have revealed lipid variants and their metabolic pathways, in specific tissues, impact development and behaviors by regulating specific signaling events. The review also discusses the general research approach, style of lab management, and funding mechanisms that have facilitated the frequent research direction changes in the lab, including the journey into the lipid field.
Reweighting twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2015-01-01
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, $\\theta$. As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of $\\theta=\\pi/2$ in a volume $16\\times 8^3$, and we observe a syst...
Aschwanden, Markus J; Nitta, Nariaki V; Lemen, James R; DeRosa, Marc L; Malanushenko, Anna
2012-01-01
The three-dimensional (3D) coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here we use STEREO/A and B data from some 500 stereoscopically triangulated loops observed in four active regions (2007 Apr 30, May 9, May 19, Dec 11), together with SOHO/MDI line-of-sight magnetograms. We measure the average misalignment angle between the stereoscopic loops and theoretical magnetic field models, finding a mismatch of $\\mu=19^\\circ-46^\\circ$ for a potential field model, which is reduced to $\\mu=14^\\circ-19^\\circ$ for a non-potential field model parameterized by twist parameters. The residual error is commensurable with stereoscopic measurement errors ($\\mu_{SE} \\approx 8^\\circ-12^\\circ$). We developed a potential field code that deconvolves a line-of-sight magnetogram into three magnetic field components $(B_x, B_y, B_z)$, as well as a non-potential field forward-fitting code that determines the full length of twisted loops (...
Energy Technology Data Exchange (ETDEWEB)
Lim, Eun-Kyung; Yurchyshyn, Vasyl; Kim, Sujin; Cho, Kyung-Suk; Kumar, Pankaj; Kim, Yeon-Han [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Park, Sung-Hong [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS), National Observatory of Athens, Penteli 15236 (Greece); Chae, Jongchul; Yang, Heesu; Cho, Kyuhyoun; Song, Donguk, E-mail: eklim@kasi.re.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)
2016-01-20
We studied temporal changes of morphological and magnetic properties of a succession of four confined flares followed by an eruptive flare using the high-resolution New Solar Telescope (NST) operating at the Big Bear Solar Observatory (BBSO) and Helioseismic and Magnetic Imager (HMI) magnetograms and Atmospheric Image Assembly (AIA) EUV images provided by the Solar Dynamics Observatory (SDO). From the NST/Hα and the SDO/AIA 304 Å observations we found that each flare developed a jet structure that evolved in a manner similar to evolution of the blowout jet: (1) an inverted-Y-shaped jet appeared and drifted away from its initial position; (2) jets formed a curtain-like structure that consisted of many fine threads accompanied by subsequent brightenings near the footpoints of the fine threads; and finally, (3) the jet showed a twisted structure visible near the flare maximum. Analysis of the HMI data showed that both the negative magnetic flux and the magnetic helicity have been gradually increasing in the positive-polarity region, indicating the continuous injection of magnetic twist before and during the series of flares. Based on these results, we suggest that the continuous emergence of twisted magnetic flux played an important role in producing successive flares and developing a series of blowout jets.
基于FLUENT的内插扭带波纹管内流场分析%Flow Field Analysis of Bellows with Twist Tape Inserts Using FLUENT
Institute of Scientific and Technical Information of China (English)
王晓静; 李文艳; 孙启蒙
2016-01-01
利用流体力学软件FLUENT对波纹管与扭带结合时的流场及传热进行了数值模拟，结合场协同原理考察了不同结构参数和操作参数对流动和传热的影响。结果表明：在入口雷诺数5000~60000，内插扭带波纹管由于扭带的螺旋导流作用，使壁面边界层减薄，在流动区域形成漩涡产生二次流，强化了对流传热过程；插入扭带后的波纹管内的流动仍具有周期性的特点，压降比普通的波纹管增加了2~3倍，且扭率较小时压降较高；场协同角在管子入口处较小，随流动的进行逐渐增大并趋于稳定；协同角随入口速度的增大呈递增趋势；有扭带的波纹管较光管协同角减小了约10%，较普通波纹管减小了约2%，场协同程度随扭率减小而增强。%The object of the study is using CFD software FLUENT to numerically analyze the flow and heat transfer characteristics of bellows with twisted tape inserts within a Reynolds number range of 5000-60000. The convective heat transfer enhancement with different structurals and operating parameters were also investigated by combining field synergy principle. The results show that the velocity boundary layer is thinner and vortexes appear in the vicinity of the twisted tape due to its spiral effect. The secondary flows in the flow regime contribute to the convective heat transfer performance. The periodic flow is also found in bellows with twisted tape inserts. However, its pressure drop is 2~3 times higher than ordinary bellows, and the pressure drop increases with the decrease of twist ratio. The average intersection angle is small at the entrance, and it increases with the development of flow and then becomes stable. The average intersection angle also increases with the increase of entrance velocity. Compared with smooth tubes and normal bellows, the average intersection angle of bellows with twisted tape inserts decreases by about 10% and 2%, respectively, and
Noncommutative geometry in string and twisted Hopf algebra of diffeomorphism
Watamura, Satoshi
2011-09-01
We discuss the Hopf algebra structure in string theory and present the twist quantization as a unified formulation of the world sheet quantization of the string and the symmetry of the target spacetime. Applying it to the case with a nonzero B-field background, we explain a method to decompose the twist into two successive twists. There are two different possibilities of decomposition: The first is a natural decomposition from the viewpoint of the twist quantization, leading to a new type of twisted Poincaré symmetry. The second decomposition reveals the relation of our formulation to the twisted Poincaré symmetry on the Moyal type noncommutative space.
The Twist Limit for Bipolar Active Regions
Moore, Ron; Falconer, David; Gary, Allen
2008-01-01
We present new evidence that further supports the standard idea that active regions are emerged magnetic-flux-rope omega loops. When the axial magnetic twist of a cylindrical flux rope exceeds a critical amount, the flux rope becomes unstable to kinking, and the excess axial twist is converted into writhe twist by the kinking. This suggests that, if active regions are emerged omega loops, then (1) no active region should have magnetic twist much above the limit set by kinking, (2) active regions having twist near the limit should often arise from kinked omega loops, and (3) since active regions having large delta sunspots are outstandingly twisted, these arise from kinked omega loops and should have twist near the limit for kinking. From each of 36 vector magnetograms of bipolar active regions, we have measured (1) the total flux of the vertical field above 100 G, (2) the area covered by this flux, and (3) the net electric current that arches over the polarity inversion line. These three quantities yield an estimate of the axial magnetic twist in a simple model cylindrical flux rope that corresponds to the top of the active region s hypothetical omega loop prior to emergence. In all 36 cases, the estimated twist is below the critical limit for kinking. The 11 most twisted active regions (1) have estimated twist within a factor of approx.3 of the limit, and (2) include all of our 6 active regions having large delta sunspots. Thus, our observed twist limit for bipolar active regions is in good accord with active regions being emerged omega loops.
Polarization twist in perovskite ferrielectrics.
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-02
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of 'polarization twist', which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-07-01
In noncommutative geometry, the spectral triple of a manifold does not generate bosonic fields, for fluctuations of the Dirac operator vanish. A Connes-Moscovici twist forces the commutative algebra to be multiplied by matrices. Keeping the space of spinors untouched, twisted-fluctuations then yield perturbations of the spin connection. Applied to the spectral triple of the Standard Model, a similar twist yields the scalar field needed to stabilize the vacuum and to make the computation of the Higgs mass compatible with its experimental value.
Lim, Eun-Kyung; Park, Sung-Hong; Kim, Sujin; Cho, Kyung-Suk; Kumar, Pankaj; Chae, Jongchul; Yang, Heesu; Cho, Kyuhyoun; Song, Donguk; Kim, Yeon-Han
2015-01-01
We studied temporal changes of morphological and magnetic properties of a succession of four confined flares followed by an eruptive flare using the high-resolution New Solar Telescope (NST) operating at the Big Bear Solar Observatory (BBSO), Helioseismic and Magnetic Imager (HMI) magnetograms and Atmospheric Image Assembly (AIA) EUV images provided by Solar Dynamics Observatory (SDO). From the NST/Halpha and the SDO/AIA~304 A observations we found that each flare developed a jet structure that evolved in a manner similar to evolution of the blowout jet : 1) an inverted-Y shape jet appeared and drifted away from its initial position; 2) jets formed a curtain-like structure that consisted of many fine threads accompanied with subsequent brightenings near the footpoints of the fine threads; and finally 3) the jet showed a twisted structure visible near the flare maximum. Analysis of the HMI data showed that both the negative magnetic flux and the magnetic helicity have been gradually increasing in the positive ...
Twisted Covariant Noncommutative Self-dual Gravity
Estrada-Jimenez, S; Obregón, O; Ramírez, C
2008-01-01
A twisted covariant formulation of noncommutative self-dual gravity is presented. The recent formulation introduced by J. Wess and coworkers for constructing twisted Yang-Mills fields is used. It is shown that the noncommutative torsion is solved at any order of the $\\theta$-expansion in terms of the tetrad and the extra fields of the theory. In the process the first order expansion in $\\theta$ for the Pleba\\'nski action is explicitly obtained.
Casey, E. J.; Commadore, C. C.; Ingles, M. E.
1980-01-01
Long wire bundles twist into uniform spiral harnesses with help of simple apparatus. Wires pass through spacers and through hand-held tool with hole for each wire. Ends are attached to low speed bench motor. As motor turns, operator moves hand tool away forming smooth twists in wires between motor and tool. Technique produces harnesses that generate less radio-frequency interference than do irregularly twisted cables.
Twisted network programming essentials
Fettig, Abe
2005-01-01
Twisted Network Programming Essentials from O'Reilly is a task-oriented look at this new open source, Python-based technology. The book begins with recommendations for various plug-ins and add-ons to enhance the basic package as installed. It then details Twisted's collection simple network protocols, and helper utilities. The book also includes projects that let you try out the Twisted framework for yourself. For example, you'll find examples of using Twisted to build web services applications using the REST architecture, using XML-RPC, and using SOAP. Written for developers who want to s
The gradient flow in a twisted box
Energy Technology Data Exchange (ETDEWEB)
Ramos, Alberto [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2013-08-15
We study the perturbative behavior of the gradient flow in a twisted box. We apply this information to define a running coupling using the energy density of the flow field. We study the step-scaling function and the size of cutoff effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow running coupling scheme is a valid strategy for step-scaling purposes due to the relatively mild cutoff effects and high precision.
Force-free field modeling of twist and braiding-induced magnetic energy in an active-region corona
Thalmann, J K; Wiegelmann, T
2013-01-01
The theoretical concept that braided magnetic field lines in the solar corona may dissipate a sufficient amount of energy to account for the brightening observed in the active-region corona, has been substantiated by high-resolution observations only recently. From the analysis of coronal images obtained with the High Resolution Coronal Imager, first observational evidence of the braiding of magnetic field lines was reported by Cirtain et al. 2013 (hereafter CG13). We present nonlinear force-free reconstructions of the associated coronal magnetic field based on vector SDO/HMI magnetograms. We deliver estimates of the free magnetic energy associated to a braided coronal structure. Our model results suggest (~100 times) more free energy at the braiding site than analytically estimated by CG13, strengthening the possibility of the active-region corona being heated by field line braiding. We were able to assess the coronal free energy appropriately by using vector field measurements and attribute the lower energy...
Overregularity in Oliver Twist
Institute of Scientific and Technical Information of China (English)
孔祥曼
2015-01-01
Oliver Twist is one of the earliest works of Charles Dickens. In this novel, the author uses many writing skills which impress the readers a lot. This paper gives a brief description of overregularity in Oliver Twist at the phonological and syntactical levels.
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-01-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms. PMID:27586824
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Renormalization constants for 2-twist operators in twisted mass QCD
Alexandrou, C; Korzec, T; Panagopoulos, H; Stylianou, F
2010-01-01
Perturbative and non-perturbative results on the renormalization constants of the fermion field and the twist-2 fermion bilinears are presented with emphasis on the non-perturbative evaluation of the one-derivative twist-2 vector and axial vector operators. Non-perturbative results are obtained using the twisted mass Wilson fermion formulation employing two degenerate dynamical quarks and the tree-level Symanzik improved gluon action. The simulations have been performed for pion masses in the range of about 450-260 MeV and at three values of the lattice spacing $a$ corresponding to $\\beta=3.9, 4.05, 4.20$. Subtraction of ${\\cal O}(a^2)$ terms is carried out by performing the perturbative evaluation of these operators at 1-loop and up to ${\\cal O}(a^2)$. The renormalization conditions are defined in the RI$'$-MOM scheme, for both perturbative and non-perturbative results. The renormalization factors, obtained for different values of the renormalization scale, are evolved perturbatively to a reference scale set...
Freed, Daniel S
2012-01-01
We show how general principles of symmetry in quantum mechanics lead to twisted notions of a group representation. This framework generalizes both the classical 3-fold way of real/complex/quaternionic representations as well as a corresponding 10-fold way which has appeared in condensed matter and nuclear physics. We establish a foundation for discussing continuous families of quantum systems. Having done so, topological phases of quantum systems can be defined as deformation classes of continuous families of gapped Hamiltonians. For free particles there is an additional algebraic structure on the deformation classes leading naturally to notions of twisted equivariant K-theory. In systems with a lattice of translational symmetries we show that there is a canonical twisting of the equivariant K-theory of the Brillouin torus. We give precise mathematical definitions of two invariants of the topological phases which have played an important role in the study of topological insulators. Twisted equivariant K-theor...
Institute of Scientific and Technical Information of China (English)
MATHAI; Varghese
2010-01-01
We review the Reidemeister, Ray-Singer’s analytic torsion and the Cheeger-Mller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsion of invariant forms are inverse to each other for any dimension.
Mathai, Varghese
2009-01-01
We review the Reidemeister and Ray-Singer's analytic torsions and the Cheeger-M"uller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsions are inverse to each other for any dimensions.
Twisted Boundary Conditions in Lattice Simulations
Sachrajda, Christopher T C
2004-01-01
By imposing twisted boundary conditions on quark fields it is possible to access components of momenta other than integer multiples of 2pi/L on a lattice with spatial volume L^3. We use Chiral Perturbation Theory to study finite-volume effects with twisted boundary conditions for quantities without final-state interactions, such as meson masses, decay constants and semileptonic form factors, and confirm that they remain exponentially small with the volume. We show that this is also the case for "partially twisted" boundary conditions, in which (some of) the valence quarks satisfy twisted boundary conditions but the sea quarks satisfy periodic boundary conditions. This observation implies that it is not necessary to generate new gluon configurations for every choice of the twist angle, making the method much more practicable. For K->pipi decays we show that the breaking of isospin symmetry by the twisted boundary conditions implies that the amplitudes cannot be determined in general (on this point we disagree ...
Nematic twist cell: Strong chirality induced at the surfaces
Lin, Tzu-Chieh; Nemitz, Ian R.; Pendery, Joel S.; Schubert, Christopher P. J.; Lemieux, Robert P.; Rosenblatt, Charles
2013-04-01
A nematic twist cell having a thickness gradient was filled with a mixture containing a configurationally achiral liquid crystal (LC) and chiral dopant. A chiral-based linear electrooptic effect was observed on application of an ac electric field. This "electroclinic effect" varied monotonically with d, changing sign at d =d0 where the chiral dopant exactly compensated the imposed twist. The results indicate that a significant chiral electrooptic effect always exists near the surfaces of a twist cell containing molecules that can be conformationally deracemized. Additionally, this approach can be used to measure the helical twisting power (HTP) of a chiral dopant in a liquid crystal.
Optical Möbius strips and twisted ribbon cloaks.
Freund, Isaac
2014-02-15
Optical Möbius strips that surround points of circular polarization, C points, in a generic three-dimensional optical field are cloaked by lines of twisted ribbons attached to the C points. When cloaking occurs, the observable signed twist index that counts the number of half-twists (one or three), and also measures the handedness (right or left), of a generic Möbius strip is determined by the twisted ribbon cloaks. Although some cloaks can be detached, they can never all be removed.
Finite-dimensional representations of twisted hyper loop algebras
Bianchi, Angelo
2012-01-01
We investigate the category of finite-dimensional representations of twisted hyper loop algebras, i.e., the hyperalgebras associated to twisted loop algebras over finite-dimensional simple Lie algebras. The main results are the classification of the irreducible modules, the definition of the universal highest-weight modules, called the Weyl modules, and, under a certain mild restriction on the characteristic of the ground field, a proof that the simple modules and the Weyl modules for the twisted hyper loop algebras are isomorphic to appropriate simple and Weyl modules for the non-twisted hyper loop algebras, respectively, via restriction of the action.
Modelling of Nonthermal Microwave Emission From Twisted Magnetic Loops
Sharykin, I N
2016-01-01
Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand impact of the magnetic field twisted topology on resulted radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with peculiar polarization distribution. The polarization sign inversion line is inclined relatively to the axis of the loop. Radio emission source is more compact in the case of less twisted loop, considering anisotropic pitch-angle distribution of nonthermal electrons.
Wilson Loops and Area-Preserving Diffeomorphisms in Twisted Noncommutative Gauge Theory
Riccardi, M; Riccardi, Mauro; Szabo, Richard J.
2007-01-01
We use twist deformation techniques to analyse the behaviour under area-preserving diffeomorphisms of quantum averages of Wilson loops in Yang-Mills theory on the noncommutative plane. We find that while the classical gauge theory is manifestly twist covariant, the holonomy operators break the quantum implementation of the twisted symmetry in the usual formal definition of the twisted quantum field theory. These results are deduced by analysing general criteria which guarantee twist invariance of noncommutative quantum field theories. From this a number of general results are also obtained, such as the twisted symplectic invariance of noncommutative scalar quantum field theories with polynomial interactions and the existence of a large class of holonomy operators with both twisted gauge covariance and twisted symplectic invariance.
Twisted derivations of Hopf algebras
Davydov, Alexei
2012-01-01
In the paper we introduce the notion of twisted derivation of a bialgebra. Twisted derivations appear as infinitesimal symmetries of the category of representations. More precisely they are infinitesimal versions of twisted automorphisms of bialgebras. Twisted derivations naturally form a Lie algebra (the tangent algebra of the group of twisted automorphisms). Moreover this Lie algebra fits into a crossed module (tangent to the crossed module of twisted automorphisms). Here we calculate this crossed module for universal enveloping algebras and for the Sweedler's Hopf algebra.
Landau damping of Langmuir twisted waves with kappa distributed electrons
Energy Technology Data Exchange (ETDEWEB)
Arshad, Kashif, E-mail: kashif.arshad.butt@gmail.com; Aman-ur-Rehman [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Mahmood, Shahzad [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)
2015-11-15
The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].
Multi-twist optical Mobius strips
Freund, Isaac
2009-01-01
Circularly polarized Gauss-Laguerre GL(0,0) and GL(0,1) laser beams that cross at their waists at a small angle are shown to generate a quasi-paraxial field that contains an axial line of circular polarization, a C line, surrounded by polarization ellipses whose major and minor axes generate multi-twist Mobius strips with twist numbers that increase with distance from the C point. These Mobius strips are interpreted in terms of Berry's phase for parallel transport of the ellipse axes around the C point.
Unraveling cellulose microfibrils: a twisted tale.
Hadden, Jodi A; French, Alfred D; Woods, Robert J
2013-10-01
Molecular dynamics (MD) simulations of cellulose microfibrils are pertinent to the paper, textile, and biofuels industries for their unique capacity to characterize dynamic behavior and atomic-level interactions with solvent molecules and cellulase enzymes. While high-resolution crystallographic data have established a solid basis for computational analysis of cellulose, previous work has demonstrated a tendency for modeled microfibrils to diverge from the linear experimental structure and adopt a twisted conformation. Here, we investigate the dependence of this twisting behavior on computational approximations and establish the theoretical basis for its occurrence. We examine the role of solvent, the effect of nonbonded force field parameters [partial charges and van der Waals (vdW) contributions], and the use of explicitly modeled oxygen lone pairs in both the solute and solvent. Findings suggest that microfibril twisting is favored by vdW interactions, and counteracted by both intrachain hydrogen bonds and solvent effects at the microfibril surface.
DEFF Research Database (Denmark)
Yiu, Man Lung; Jensen, Christian Søndergaard; Xuegang, Huang
2008-01-01
-based matching generally fall short in offering practical query accuracy guarantees. Our proposed framework, called SpaceTwist, rectifies these shortcomings for k nearest neighbor (kNN) queries. Starting with a location different from the user's actual location, nearest neighbors are retrieved incrementally...
Wang, Zuoqin
2007-01-01
The "twisted Mellin transform" is a slightly modified version of the usual classical Mellin transform on $L^2(\\mathbb R)$. In this short note we investigate some of its basic properties. From the point of views of combinatorics one of its most important interesting properties is that it intertwines the differential operator, $df/dx$, with its finite difference analogue, $\
Institute of Scientific and Technical Information of China (English)
朱冬生; 石仲璟; 钱泰磊; 谭祥辉; 肖静美
2015-01-01
In order to analyze the effects of geometrical parameters on heat transfer, pressure drop performance and field synergy of both tube side and shell side in twisted oval tube heat exchanger, as well as the convective heat transfer of twisted oval tube heat exchangers with different geometrical parameters, were simulated with Fluent 6.3.26. A user defined function (UDF) was also designed to calculate the included angle between the temperature field and the velocity field, which is referred as field synergy angle. The results show that: (1) Realizablek-εmodel is relatively better than Standard k-εmodel and RNG k-εmodel for the fields simulation of both sides of the tubes in the twisted oval tube heat exchanger. The difference of calculatedNu andf with experimental results are both less than 5%. (2) The heat transfer factor and friction factor are in proportion to axial ratio of the oval tube and in inverse proportion to torque both on tube side and shell side in twisted oval tube heat exchanger. (3) Based on field synergy principle, synergy angle does not change significantly withRe. However, the twisted tubes with different geometrical parameters have different synergy angle on both sides of the tube. The secondary flow optimizes both temperature and velocity distribution, thus the angle between the velocity and temperature field is reduced and heat transfer is enhanced.%为了分析换热管几何参数对扭曲椭圆管换热器管程和壳程的传热与压降性能以及场协同关系的影响，今运用Fluent 6.3.26对不同几何参数的扭曲椭圆管换热器的管内和管外对流传热进行了数值模拟，并编写UDF程序计算温度场与速度场的夹角，即场协同角。结果表明： Realizablek-ε模型相对更好地模拟出扭曲椭圆管换热器管内和管外的流场和温度场，努赛尔数 Nu 以及摩擦系数 f 与实验结果的差别都在5%以内。在扭曲椭圆管换热器的管程和壳程， Nu和f都随着扭曲
Cui, Xiaoyan; Rohl, Andrew L; Shtukenberg, Alexander; Kahr, Bart
2013-03-06
Banded spherulites of aspirin have been crystallized from the melt in the presence of salicylic acid either generated from aspirin decomposition or added deliberately (2.6-35.9 mol %). Scanning electron microscopy, X-ray diffraction analysis, and optical polarimetry show that the spherulites are composed of helicoidal crystallites twisted along the growth directions. Mueller matrix imaging reveals radial oscillations in not only linear birefringence, but also circular birefringence, whose origin is explained through slight (∼1.3°) but systematic splaying of individual lamellae in the film. Strain associated with the replacement of aspirin molecules by salicylic acid molecules in the crystal structure is computed to be large enough to work as the driving force for the twisting of crystallites.
Directory of Open Access Journals (Sweden)
Daijiro Fukuda
2004-01-01
Full Text Available Using diagrammatic pictures of tensor contractions, we consider a Hopf algebra (Aop⊗ℛλA** twisted by an element ℛλ∈A*⊗Aop corresponding to a Hopf algebra morphism λ:A→A. We show that this Hopf algebra is quasitriangular with the universal R-matrix coming from ℛλ when λ2=idA, generalizing the quantum double construction which corresponds to the case λ=idA.
Vranish, John M. (Inventor)
1996-01-01
A planetary gear system includes a sun gear coupled to an annular ring gear through a plurality of twist-planet gears, a speeder gear, and a ground structure having an internal ring gear. Each planet gear includes a solid gear having a first half portion in the form of a spur gear which includes vertical gear teeth and a second half portion in the form of a spur gear which includes helical gear teeth that are offset from the vertical gear teeth and which contact helical gear teeth on the speeder gear and helical gear teeth on the outer ring gear. One half of the twist planet gears are preloaded downward, while the other half are preloaded upwards, each one alternating with the other so that each one twists in a motion opposite to its neighbor when rotated until each planet gear seats against the sun gear, the outer ring gear, the speeder gear, and the inner ring gear. The resulting configuration is an improved stiff anti-backlash gear system.
General relativistic neutron stars with twisted magnetosphere
Pili, A G; Del Zanna, L
2014-01-01
Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-01-01
The Higgs field is a connection one-form as the other bosonic fields, provided one describes space no more as a manifold M but as a slightly non-commutative generalization of it. This is well encoded within the theory of spectral triples: all the bosonic fields of the standard model - including the Higgs - are obtained on the same footing, as fluctuations of a generalized Dirac operator by a matrix-value algebra of functions on M. In the commutative case, fluctuations of the usual free Dirac operator by the complex-value algebra A of smooth functions on M vanish, and so do not generate any bosonic field. We show that imposing a twist in the sense of Connes-Moscovici forces to double the algebra A, but does not require to modify the space of spinors on which it acts. This opens the way to twisted fluctuations of the free Dirac operator, that yield a perturbation of the spin connection. Applied to the standard model, a similar twist yields in addition the extra scalar field needed to stabilize the electroweak v...
Properties of twisted ferromagnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-02-01
The full set of equations for twisted ferromagnetic filaments is derived. The linear stability analysis of twisted ferromagnetic filament is carried out. Two different types of the buckling instability are found - monotonous and oscillatory. The first in the limit of large twist leads to the shape of filament reminding pearls on the string, the second to spontaneous rotation of the filament, which may constitute the working of chiral microengine.
Energy Release in Driven Twisted Coronal Loops
Bareford, M. R.; Gordovskyy, M.; Browning, P. K.; Hood, A. W.
2016-01-01
We investigate magnetic reconnection in twisted magnetic fluxtubes, representing coronal loops. The main goal is to establish the influence of the field geometry and various thermodynamic effects on the stability of twisted fluxtubes and on the size and distribution of heated regions. In particular, we aim to investigate to what extent the earlier idealised models, based on the initially cylindrically symmetric fluxtubes, are different from more realistic models, including the large-scale curvature, atmospheric stratification, thermal conduction and other effects. In addition, we compare the roles of Ohmic heating and shock heating in energy conversion during magnetic reconnection in twisted loops. The models with straight fluxtubes show similar distribution of heated plasma during the reconnection: it initially forms a helical shape, which subsequently becomes very fragmented. The heating in these models is rather uniformly distributed along fluxtubes. At the same time, the hot plasma regions in curved loops are asymmetric and concentrated close to the loop tops. Large-scale curvature has a destabilising influence: less twist is needed for instability. Footpoint convergence normally delays the instability slightly, although in some cases, converging fluxtubes can be less stable. Finally, introducing a stratified atmosphere gives rise to decaying wave propagation, which has a destabilising effect.
Energy Technology Data Exchange (ETDEWEB)
Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-07-15
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Twisting cracks in Bouligand structures.
Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo
2017-06-10
The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.
Geometry of Quantum Group Twists, Multidimensional Jackson Calculus and Regularization
Demichev, A. P.
1995-01-01
We show that R-matricies of all simple quantum groups have the properties which permit to present quantum group twists as transitions to other coordinate frames on quantum spaces. This implies physical equivalence of field theories invariant with respect to q-groups (considered as q-deformed space-time groups of transformations) connected with each other by the twists. Taking into account this freedom we study quantum spaces of the special type: with commuting coordinates but with q-deformed ...
Topological Twisted Sigma Model with H-flux Revisited
Energy Technology Data Exchange (ETDEWEB)
Chuang, Wu-yen
2006-08-18
In this paper we revisit the topological twisted sigma model with H-flux. We explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian geometry. we show that the resulting action consists of a BRST exact term and pullback terms, which only depend on one of the two generalized complex structures and the B-field. We then discuss the topological feature of the model.
Ferromagnetic nanoparticles suspensions in twisted nematic
Cîrtoaje, Cristina; Petrescu, Emil; Stan, Cristina; Creangă, Dorina
2016-05-01
Ferromagnetic nanoparticles insertions in nematic liquid crystals (NLC) in twisted configuration are studied and a theoretical model is proposed to explain the results. Experimental observation revealed that nanoparticles tend to overcrowd in long strings parallel to the rubbing direction of the alignment substrate of the LC cell. Their behavior under external field was studied and their interaction with their nematic host is described using elastic continuum theory.
Twisted bialgebroids versus bialgebroids from a Drinfeld twist
Borowiec, Andrzej; Pachoł, Anna
2017-02-01
Bialgebroids (respectively Hopf algebroids) are bialgebras (Hopf algebras) over noncommutative rings. Drinfeld twist techniques are particularly useful in the (deformation) quantization of Lie algebras as well as the underlying module algebras (=quantum spaces). A smash product construction combines both of them into the new algebra which, in fact, does not depend on the twist. However, we can turn it into a bialgebroid in a twist-dependent way. Alternatively, one can use Drinfeld twist techniques in a category of bialgebroids. We show that both the techniques indicated in the title—the twisting of a bialgebroid or constructing a bialgebroid from the twisted bialgebra—give rise to the same result in the case of a normalized cocycle twist. This can be useful for the better description of a quantum deformed phase space. We argue that within this bialgebroid framework one can justify the use of deformed coordinates (i.e. spacetime noncommutativity), which are frequently postulated in order to explain quantum gravity effects.
Quarks with Twisted Boundary Conditions in the Epsilon Regime
Energy Technology Data Exchange (ETDEWEB)
Thomas Mehen; Brian C. Tiburzi
2005-05-01
We study the effects of twisted boundary conditions on the quark fields in the epsilon regime of chiral perturbation theory. We consider the SU(2){sub L} x SU(2){sub R} chiral theory with non-degenerate quarks and the SU(3){sub L} x SU(3){sub R} chiral theory with massless up and down quarks and massive strange quarks. The partition function and condensate are derived for each theory. Because flavor-neutral Goldstone bosons are unaffected by twisted boundary conditions chiral symmetry is still restored in finite volumes. The dependence of the condensate on the twisting parameters can be used to extract the pion decay constant from simulations in the epsilon regime. The relative contribution to the partition function from sectors of different topological charge is numerically insensitive to twisted boundary conditions.
Twist-induced Magnetosphere Reconfiguration for Intermittent Pulsars
Huang, Lei; Tong, Hao
2016-01-01
We propose that the magnetosphere reconfiguration induced by magnetic twists in the closed field line region can account for the mode-switching of intermittent pulsars. We carefully investigate the properties of axisymmetric force-free pulsar magnetospheres with magnetic twists in closed field line region around the polar caps. The magnetosphere with twisted closed lines leads to enhanced spin-down rates. The enhancement in spin-down rate depends on the size of region with twisted closed lines. Typically, it is increased by a factor of $\\sim2$, which is consistent with the intermittent pulsars' spin down behavior during the `off' and `on' states. We find there is a threshold of maximal twist angle $\\Delta\\phi_{\\rm thres}\\sim1$. The magnetosphere is stable only if the closed line twist angle is less than $\\Delta\\phi_{\\rm thres}$. Beyond this value, the magnetosphere becomes unstable and gets untwisted. The spin-down rate would reduce to its off-state value. The quasi-periodicity in spin-down rate change can be...
Twisted black hole is Taub-NUT
Ong, Yen Chin
2017-01-01
Recently a purportedly novel solution of the vacuum Einstein field equations was discovered: it supposedly describes an asymptotically flat twisted black hole in 4-dimensions whose exterior spacetime rotates in a peculiar manner—the frame dragging in the northern hemisphere is opposite from that of the southern hemisphere, which results in a globally vanishing angular momentum. Furthermore it was shown that the spacetime has no curvature singularity. We show that the geometry of this black hole spacetime is nevertheless not free of pathological features. In particular, it harbors a rather drastic conical singularity along the axis of rotation. In addition, there exist closed timelike curves due to the fact that the constant r and constant t surfaces are not globally Riemannian. In fact, none of these are that surprising since the solution is just the Taub-NUT geometry. As such, despite the original claim that the twisted black hole might have observational consequences, it cannot be.
Tinkertoys for the Twisted D-Series
Chacaltana, Oscar; Trimm, Anderson
2013-01-01
We study 4D N=2 superconformal field theories that arise from the compactification of 6D N=(2,0) theories of type D_N on a Riemann surface, in the presence of punctures twisted by a Z_2 outer automorphism. Unlike the untwisted case, the family of SCFTs is in general parametrized, not by M_{g,n}, but by a branched cover thereof. The classification of these SCFTs is carried out explicitly in the case of the D_4 theory, in terms of three-punctured spheres and cylinders, and we provide tables of properties of twisted punctures for the D_5 and D_6 theories. We find realizations of Spin(8) and Spin(7) gauge theories with matter in all combinations of vector and spinor representations with vanishing beta-function, as well as Sp(3) gauge theories with matter in the 3-index traceless antisymmetric representation.
Grützmann, Melchior; Strobl, Thomas
2015-10-01
Starting with minimal requirements from the physical experience with higher gauge theories, i.e. gauge theories for a tower of differential forms of different form degrees, we discover that all the structural identities governing such theories can be concisely recombined into what is called a Q-structure or, equivalently, an L∞-algebroid. This has many technical and conceptual advantages: complicated higher bundles become just bundles in the category of Q-manifolds in this approach (the many structural identities being encoded in the one operator Q squaring to zero), gauge transformations are generated by internal vertical automorphisms in these bundles and even for a relatively intricate field content the gauge algebra can be determined in some lines and is given by what is called the derived bracket construction. This paper aims equally at mathematicians and theoretical physicists; each more physical section is followed by a purely mathematical one. While the considerations are valid for arbitrary highest form degree p, we pay particular attention to p = 2, i.e. 1- and 2-form gauge fields coupled nonlinearly to scalar fields (0-form fields). The structural identities of the coupled system correspond to a Lie 2-algebroid in this case and we provide different axiomatic descriptions of those, inspired by the application, including e.g. one as a particular kind of a vector-bundle twisted Courant algebroid.
Higher-twist effects in the B → π transition form factor from QCD light-cone sum rules
Energy Technology Data Exchange (ETDEWEB)
Khodjamirian, Alexander; Rusov, Aleksey [Universitaet Siegen (Germany). Fakultaet IV, Department Physik, Theoretische Physik 1 Walter-Flex-Strasse 3 57068 Siegen
2016-07-01
I report on the progress in calculating new higher-twist corrections to the QCD light-cone sum rule for the B → π transition form factor. First, the expansion of the massive heavy-quark propagator in the external gluonic field near the light-cone was extended to include new terms containing the gluon-field strength derivatives. The resulting analytical expressions for the twist-5 and twist-6 contributions to the correlation function were obtained in a factorized approximation, expressed via the product of the quark-condensate density and the lower-twist pion distribution amplitudes. The numerical analysis of new higher-twist effects is in progress.
Equilibrium shapes of twisted magnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cirulis, Teodors; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-06-12
It is shown that ferromagnetic filaments with free and unclamped ends undergo buckling instabilities under the action of twist. Solutions of nonlinear equations describing the buckled shapes are found, and it is shown that the transition to the buckled shape is subcritical if the magnetization is parallel to the field and supercritical when the magnetization of the straight filament is opposite to the external field. Solutions with the localized curvature distribution are found in the case of long filaments. The class of solutions corresponding to helices is described, and the behavior of coiled ferromagnetic and superparamagnetic filaments is compared.
Semantic Deviation in Oliver Twist
Institute of Scientific and Technical Information of China (English)
康艺凡
2016-01-01
Dickens, with his adeptness with language, applies semantic deviation skillfully in his realistic novel Oliver Twist. However, most studies and comments home and abroad on it mainly focus on such aspects as humanity, society, and characters. Therefore, this thesis will take a stylistic approach to Oliver Twist from the perspective of semantic deviation, which is achieved by the use of irony, hyperbole, and pun and analyze how the application of the technique makes the novel attractive.
Role of left ventricular twist mechanics in cardiomyopathies, dance of the helices
Institute of Scientific and Technical Information of China (English)
Floris; Kauer; Marcel; Leonard; Geleijnse; Bastiaan; Martijn; van; Dalen
2015-01-01
Left ventricular twist is an essential part of left ventricular function. Nevertheless, knowledge is limited in "the cardiology community" as it comes to twist mechanics. Fortunately the development of speckle tracking echocardiography, allowing accurate, reproducible and rapid bedside assessment of left ventricular twist, has boosted the interest in this important mechanical aspect of left ventricular deformation. Although the fundamental physiological role of left ventricular twist is undisputable, the clinical relevance of assessment of left ventricular twist in cardiomyopathies still needs to be established. The fact remains; analysis of left ventricular twist mechanics has already provided substantial pathophysiological understanding on a comprehensive variety of cardiomyopathies. It has become clear that increased left ventricular twist in for example hypertrophic cardiomyopathy may be an early sign of subendocardial(microvascular) dysfunction. Furthermore, decreased left ventricular twist may be caused by left ventricular dilatation or an extensive myocardial scar. Finally, the detection of left ventricular rigid body rotation in noncompaction cardiomyopathy may provide an indispensible method to objectively confirm this difficult diagnosis. All this endorses the value of left ventricular twist in the field of cardiomyopathies and may further encourage the implementation of left ventricular twist parameters in the "diagnostic toolbox" for cardiomyopathies.
Speziale, Simone
2013-01-01
We define and investigate a quantisation of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrisation of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with space-like faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalims are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, abelian geometric picture. It can be described by an Euclidean singular structure on the 2-dimensional space-like surface defined by a foliation of space-time by null hypersurfaces. This geometric structure is na...
The trouble with twisting (2,0) theory
Energy Technology Data Exchange (ETDEWEB)
Anderson, Louise; Linander, Hampus [Department of Fundamental Physics, Chalmers University of Technology,S-412 96 Göteborg (Sweden)
2014-03-12
We consider a twisted version of the abelian (2,0) theory placed upon a Lorentzian six-manifold with a product structure, M{sub 6}=C×M{sub 4}. This is done by an investigation of the free tensor multiplet on the level of equations of motion, where the problem of its formulation in Euclidean signature is circumvented by letting the time-like direction lie in the two-manifold C and performing a topological twist along M{sub 4} alone. A compactification on C is shown to be necessary to enable the possibility of finding a topological field theory. The hypothetical twist along a Euclidean C is argued to amount to the correct choice of linear combination of the two supercharges scalar on M{sub 4}. This procedure is expected and conjectured to result in a topological field theory, but we arrive at the surprising conclusion that this twisted theory contains no Q-exact and covariantly conserved stress tensor unless M{sub 4} has vanishing curvature. This is to our knowledge a phenomenon which has not been observed before in topological field theories. In the literature, the setup of the twisting used here has been suggested as the origin of the conjectured AGT-correspondence, and our hope is that this work may somehow contribute to the understanding of it.
Twisted N=4 Super Yang-Mills Theory in Omega-background
Ito, Katsushi; Sasaki, Shin
2013-01-01
We study the twisted N=4 super Yang-Mills theories in the Omega-background with the constant R-symmetry Wilson line gauge field. Based on the classification of topological twists of N=4 supersymmetry (the half, the Vafa-Witten and the Marcus twists), we construct the deformed off-shell supersymmetry associated with the scalar supercharges for these twists. We find that the Omega-deformed action is written in the exact form with respect to the scalar supercharges as in the undeformed case.
Noncommutative geometry, Grand Symmetry and twisted spectral triple
Devastato, Agostino
2015-01-01
In the noncommutative geometry approach to the standard model we discuss the possibility to derive the extra scalar field sv- initially suggested by particle physicist to stabilize the electroweak vacuum - from a "grand algebra" that contains the usual standard model algebra. We introduce the Connes-Moscovici twisted spectral triples for the Grand Symmetry model, to cure a technical problem, that is the appearance, together with the field sv, of unbounded vectorial terms. The twist makes these terms bounded, and also permits to understand the breaking making the computation of the Higgs mass compatible with the 126 GeV experimental value.
Noncommutative geometry, Grand Symmetry and twisted spectral triple
Devastato, Agostino
2015-08-01
In the noncommutative geometry approach to the standard model we discuss the possibility to derive the extra scalar field sv - initially suggested by particle physicist to stabilize the electroweak vacuum - from a “grand algebra” that contains the usual standard model algebra. We introduce the Connes-Moscovici twisted spectral triples for the Grand Symmetry model, to cure a technical problem, that is the appearance, together with the field sv, of unbounded vectorial terms. The twist makes these terms bounded, and also permits to understand the breaking making the computation of the Higgs mass compatible with the 126 GeV experimental value.
Exact special twist method for quantum Monte Carlo simulations
Dagrada, Mario; Karakuzu, Seher; Vildosola, Verónica Laura; Casula, Michele; Sorella, Sandro
2016-12-01
We present a systematic investigation of the special twist method introduced by Rajagopal et al. [Phys. Rev. B 51, 10591 (1995), 10.1103/PhysRevB.51.10591] for reducing finite-size effects in correlated calculations of periodic extended systems with Coulomb interactions and Fermi statistics. We propose a procedure for finding special twist values which, at variance with previous applications of this method, reproduce the energy of the mean-field infinite-size limit solution within an adjustable (arbitrarily small) numerical error. This choice of the special twist is shown to be the most accurate single-twist solution for curing one-body finite-size effects in correlated calculations. For these reasons we dubbed our procedure "exact special twist" (EST). EST only needs a fully converged independent-particles or mean-field calculation within the primitive cell and a simple fit to find the special twist along a specific direction in the Brillouin zone. We first assess the performances of EST in a simple correlated model such as the three-dimensional electron gas. Afterwards, we test its efficiency within ab initio quantum Monte Carlo simulations of metallic elements of increasing complexity. We show that EST displays an overall good performance in reducing finite-size errors comparable to the widely used twist average technique but at a much lower computational cost since it involves the evaluation of just one wave function. We also demonstrate that the EST method shows similar performances in the calculation of correlation functions, such as the ionic forces for structural relaxation and the pair radial distribution function in liquid hydrogen. Our conclusions point to the usefulness of EST for correlated supercell calculations; our method will be particularly relevant when the physical problem under consideration requires large periodic cells.
Design optimization for active twist rotor blades
Mok, Ji Won
This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to
Correlators of arbitrary untwisted operators and excited twist operators for N branes at angles
Directory of Open Access Journals (Sweden)
Igor Pesando
2014-09-01
Full Text Available We compute the generic correlator with L untwisted operators and N (excited twist fields for branes at angles on T2 and show that it is given by a generalization of the Wick theorem. We give also the recipe to compute efficiently the generic OPE between an untwisted operator and an excited twisted state.
Berry phase transition in twisted bilayer graphene
Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.
2016-09-01
The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.
Allanson, O; Neukirch, T
2016-01-01
We calculate exact one-dimensional collisionless plasma equilibria for a continuum of flux tube models, for which the total magnetic field is made up of the `force-free' Gold-Hoyle magnetic flux tube embedded in a uniform and anti-parallel background magnetic field. For a sufficiently weak background magnetic field, the axial component of the total magnetic field reverses at some finite radius. The presence of the background magnetic field means that the total system is not exactly force-free, but by reducing its magnitude the departure from force-free can be made as small as desired. The distribution function for each species is a function of the three constants of motion; namely the Hamiltonian and the canonical momenta in the axial and azimuthal directions. Poisson's Equation and Amp\\`{e}re's Law are solved exactly, and the solution allows either electrically neutral or non-neutral configurations, depending on the values of the bulk ion and electron flows. These equilibria have possible applications in var...
Energy release in driven twisted coronal loops
Bareford, M R; Browning, P K; Hood, A W
2015-01-01
In the present study we investigate magnetic reconnection in twisted magnetic fluxtubes with different initial configurations. In all considered cases, energy release is triggered by the ideal kink instability, which is itself the result of applying footpoint rotation to an initially potential field. The main goal of this work is to establish the influence of the field topology and various thermodynamic effects on the energy release process. Specifically, we investigate convergence of the magnetic field at the loop footpoints, atmospheric stratification, as well as thermal conduction. In all cases, the application of vortical driving at the footpoints of an initally potential field leads to an internal kink instability. With the exception of the curved loop with high footpoint convergence, the global geometry of the loop change little during the simulation. Footpoint convergence, curvature and atmospheric structure clearly influences the rapidity with which a loop achieves instability as well as the size of t...
Twist deformations leading to kappa-Poincare Hopf algebra and their application to physics
Jurić, Tajron; Samsarov, Andjelo
2016-01-01
We consider two twist operators that lead to kappa-Poincare Hopf algebra, the first being an Abelian one and the second corresponding to a light-like kappa-deformation of Poincare algebra. The advantage of the second one is that it is expressed solely in terms of Poincare generators. In contrast to this, the Abelian twist goes out of the boundaries of Poincare algebra and runs into envelope of the general linear algebra. Some of the physical applications of these two different twist operators are considered. In particular, we use the Abelian twist to construct the statistics flip operator compatible with the action of deformed symmetry group. Furthermore, we use the light-like twist operator to define a star product and subsequently to formulate a free scalar field theory compatible with kappa-Poincare Hopf algebra and appropriate for considering the interacting phi^4 scalar field model on kappa-deformed space.
Kinetic study of ion acoustic twisted waves with kappa distributed electrons
Arshad, Kashif; Aman-ur-Rehman, Mahmood, Shahzad
2016-05-01
The kinetic theory of Landau damping of ion acoustic twisted modes is developed in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons and Maxwellian ions. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the ion acoustic twisted waves in a non-thermal plasma. The strong damping effects of ion acoustic twisted waves at low values of temperature ratio of electrons and ions are also obtained by using exact numerical method and illustrated graphically, where the weak damping wave theory fails to explain the phenomenon properly. The obtained results of Landau damping rates of the twisted ion acoustic wave are discussed at different values of azimuthal wave number and non-thermal parameter kappa for electrons.
Drinfel'd basis of twisted Yangians
Belliard, Samuel
2014-01-01
We present a quantization of a Lie bi-ideal structure for twisted half-loop algebras of finite dimensional simple complex Lie algebras. We obtain Drinfel'd basis formalism and algebra closure relations of twisted Yangians for all symmetric pairs of simple Lie algebras and for simple twisted even half-loop Lie algebras. We also give an explicit form of twisted Yangians in Drinfel'd basis for the sl3 Lie algebra.
The trouble with twisting (2,0) theory
Anderson, Louise
2013-01-01
We consider a twisted version of the abelian (2,0) theory placed upon a Lorenzian six-manifold with a product structure, $M_6=C \\times M_4 $. This is done by an investigation of the free tensor multiplet on the level of equations of motion, where the problem of its formulation in Euclidean signature is circumvented by letting the time-like direction lie in the two-manifold $C$ and performing a topological twist along $M_4$ alone. A compactification on $C$ is shown to be necessary to enable the possibility of finding a topological field theory. The hypothetical twist along a Euclidean $C$ is argued to amount to the correct choice of linear combination of the two supercharges scalar on $M_4$. It may be slightly surprising that this is not the same linear combination as in the well known Donaldson-Witten twist. A more surprising fact however, is that this twisted theory contains no $Q$-exact and covariantly conserved stress tensor unless $M_4$ has vanishing curvature. This is to our knowledge a phenomenon which ...
Interfacial Atomic Structure of Twisted Few-Layer Graphene.
Ishikawa, Ryo; Lugg, Nathan R; Inoue, Kazutoshi; Sawada, Hidetaka; Taniguchi, Takashi; Shibata, Naoya; Ikuhara, Yuichi
2016-02-18
A twist in bi- or few-layer graphene breaks the local symmetry, introducing a number of intriguing physical properties such as opening new bandgaps. Therefore, determining the twisted atomic structure is critical to understanding and controlling the functional properties of graphene. Combining low-angle annular dark-field electron microscopy with image simulations, we directly determine the atomic structure of twisted few-layer graphene in terms of a moiré superstructure which is parameterized by a single twist angle and lattice constant. This method is shown to be a powerful tool for accurately determining the atomic structure of two-dimensional materials such as graphene, even in the presence of experimental errors. Using coincidence-site-lattice and displacement-shift-complete theories, we show that the in-plane translation state between layers is not a significant structure parameter, explaining why the present method is adequate not only for bilayer graphene but also a few-layered twisted graphene.
Interfacial Atomic Structure of Twisted Few-Layer Graphene
Ishikawa, Ryo; Lugg, Nathan R.; Inoue, Kazutoshi; Sawada, Hidetaka; Taniguchi, Takashi; Shibata, Naoya; Ikuhara, Yuichi
2016-02-01
A twist in bi- or few-layer graphene breaks the local symmetry, introducing a number of intriguing physical properties such as opening new bandgaps. Therefore, determining the twisted atomic structure is critical to understanding and controlling the functional properties of graphene. Combining low-angle annular dark-field electron microscopy with image simulations, we directly determine the atomic structure of twisted few-layer graphene in terms of a moiré superstructure which is parameterized by a single twist angle and lattice constant. This method is shown to be a powerful tool for accurately determining the atomic structure of two-dimensional materials such as graphene, even in the presence of experimental errors. Using coincidence-site-lattice and displacement-shift-complete theories, we show that the in-plane translation state between layers is not a significant structure parameter, explaining why the present method is adequate not only for bilayer graphene but also a few-layered twisted graphene.
Stability Analysis of The Twisted Superconducting Semilocal Strings
Garaud, Julien
2007-01-01
We study the stability properties of the twisted vortex solutions in the semilocal Abelian Higgs model with a global $\\mathbf{SU}(2)$ invariance. This model can be viewed as the Weinberg-Salam theory in the limit where the non-Abelian gauge field decouples, or as a two component Ginzburg-Landau theory. The twisted vortices are characterized by a constant global current ${\\cal I}$, and for ${\\cal I}\\to 0$ they reduce to the semilocal strings, that is to the Abrikosov-Nielsen-Olesen vortices embedded into the semilocal model. Solutions with ${\\cal I}\
Twisting Fluorescence through Extrinsic Chiral Antennas.
Yan, Chen; Wang, Xiaolong; Raziman, T V; Martin, Olivier J F
2017-03-22
Plasmonic antennas and planar structures have been undergoing intensive developments in order to control the scattering and absorption of light. One specific class, extrinsic chiral surfaces, that does not possess 2-fold rotational symmetry exhibits strong asymmetric transmission for different circular polarizations under obliquely incident illumination. In this work, we show that the design of those surfaces can be optimized with complex multipolar resonances in order to twist the fluorescence emission from nearby molecules. While this emission is usually dipolar and linearly polarized, the interaction with these resonances twists it into a multipolar radiation pattern with opposite helicity in different directions. The proposed structure maximizes this effect and provides control over the polarization of light. Splitting of left- and right-handed circularly polarized light is experimentally obtained in the backward direction. These results highlight the intricate interplay between the near-field absorption and the far-field scattering of a plasmonic nanostructure and are further used for modifying the emission of incoherent quantum sources. Our finding can potentially lead to the development of polarization- and angle-resolved ultracompact optical devices.
Twisted Alexander polynomials of hyperbolic knots
Dunfield, Nathan M; Jackson, Nicholas
2011-01-01
We study a twisted Alexander polynomial naturally associated to a hyperbolic knot in an integer homology 3-sphere via a lift of the holonomy representation to SL(2, C). It is an unambiguous symmetric Laurent polynomial whose coefficients lie in the trace field of the knot. It contains information about genus, fibering, and chirality, and moreover is powerful enough to sometimes detect mutation. We calculated this invariant numerically for all 313,209 hyperbolic knots in S^3 with at most 15 crossings, and found that in all cases it gave a sharp bound on the genus of the knot and determined both fibering and chirality. We also study how such twisted Alexander polynomials vary as one moves around in an irreducible component X_0 of the SL(2, C)-character variety of the knot group. We show how to understand all of these polynomials at once in terms of a polynomial whose coefficients lie in the function field of X_0. We use this to help explain some of the patterns observed for knots in S^3, and explore a potential...
Properly twisted groups and their algebras
Bales, John W
2011-01-01
A twist property is developed which imparts certain properties on the twisted group algebra. These include an involution * satisfying (xy)*=y*x* and an inner product satisfying = and =. Examples of twisted group algebras having this property are the Cayley-Dickson algebras and Clifford algebras.
Bend-twist coupling potential of wind turbine blades
DEFF Research Database (Denmark)
Fedorov, Vladimir; Berggreen, Christian
2014-01-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed...... and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend......-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling...
"Oliver Twist": A Teacher's Guide.
Cashion, Carol; Fischer, Diana
This teacher's guide for public television's 3-part adaptation of Charles Dickens's "Oliver Twist" provides information that will help enrich students' viewing of the series, whether or not they read the novel. The guide includes a wide range of discussion and activity ideas; there is also a series Web site and a list of Web resources.…
Helically twisted photonic crystal fibres.
Russell, P St J; Beravat, R; Wong, G K L
2017-02-28
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic 'space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of 'numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Authors.
Helically twisted photonic crystal fibres
Russell, P. St. J.; Beravat, R.; Wong, G. K. L.
2017-02-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic `space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of `numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue 'Optical orbital angular momentum'.
Helically twisted photonic crystal fibres
Beravat, R.; Wong, G. K. L.
2017-01-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic ‘space’, cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of ‘numerical experiments’ based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069771
Indian Academy of Sciences (India)
Ziauddin Khan; Ananya Kundu; Subrata Pradhan
2013-10-01
Critical current (c) characteristics of 2G YBCO superconducting tape under the influence of twisting moment was experimentally investigated at varying current ramp rates in the self-field. Under a uniform twist, the degradation in the current-carrying capacity of YBCO tape up to 30% was observed at 77 K. The degradation is largely attributed to the shear stress and torsional shear strain resulting from the twisting. The superconductor to resistive transition index, , is also found to behave in an identical manner with increase in the twisting. Finite element analysis (FEA) of the tape in the experimental configuration with twisting moment being applied on to it has been carried out in COMSOL. The torsional strain calculated analytically as per the experimental configuration matches closely with that of FEA results, which shows that the critical current degradation is a function of strain.
The twist box domain is required for Twist1-induced prostate cancer metastasis.
Gajula, Rajendra P; Chettiar, Sivarajan T; Williams, Russell D; Thiyagarajan, Saravanan; Kato, Yoshinori; Aziz, Khaled; Wang, Ruoqi; Gandhi, Nishant; Wild, Aaron T; Vesuna, Farhad; Ma, Jinfang; Salih, Tarek; Cades, Jessica; Fertig, Elana; Biswal, Shyam; Burns, Timothy F; Chung, Christine H; Rudin, Charles M; Herman, Joseph M; Hales, Russell K; Raman, Venu; An, Steven S; Tran, Phuoc T
2013-11-01
Twist1, a basic helix-loop-helix transcription factor, plays a key role during development and is a master regulator of the epithelial-mesenchymal transition (EMT) that promotes cancer metastasis. Structure-function relationships of Twist1 to cancer-related phenotypes are underappreciated, so we studied the requirement of the conserved Twist box domain for metastatic phenotypes in prostate cancer. Evidence suggests that Twist1 is overexpressed in clinical specimens and correlated with aggressive/metastatic disease. Therefore, we examined a transactivation mutant, Twist1-F191G, in prostate cancer cells using in vitro assays, which mimic various stages of metastasis. Twist1 overexpression led to elevated cytoskeletal stiffness and cell traction forces at the migratory edge of cells based on biophysical single-cell measurements. Twist1 conferred additional cellular properties associated with cancer cell metastasis including increased migration, invasion, anoikis resistance, and anchorage-independent growth. The Twist box mutant was defective for these Twist1 phenotypes in vitro. Importantly, we observed a high frequency of Twist1-induced metastatic lung tumors and extrathoracic metastases in vivo using the experimental lung metastasis assay. The Twist box was required for prostate cancer cells to colonize metastatic lung lesions and extrathoracic metastases. Comparative genomic profiling revealed transcriptional programs directed by the Twist box that were associated with cancer progression, such as Hoxa9. Mechanistically, Twist1 bound to the Hoxa9 promoter and positively regulated Hoxa9 expression in prostate cancer cells. Finally, Hoxa9 was important for Twist1-induced cellular phenotypes associated with metastasis. These data suggest that the Twist box domain is required for Twist1 transcriptional programs and prostate cancer metastasis. Targeting the Twist box domain of Twist1 may effectively limit prostate cancer metastatic potential. ©2013 AACR.
Experiments with twisted light
Courtial, J.; O'Holleran, K.
2007-06-01
The generic that is, stable under perturbations nodes of the field in a monochromatic light beam are optical vortices. We describe here their connection to Chladni's nodal lines in the oscillations of metal plates, as well as a few experiments that have been performed with optical vortices. We will describe how optical vortices can be generated experimentally; how it can be shown that they possess orbital angular momentum; how individual photons can be sorted according to their vortex state; and how optical vortices can be used to demonstrate higher-dimensional quantum entanglement.
"Twisted" black holes are unphysical
Gray, Finnian; Schuster, Sebastian; Visser, Matt
2016-01-01
So-called "twisted" black holes have recently been proposed by Zhang (1609.09721 [gr-qc]), and further considered by Chen and Jing (1610.00886 [gr-qc]), and more recently by Ong (1610.05757 [gr-qc]). While these spacetimes are certainly Ricci-flat, and so mathematically satisfy the vacuum Einstein equations, they are also merely minor variants on Taub--NUT spacetimes. Consequently they exhibit several unphysical features that make them quite unreasonable as realistic astrophysical objects. Specifically, these "twisted" black holes are not (globally) asymptotically flat. Furthermore, they contain closed timelike curves that are not hidden behind any event horizon --- the most obvious of these closed timelike curves are small azimuthal circles around the rotation axis, but the effect is more general. The entire region outside the horizon is infested with closed timelike curves.
ON THE SATURATION BEHAVIOUR OF TWISTED NEMATIC LIQUID CRYSTAL CELLS WITH A NONZERO PRETILT ANGLE
Institute of Scientific and Technical Information of China (English)
ZHANG ZHI-DONG; YU HUI; LI LI
2001-01-01
Equations are obtained for the surface tilt angle and the twist angle of the director in a twisted nematic liquid crystal cell under a high magnetic field. Under a zero pretilt angle, the two equations reduce to those obtained by Sugimura et al.[2,3] This fact has also been demonstrated numerically. With finite field strength and nonzero pretilt angle, no saturation transition exists.
Twisted Chern-Simons supergravity
Energy Technology Data Exchange (ETDEWEB)
Castellani, L. [Dipartimento di Scienze e Innovazione Tecnologica, Univ. del Piemonte Orientale, Alessandria (Italy); INFN Gruppo collegato di Alessandria (Italy)
2014-09-11
We present a noncommutative version of D = 5 Chern-Simons supergravity, where noncommutativity is encoded in a *-product associated to an abelian Drinfeld twist. The theory is invariant under diffeomorphisms, and under the *-gauge supergroup SU(2,2 vertical stroke 4), including Lorentz and N = 4 local supersymmetries. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Counting Polyominoes on Twisted Cylinders
Barequet, Gill; Moffie, Micha; Ribó, Ares; Rote, Günter
2005-01-01
International audience; We improve the lower bounds on Klarner's constant, which describes the exponential growth rate of the number of polyominoes (connected subsets of grid squares) with a given number of squares. We achieve this by analyzing polyominoes on a different surface, a so-called $\\textit{twisted cylinder}$ by the transfer matrix method. A bijective representation of the "states'' of partial solutions is crucial for allowing a compact representation of the successive iteration vec...
New twist on artificial muscles
Haines, Carter S.; Li, Na; Spinks, Geoffrey M.; Aliev, Ali E.; Di, Jiangtao; Baughman, Ray H.
2016-01-01
Lightweight artificial muscle fibers that can match the large tensile stroke of natural muscles have been elusive. In particular, low stroke, limited cycle life, and inefficient energy conversion have combined with high cost and hysteretic performance to restrict practical use. In recent years, a new class of artificial muscles, based on highly twisted fibers, has emerged that can deliver more than 2,000 J/kg of specific work during muscle contraction, compared with just 40 J/kg for natural muscle. Thermally actuated muscles made from ordinary polymer fibers can deliver long-life, hysteresis-free tensile strokes of more than 30% and torsional actuation capable of spinning a paddle at speeds of more than 100,000 rpm. In this perspective, we explore the mechanisms and potential applications of present twisted fiber muscles and the future opportunities and challenges for developing twisted muscles having improved cycle rates, efficiencies, and functionality. We also demonstrate artificial muscle sewing threads and textiles and coiled structures that exhibit nearly unlimited actuation strokes. In addition to robotics and prosthetics, future applications include smart textiles that change breathability in response to temperature and moisture and window shutters that automatically open and close to conserve energy. PMID:27671626
Obregón, O; Ryan, M P; Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.
2004-01-01
We construct a family of time and angular dependent, regular S-brane solutions which corresponds to a simple analytical continuation of the Zipoy-Voorhees 4-dimensional vacuum spacetime. The solutions are asymptotically flat and turn out to be free of singularities without requiring a twist in space. They can be considered as the simplest non-singular generalization of the singular S0-brane solution. We analyze the properties of a representative of this family of solutions and show that it resembles to some extent the asymptotic properties of the regular Kerr S-brane. The R-symmetry corresponds, however, to the general Lorentzian symmetry. Several generalizations of this regular solution are derived which include a charged S-brane and an additional dilatonic field.
Optical twists in phase and amplitude
DEFF Research Database (Denmark)
Daria, Vincent R.; Palima, Darwin; Glückstad, Jesper
2011-01-01
beams, the far field projection of the twisted optical beam maintains a high photon concentration even at higher values of topological charge. Optical twisters have therefore profound applications to fundamental studies of light and atoms such as in quantum entanglement of the OAM, toroidal traps......Light beams with helical phase profile correspond to photons having orbital angular momentum (OAM). A Laguerre-Gaussian (LG) beam is an example where its helical phase sets a phase-singularity at the optical axis and forms a ring-shaped transverse amplitude profile. Here, we describe a unique beam...... where both phase and amplitude express a helical profile as the beam propagates in free space. Such a beam can be accurately referred to as an optical twister. We characterize optical twisters and demonstrate their capacity to induce spiral motion on particles trapped along the twisters’ path. Unlike LG...
Twisted Black Hole Is Taub-NUT
Ong, Yen Chin
2016-01-01
Recently a purportedly novel solution of the vacuum Einstein field equations was discovered: it supposedly describes an asymptotically flat twisted black hole in 4-dimensions whose exterior spacetime rotates in a peculiar manner -- the frame dragging in the northern hemisphere is opposite from that of the southern hemisphere, which results in a globally vanishing angular momentum. Furthermore it was shown that the spacetime has no curvature singularity. We show that the geometry of this black hole spacetime is nevertheless not free of pathological features. In particular, it harbors a rather drastic conical singularity along the axis of rotation. In addition, there exist closed timelike curves due to the fact that the constant r and constant t surfaces are not globally Riemannian. In fact, none of these are that surprising since the solution is just the Taub-NUT geometry.
Noncommutative principal bundles through twist deformation
Aschieri, Paolo; Pagani, Chiara; Schenkel, Alexander
2016-01-01
We construct noncommutative principal bundles deforming principal bundles with a Drinfeld twist (2-cocycle). If the twist is associated with the structure group then we have a deformation of the fibers. If the twist is associated with the automorphism group of the principal bundle, then we obtain noncommutative deformations of the base space as well. Combining the two twist deformations we obtain noncommutative principal bundles with both noncommutative fibers and base space. More in general, the natural isomorphisms proving the equivalence of a closed monoidal category of modules and its twist related one are used to obtain new Hopf-Galois extensions as twists of Hopf-Galois extensions. A sheaf approach is also considered, and examples presented.
DVCS amplitude with kinematical twist-3 terms
Radyushkin, A V
2000-01-01
We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.
On the twists of interplanetary magnetic flux ropes observed at 1 AU
Wang, Yuming; Zhuang, Bin; Hu, Qiang; Liu, Rui; Shen, Chenglong; Chi, Yutian
2016-01-01
Magnetic flux ropes (MFRs) are one kind of fundamental structures in the solar physics, and involved in various eruption phenomena. Twist, characterizing how the magnetic field lines wind around a main axis, is an intrinsic property of MFRs, closely related to the magnetic free energy and stableness. So far it is unclear how much amount of twist is carried by MFRs in the solar atmosphere and in heliosphere and what role the twist played in the eruptions of MFRs. Contrasting to the solar MFRs,...
Quinteiro, G F; Kuhn, T
2014-01-01
Twisted light is light carrying orbital angular momentum. The profile of such a beam is a ring-like structure with a node at the beam axis, where a phase singularity exits. Due to the strong spatial inhomogeneity the mathematical description of twisted light-matter interaction is non-trivial, in particular at the phase singularity, where the commonly used dipole-moment approximation cannot be applied. In this paper we show theoretically that, if the polarization and the orbital angular momentum of the twisted light beam have the same sign, a Hamiltonian similar to the dipole-moment approximation can be derived. However, if the signs of polarization and orbital angular momentum differ, the magnetic parts of the light beam become of significant importance and an interaction Hamiltonian which only accounts for electric fields, as in the dipole moment approximation, is inappropriate. We discuss the consequences of these findings for twisted light excitation of semiconductor nanostructures, e. g. a quantum dot, pl...
Twisted conjugacy in braid groups
González-Meneses, Juan
2011-01-01
In this note we solve the twisted conjugacy problem for braid groups, i.e. we propose an algorithm which, given two braids $u,v\\in B_n$ and an automorphism $\\phi \\in Aut (B_n)$, decides whether $v=(\\phi (x))^{-1}ux$ for some $x\\in B_n$. As a corollary, we deduce that each group of the form $B_n \\rtimes H$, a semidirect product of the braid group $B_n$ by a torsion-free hyperbolic group $H$, has solvable conjugacy problem.
Do twisted laser beams evoke nuclear hyperpolarization?
Schmidt, A. B.; Andrews, D. L.; Rohrbach, A.; Gohn-Kreuz, C.; Shatokhin, V. N.; Kiselev, V. G.; Hennig, J.; von Elverfeldt, D.; Hövener, J.-B.
2016-07-01
The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5 nm and various topological charges. We acquired 1H and 19F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5 mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be
A laser speckle sensor to measure the distribution of static torsion angles of twisted targets
DEFF Research Database (Denmark)
Rose, B.; Imam, H.; Hanson, Steen Grüner
1998-01-01
A novel method for measuring the distribution of static torsion angles of twisted targets is presented. The method is based on Fourier transforming the scattered field in the direction perpendicular to the twist axis, while performing an imaging operation in the direction parallel to the axis....... The Fourier transform serves to map the angular distribution of the scattered light field at the target into a linear displacement on a two-dimensional array image sensor placed in the Fourier plane. Measuring this displacement facilitates the determination of the angular displacement of the target....... A cylindrical lens serves to image the closely spaced lateral positions of the target along the twist axis onto corresponding lines of the two dimensional image sensor. Thus, every single line of the image sensor measures the torsion angle of the corresponding surface position along the twist axis of the target...
Thermal and non-thermal emission from reconnecting twisted coronal loops
Pinto, R; Browning, P K; Vilmer, N
2016-01-01
Twisted magnetic fields should be ubiquitous in the solar corona. The magnetic energy contained in such twisted fields can be released during solar flares and other explosive phenomena. Reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops, and can be a viable alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. The goal of this study is to investigate the observational signatures of plasma heating and particle acceleration in kink-unstable twisted coronal loops using combination of MHD simulations and test-particle methods. The simulations describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD, and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us est...
Energy Technology Data Exchange (ETDEWEB)
Wilson, Joshua Lee [Univ. of Tennessee, Knoxville, TN (United States)
2008-12-01
A new class of accelerating structures employing a uniformly twisted waveguide is investigated. Twisted waveguides of various cross-sectional geometries are considered and analyzed. It is shown that such a twisted waveguide can support waves that travel at a speed slower than the speed of light c. The slow-wave properties of twisted structures are of interest because these slow-wave electromagnetic fields can be used in applications such as electron traveling wave tubes and linear particle accelerators. Since there is no exact closed form solution for the electromagnetic fields within a twisted waveguide or cavity, several previously proposed approximate methods are examined, and more effcient approaches are developed. It is found that the existing perturbation theory methods yield adequate results for slowly twisted structures; however, our efforts here are geared toward analyzing rapidly twisted structures using modifed finite difference methods specially suited for twisted structures. Although the method can handle general twisted structures, three particular cross sections are selected as representative cases for careful analysis. First, a slowly twisted rectangular cavity is analyzed as a reference case. This is because its shape is simple and perturbation theory already gives a good approximate solution for such slow twists rates. Secondly, a symmetrically notched circular cross section is investigated, since its longitudinal cross section is comparable to the well known disk-loaded cavity (used in many practical accelerator designs, including SLAC). Finally, a "dumbbell" shaped cross section is analyzed because of its similarity to the well-known TESLA-type accelerating cavity, which is of great importance because of its wide acceptance as a superconducting cavity. To validate the results of the developed theory and our extensive simulations, the newly developed numerical models are compared to commercial codes. Also, several prototypes are developed
Geometry of quantum group twists, multidimensional Jackson calculus and regularization
Demichev, A P
1995-01-01
We show that R-matricies of all simple quantum groups have the properties which permit to present quantum group twists as transitions to other coordinate frames on quantum spaces. This implies physical equivalence of field theories invariant with respect to q-groups (considered as q-deformed space-time groups of transformations) connected with each other by the twists. Taking into account this freedom we study quantum spaces of the special type: with commuting coordinates but with q-deformed differential calculus and construct GL_r(N) invariant multidimensional Jackson derivatives. We consider a particle and field theory on a two-dimensional q-space of this kind and come to the conclusion that only one (time-like) coordinate proved to be discretized.
Sweep-twist adaptive rotor blade : final project report.
Energy Technology Data Exchange (ETDEWEB)
Ashwill, Thomas D.
2010-02-01
Knight & Carver was contracted by Sandia National Laboratories to develop a Sweep Twist Adaptive Rotor (STAR) blade that reduced operating loads, thereby allowing a larger, more productive rotor. The blade design used outer blade sweep to create twist coupling without angled fiber. Knight & Carver successfully designed, fabricated, tested and evaluated STAR prototype blades. Through laboratory and field tests, Knight & Carver showed the STAR blade met the engineering design criteria and economic goals for the program. A STAR prototype was successfully tested in Tehachapi during 2008 and a large data set was collected to support engineering and commercial development of the technology. This report documents the methodology used to develop the STAR blade design and reviews the approach used for laboratory and field testing. The effort demonstrated that STAR technology can provide significantly greater energy capture without higher operating loads on the turbine.
Generalized Rogers-Ramanujan identities for twisted affine algebras
Genish, Arel; Gepner, Doron
2017-07-01
The characters of parafermionic conformal field theories are given by the string functions of affine algebras, which are either twisted or untwisted algebras. Expressions for these characters as generalized Rogers-Ramanujan algebras have been established for the untwisted affine algebras. However, we study the identities for the string functions of the twisted affine Lie algebras. A conjecture for the string functions was proposed by Hatayama et al., for the unit fields, which expresses the string functions as Rogers-Ramanujan type sums. Here we propose to check the Hatayama et al. conjecture, using Lie algebraic theoretic methods. We use Freudenthal’s formula, which we computerized, to verify the identities for all the algebras at low rank and low level. We find complete agreement with the conjecture.
Green functions and twist correlators for $N$ branes at angles
Pesando, Igor
2012-01-01
We compute the Green functions and correlator functions for N twist fields for branes at angles on T^2 and we show that there are N-2 different configurations labeled by an integer M which is roughly associated with the number of obtuse angles of the configuration. In order to perform this computation we use a SL(2,R) invariant formulation and geometric constraints instead of Pochammer contours. In particular the M=1 or M=N-1 amplitude can be expressed without using transcendental functions. We determine the amplitudes normalization from N -> N-1 reduction without using the factorization into the untwisted sector. Both the amplitudes normalization and the OPE of two twist fields are unique (up to one constant) when the \\epsilon 1-\\epsilon symmetry is imposed. For consistency we find also an infinite number of relations among Lauricella hypergeometric functions.
On the twists of interplanetary magnetic flux ropes observed at 1 AU
Wang, Yuming; Hu, Qiang; Liu, Rui; Shen, Chenglong; Chi, Yutian
2016-01-01
Magnetic flux ropes (MFRs) are one kind of fundamental structures in the solar physics, and involved in various eruption phenomena. Twist, characterizing how the magnetic field lines wind around a main axis, is an intrinsic property of MFRs, closely related to the magnetic free energy and stableness. So far it is unclear how much amount of twist is carried by MFRs in the solar atmosphere and in heliosphere and what role the twist played in the eruptions of MFRs. Contrasting to the solar MFRs, there are lots of in-situ measurements of magnetic clouds (MCs), the large-scale MFRs in interplanetary space, providing some important information of the twist of MFRs. Thus, starting from MCs, we investigate the twist of interplanetary MFRs with the aid of a velocity-modified uniform-twist force-free flux rope model. It is found that most of MCs can be roughly fitted by the model and nearly half of them can be fitted fairly well though the derived twist is probably over-estimated by a factor of 2.5. By applying the mod...
Energy Technology Data Exchange (ETDEWEB)
Holmes, Jeffrey A [ORNL; Zhang, Yan [ORNL; Kang, Yoon W [ORNL; Galambos, John D [ORNL; Hassan, Mohamed H [ORNL; Wilson, Joshua L [ORNL
2009-01-01
Investigations of the RF properties of certain twisted waveguide structures show that they support favorable accelerating fields. This makes them potential candidates for accelerating cavities. Using the particle tracking code, ORBIT, We examine the beam - RF interaction in the twisted cavity structures to understand their beam transport and acceleration properties. The results will show the distinctive properties of these new structures for particle transport and acceleration, which have not been previously analyzed.
Continuous nanofiber yarns twisted through three-dimensional high-speed swirling airflow
Directory of Open Access Journals (Sweden)
He Jian-Xin
2013-01-01
Full Text Available A new method is proposed to fabricate continuous twisted nanofiber yarns. Nanofibers are bunched by a double conjugate electrospinning, and then twisted through a three-dimensional high-speed swirling airflow. Its principle and process are analyzed theoretically, and the airflow field inside the nozzle chamber is studied numerically, and mechanical properties of nanofiber yarns at different spinning conditions are systematically discussed.
Ketov, Sergei V.; Lechtenfeld, Olaf; Parkes, Andrew J.
1995-03-01
The most general homogeneous monodromy conditions in N=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)⊗openZ2. For classes which generate a discrete subgroup Γ, the corresponding target space backgrounds openC1,1/Γ include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for Γ=open1 (untwisted) and Γ=openZ2 (in the manner of Mathur and Mukhi), as well as for Γ being a parabolic element of U(1,1). In particular, the 16 openZ2-twisted sectors of the N=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of ``spacetime'' supersymmetry, with the number of supersymmetries being dependent on global ``spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless ``spacetime'' fermions.
Symmetry fractionalization and twist defects
Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz
2016-03-01
Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.
Multiple Twisted -Euler Numbers and Polynomials Associated with -Adic -Integrals
Directory of Open Access Journals (Sweden)
Jang Lee-Chae
2008-01-01
Full Text Available By using -adic -integrals on , we define multiple twisted -Euler numbers and polynomials. We also find Witt's type formula for multiple twisted -Euler numbers and discuss some characterizations of multiple twisted -Euler Zeta functions. In particular, we construct multiple twisted Barnes' type -Euler polynomials and multiple twisted Barnes' type -Euler Zeta functions. Finally, we define multiple twisted Dirichlet's type -Euler numbers and polynomials, and give Witt's type formula for them.
Large N reduction on a twisted torus
González-Arroyo, A; Neuberger, H
2005-01-01
We consider SU(N) lattice gauge theory at infinite N defined on a torus with a CP invariant twist. Massless fermions are incorporated in an elegant way, while keeping them quenched. We present some numerical results which suggest that twisting can make numerical simulations of planar QCD more efficient.
Stress effects in twisted highly birefringent fibers
Wolinski, Tomasz R.
1994-03-01
Hydrostatic pressure and uniaxial longitudinal strain effects in twisted highly birefringent optical fibers have been investigated from the point of the Marcuse mode-coupling theory. The problem is analyzed in terms of local normal modes of the ideal fiber and in the limit of weak twist, where large linear birefringence dominates over twist effect, and therefore twist coupling between local modes is not effective. The authors present the results of birefringence measurements in highly birefringent bow-tie fibers influenced simultaneously by hydrostatic pressure up to 100 MPa and twisting the result for highly birefringent elliptical-core fibers influenced by uniaxial longitudinal strain up to 4000 (mu) (epsilon) and twisting effect. The birefringence measurement method is based on twist-induced effects and has been successfully applied in a stress environment. The experiment was conducted with a specially designed stress generating device that makes it possible to simultaneously generate various mechanical perturbations such as hydrostatic and radial pressure, axial strain and twist, allowing study of their influence on mode propagation in optical fibers. A comparison with theoretical results as well as with pervious experimental data on stress influence on the beat length parameter in highly birefringent fibers is also provided.
Decay constants from twisted mass QCD
Dimopoulos, P; Michael, C; Simula, S; Urbach, C
2008-01-01
We present results for chiral extrapolations of the mass and decay constants of the rho meson. The data sets used are the nf=2 unquenched gauge configurations generated with twisted mass fermions by the European Twisted Mass Collaboration. We describe a calculation of three decay constants in charmonium and explain why they are required.
Twisting theory for weak Hopf algebras
Institute of Scientific and Technical Information of China (English)
CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong
2008-01-01
The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).
Kato, J; Miyake, A; Kato, Junji; Kawamoto, Noboru; Miyake, Akiko
2005-01-01
We propose N=4 twisted superspace formalism in four dimensions by introducing Dirac-Kahler twist. In addition to the BRST charge as a scalar counter part of twisted supercharge we find vector and tensor twisted supercharges. By introducing twisted chiral superfield we explicitly construct off-shell twisted N=4 SUSY invariant action. We can propose variety of supergauge invariant actions by introducing twisted vector superfield. We may, however, need to find further constraints to identify twisted N=4 super Yang-Mills action. We propose a superconnection formalism of twisted superspace where constraints play a crucial role. It turns out that N=4 superalgebra of Dirac-Kahler twist can be decomposed into N=2 sectors. We can then construct twisted N=2 super Yang-Mills actions by the superconnection formalism of twisted superspace in two and four dimensions.
Unwinding motion of a twisted active region filament
Energy Technology Data Exchange (ETDEWEB)
Yan, X. L.; Xue, Z. K.; Kong, D. F. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Liu, J. H. [Department of Physics, Shijiazhuang University, Shijiazhuang 050035 (China); Xu, C. L. [Yunnan Normal University, Kunming 650092 (China)
2014-12-10
To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.
Unwinding Motion of a Twisted Active Region Filament
Yan, X. L.; Xue, Z. K.; Liu, J. H.; Kong, D. F.; Xu, C. L.
2014-12-01
To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.
Reversal of helicoidal twist handedness near point defects of confined chiral liquid crystals
Ackerman, Paul J.; Smalyukh, Ivan I.
2016-05-01
Handedness of the director twist in cholesteric liquid crystals is commonly assumed to be the same throughout the medium, determined solely by the chirality of constituent molecules or chiral additives, albeit distortions of the ground-state helicoidal configuration often arise due to the effects of confinement and external fields. We directly probe the twist directionality of liquid crystal director structures through experimental three-dimensional imaging and numerical minimization of the elastic free energy and show that spatially localized regions of handedness opposite to that of the chiral liquid crystal ground state can arise in the proximity of twisted-soliton-bound topological point defects. In chiral nematic liquid crystal confined to a film that has a thickness less than the cholesteric pitch and perpendicular surface boundary conditions, twisted solitonic structures embedded in a uniform unwound far-field background with chirality-matched handedness locally relieve confinement-imposed frustration and tend to be accompanied by point defects and smaller geometry-required, energetically costly regions of opposite twist handedness. We also describe a spatially localized structure, dubbed a "twistion," in which a twisted solitonic three-dimensional director configuration is accompanied by four point defects. We discuss how our findings may impinge on the stability of localized particlelike director field configurations in chiral and nonchiral liquid crystals.
Hidden Beauty in Twisted Viking Neck Rings
Olsen, Kasper
2010-01-01
Many hoards found in Ireland, Scotland, Orkney Islands, and Scandinavia demonstrate the vikings ability to fabricate beautiful arm and neck rings of twisted silver and gold rods. Characteristic for such rings is the uniform appearance of the twisted pattern along the length of the arm ring, as well as from one arm ring to another, also when found at distant geographical locations. How can the appearance of the twisted wires be so perfectly repetitive? We demonstrate that the answer is that the vikings utilized a self-forming motif: The pattern arises from a twisting of the wires to a maximally rotated configuration. That is why the twist patterns in these arm and neck rings are beautiful, repetitive, and universal.
Gate induced monolayer behavior in twisted bilayer black phosphorus
Sevik, Cem; Wallbank, John R.; Gülseren, Oğuz; Peeters, François M.; Çakır, Deniz
2017-09-01
Optical and electronic properties of black phosphorus strongly depend on the number of layers and type of stacking. Using first-principles calculations within the framework of density functional theory, we investigate the electronic properties of bilayer black phosphorus with an interlayer twist angle of 90°. These calculations are complemented with a simple k\\centerdot p model which is able to capture most of the low energy features and is valid for arbitrary twist angles. The electronic spectrum of 90° twisted bilayer black phosphorus is found to be x-y isotropic in contrast to the monolayer. However x-y anisotropy, and a partial return to monolayer-like behavior, particularly in the valence band, can be induced by an external out-of-plane electric field. Moreover, the preferred hole effective mass can be rotated by 90° simply by changing the direction of the applied electric field. In particular, a + 0.4 (-0.4) V {{{\\mathringA}}-1} out-of-plane electric field results in a ˜60% increase in the hole effective mass along the \\mathbf{y} (\\mathbf{x} ) axis and enhances the m\\mathbf{y}\\ast/m\\mathbf{x}\\ast (m\\mathbf{x}\\ast/m\\mathbf{y}\\ast ) ratio as much as by a factor of 40. Our DFT and k\\centerdot p simulations clearly indicate that the twist angle in combination with an appropriate gate voltage is a novel way to tune the electronic and optical properties of bilayer phosphorus and it gives us a new degree of freedom to engineer the properties of black phosphorus based devices.
Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering
Vieira, J; Alves, E P; Fonseca, R A; Mendonça, J T; Bingham, R; Norreys, P; Silva, L O
2016-01-01
Twisted Laguerre-Gaussian lasers, with orbital angular momentum and characterised by doughnut shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high gradient positron acceleration. The production of ultrahigh intensity twisted laser pulses could then also have a broad influence on relativistic laser-matter interactions. Here we show theoretically and with ab-initio three-dimensional particle-in-cell simulations, that stimulated Raman backscattering can generate and amplify twisted lasers to Petawatt intensities in plasmas. This work may open new research directions in non-linear optics and high energy density science, compact plasma based accelerators and ...
Low-lying spectrum for lattice Dirac operators with twisted mass
Gattringer, C; Gattringer, Christof; Solbrig, Stefan
2005-01-01
We analyze the low-lying spectrum and eigenmodes of lattice Dirac operators with a twisted mass term. The twist term expels the eigenvalues from a strip in the complex plane and all eigenmodes obtain a non-vanishing matrix element with gamma-5. For a twisted Ginsparg-Wilson operator the spectrum is located on two arcs in the complex plane. Modes due to non-trivial topological charge of the underlying gauge field have their eigenvalues at the edges of these arcs and obey a remnant index theorem. For configurations in the confined phase we find that the twist mainly affects the zero modes, while the bulk of the spectrum is essentially unchanged.
Remnant index theorem and low-lying eigenmodes for twisted mass fermions
Gattringer, C; Gattringer, Christof; Solbrig, Stefan
2005-01-01
We analyze the low-lying spectrum and eigenmodes of lattice Dirac operators with a twisted mass term. The twist term expels the eigenvalues from a strip in the complex plane and all eigenmodes obtain a non-vanishing matrix element with gamma-5. For a twisted Ginsparg-Wilson operator the spectrum is located on two arcs in the complex plane. Modes due to non-trivial topological charge of the underlying gauge field have their eigenvalues at the edges of these arcs and obey a remnant index theorem. For configurations in the confined phase we find that the twist mainly affects the zero modes, while the bulk of the spectrum is essentially unchanged.
Twisted spacetime in Einstein gravity
Zhang, Hongsheng
2016-01-01
We find a vacuum stationary twisted solution in four-dimensional Einstein gravity. Its frame dragging angular velocities are antisymmetric with respect to the equatorial plane. It possesses a symmetry of joint inversion of time and parity with respect to the equatorial plane. Its Arnowitt-Deser-Misner (ADM) mass and angular momentum are zero. It is curved but regular all over the manifold. Its Komar mass and Komar angular momentum are also zero. Its infinite red-shift surface coincides with its event horizon, since the event horizon does not rotate. Furthermore we extend this solution to the massive case, and find some similar properties. This solution is a stationary axisymmetric solution, but not Kerr. It explicitly proves that pure Einstein gravity permits different rotational mode other than Kerr. Our results demonstrate that the Einstein theory may have much more rich structures than what we ever imagine.
Noncommutative connections on bimodules and Drinfeld twist deformation
Aschieri, Paolo
2012-01-01
Given a Hopf algebra H, we study modules and bimodules over an algebra A that carry an H-action, as well as their morphisms and connections. Bimodules naturally arise when considering noncommutative analogues of tensor bundles. For quasitriangular Hopf algebras and bimodules with an extra quasi-commutativity property we induce connections on the tensor product over A of two bimodules from connections on the individual bimodules. This construction applies to arbitrary connections, i.e. not necessarily H-equivariant ones, and further extends to the tensor algebra generated by a bimodule and its dual. Examples of these noncommutative structures arise in deformation quantization via Drinfeld twists of the commutative differential geometry of a smooth manifold, where the Hopf algebra H is the universal enveloping algebra of vector fields (or a finitely generated Hopf subalgebra). We extend the Drinfeld twist deformation theory of modules and algebras to morphisms and connections that are not necessarily H-equivari...
On Signatures of Twisted Magnetic Flux Tube Emergence
Dominguez, Santiago Vargas; Green, Lucie; van Driel-Gesztelyi, Lidia; Hood, Alan
2011-01-01
Recent studies of NOAA active region 10953, by Okamoto {\\it et al.} ({\\it Astrophys. J. Lett.} {\\bf 673}, 215, 2008; {\\it Astrophys. J.} {\\bf 697}, 913, 2009), have interpreted photospheric observations of changing widths of the polarities and reversal of the horizontal magnetic field component as signatures of the emergence of a twisted flux tube within the active region and along its internal polarity inversion line (PIL). A filament is observed along the PIL and the active region is assumed to have an arcade structure. To investigate this scenario, MacTaggart and Hood ({\\it Astrophys. J. Lett.} {\\bf 716}, 219, 2010) constructed a dynamic flux emergence model of a twisted cylinder emerging into an overlying arcade. The photospheric signatures observed by Okamoto {\\it et al.} (2008, 2009) are present in the model although their underlying physical mechanisms differ. The model also produces two additional signatures that can be verified by the observations. The first is an increase in the unsigned magnetic fl...
Evolution of chirality-odd twist-3 fragmentation functions
Ma, J. P.; Zhang, G. P.
2017-09-01
We derive the complete set of evolutions of chirality-odd twist-3 fragmentation functions at one-loop level. There are totally nine real twist-3 fragmentation functions, among which seven are independent. The renormalization-scale dependence of the nine functions has an important implication for studies of single transverse-spin asymmetries. We find that the evolutions of the three complex fragmentation functions defined by quark-gluon-quark operator are mixed with themselves. There is no mixing with the fragmentation functions defined only with bilinear quark field operators. In the large-Nc limit the evolutions of the three complex fragmentation functions are simplified and reduced to six homogeneous equations.
DYNAMICS OF STRONGLY TWISTED RELATIVISTIC MAGNETOSPHERES
Energy Technology Data Exchange (ETDEWEB)
Parfrey, Kyle [Astronomy Department, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Beloborodov, Andrei M.; Hui, Lam, E-mail: parfrey@astro.princeton.edu [Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street, New York, NY 10027 (United States)
2013-09-10
Magnetar magnetospheres are believed to be strongly twisted due to shearing of the stellar crust by internal magnetic stresses. We present time-dependent axisymmetric simulations showing in detail the evolution of relativistic force-free magnetospheres subjected to slow twisting through large angles. When the twist amplitude is small, the magnetosphere moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the magnetosphere becomes tearing-mode unstable to forming a resistive current sheet, initiating large-scale magnetic reconnection in which a significant fraction of the magnetic free energy can be dissipated. This ''critical'' twist angle is insensitive to the resistive length scale. Rapid shearing temporarily stabilizes the magnetosphere beyond the critical angle, allowing the magnetosphere of a rapidly differentially rotating star to store and dissipate more free energy. In addition to these effects, shearing the surface of a rotating star increases the spindown torque applied to the star. If shearing is much slower than rotation, the resulting spikes in spindown rate can occur on timescales anywhere from the long twisting timescale to the stellar spin period or shorter, depending both on the stellar shear distribution and the existing distribution of magnetospheric twists. A model in which energy is stored in the magnetosphere and released by a magnetospheric instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.
Novel Properties of Twisted-Photon Absorption
Afanasev, Andrei; Mukherjee, Asmita
2014-01-01
We discuss novel features of twisted-photon absorption both by atoms and by micro-particles. First, we extend the treatment of atomic photoexcitation by twisted photons to include atomic recoil, derive generalized quantum selection rules and consider phenomena of forbidden atomic transitions. Second, we analyze the radiation pressure from twisted-photon beams on micro- and nano-sized particles and observe that for particular conditions the pressure is negative in a small area near the beam axis. A central part of the beam therefore acts as a "tractor beam".
Twisted versus braided magnetic flux ropes in coronal geometry. II. Comparative behaviour
Prior, C.; Yeates, A. R.
2016-06-01
Aims: Sigmoidal structures in the solar corona are commonly associated with magnetic flux ropes whose magnetic field lines are twisted about a mutual axis. Their dynamical evolution is well studied, with sufficient twisting leading to large-scale rotation (writhing) and vertical expansion, possibly leading to ejection. Here, we investigate the behaviour of flux ropes whose field lines have more complex entangled/braided configurations. Our hypothesis is that this internal structure will inhibit the large-scale morphological changes. Additionally, we investigate the influence of the background field within which the rope is embedded. Methods: A technique for generating tubular magnetic fields with arbitrary axial geometry and internal structure, introduced in part I of this study, provides the initial conditions for resistive-MHD simulations. The tubular fields are embedded in a linear force-free background, and we consider various internal structures for the tubular field, including both twisted and braided topologies. These embedded flux ropes are then evolved using a 3D MHD code. Results: Firstly, in a background where twisted flux ropes evolve through the expected non-linear writhing and vertical expansion, we find that flux ropes with sufficiently braided/entangled interiors show no such large-scale changes. Secondly, embedding a twisted flux rope in a background field with a sigmoidal inversion line leads to eventual reversal of the large-scale rotation. Thirdly, in some cases a braided flux rope splits due to reconnection into two twisted flux ropes of opposing chirality - a phenomenon previously observed in cylindrical configurations. Conclusions: Sufficiently complex entanglement of the magnetic field lines within a flux rope can suppress large-scale morphological changes of its axis, with magnetic energy reduced instead through reconnection and expansion. The structure of the background magnetic field can significantly affect the changing morphology of a
Twist1 Is Essential for Tooth Morphogenesis and Odontoblast Differentiation.
Meng, Tian; Huang, Yanyu; Wang, Suzhen; Zhang, Hua; Dechow, Paul C; Wang, Xiaofang; Qin, Chunlin; Shi, Bing; D'Souza, Rena N; Lu, Yongbo
2015-12-04
Twist1 is a basic helix-loop-helix-containing transcription factor that is expressed in the dental mesenchyme during the early stages of tooth development. To better delineate its roles in tooth development, we generated Twist1 conditional knockout embryos (Twist2(Cre) (/+);Twist1(fl/fl)) by breeding Twist1 floxed mice (Twist1(fl/fl)) with Twist2-Cre recombinase knockin mice (Twist2(Cre) (/+)). The Twist2(Cre) (/+);Twist1(fl/fl) embryos formed smaller tooth germs and abnormal cusps during early tooth morphogenesis. Molecular and histological analyses showed that the developing molars of the Twist2(Cre) (/+);Twist1(fl/fl) embryos had reduced cell proliferation and expression of fibroblast growth factors 3, 4, 9, and 10 and FGF receptors 1 and 2 in the dental epithelium and mesenchyme. In addition, 3-week-old renal capsular transplants of embryonic day 18.5 Twist2(Cre) (/+);Twist1(fl/fl) molars showed malformed crowns and cusps with defective crown dentin and enamel. Immunohistochemical analyses revealed that the implanted mutant molars had defects in odontoblast differentiation and delayed ameloblast differentiation. Furthermore, in vitro ChIP assays demonstrated that Twist1 was able to bind to a specific region of the Fgf10 promoter. In conclusion, our findings suggest that Twist1 plays crucial roles in regulating tooth development and that it may exert its functions through the FGF signaling pathway. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
Topological twist of osp(2|2) + osp(2|2) conformal super algebra in two dimensions
Ano, N
1995-01-01
A Lagrangian of the topological field theory is found in the twisted osp(2|2)\\oplus osp(2|2)conformal super algebra. The reduction on a moduli space is then elaborated through the vanishing Noether current.
Topological hypermultiplet on N=2 twisted superspace in four dimensions
Kato, J; Kato, Junji; Miyake, Akiko
2005-01-01
We propose a N=2 twisted superspace formalism with a central charge in four dimensions by introducing a Dirac-K\\"ahler twist. Using this formalism, we construct a twisted hypermultiplet action and find an explicit form of fermionic scalar, vector and tensor transformations. We construct a off-shell Donaldson-Witten theory coupled to the twisted hypermultiplet. We show that this action possesses N=4 twisted supersymmetry at on-shell level. It turns out that four-dimensional Dirac-K\\"ahler twist is equivalent to the Marcus's twist.
Wigner oscillators, twisted Hopf algebras and second quantization
Energy Technology Data Exchange (ETDEWEB)
Castro, P.G.; Toppan, F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mails: pgcastro@cbpf.br; toppan@cbpf.br; Chakraborty, B. [S. N. Bose National Center for Basic Sciences, Kolkata (India)]. E-mail: biswajit@bose.res.in
2008-07-01
By correctly identifying the role of central extension in the centrally extended Heisenberg algebra h, we show that it is indeed possible to construct a Hopf algebraic structure on the corresponding enveloping algebra U(h) and eventually deform it through Drinfeld twist. This Hopf algebraic structure and its deformed version U{sup F}(h) is shown to be induced from a more 'fundamental' Hopf algebra obtained from the Schroedinger field/oscillator algebra and its deformed version, provided that the fields/oscillators are regarded as odd-elements of a given superalgebra. We also discuss the possible implications in the context of quantum statistics. (author)
Transmission properties of cryogenic twisted pair filters
Energy Technology Data Exchange (ETDEWEB)
Song, Woon; Rehman, Mushtaq; Chong, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Ryu, Sangwan [Chonnam National University, Gwangju (Korea, Republic of)
2010-12-15
We fabricated a cryogenic low pass filter that consists of twisted pairs of manganin wires wrapped in copper tape and measured its transmission characteristics at frequencies up to 18 GHz. The dependence of the microwave transmission characteristics on the filter length was studied, which showed that a filter of length 1.0 m had a 70-dB attenuation at 1 GHz. We also studied the dependence of common- and differential-mode transmission on the number of twists per unit length and found that the number of twists per unit length affects differential-mode transmission but not common-mode transmission. Because the shielded twisted pair filter is more compact than a conventional copper powder filter, it can solve the space and thermal load issues when many cables are required for precision electronic transport experiments at low temperatures.
Mutations in the human TWIST gene.
Gripp, K W; Zackai, E H; Stolle, C A
2000-01-01
Saethre-Chotzen syndrome is a relatively common craniosynostosis disorder with autosomal dominant inheritance. Mutations in the TWIST gene have been identified in patients with Saethre-Chotzen syndrome. The TWIST gene product is a transcription factor with DNA binding and helix-loop-helix domains. Numerous missense and nonsense mutations cluster in the functional domains, without any apparent mutational hot spot. Two novel point mutations and one novel polymorphism are included in this review. Large deletions including the TWIST gene have been identified in some patients with learning disabilities or mental retardation, which are not typically part of the Saethre-Chotzen syndrome. Comprehensive studies in patients with the clinical diagnosis of Saethre-Chotzen syndrome have demonstrated a TWIST gene abnormality in about 80%, up to 37% of which may be large deletions [Johnson et al., 1998]. The gene deletions and numerous nonsense mutations are suggestive of haploinsufficiency as the disease-causing mechanism. No genotype phenotype correlation was apparent.
Observation of subluminal twisted light in vacuum
Bouchard, Frédéric; Mand, Harjaspreet; Boyd, Robert W; Karimi, Ebrahim
2015-01-01
Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over the speed of light in such media, no experimental demonstration of altered light speeds has hitherto been achieved in vacuum for ``twisted'' optical beams. We show that ``twisted'' light pulses exhibit subluminal velocities in vacuum, being slowed by 0.1\\% relative to c. This work does not challenge relativity theory, but experimentally supports a body of theoretical work on the counterintuitive vacuum group velocities of twisted pulses. These results are particularly important given recent interest in applications of twisted light to quantum information, communication and quantum key distribution.
Twisted Vector Bundles on Pointed Nodal Curves
Indian Academy of Sciences (India)
Ivan Kausz
2005-05-01
Motivated by the quest for a good compactification of the moduli space of -bundles on a nodal curve we establish a striking relationship between Abramovich’s and Vistoli’s twisted bundles and Gieseker vector bundles.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper,we construct an orbifold quantum cohomology twisted by a flat gerbe. Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtous, Pavel; Frolov, Valeri P; Kolar, Ivan
2015-01-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by `unspinning' the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of deformed and/or twisted sphere, with the deformation and twist characterized by the `Euclidean NUT' parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
PAN JianZhong; RUAN YongBin; YIN XiaoQin
2008-01-01
In this paper, we construct an orbifold quantum cohomology twisted by a flat gerbe.Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtouš, Pavel; Kubizňák, David; Frolov, Valeri P.; Kolář, Ivan
2016-06-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by ‘unspinning’ the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of a deformed and/or twisted sphere, with the deformation and twist characterized by the ‘Euclidean NUT’ parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Tri-Bimaximal Mixing from Twisted Friedberg-Lee Symmetry
Araki, Takeshi
2008-01-01
We consider the tri-bimaximal generation mixing in terms of the Friedberg-Lee (FL) symmetry. The symmetry is a kind of translational one for the fermion field operators. The symmetry with uniform translation for each generation of neutrinos can partially realize the desired form of the neutrino mass matrix for the tri-bimaximal mixing but should be improved to obtain the experimentally favored neutrino mass spectrum. It is firstly pointed out that patterns of the uniformity breaking are important for resulting form of the neutrino mass matrix. Then we propose a promotion of the FL symmetry to have the $\\mu - \\tau$ one, and call that the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are also presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. The first possible scheme is that the uniformity of the FL symmetry is broken by terms preserving the twisted FL one. The second one is based on the $S_3$ permutation family symmetry. The breaking terms, which ...
Noncommutative spaces with twisted symmetries and second quantization
Fiore, Gaetano
2010-01-01
In a minimalistic view, the use of noncommutative coordinates can be seen just as a way to better express non-local interactions of a special kind: 1-particle solutions (wavefunctions) of the equation of motion in the presence of an external field may look simpler as functions of noncommutative coordinates. It turns out that also the wave-mechanical description of a system of n such bosons/fermions and its second quantization is simplified if we translate them in terms of their deformed counterparts. The latter are obtained by a general twist-induced *-deformation procedure which deforms in a coordinated way not just the spacetime algebra, but the larger algebra generated by any number n of copies of the spacetime coordinates and by the particle creation and annihilation operators. On the deformed algebra the action of the original spacetime transformations looks twisted. In a non-conservative view, we thus obtain a twisted covariant framework for QFT on the corresponding noncommutative spacetime consistent w...
Unwinding motion of a twisted active-region filament
Yan, X L; Liu, J H; Kong, D F; Xu, C L
2014-01-01
To better understand the structures of active-region filaments and the eruption process, we study an active-region filament eruption in active region NOAA 11082 in detail on June 22, 2010. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament is consisted of twisted magnetic field lines. The total twist of the filament is at least 5$\\pi$ obtained by using time slice method. According to the morphology change during the filament eruption, it is found that the active-region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magn...
Twist, Writhe & Helicity in the inner penumbra of a sunspot
Cobo, Basilio Ruiz
2011-01-01
The aim of this work is the determination of the twist, writhe, and self magnetic helicity of penumbral filaments located in an inner Sunspot penumbra. To this extent, we inverted data taken with the spectropolarimeter (SP) aboard {\\it Hinode} with the SIR (Stokes Inversion based on Response function) code. For the construction of a 3D geometrical model we applied a genetic algorithm minimizing the divergence of $\\vec{B}$ and the net magnetohydrodynamic force, consequently a force-free solution would be reached if possible. We estimated two proxies to the magnetic helicity frequently used in literature: the force-free parameter $\\alpha_z$ and the current helicity term $h_{c_{z}}$. We show that both proxies are only qualitative indicators of the local twist as the magnetic field in the area under study significantly departures from a force-free configuration. The local twist shows significant values only at the borders of bright penumbral filaments with opposite signs on each side. These locations are precisel...
Bend-twist coupling potential of wind turbine blades
Fedorov, V.; Berggreen, C.
2014-06-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling into a blade on such important blade structural properties as bending and torsional stiffness is demonstrated.
Phase Diagram of Dynamical Twisted Mass Wilson Fermions at Finite Isospin Chemical Potential
Janssen, Oliver; Splittorff, K; Verbaarschot, Jacobus J M; Zafeiropoulos, Savvas
2015-01-01
We consider the phase diagram of twisted mass Wilson fermions of two-flavor QCD in the parameter space of the quark mass, the isospin chemical potential, the twist angle and the lattice spacing. This work extends earlier studies in the continuum and those at zero chemical potential. We evaluate the phase diagram as well as the spectrum of the (pseudo-)Goldstone bosons using the chiral Lagrangian for twisted mass Wilson fermions at non-zero isospin chemical potential. The phases are obtained from a mean field analysis. At zero twist angle we find that already an infinitesimal isospin chemical potential destroys the Aoki phase. The reason is that in this phase we have massless Goldstone bosons with a non-zero isospin charge. At finite twist angle only two different phases are present, one phase which is continuously connected to the Bose condensed phase at non-zero chemical potential and another phase which is continuously connected to the normal phase. For either zero or maximal twist the phase diagram is more...
Genomic pathways modulated by Twist in breast cancer
Vesuna, Farhad; Bergman, Yehudit; Raman, Venu
2017-01-01
Background The basic helix-loop-helix transcription factor TWIST1 (Twist) is involved in embryonic cell lineage determination and mesodermal differentiation. There is evidence to indicate that Twist expression plays a role in breast tumor formation and metastasis, but the role of Twist in dysregulating pathways that drive the metastatic cascade is unclear. Moreover, many of the genes and pathways dysregulated by Twist in cell lines and mouse models have not been validated against data obtaine...
DDalphaAMG for Twisted Mass Fermions
Bacchio, Simone; Finkenrath, Jacob; Frommer, Andreas; Kahl, Karsten; Rottmann, Matthias
2016-01-01
We present the Adaptive Aggregation-based Domain Decomposition Multigrid method extended to the twisted mass fermion discretization action. We show comparisons of results as a function of tuning the parameters that enter the twisted mass version of the DDalphaAMG library (https://github.com/sbacchio/DDalphaAMG). Moreover, we linked the DDalphaAMG library to the tmLQCD software package and give details on the performance of the multigrid solver during HMC simulations at the physical point.
OAM mode converter in twisted fibers
DEFF Research Database (Denmark)
Usuga Castaneda, Mario A.; Beltran-Mejia, Felipe; Cordeiro, Cristiano
2014-01-01
We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA.......We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA....
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this type of twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets.
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if non-trivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all...
Universal corner entanglement from twist operators
Bueno, Pablo; Witczak-Krempa, William
2015-01-01
The entanglement entropy in three-dimensional conformal field theories (CFTs) receives a logarithmic contribution characterized by a regulator-independent function $a(\\theta)$ when the entangling surface contains a sharp corner with opening angle $\\theta$. In the limit of a smooth surface ($\\theta\\rightarrow\\pi$), this corner contribution vanishes as $a(\\theta)=\\sigma\\,(\\theta-\\pi)^2$. In arXiv:1505.04804, we provided evidence for the conjecture that for any $d=3$ CFT, this corner coefficient $\\sigma$ is determined by $C_T$, the coefficient appearing in the two-point function of the stress tensor. Here, we argue that this is a particular instance of a much more general relation connecting the analogous corner coefficient $\\sigma_n$ appearing in the $n$th R\\'enyi entropy and the scaling dimension $h_n$ of the corresponding twist operator. In particular, we find the simple relation $h_n/\\sigma_n=(n-1)\\pi$. We show how it reduces to our previous result as $n\\rightarrow 1$, and explicitly check its validity for f...
Abe, Yasumi
2007-01-01
The space-time symmetry of noncommutative quantum field theories with a deformed quantization is described by the twisted Poincar\\'e algebra, while that of standard commutative quantum field theories is described by the Poincar\\'e algebra. Based on the equivalence of the deformed theory with a commutative field theory, the correspondence between the twisted Poincar\\'e symmetry of the deformed theory and the Poincar\\'e symmetry of a commutative theory is established. As a by-product, we obtain the conserved charge associated with the twisted Poincar\\'e transformation to make the twisted Poincar\\'e symmetry evident in the deformed theory. Our result implies that the equivalence between the commutative theory and the deformed theory holds in a deeper level, i.e., it holds not only in correlation functions but also
Kinetic study of electrostatic twisted waves instability in nonthermal dusty plasmas
Arshad, Kashif; Lazar, M.; Mahmood, Shahzad; Aman-ur-Rehman, Poedts, S.
2017-03-01
The kinetic theory of electrostatic twisted waves' instability in a dusty plasma is developed in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons, ions, and dust particles. The kappa distributed electrons are considered to have a drift velocity. The perturbed distribution function and helical electric field are decomposed by Laguerre-Gaussian mode functions defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to investigate the growth rates of the electrostatic twisted waves in a non-thermal dusty plasma. The growth rates of the dust ion acoustic twisted mode (DIATM) and dust acoustic twisted mode (DATM) are obtained analytically and also pictorial presented numerically. The instability condition for the DIATM and DATM is also discussed with different plasma parameters. The growth rates of DIATM and DATM are larger when the drifted electrons are non-Maxwellian distributed and smaller for the Maxwellian distributed drifted electrons in the presence of the helical electric field.
Soft tissue twisting injuries of the knee
Energy Technology Data Exchange (ETDEWEB)
Magee, T.; Shapiro, M. [Neuroimaging Inst., Melbourne, FL (United States)
2001-08-01
Twisting injuries occur as a result of differential motion of different tissue types in injuries with some rotational force. These injuries are well described in brain injuries but, to our knowledge, have not been described in the musculoskeletal literature. We correlated the clinical examination and MR findings of 20 patients with twisting injuries of the soft tissues around the knee. Design and patients: We prospectively followed the clinical courses of 20 patients with knee injuries who had clinical histories and MR findings to suggest twisting injuries of the subcutaneous tissues. Patients with associated internal derangement of the knee (i.e., meniscal tears, ligamentous or bone injuries) were excluded from this study. MR findings to suggest twisting injuries included linear areas of abnormal dark signal on T1-weighted sequences and abnormal bright signal on T2-weighted or short tau inversion recovery (STIR) sequences and/or signal to suggest hemorrhage within the subcutaneous tissues. These MR criteria were adapted from those established for indirect musculotendinous junction injuries. Results: All 20 patients presented with considerable pain that suggested internal derangement on physical examination by the referring orthopedic surgeons. All presented with injuries associated with rotational force. The patients were placed on a course of protected weight-bearing of the affected extremity for 4 weeks. All patients had pain relief by clinical examination after this period of protected weight-bearing. Twisting injuries of the soft tissues can result in considerable pain that can be confused with internal derangement of the knee on physical examination. Soft tissue twisting injuries need to be recognized on MR examinations as they may be the cause of the patient's pain despite no MR evidence of internal derangement of the knee. The demonstration of soft tissue twisting injuries in a patient with severe knee pain but no documented internal derangement on MR
Song, Dong Han; Kim, Ki-Han; Kim, Jung-Wook; Kim, Jae Chang; Yoon, Tae-Hoon
2011-06-01
We propose a twisted nematic liquid crystal device that can be operated in dynamic or memory mode, based on the information content to be displayed at that time. +90°-twisted and -90°-twisted states are used as two stable states for operation in the memory mode. A vertical electric field is applied to realize gray levels for operation in the dynamic mode. The proposed device has a memory retention time of over a month for the memory mode and a response time of 12 ms for the dynamic mode. Contrast ratios of over 500∶1 can be obtained in both the dynamic and memory modes.
Numerical simulations of magnetic Kelvin-Helmholtz instability at a twisted solar flux tube
Murawski, K.; Chmielewski, P.; Zaqarashvili, T. V.; Khomenko, E.
2016-07-01
The paper aims to study the response of a solar small-scale and weak magnetic flux tube to photospheric twisting motions. We numerically solve three-dimensional ideal magnetohydrodynamic equations to describe the evolution of the perturbation within the initially static flux tube, excited by twists in the azimuthal component of the velocity. These twists produce rotation of the magnetic field lines. Perturbation of magnetic field lines propagates upwardly, driving vertical and azimuthal flow as well as plasma compressions and rarefactions in the form of eddies. We conclude that these eddies result from the sheared azimuthal flow which seeds Kelvin-Helmholtz instability (KHI) between the flux tube and the ambient medium. Numerically obtained properties of the KHI confirm the analytical predictions for the occurrence of the instability.
ABOUT THE GEOMETRY AND THE APPLICATIONS OF THE TWISTED SURFACES
Directory of Open Access Journals (Sweden)
MÂRZA Carmen
2015-06-01
Full Text Available The helical and spiral surfaces are used in various fields. These surfaces are obtained by rotating a segment line called generatrix around directrices lines, respectively the spiral surfaces are obtained by composing simultaneously the movements of translation and rotation of a plane figure around an axis - which can be a straight line or a curved line, or around a real or imaginary surface - called core. After an overview of these surfaces, the attention of the authors will be focused on the geometrical and graphical analysis of the twisted surfaces in civil engineering branch, such as: columns, helical ramps and stairs, respectively buildings having a futuristic design.
Twisting dirac fermions: circular dichroism in bilayer graphene
Suárez Morell, E.; Chico, Leonor; Brey, Luis
2017-09-01
Twisted bilayer graphene is a chiral system which has been recently shown to present circular dichroism. In this work we show that the origin of this optical activity is the rotation of the Dirac fermions’ helicities in the top and bottom layer. Starting from the Kubo formula, we obtain a compact expression for the Hall conductivity that takes into account the dephasing of the electromagnetic field between the top and bottom layers and gathers all the symmetries of the system. Our results are based in both a continuum and a tight-binding model, and they can be generalized to any two-dimensional Dirac material with a chiral stacking between layers.
Resonant absorption of kink magnetohydrodynamic waves by a magnetic twist in coronal loops
Ebrahimi, Zanyar; Karami, Kayoomars
2016-10-01
There is ample evidence of twisted magnetic structures in the solar corona. This motivates us to consider the magnetic twist as the cause of Alfvén frequency continuum in coronal loops, which can support the resonant absorption as a rapid damping mechanism for the observed coronal kink magnetohydrodynamic (MHD) oscillations. We model a coronal loop with a straight cylindrical magnetic flux tube, which has constant but different densities in the interior and exterior regions. The magnetic field is assumed to be constant and aligned with the cylinder axis everywhere except for a thin layer near the boundary of the flux tube, which has an additional small magnetic field twist. Then, we investigate a number of possible instabilities that may arise in our model. In the thin tube thin boundary approximation, we derive the dispersion relation and solve it analytically to obtain the frequencies and damping rates of the fundamental (l = 1) and first/second overtone (l = 2, 3) kink (m = 1) MHD modes. We conclude that the resonant absorption by the magnetic twist can justify the rapid damping of kink MHD waves observed in coronal loops. Furthermore, the magnetic twist in the inhomogeneous layer can cause deviations from P1/P2 = 2 and P1/P3 = 3, which are comparable with the observations.
Twisted electron-acoustic waves in plasmas
Aman-ur-Rehman, Ali, S.; Khan, S. A.; Shahzad, K.
2016-08-01
In the paraxial limit, a twisted electron-acoustic (EA) wave is studied in a collisionless unmagnetized plasma, whose constituents are the dynamical cold electrons and Boltzmannian hot electrons in the background of static positive ions. The analytical and numerical solutions of the plasma kinetic equation suggest that EA waves with finite amount of orbital angular momentum exhibit a twist in its behavior. The twisted wave particle resonance is also taken into consideration that has been appeared through the effective wave number qeff accounting for Laguerre-Gaussian mode profiles attributed to helical phase structures. Consequently, the dispersion relation and the damping rate of the EA waves are significantly modified with the twisted parameter η, and for η → ∞, the results coincide with the straight propagating plane EA waves. Numerically, new features of twisted EA waves are identified by considering various regimes of wavelength and the results might be useful for transport and trapping of plasma particles in a two-electron component plasma.
Exotic twisted equivariant cohomology of loop spaces,twisted Bismut-Chern character and T-duality
Han, Fei
2014-01-01
We define completed periodic {\\em exotic twisted $\\mathbb{T}$-equivariant cohomology} for loop spaces of smooth manifolds. We then show that the twisted Bismut-Chern character, defined on the twisted K-theory of the smooth manifold, twisted by a gerbe with connection, takes values in the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology of the loop space of the smooth manifold. We establish a localisation theorem for the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology for loop spaces and apply it to establish T-duality in a background flux in type II String Theory from a loop space perspective.
Analysis of gun barrel rifling twist
Sun, Jia; Chen, Guangsong; Qian, Linfang; Liu, Taisu
2017-05-01
Aiming at the problem of gun barrel rifling twist, the constraint relation between rifling and projectile is investigated. The constraint model of rifling and projectile is established and the geometric relation between the twist and the motion of projectile is analyzed. Based on the constraint model, according to the rotating band that is fired, the stress and the motion law of the rotating band in bore are analyzed. The effects to rotating band (double rotating band or wide driving band) caused by different rifling (rib rifling, increasing rifling and combined rifling) are also investigated. The model is demonstrated by several examples. The results of numerical examples and the constraint mode show that the uncertainty factors will be brought in the increasing rifling and combined rifling during the projectile move in the bore. According to the amplitude and the strength of the twist acting on rotating band, the steady property of rotational motion of the projectile, the rib rifling is a better choose.
Blind analysis results of the TWIST experiment
Hillairet, A; Bueno, J F; Davydov, Y I; Depommier, P; Faszer, W; Fujiwara, M C; Gagliardi, C A; Gaponenko, A; Grossheim, A; Gill, D R; Gumplinger, P; Hasinoff, M D; Henderson, R S; Hu, J; Koetke, D D; MacDonald, R P; Marshall, G M; Mathie, E W; Mischke, R E; Olchanski, K; Olin, A; Openshaw, R; Poutissou, J -M; Poutissou, R; Selivanov, V; Sheffer, G; Shin, B; Stanislaus, T D S; Tacik, R; Tribble, R E
2010-01-01
The TRIUMF Weak Interaction Symmetry Test (TWIST) experiment was designed to test the standard model at high precision in the purely leptonic decay of polarized muons. A general four-fermion interaction model is used to describe the muon decay. TWIST measures three of the four muon decay parameters of this model, $\\rho$, $\\delta$ and $P_{\\mu}^{\\pi} \\xi$, from the shape of the momentum-angle spectrum. The results of this model independent approach are compared to the standard model predictions and used to constrain new physics. Our collaboration has finalized the blind analysis of the final experimental data taken in 2006 and 2007. This analysis mostly reached our goal of a precision of an order of magnitude improvement over the pre-TWIST measurements.
Helicoids, wrinkles, and loops in twisted ribbons.
Chopin, Julien; Kudrolli, Arshad
2013-10-25
We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales.
Dynamical Twisted Mass Fermions with Light Quarks
Boucaud, P; Farchioni, F; Frezzotti, R; Giménez, V; Herdoiza, G; Jansen, K; Lubicz, V; Martinelli, G; McNeile, C; Michael, C; Montvay, I; Palao, D; Papinutto, Mauro; Pickavance, J; Rossi, G C; Scorzato, L; Shindler, A; Simula, S; Urbach, C; Wenger, U; Boucaud, Ph.
2007-01-01
We present results of dynamical simulations with 2 flavours of degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses from 300 to 550 MeV. The simulations are performed at one value of the lattice spacing a \\lesssim 0.1 fm. In order to have O(a) improvement and aiming at small residual cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, \\bar{l}_3 and \\bar{l}_4 are evaluated with small statistical errors.
Matrix theory compactifications on twisted tori
Chatzistavrakidis, Athanasios
2012-01-01
We study compactifications of Matrix theory on twisted tori and non-commutative versions of them. As a first step, we review the construction of multidimensional twisted tori realized as nilmanifolds based on certain nilpotent Lie algebras. Subsequently, matrix compactifications on tori are revisited and the previously known results are supplemented with a background of a non-commutative torus with non-constant non-commutativity and an underlying non-associative structure on its phase space. Next we turn our attention to 3- and 6-dimensional twisted tori and we describe consistent backgrounds of Matrix theory on them by stating and solving the conditions which describe the corresponding compactification. Both commutative and non-commutative solutions are found in all cases. Finally, we comment on the correspondence among the obtained solutions and flux compactifications of 11-dimensional supergravity, as well as on relations among themselves, such as Seiberg-Witten maps and T-duality.
On reweighting for twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2016-01-01
We consider the possibility of using reweighting techniques in order to correct for the breaking of unitarity when twisted boundary conditions are imposed on valence fermions in simulations of lattice gauge theories. We start by studying the properties of reweighting factors and their variances at tree-level. That leads us to the introduction of a factorization for the fermionic reweighting determinant. In the numerical, stochastic, implementation of the method, we find that the effect of reweighting is negligible in the case of large volumes but it is sizeable when the volumes are small and the twisting angles are large. More importantly, we find that for un-improved Wilson fermions, and in small volumes, the dependence of the critical quark mass on the twisting angle is quite pronounced and results in large violations of the continuum dispersion relation.
Local index formula and twisted spectral triples
Moscovici, Henri
2009-01-01
We prove a local index formula for a class of twisted spectral triples of type III modeled on the transverse geometry of conformal foliations with locally constant transverse conformal factor. Compared with the earlier proof of the untwisted case, the novel aspect resides in the fact that the twisted analogues of the JLO entire cocycle and of its retraction are no longer cocycles in their respective Connes bicomplexes. We show however that the passage to the infinite temperature limit, respectively the integration along the full temperature range against the Haar measure of the positive half-line, has the remarkable effect of curing in both cases the deviations from the cocycle identity.
On Supermultiplet Twisting and Spin-Statistics
Hübsch, T.
2013-10-01
Twisting of off-shell supermultiplets in models with (1+1)-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all fully off-shell supersymmetric models with (BV/BRST-treated) constraints.
Effects Of Twist On Ceramic Threads
Sawko, Paul M.; Tran, Huy Kim
1989-01-01
Report describes study of effects of yarn twist and other manufacturing parameters on strength of ceramic sewing threads. Three types of thread considered; silica, aluminoborosilicate (ABS) with 14 percent boria, and ABS with 2 percent boria. For silica thread, best twist found 300 turns per meter. Produced highest break strength at temperatures up to about 540 degree C. Overall strengths of both ABS threads higher than silica thread. Threads used to stitch insulating blankets for reusable spacraft; must resist high temperatures and high aerodynamic loads of reentry into atmosphere of Earth.
Spectral flows and twisted topological theories
Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio
1995-01-01
We analyze the action of the spectral flows on N=2 twisted topological theories. We show that they provide a useful mapping between the two twisted topological theories associated to a given N=2 superconformal theory. This mapping can also be viewed as a topological algebra automorphism. In particular null vectors are mapped into null vectors, considerably simplifying their computation. We give the level 2 results. Finally we discuss the spectral flow mapping in the case of the DDK and KM realizations of the topological algebra.
A non-commuting twist in the partition function
Govindarajan, Suresh
2012-01-01
We compute a twisted index for an orbifold theory when the twist generating group does not commute with the orbifold group. The twisted index requires the theory to be defined on moduli spaces that are compatible with the twist. This is carried out for CHL models at special points in the moduli space where they admit dihedral symmetries. The commutator subgroup of the dihedral groups are cyclic groups that are used to construct the CHL orbifolds. The residual reflection symmetry is chosen to act as a `twist' on the partition function. The reflection symmetries do not commute with the orbifolding group and hence we refer to this as a non-commuting twist. We count the degeneracy of half-BPS states using the twisted partition function and find that the contribution comes mainly from the untwisted sector. We show that the generating function for these twisted BPS states are related to the Mathieu group M_{24}.
Resonant absorption of kink MHD waves by magnetic twist in coronal loops
Ebrahimi, Z
2015-01-01
There is ample evidences of twisted magnetic structures in the corona. This motivates us to consider the magnetic twist as the cause of Alfven frequency continuum in coronal loops, which can support the resonant absorption as the rapid damping mechanism for the observed coronal kink MHD oscillations. For a straight cylindrical compressible zero-beta thin flux tube with a magnetic twist in a thin boundary and straight magnetic field in the interior and exterior regions as well as a step-like radial density profile, we derive the dispersion relation and solve it analytically. Consequently, we obtain the frequencies and damping rates of the fundamental (l=1) and first/second overtones (l=2,3) kink (m=1) MHD modes. We conclude that the resonant absorption by the magnetic twist can justify the rapid damping of kink MHD waves observed in coronal loops. Furthermore, the magnetic twist in the inhomogeneous layer can achieve deviations from P_1/P_2=2 and P_1/P_3=3 of the same order of magnitude as in the observations.
Bogoliubov coefficients for the twist operator in the D1D5 CFT
Energy Technology Data Exchange (ETDEWEB)
Carson, Zaq, E-mail: carson.231@osu.edu; Mathur, Samir D., E-mail: mathur.16@osu.edu; Turton, David, E-mail: turton.7@osu.edu
2014-12-15
The D1D5 CFT is a holographic dual of a near-extremal black hole in string theory. The interaction in this theory involves a twist operator which joins together different copies of a free CFT. Given a large number of D1 and D5 branes, the effective length of the circle on which the CFT lives is very large. We develop a technique to study the effect of the twist operator in the limit where the wavelengths of excitations are short compared to this effective length, which we call the ‘continuum limit’. The method uses Bogoliubov coefficients to compute the effect of the twist operator in this limit. For bosonic fields, we use the method to reproduce recent results describing the effect of the twist operator when it links together CFT copies with windings M and N, producing a copy of winding M+N. We also comment on possible generalizations of our results. The methods developed here may help in understanding the twist interaction at higher orders. This in turn should provide insight into the thermalization process in the D1D5 CFT, which gives a holographic description of black hole formation.
Bogoliubov coefficients for the twist operator in the D1D5 CFT
Carson, Zaq; Turton, David
2014-01-01
The D1D5 CFT is a holographic dual of a near-extremal black hole in string theory. The interaction in this theory involves a twist operator which joins together different copies of a free CFT. Given a large number of D1 and D5 branes, the effective length of the circle on which the CFT lives is very large. We develop a technique to study the effect of the twist operator in the limit where the wavelengths of excitations are short compared to this effective length, which we call the 'continuum limit'. The method uses Bogoliubov coefficients to compute the effect of the twist operator in this limit. For bosonic fields, we use the method to reproduce recent results describing the effect of the twist operator when it links together CFT copies with windings M and N, producing a copy of winding M+N. We also comment on possible generalizations of our results. The methods developed here may help in understanding the twist interaction at higher orders. This in turn should provide insight into the thermalization process...
Cutoff effects for Wilson twisted mass fermions at tree-level of perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Cichy, K.; Kujawa, A. [Poznan Univ. (Poland). Faculty of Physics; Gonzalez Lopez, J. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik]|[Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-10-15
We study cutoff effects at tree-level of perturbation theory for standardWilson andWilson twisted mass fermionic lattice actions with N{sub f}=2 flavour degenerate quarks. The discretization effects are investigated by computing the mass spectrum and decay amplitudes for different hadron interpolating fields and the scaling behaviour towards the continuum limit is analyzed. It is shown that the Wilson and the mass average methods are equivalent and lead to O(a) improved R{sub 5}-parity even lattice observables. We also demonstrate that automatic O(a) improvement works in case of Wilson twisted mass fermions at maximal twist and that this improvement is realized even if the condition of maximal twist is achieved only up to O(a) cutoff effects. We demonstrate that in the chiral limit standard Wilson fermions show scaling violations of O(a{sup 2}) while for maximally twisted mass fermions these violations are only of O(a{sup 4}). For our analytical calculations, lattices with sizes L=aN and periodic boundary conditions in the spatial directions have been chosen while infinite extension in the time direction, L4={infinity}, is considered. (orig.)
Angular Momentum of Twisted Radiation from an Electron in Spiral Motion
Katoh, M; Kawaguchi, H; Tsuchiya, K; Ohmi, K; Kaneyasu, T; Taira, Y; Hosaka, M; Mochihashi, A; Takashima, Y
2016-01-01
We theoretically demonstrate for the first time that a single free electron in circular/spiral motion emits twisted photons carrying well defined orbital angular momentum along the axis of the electron circulation, in adding to spin angular momentum. We show that, when the electron velocity is relativistic, the radiation field contains harmonic components and the photons of l-th harmonic carry lhbar total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and more ubiquitous in laboratories and in nature than ever been thought.
Chaichian, M; Presnajder, P; Tureanu, A
2005-04-22
We present a systematic framework for noncommutative (NC) quantum field theory (QFT) within the new concept of relativistic invariance based on the notion of twisted Poincare symmetry, as proposed by Chaichian et al. [Phys. Lett. B 604, 98 (2004)]. This allows us to formulate and investigate all fundamental issues of relativistic QFT and offers a firm frame for the classification of particles according to the representation theory of the twisted Poincare symmetry and as a result for the NC versions of CPT and spin-statistics theorems, among others, discussed earlier in the literature. As a further application of this new concept of relativism we prove the NC analog of Haag's theorem.
Topologically twisted renormalization group flow and its holographic dual
Nakayama, Yu
2017-03-01
Euclidean field theories admit more general deformations than usually discussed in quantum field theories because of mixing between rotational symmetry and internal symmetry (also known as topological twist). Such deformations may be relevant, and if the subsequent renormalization group flow leads to a nontrivial fixed point, it generically gives rise to a scale invariant Euclidean field theory without conformal invariance. Motivated by an ansatz studied in cosmological models some time ago, we develop a holographic dual description of such renormalization group flows in the context of AdS /CFT . We argue that the nontrivial fixed points require fine-tuning of the bulk theory, in general, but remarkably we find that the O (3 ) Yang-Mills theory coupled with the four-dimensional Einstein gravity in the minimal manner supports such a background with the Euclidean anti-de Sitter metric.
Coronal heating by the partial relaxation of twisted loops
Bareford, Michael; Browning, Philippa
2012-01-01
Context: Relaxation theory offers a straightforward method for estimating the energy that is released when a magnetic field becomes unstable, as a result of continual convective driving. Aims: We present new results obtained from nonlinear magnetohydrodynamic (MHD) simulations of idealised coronal loops. The purpose of this work is to determine whether or not the simulation results agree with Taylor relaxation, which will require a modified version of relaxation theory applicable to unbounded field configurations. Methods: A three-dimensional (3D) MHD Lagrangian-remap code is used to simulate the evolution of a line-tied cylindrical coronal loop model. This model comprises three concentric layers surrounded by a potential envelope; hence, being twisted locally, each loop configuration is distinguished by a piecewise-constant current profile. Initially, all configurations carry zero-net-current fields and are in ideally unstable equilibrium. The simulation results are compared with the predictions of helicity ...
Topologically twisted renormalization group flow and its holographic dual
Nakayama, Yu
2016-01-01
Euclidean field theories admit more general deformations than usually discussed in quantum field theories because of mixing between rotational symmetry and internal symmetry (a.k.a topological twist). Such deformations may be relevant, and if the subsequent renormalization group flow leads to a non-trivial fixed point, it generically gives rise to a scale invariant Euclidean field theory without conformal invariance. Motivated by an ansatz studied in cosmological models some time ago, we develop a holographic dual description of such renormalization group flows in the context of AdS/CFT. We argue that the non-trivial fixed points require fine-tuning of the bulk theory in general, but remarkably we find that the $O(3)$ Yang-Mills theory coupled with the four-dimensional Einstein gravity in the minimal manner supports such a background with the Euclidean AdS metric.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-11-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-08-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
Coupling Current and Hysteresis Losses of Bi2212 Round Wires with Twisted Filaments
Yang, I; Young, EA; Falorio, I; Ballarino, A; Bottura, L; Miao, H; Huang, Y
2015-01-01
AC loss measurements have been carried out on Bi2212 round wires of different twist pitches. With systematical variation of sample temperature (5 K – 70 K) and ac field amplitude (≤0.2 T) as well as frequency (20 Hz – 2 kHz), this work shows (a) the full coupling of the non-twisted wire, (b) the uncoupling of sub-wires by twisting at moderate pitch up to 12 mm, (c) a relatively short time constant of milliseconds for the coupling current due to a high transverse resistivity, and (d) an effective (de)coupling diameter of 0.4mm about 1.6x of sub-wire bundles. The results suggest a promising potential for improving filament decoupling.
Chern character in twisted K-theory equivariant and holomorphic cases
Mathai, V; Mathai, Varghese; Stevenson, Danny
2003-01-01
It has been argued by Witten and others that in the presence of a nontrivial B-field, D-brane charges in type IIB string theories are measured by twisted K-theory. In joint work with Bouwknegt, Carey and Murray it was proved that twisted K-theory is canonically isomorphic to bundle gerbe K-theory, whose elements are ordinary vector bundles on a principal projective unitary bundle, with an action of the bundle gerbe determined by the principal projective unitary bundle. The principal projective unitary bundle is in turn determined by the twist. In this paper, we study in more detail the Chern-Weil representative of the Chern character of bundle gerbe K-theory that was introduced previously, and we also extend it to the equivariant and holomorphic cases. Included is a discussion of interesting examples.
Twisting singular solutions of Bethe's equations
Nepomechie, Rafael I
2014-01-01
The Bethe equations for the periodic XXX and XXZ spin chains admit singular solutions, for which the corresponding eigenvalues and eigenvectors are ill-defined. We use a twist regularization to derive conditions for such singular solutions to be physical, in which case they correspond to genuine eigenvalues and eigenvectors of the Hamiltonian.
Disconnected Loops with Twisted Mass Lattice QCD
Wilcox, W; Morgan, R; Lewis, R; Wilcox, Walter; Darnell, Dean; Morgan, Ron; Lewis, Randy
2005-01-01
We give a general introduction and discussion of the issues involved in using the twisted mass formulation of lattice fermions in the context of disconnected loop calculations, including a short orientation on the present experimental situation for nucleon strange quark form factors. A prototype calculation of the disconnected part of the nucleon scalar form factor is described.
Phase diagram of twisted mass lattice QCD
Sharpe, Stephen R.; Wu, Jackson M.
2004-11-01
We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m2π/(4πfπ)2˜aΛ (a being the lattice spacing, and Λ=ΛQCD). We then focus on the region where m2π/(4πfπ)2˜(aΛ)2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is nonvanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transition extends into the twisted mass plane, ending with two symmetrical second order points at which the mass of the neutral pion vanishes. We provide graphs of the condensate and pion masses for both scenarios, and note a simple mathematical relation between them. These results may be of importance to numerical simulations.
Gluon polarization and higher twist effects
Leader, Elliot; Stamenov, Dimiter
2008-01-01
We examine the influence of the recent CLAS and COMPASS experiments on our understanding of higher twist (HT) effects and the gluon polarization, and show how EIC could discriminate between negative and positive gluon polarizations. We comment on the issue of HT and the recent DSSV analysis.
Twisted Ribbons: Theory, Experiment and Applications
Chopin, Julien; Davidovitch, Benjamin; Silva, Flavio A.; Toledo Filho, Romildo D.; Kudrolli, Arshad
2014-03-01
We investigate, experimentally and theoretically, the buckling and wrinkling instabilities of a pre-stretched ribbon upon twisting and propose strategies for the fabrication of structured yarns. Our experiment consists in a thin elastic sheet in the form of a ribbon which is initially stretched by a fixed load and then subjected to a twist by rotating the ends through a prescribed angle. We show that a wide variety of shapes and instabilities can be obtained by simply varying the applied twist and tension. The observed structures which include helicoids with and without longitudinal and transverse wrinkles, and spontaneous creases, can be organized in a phase diagram with the tension and twist angle as control parameters [J. Chopin and A. Kudrolli, PRL (2013)]. Using a far-from-threshold analysis and a slender body approximation, we provide a comprehensive understanding of the longitudinal and transverse instabilities and show that several regimes emerge depending on subtle combinations of loading and geometrical parameters. Further, we show that the wrinkling instabilities can be manipulated to fabricate structured yarns which may be used to encapsulate amorphous materials or serve as efficient reinforcements for cement-based composites. COPPETEC / CNPq - Science Without Border Program
HOMOCLINIC TWIST BIFURCATIONS WITH Z(2) SYMMETRY
ARONSON, DG; VANGILS, SA; KRUPA, M
1994-01-01
We analyze bifurcations occurring in the vicinity of a homoclinic twist point for a generic two-parameter family of Z2 equivariant ODEs in four dimensions. The results are compared with numerical results for a system of two coupled Josephson junctions with pure capacitive load.
Redefining B twisted topological sigma models
Jonghe, F. de; Termonia, P.; Troost, W.; Vandoren, S.
2007-01-01
The recently proposed procedure to perform the topological B-twist in rigid N = 2 models is applied to the case of the o model on a Kähler manifold. This leads to an alternative description of Witten’s topological o model, which allows for a proper BRST interpretation and ghost number assignement. W
Generalized Weyl modules for twisted current algebras
Makedonskyi, I. A.; Feigin, E. B.
2017-08-01
We introduce the notion of generalized Weyl modules for twisted current algebras. We study their representation-theoretic and combinatorial properties and also their connection with nonsymmetric Macdonald polynomials. As an application, we compute the dimension of the classical Weyl modules in the remaining unknown case.
Analysis of Cohesion inOliver Twist
Institute of Scientific and Technical Information of China (English)
程文文
2016-01-01
Cohesion is an important concept in the study of stylistics. This thesis aims to study the applications of cohesion in the Charles Dicken’ world-famous novelOliver Twist, including both the grammatical and lexical cohesive devices in the work.
Vacuum Polarization of Twisted Scalars in a Non-simply Connected Space-time and Its Effects
Institute of Scientific and Technical Information of China (English)
吴普训; 余洪伟
2002-01-01
The vacuum polarization due to twisted scalar fields is investigated in a non-simply connected space time. It is found that some photon modes acquire an imaginary topological mass, thus travelling at a superluminal speed.Topological bi-refringence is expected for photons propagating perpendicularly to the compactification direction.The effect of a topological photon mass on the static properties of electromagnetic fields is also considered for the cases of both twisted and untwisted scalar fields. Our result shows that in the untwisted case the magnetic field is screened along the radial direction for massive photon modes, while in the twisted case no screening occurs and the magnetic fields merely oscillate.
Twisted 3D holograms for self-referencing interferometers in metrology and imaging
Berz, Martin
2016-01-01
The interference between radiation fields superposed appropriately contains all available information about the source. This will be recapitulated for coherent and incoherent fields. We will further analyze a new kind of twisted 3D interferometer which allows us to generate interferograms with high information content. The physical basis for these devices is the geometric parallel transport of electric fields along a 3D path in space. This concept enables us to build very compact 3D interferometers.
Higher Twist Distribution Amplitudes of the Nucleon in QCD
Braun, V M; Mahnke, N; Stein, E
2000-01-01
We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A complete set of distribution amplitudes is constructed, which satisfies equations of motion and constraints that follow from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules.
Charged Magnetic Brane Correlators and Twisted Virasoro Algebras
D'Hoker, Eric
2011-01-01
Prior work using gauge/gravity duality has established the existence of a quantum critical point in the phase diagram of 3+1-dimensional gauge theories at finite charge density and background magnetic field. The critical theory, obtained by tuning the dimensionless charge density to magnetic field ratio, exhibits nontrivial scaling in its thermodynamic properties, and an associated nontrivial dynamical critical exponent. In the present work, we analytically compute low energy correlation functions in the background of the charged magnetic brane solution to 4+1-dimensional Einstein-Maxwell-Chern-Simons theory, which represents the bulk description of the critical point. Results are obtained for neutral scalar operators, the stress tensor, and the U(1)-current. The theory is found to exhibit a twisted Virasoro algebra, constructed from a linear combination of the original stress tensor and chiral U(1)-current. The effective speed of light in the IR is renormalized downward for one chirality, but not the other, ...
Twisted accretion curtains in the intermediate polar FO Aquarii
Evans, P A; Cropper, G R M; Hellier, Coel; Cropper, Gavin Ramsay & Mark
2004-01-01
We report on a ~37-ks XMM-Newton observation of the intermediate polar FO Aquarii, presenting X-ray and UV data from the EPIC and OM cameras. We find that the system has changed from its previously reported state of disc-overflow accretion to one of purely disc-fed accretion. We detect the previously reported `notch' feature in the X-ray spin pulse, and explain it as a partial occultation of the upper accretion pole. Maximum flux of the quasi-sinusoidal UV pulse coincides with the notch, in keeping with this idea. However, an absorption dip owing to the outer accretion curtains occurs 0.27 later than the expected phase, which implies that the accretion curtains are twisted, trailing the magnetic poles. This result is the opposite of that reported in PQ Gem, where accreting field lines were found to lead the pole. We discuss how such twists relate to the accretion torques and thus the observed period changes of the white dwarfs, but find no simple connection.
The force-free twisted magnetosphere of a neutron star
Akgün, T.; Miralles, J. A.; Pons, J. A.; Cerdá-Durán, P.
2016-10-01
We present a detailed analysis of the properties of twisted, force-free magnetospheres of non-rotating neutron stars, which are of interest in the modelling of magnetar properties and evolution. In our models the magnetic field smoothly matches to a current-free (vacuum) solution at some large external radius, and they are specifically built to avoid pathological surface currents at any of the interfaces. By exploring a large range of parameters, we find a few remarkable general trends. We find that the total dipolar moment can be increased by up to 40 per cent with respect to a vacuum model with the same surface magnetic field, due to the contribution of magnetospheric currents to the global magnetic field. Thus, estimates of the surface magnetic field based on the large-scale dipolar braking torque are slightly overestimating the surface value by the same amount. Consistently, there is a moderate increase in the total energy of the model with respect to the vacuum solution of up to 25 per cent, which would be the available energy budget in the event of a fast, global magnetospheric reorganization commonly associated with magnetar flares. We have also found the interesting result of the existence of a critical twist (ϕmax ≲ 1.5 rad), beyond which we cannot find any more numerical solutions. Combining the models considered in this paper with the evolution of the interior of neutron stars will allow us to study the influence of the magnetosphere on the long-term magnetic, thermal, and rotational evolution.
Evolution of twist-shear and dip-shear in Faring active region NOAA 10930
Gosain, Sanjay
2010-01-01
We study the evolution of magnetic shear angle in a flare productive active region NOAA 10930. The magnetic shear angle is defined as the deviation in the orientation of the observed magnetic field vector with respect to the potential field vector. The shear angle is measured in horizontal as well as vertical plane. The former is computed by taking the difference between the azimuth angles of the observed and potential field and is called the twist-shear, while the latter is computed by taking the difference between the inclination angles of the observed and potential field and is called the dip-shear. The evolution of the two shear angles is then tracked over a small region located over the sheared penumbra of the delta sunspot in NOAA 10930. We find that, while the twist-shear shows an increasing trend after the flare the dip-shear shows a significant drop after the flare.
Twisted mass QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, E.M.; Mueller-Preussker, M.; Petschlies, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Lombardo, M.P. [Istituto Nazionale di Fisica Nucleare, LNF, Frascati (Italy); Philipsen, O.; Zeidlewicz, L. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Sternbeck, A. [Adelaide Univ. (Australia). CSSM School of Chemistry and Physics
2007-10-15
We discuss the use of Wilson fermions with twisted mass for simulations of QCD thermodynamics. As a prerequisite for a future analysis of the finite-temperature transition making use of automatic {partial_derivative} (a) improvement, we investigate the phase structure in the space spanned by the hopping parameter {kappa}, the coupling {beta}, and the twisted mass parameter {mu}. We present results for N{sub f}=2 degenerate quarks on a 16{sup 3} x 8 lattice, for which we investigate the possibility of an Aoki phase existing at strong coupling and vanishing {mu}, as well as of a thermal phase transition at moderate gauge couplings and non-vanishing {mu}. (orig.)
Factorising the 3D Topologically Twisted Index
Cabo-Bizet, Alejandro
2016-01-01
In this work, path integral representations of the 3D topologically twisted index were studied. First, the index can be "factorised" into a couple of "blocks". The "blocks" being the partition functions of a type A semi-topological twisting of 3D N = 2 SYM placed on $\\mathbb{S}_2\\times (0, \\pi)$ and $\\mathbb{S}_2 \\times (\\pi, 2 \\pi)$ respectively. Second, as the path integral of the aforementioned theory over $\\mathbb{S}_2$ times $\\mathbb{S}_1$ with a point excluded. In this way we recover the sum over fluxes from integration over the real path and without sacrificing positive definiteness of the bosonic part of the localising action. We also reproduce the integration over the complex contour by using the localising term with positive definite bosonic part.
Valve-aided twisted Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Jaya Rajkumar, M.; Saha, U.K.
2006-05-15
Accessories, such as end plates, deflecting plates, shielding and guide vanes, may increase the power of a Savonius rotor, but make the system structurally complex. In such cases, the rotor can develop a relatively large torque at small rotational speeds and is cheap to build, however it harnesses only a small fraction of the incident wind energy. Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades. Such methods have been studied experimentally with a twisted-blade Thus improving a Savonius rotor's energy capture. This new concept has been named as the 'Valve-Aided Twisted Savonius'rotor. Tests were conducted in a low-speed wind tunnel to evaluate performance. This mechanism is found to be independent of flow direction, and shows potential for large machines. [Author].
Overlap fermions on a twisted mass sea
Bär, O; Schäefer, S; Scorzato, L; Shindler, A
2006-01-01
We present first results of a mixed action project. We analyze gauge configurations generated with two flavors of dynamical twisted mass fermions. Neuberger's overlap Dirac operator is used for the valence sector. The various choices in the setup of the simulation are discussed. We employ chiral perturbation theory to describe the effects of using different actions in the sea and valence sector at non-zero lattice spacing.
Disconnected diagrams with twisted-mass fermions
Abdel-Rehim, Abdou; Constantinou, Martha; Finkenrath, Jacob; Hadjiyiannakou, Kyriakos; Jansen, Karl; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, Alejandro Vaquero
2016-01-01
The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction, all of them for the nucleon. A detailed error analysis for each observable follows, showing the strengths and weaknesses of the one-end trick. Alternatives are discussed.
DNA Packaging in Bacteriophage: Is Twist Important?
Spakowitz, Andrew James; Wang, Zhen-Gang
2005-01-01
We study the packaging of DNA into a bacteriophage capsid using computer simulation, specifically focusing on the potential impact of twist on the final packaged conformation. We perform two dynamic simulations of packaging a polymer chain into a spherical confinement: one where the chain end is rotated as it is fed, and one where the chain is fed without end rotation. The final packaged conformation exhibits distinct differences in these two cases: the packaged conformation from feeding with...
On rectangular HOMFLY for twist knots
Kononov, Ya
2016-01-01
As a new step in the study of rectangularly-colored knot polynomials, we reformulate the prescription of arXiv:1606.06015 for twist knots in the double-column representations $R=[rr]$ in terms of skew Schur polynomials. These, however, are mysteriously shifted from the standard topological locus, what makes further generalization to arbitrary $R=[r^s]$ not quite straightforward.
Twisted Radiation by Electrons in Spiral Motion
Katoh, M; Mirian, N S; Konomi, T; Taira, Y; Kaneyasu, T; Hosaka, M; Yamamoto, N; Mochihashi, A; Takashima, Y; Kuroda, K; Miyamoto, A; Miyamoto, K; Sasaki, S
2016-01-01
We theoretically show that a single free electron in circular/spiral motion radiates an electromagnetic wave possessing helical phase structure and carrying orbital angular momentum. We experimentally demonstrate it by double-slit diffraction on radiation from relativistic electrons in spiral motion. We show that twisted photons should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in astrophysics. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.
Structure and deformations of strongly magnetized neutron stars with twisted torus configurations
Ciolfi, R; Gualtieri, L
2010-01-01
We construct general relativistic models of stationary, strongly magnetized neutron stars. The magnetic field configuration, obtained by solving the relativistic Grad-Shafranov equation, is a generalization of the twisted torus model recently proposed in the literature; the stellar deformations induced by the magnetic field are computed by solving the perturbed Einstein's equations; stellar matter is modeled using realistic equations of state. We find that in these configurations the poloidal field dominates over the toroidal field and that, if the magnetic field is sufficiently strong during the first phases of the stellar life, it can produce large deformations.
Twisted spectral triple for the Standard Model and spontaneous breaking of the Grand Symmetry
Devastato, Agostino
2014-01-01
Grand symmetry models in noncommutative geometry have been introduced to explain how to generate minimally (i.e. without adding new fermions) an extra scalar field beyond the standard model, which both stabilizes the electroweak vacuum and makes the computation of the mass of the Higgs compatible with its experimental value. In this paper, we use Connes-Moscovici twisted spectral triples to cure a technical problem of the grand symmetry, that is the appearance together with the extra scalar field of unbounded vectorial terms. The twist makes these terms bounded, and also permits to understand the breaking to the standard model as a dynamical process induced by the spectral action. This is a spontaneous breaking from a pre-geometric Pati-Salam model to the almost-commutative geometry of the standard model, with two Higgs-like fields: scalar and vector.
Helical ${\\alpha}$-dynamos as twisted magnetic flux tubes in Riemannian space
de Andrade, Garcia
2007-01-01
Analytical solution of ${\\alpha}$-dynamo equation representing strongly torsioned helical dynamo is obtained in the thin twisted Riemannian flux tubes approximation. The $\\alpha$ factor possesses a fundamental contribution from torsion which is however weaken in the thin tubes approximation. It is shown that assuming that the poloidal component of the magnetic field is in principle time-independent, the toroidal magnetic field component grows very fast in time, actually it possesses a linear time dependence, while the poloidal component grows under the influence of torsion or twist of the flux tube. The toroidal component decays spatially with as $r^{-2}$ while vorticity may decay as $r^{-5}$ (poloidal component) where r represents the radial distance from the magnetic axis of flux tube. Toroidal component of vorticity decays as $r^{-1}$. In turbulent dynamos unbounded magnetic fields may decay at least as $r^{-3}$.
Electrostatic twisted modes in multi-component dusty plasmas
Energy Technology Data Exchange (ETDEWEB)
Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Pohang University of Sciences and Technology, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ikram, M. [Department of Physics, Hazara University, Mansehra 21300 (Pakistan)
2016-01-15
Various electrostatic twisted modes are re-investigated with finite orbital angular momentum in an unmagnetized collisionless multi-component dusty plasma, consisting of positive/negative charged dust particles, ions, and electrons. For this purpose, hydrodynamical equations are employed to obtain paraxial equations in terms of density perturbations, while assuming the Gaussian and Laguerre-Gaussian (LG) beam solutions. Specifically, approximated solutions for potential problem are studied by using the paraxial approximation and expressed the electric field components in terms of LG functions. The energy fluxes associated with these modes are computed and corresponding expressions for orbital angular momenta are derived. Numerical analyses reveal that radial/angular mode numbers as well as dust number density and dust charging states strongly modify the LG potential profiles attributed to different electrostatic modes. Our results are important for understanding particle transport and energy transfer due to wave excitations in multi-component dusty plasmas.
Accurate measurement of the helical twisting power of chiral dopants
Kosa, Tamas; Bodnar, Volodymyr; Taheri, Bahman; Palffy-Muhoray, Peter
2002-03-01
We propose a method for the accurate determination of the helical twisting power (HTP) of chiral dopants. In the usual Cano-wedge method, the wedge angle is determined from the far-field separation of laser beams reflected from the windows of the test cell. Here we propose to use an optical fiber based spectrometer to accurately measure the cell thickness. Knowing the cell thickness at the positions of the disclination lines allows determination of the HTP. We show that this extension of the Cano-wedge method greatly increases the accuracy with which the HTP is determined. We show the usefulness of this method by determining the HTP of ZLI811 in a variety of hosts with negative dielectric anisotropy.
Magnetic Plasmon Sensing in Twisted Split-Ring Resonators
Directory of Open Access Journals (Sweden)
J. X. Cao
2012-01-01
Full Text Available We studied the sensing properties of stereo-SRRs metamaterials composed from two twisted split-ring resonators (SRRs. Due to the strong hybridization effect in the system, the polarization state of the transmitted wave is greatly changed at resonances. Since the stereo-SRRs structure is strongly coupled to the surrounding medium, the polarization change of the transmitted waves is quite sensitive to the refractive index change of the environment medium. The polarization ratio PRtran = Ty/Tx is used as sensing parameter and its figure of merit can reach 22.3 at the hybridized magnetic plasmon resonance. The results showed that the stereo-SRRs metamaterial can be applied to optical sensors an or other related field.
The Instanton-Dyon Liquid Model V: Twisted Light Quarks
Liu, Yizhuang; Zahed, Ismail
2016-01-01
We discuss an extension of the instanton-dyon liquid model that includes twisted light quarks in the fundamental representation with explicit $Z_{N_c}$ symmetry for the case with equal number of colors $N_c$ and flavors $N_f$. We map the model on a 3-dimensional quantum effective theory, and analyze it in the mean-field approximation. The effective potential and the vacuum chiral condensates are made explicit for $N_f=N_c=2, 3$. The low temperature phase is center symmetric but breaks spontaneously flavor symmetry with $N_f-1$ massless pions. The high temperature phase breaks center symmetry but supports finite and unequal quark condensates.
Localized topological states in Bragg multihelicoidal fibers with twist defects
Alexeyev, C. N.; Lapin, B. P.; Milione, G.; Yavorsky, M. A.
2016-06-01
We have studied the influence of a twist defect in multihelicoidal Bragg fibers on the emerging of localized defect modes. We have shown that if such a fiber is excited with a Gaussian beam this leads to the appearance of a defect-localized topological state, whose topological charge coincides with the order of rotational symmetry of the fiber's refractive index. We have shown that this effect has a pronounced crossover behavior. We have also formulated a principle of creating the systems that can nestle defect-localized topologically charged modes. According to this principle, such systems have to possess topological activity, that is, the ability to change the topological charge of the incoming field, and operate in the Bragg regime.
Expression of Twist Gene in Primary Liver Cancer
Institute of Scientific and Technical Information of China (English)
XU Jing; CHEN Xiaoping
2007-01-01
In order to investigate the possibility of overexpression of Twist in primary liver cancer (PLC), the Twist expression was detected by using immunohistochemical analysis and RT-PCR assay in 45 patients with PLC. Control tissues were obtained from 9 patients with liver hemangioma. It was found that in 36 (80.0%) out of 45 PLC patients, cancerous regions showed positive cytoplasm and nucleus staining for Twist with a diffuse pattern. In noncancerous adjacent areas and control liver tissues, the expression of Twist was 57.8% and 22.2% respectively. The results of RT-PCR assay re- vealed that the expression of Twist was stronger in the cancerous tissues than that in the noncancer- ous adjacent tissues. It was suggested that the expression of Twist was up-regulated in PLC, which play an important role in the progression of PLC.
Twisted exponential sums of polynomials in one variable
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The twisted T-adic exponential sums associated to a polynomial in one variable are studied.An explicit arithmetic polygon in terms of the highest two exponents of the polynomial is proved to be a lower bound of the Newton polygon of the C-function of the twisted T-adic exponential sums.This bound gives lower bounds for the Newton polygon of the L-function of twisted p-power order exponential sums.
Negative Regulatory Role of TWIST1 on SNAIL Gene Expression.
Forghanifard, Mohammad Mahdi; Ardalan Khales, Sima; Farshchian, Moein; Rad, Abolfazl; Homayouni-Tabrizi, Masoud; Abbaszadegan, Mohammad Reza
2017-01-01
Epithelial-mesenchymal transition (EMT) is crucial for specific morphogenetic movements during embryonic development as well as pathological processes of tumor cell invasion and metastasis. TWIST and SNAIL play vital roles in both developmental and pathological EMT. Our aim in this study was to investigate the functional correlation between TWIST1 and SNAIL in human ESCC cell line (KYSE-30). The packaging cell line GP293T was cotransfected with either control retroviral pruf-IRES-GFP plasmid or pruf-IRES-GFP-hTWIST1 and pGP plasmid. The KYSE-30 ESCC cells were transduced with produced viral particles and examined with inverted fluorescence microscope. DNA was extracted from transduced KYSE-30 cells and analyzed for copy number of integrated retroviral sequences in the target cell genome. The concentration of retroviral particles was determined by Real-time PCR. After RNA extraction and cDNA synthesis, the mRNA expression of TWIST1 and SNAIL was assessed by comparative real-time PCR amplification. Ectopic expression of TWIST1 in KYSE-30, dramatically reduces SNAIL expression. Retroviral transduction enforced TWIST1 overexpression in GFP-hTWIST1 nearly 9 folds in comparison with GFP control cells, and interestingly, this TWIST1 enforced expression caused a - 7 fold decrease of SNAIL mRNA expression in GFP-hTWIST1 compared to GFP control cells. Inverse correlation of TWIST1 and SNAIL mRNA levels may introduce novel molecular gene expression pathway controlling EMT process during ESCC aggressiveness and tumorigenesis. Consequently, these data extend the spectrum of biological activities of TWIST1 and propose that therapeutic repression of TWIST1 may be an effective strategy to inhibit cancer cell invasion and metastasis.
A twist tale of cancer metastasis and tumor angiogenesis.
Tseng, Jen-Chieh; Chen, Hsiao-Fan; Wu, Kou-Juey
2015-11-01
Twist1 is an evolutionally conserved transcription factor. Originally identified in Drosophila as a key regulator for mesoderm development, it was later implicated in many human diseases, including Saethre-Chotzen syndrome and cancer. Twist1's involvement in cancer has been well recognized. Driven by hypoxia-induced factor-1 (HIF-1), Twist1 has been considered as a proto-oncogene and its overexpression has been observed in a wide variety of human cancers. High expression level of Twist1 is closely related to tumor aggressiveness and metastatic potential. In cancer cells, Twist1 has been shown to function as a key regulator of epithelial-mesenchymal transition (EMT), a critical process for metastasis initiation. Twist1 has also been implicated in maintaining cancer stemness for self-renewal and chemoresistance. This review first summarizes the roles of Twist1 in embryo development and Saethre-Chotzen syndrome followed by a discussion of Twist1's critical functions in cancer. In particular, the review focuses on the recent discovery of Twist1's capability to promote endothelial transdifferentiation of cancer cells beyond EMT.
Twist1 activity thresholds define multiple functions in limb development
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson; Costantini, Frank; Behringer, Richard R.; Laufer, Ed
2010-01-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1−/− embryos die at midgestation. However, studies on early limb buds found that Twist1−/− mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional...
Twisted rudder for reducing fuel-oil consumption
Directory of Open Access Journals (Sweden)
Kim Jung-Hun
2014-09-01
Full Text Available Three twisted rudders fit for large container ships have been developed; 1 the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2 the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3 the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed
Twist decomposition of proton structure from BFKL and BK amplitudes
Motyka, Leszek
2014-01-01
An analysis of twist composition of Balitsky-Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit the BK evolution of color dipole -- proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models.
Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim
2016-06-01
We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model.
Non-destructive identification of twisted light.
Li, Pengyun; Wang, Bo; Song, Xinbing; Zhang, Xiangdong
2016-04-01
The non-destructive identification of the orbital angular momentum (OAM) is essential to various applications in the optical information processing. Here, we propose and demonstrate experimentally an efficient method to identify non-destructively the OAM by using a modified Mach-Zehnder interferometer. Our schemes are applicable not only to the case with integer charges, but also to optical vortices with noninteger charges. Our Letter presents the first experimental demonstration of the non-destructive identification of twisted light with integer or noninteger topological charges, which has potential applications in the OAM-based data transmission for optical communications.
Instanton corrections to twist-two operators
Alday, Luis F
2016-01-01
We present the calculation of the leading instanton contribution to the scaling dimensions of twist-two operators with arbitrary spin and to their structure constants in the OPE of two half-BPS operators in $\\mathcal N=4$ SYM. For spin-two operators we verify that, in agreement with $\\mathcal N=4$ superconformal Ward identities, the obtained expressions coincide with those for the Konishi operator. For operators with high spin we find that the leading instanton correction vanishes. This arises as the result of a rather involved calculation and requires a better understanding.
Quantum mass correction for the twisted kink
Pawellek, Michael
2008-01-01
We present an analytic result for the 1-loop quantum mass correction in semiclassical quantization for the twisted \\phi^4 kink on S^1 without explicit knowledge of the fluctuation spectrum. For this purpose we use the contour integral representation of the spectral zeta function. By solving the Bethe ansatz equations for the n=2 Lame equation we obtain an analytic expression for the corresponding spectral discriminant. We discuss the renormalization issues of this model. An energetically preferred size for the compact space is finally obtained.
Least-Squares Fitting Methods for Estimating the Winding Rate in Twisted Magnetic-Flux Tubes
Crouch, Ashley D
2012-01-01
We investigate least-squares fitting methods for estimating the winding rate of field lines about the axis of twisted magnetic-flux tubes. These methods estimate the winding rate by finding the values for a set of parameters that correspond to the minimum of the discrepancy between magnetic-field measurements and predictions from a twisted flux-tube model. For the flux-tube model used in the fitting, we assume that the magnetic field is static, axisymmetric, and does not vary in the vertical direction. Using error-free, synthetic vector magnetic-field data constructed with models for twisted magnetic-flux tubes, we test the efficacy of fitting methods at recovering the true winding rate. Furthermore, we demonstrate how assumptions built into the flux-tube models used for the fitting influence the accuracy of the winding-rate estimates. We identify the radial variation of the winding rate within the flux tube as one assumption that can have a significant impact on the winding-rate estimates. We show that the e...
The force-free twisted magnetosphere of a neutron star
Akgün, Taner; Pons, José A; Cerdá-Durán, Pablo
2016-01-01
We present a detailed analysis of the properties of twisted, force-free magnetospheres of non-rotating neutron stars, which are of interest in the modelling of magnetar properties and evolution. In our models the magnetic field smoothly matches to a current-free (vacuum) solution at some large external radius, and they are specifically built to avoid pathological surface currents at any of the interfaces. By exploring a large range of parameters, we find a few remarkable general trends. We find that the total dipolar moment can be increased by up to 40% with respect to a vacuum model with the same surface magnetic field, due to the contribution of magnetospheric currents to the global magnetic field. Thus, estimates of the surface magnetic field based on the large scale dipolar braking torque are slightly overestimating the surface value by the same amount. Consistently, there is a moderate increase in the total energy of the model with respect to the vacuum solution of up to 25%, which would be the available...
Some Relations between Twisted K-theory and E8 Gauge Theory
Mathai, V; Mathai, Varghese; Sati, Hisham
2004-01-01
Recently, Diaconescu, Moore and Witten provided a nontrivial link between K-theory and M-theory, by deriving the partition function of the Ramond-Ramond fields of Type IIA string theory from an E8 gauge theory in eleven dimensions. We give some relations between twisted K-theory and M-theory by adapting the method of Diaconescu-Moore-Witten and Moore-Saulina. In particular, we construct the twisted K-theory torus which defines the partition function, and also discuss the problem from the E8 loop group picture, in which the Dixmier-Douady class is the Neveu-Schwarz field. In the process of doing this, we encounter some mathematics that is new to the physics literature. In particular, the eta differential form, which is the generalization of the eta invariant, arises naturally in this context. We conclude with several open problems in mathematics and string theory.
Gruetzmann, Melchior
2014-01-01
Starting with minimal requirements from the physical experience with higher gauge theories, i.e. gauge theories for a tower of differential forms of different form degrees, we discover that all the structural identities governing such theories can be concisely recombined into a so-called Q-structure or, equivalently, a Lie infinity algebroid. This has many technical and conceptual advantages: Complicated higher bundles become just bundles in the category of Q-manifolds in this approach (the many structural identities being encoded in the one operator Q squaring to zero), gauge transformations are generated by internal vertical automorphisms in these bundles and even for a relatively intricate field content the gauge algebra can be determined in some lines only and is given by the so-called derived bracket construction. This article aims equally at mathematicians and theoretical physicists; each more physical section is followed by a purely mathematical one. While the considerations are valid for arbitrary hig...
Arshad, Kashif; Poedts, Stefaan; Lazar, Marian
2017-04-01
Nowadays electromagnetic (EM) fields have various applications in fundamental research, communication, and home appliances. Even though, there are still some subtle features of electromagnetic field known to us a century ago, yet to be utilized. It is because of the technical complexities to sense three dimensional electromagnetic field. An important characteristic of electromagnetic field is its orbital angular momentum (OAM). The angular momentum consists of two distinct parts; intrinsic part associated with the wave polarization or spin, and the extrinsic part associated with the orbital angular momentum (OAM). The orbital angular momentum (OAM) is inherited by helically phased light or helical (twisted) electric field. The investigations of Allen on lasers carrying orbital angular momentum (OAM), has initiated a new scientific and technological advancement in various growing fields, such as microscopy and imaging, atomic and nano-particle manipulation, ultra-fast optical communications, quantum computing, ionospheric radar facility to observe 3D plasma dynamics in ionosphere, photonic crystal fibre, OAM entanglement of two photons, twisted gravitational waves, ultra-intense twisted laser pulses and astrophysics. Recently, the plasma modes are also investigated with orbital angular momentum. The production of electron vortex beams and its applications are indicated by Verbeeck et al. The magnetic tornadoes (rotating magnetic field structures) exhibit three types of morphology i.e., spiral, ring and split. Leyser pumped helical radio beam carrying OAM into the Ionospheric plasma under High Frequency Active Auroral Research Program (HAARP) and characteristic ring shaped morphology is obtained by the optical emission spectrum of pumped plasma turbulence. The scattering phenomenon like (stimulated Raman and Brillouin backscattering) is observed to be responsible for the interaction between electrostatic and electromagnetic waves through orbital angular momentum. The
Directory of Open Access Journals (Sweden)
Yu. V. Razvin
2014-01-01
Full Text Available The paper demonstrates that the process of twist LC-pixel switching can be associated not only with a reorientation of liquid crystal molecules in the controlling electric field, but also with the effect of compression of the LC-spiral to the central area through layer thickness. In this case the time of LC-pixel total switching is decreased by almost three orders.
Yu. V. Razvin; V. A. Potachits
2014-01-01
The paper demonstrates that the process of twist LC-pixel switching can be associated not only with a reorientation of liquid crystal molecules in the controlling electric field, but also with the effect of compression of the LC-spiral to the central area through layer thickness. In this case the time of LC-pixel total switching is decreased by almost three orders.
Achiral boundaries and the twisted Yangian of the D5-brane
MacKay, Niall
2011-01-01
We consider integrable field theories with achiral boundary conditions and uncover the underlying achiral twisted Yangian algebra. This construction arises from old work on the bosonic principal chiral model on a half-line, but finds a modern realization as the hidden symmetry in the planar limit of the scattering of worldsheet excitations of the AdS/CFT light-cone superstring off a D5-brane.
Needleless electrospinning with twisted wire spinneret.
Holopainen, Jani; Penttinen, Toni; Santala, Eero; Ritala, Mikko
2015-01-16
A needleless electrospinning setup named 'Needleless Twisted Wire Electrospinning' was developed. The polymer solution is electrospun from the surface of a twisted wire set to a high voltage and collected on a cylindrical collector around the wire. Multiple Taylor cones are simultaneously self-formed on the downward flowing solution. The system is robust and simple with no moving parts aside from the syringe pump used to transport the solution to the top of the wire. The structure and process parameters of the setup and the results on the preparation of polyvinyl pyrrolidone (PVP), hydroxyapatite (HA) and bioglass fibers with the setup are presented. PVP fiber sheets with areas of 40 × 120 cm(2) and masses up to 1.15 g were prepared. High production rates of 5.23 g h(-1) and 1.40 g h(-1) were achieved for PVP and HA respectively. The major limiting factor of the setup is drying of the polymer solution on the wire during the electrospinning process which will eventually force to interrupt the process for cleaning of the wire. Possible solutions to this problem and other ways to develop the setup are discussed. The presented system provides a simple way to increase the production rate and area of fiber sheet as compared with the conventional needle electrospinning.
Holographic generation of highly twisted electron beams
Grillo, Vincenzo; Mafakheri, Erfan; Frabboni, Stefano; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wavefront corresponding to the electron's wavefunction forms a helical structure with a number of twists given by the \\emph{angular speed}. Beams with a high number of twists are of particular interest because they carry a high magnetic moment about the propagation axis. Among several different techniques, electron holography seems to be a promising approach to shape a \\emph{conventional} electron beam into a helical form with large values of angular momentum. Here, we propose and manufacture a nano-fabricated phase hologram for generating a beam of this kind with an orbital angular momentum up to 200$\\hbar$. Based on a novel technique the value of orbital angular momentum of the generated beam are measured, then compared with simulations. Our work, apart from the technological achievements, may lead to a way of generating electron beams with a high quanta of magnetic momen...
Twisting the [ital N]=2 string
Energy Technology Data Exchange (ETDEWEB)
Ketov, S.V.; Lechtenfeld, O. (Institut fuer Theoretische Physik, Universitaet Hannover, Appelstrasse 2, 30167 Hannover (Germany)); Parkes, A.J. (Department of Artificial Intelligence, 80 South Bridge, Edinburgh EH1 9HN (United Kingdom))
1995-03-15
The most general homogeneous monodromy conditions in [ital N]=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)[direct product][ital openZ][sub 2]. For classes which generate a discrete subgroup [Gamma], the corresponding target space backgrounds [ital openC][sup 1,1]/[Gamma] include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for [Gamma]=[ital open]1 (untwisted) and [Gamma]=[ital openZ][sub 2] (in the manner of Mathur and Mukhi), as well as for [Gamma] being a parabolic element of U(1,1). In particular, the 16 [ital openZ][sub 2]-twisted sectors of the [ital N]=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of spacetime'' supersymmetry, with the number of supersymmetries being dependent on global spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless spacetime'' fermions.
Twisted geometries, twistors and conformal transformations
Långvik, Miklos
2016-01-01
The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a time-like direction singled out. The isomorphism depends on the Immirzi parameter, and reduces to the identity when the parameter goes to infinity. Using this twistorial representation we study the action of the conformal group SU(2,2) on the classical phase space of loop quantum gravity, described by twisted geometry. The generators of translations and conformal boosts do not preserve the geometric structure, whereas the dilatation generator does. It corresponds to a 1-parameter family of embeddings of T*SL(2,C) in twistor space, and its action preserves the intrinsic geometry while changing the extrinsic one - that is the boosts among polyhedra. We discuss the implication of this action from a dynamical point of view, and compare it with a discretisation of the dilatation generator of the continuum phase space, given by the Lie derivative of the group character. At leading order in the continuu...
How the embryonic brain tube twists
Chen, Zi; Guo, Qiaohang; Forsch, Nickolas; Taber, Larry
2014-03-01
During early development, the tubular brain of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This deformation is one of the major organ-level symmetry-breaking events in development. Available evidence suggests that bending is caused by differential growth, but the mechanism for torsion remains poorly understood. Since the heart almost always loops in the same direction that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is virtually nonexistent, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. In addition, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model is used to interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''.
Structure of twisted and buckled bilayer graphene
Jain, Sandeep K.; Juričić, Vladimir; Barkema, Gerard T.
2017-03-01
We study the atomic structure of twisted bilayer graphene, with very small mismatch angles (θ ∼ {0.28}0), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for single-layer graphene, with a new term for out-of-plane deformations, (Jain et al 2015 J. Phys. Chem. C 119 9646) and an often-used interlayer potential (Kolmogorov et al 2005 Phys. Rev. B 71 235415). This combination of potentials is computationally cheap but accurate and precise at the same time, allowing us to study very large samples, which is necessary to reach very small mismatch angles in periodic samples. By performing large scale atomistic simulations, we show that the vortices appearing in the Moiré pattern in the twisted bilayer graphene samples converge to a constant size in the thermodynamic limit. Furthermore, the well known sinusoidal behavior of energy no longer persists once the misorientation angle becomes very small (θ \\lt {1}0). We also show that there is a significant buckling after the relaxation in the samples, with the buckling height proportional to the system size. These structural properties have direct consequences on the electronic and optical properties of bilayer graphene.
Cellularity of diagram algebras as twisted semigroup algebras
Wilcox, Stewart
2010-01-01
The Temperley-Lieb and Brauer algebras and their cyclotomic analogues, as well as the partition algebra, are all examples of twisted semigroup algebras. We prove a general theorem about the cellularity of twisted semigroup algebras of regular semigroups. This theorem, which generalises a recent result of East about semigroup algebras of inverse semigroups, allows us to easily reproduce the cellularity of these algebras.
Behaviour at infinity of solutions of twisted convolution equations
Energy Technology Data Exchange (ETDEWEB)
Volchkov, Valerii V; Volchkov, Vitaly V [Donetsk National University, Donetsk (Ukraine)
2012-02-28
We obtain a precise characterization of the minimal rate of growth at infinity of non-trivial solutions of twisted convolution equations in unbounded domains of C{sup n}. As an application, we obtain definitive versions of the two-radii theorem for twisted spherical means.
On the commutator length of a Dehn twist
Szepietowski, Blazej
2010-01-01
We show that on a nonorientable surface of genus at least 7 any power of a Dehn twist is equal to a single commutator in the mapping class group and the same is true, under additional assumptions, for the twist subgroup, and also for the extended mapping class group of an orientable surface of genus at least 3.
Quadratic Twists of Rigid Calabi–Yau Threefolds Over
DEFF Research Database (Denmark)
Gouvêa, Fernando Q.; Kiming, Ian; Yui, Noriko
2013-01-01
We consider rigid Calabi–Yau threefolds defined over Q and the question of whether they admit quadratic twists. We give a precise geometric definition of the notion of a quadratic twists in this setting. Every rigid Calabi–Yau threefold over Q is modular so there is attached to it a certain newfo...
Design optimization of a twist compliant mechanism with nonlinear stiffness
Tummala, Y.; Frecker, M. I.; Wissa, A. A.; Hubbard, J. E., Jr.
2014-10-01
A contact-aided compliant mechanism called a twist compliant mechanism (TCM) is presented in this paper. This mechanism has nonlinear stiffness when it is twisted in both directions along its axis. The inner core of the mechanism is primarily responsible for its flexibility in one twisting direction. The contact surfaces of the cross-members and compliant sectors are primarily responsible for its high stiffness in the opposite direction. A desired twist angle in a given direction can be achieved by tailoring the stiffness of a TCM. The stiffness of a compliant twist mechanism can be tailored by varying thickness of its cross-members, thickness of the core and thickness of its sectors. A multi-objective optimization problem with three objective functions is proposed in this paper, and used to design an optimal TCM with desired twist angle. The objective functions are to minimize the mass and maximum von-Mises stress observed, while minimizing or maximizing the twist angles under specific loading conditions. The multi-objective optimization problem proposed in this paper is solved for an ornithopter flight research platform as a case study, with the goal of using the TCM to achieve passive twisting of the wing during upstroke, while keeping the wing fully extended and rigid during the downstroke. Prototype TCMs have been fabricated using 3D printing and tested. Testing results are also presented in this paper.
Twisted tubular photobioreactor fluid dynamics evaluation for energy consumption minimization
Gómez-Pérez, C.A.; Espinosa Oviedo, J.J.; Montenegro Ruiz, L.C.; Boxtel, van A.J.B.
2017-01-01
This paper discusses a new tubular PhotoBioReactor (PBR) called twisted tubular PBR. The geometry of a twisted tubular PBR induces swirl mixing to guarantee good exposure of microalgae to Light-Dark (LD) cycles and to the nutrients and dissolved CO 2 . The paper analyses the energy uptake for fluid
Resonances and higher twist in polarized lepton-nucleon scattering
Edelmann, J; Kaiser, N; Weise, W
2000-01-01
We present a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g_1. For each of these moments, it is found that there exists a characteristic Q^2 region in which (perturbative) higher twist corrections coexist with (non-perturbative) resonance contribution of comparable magnitude.
Twisted Fock representations of noncommutative Kähler manifolds
Sako, Akifumi; Umetsu, Hiroshi
2016-09-01
We introduce twisted Fock representations of noncommutative Kähler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by applying creation operators to a vacuum state. "Twisted" means that creation operators are not Hermitian conjugate of annihilation operators in this representation. In deformation quantization of Kähler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the Kähler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative Kähler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative Kähler manifolds concretely.
Analysis list: Twist1 [Chip-atlas[Archive
Lifescience Database Archive (English)
Full Text Available Twist1 Embryo,Neural + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Tw...ist1.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Twist1.5.tsv http://dbarchive.biosciencedbc....jp/kyushu-u/mm9/target/Twist1.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Twist1.Embryo.tsv,http://dbarchive.bioscien...cedbc.jp/kyushu-u/mm9/colo/Twist1.Neural.tsv http://dbarchive.bioscience...dbc.jp/kyushu-u/mm9/colo/Embryo.gml,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Neural.gml ...
Twisted Fock Representations of Noncommutative K\\"ahler Manifolds
Sako, Akifumi
2016-01-01
We introduce twisted Fock representations of noncommutative K\\"ahler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by acting creation operators on a vacuum state. "Twisted" means that creation operators are not hermitian conjugate of annihilation operators in this representation. In deformation quantization of K\\"ahler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the K\\"ahler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative K\\"ahler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative K\\"ahler manifolds concretely.
On the performance analysis of Savonius rotor with twisted blades
Energy Technology Data Exchange (ETDEWEB)
Saha, U.K.; Rajkumar, M. Jaya [Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781 039 (India)
2006-09-15
The present investigation is aimed at exploring the feasibility of twisted bladed Savonius rotor for power generation. The twisted blade in a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0{sup o}). Performance analysis has been made on the basis of starting characteristics, static torque and rotational speed. Experimental evidence shows the potential of the twisted bladed rotor in terms of smooth running, higher efficiency and self-starting capability as compared to that of the conventional bladed rotor. Further experiments have been conducted in the same setup to optimize the twist angle. (author)
Direct Measurements of Magnetic Twist in the Solar Corona
Malanushenko, A; Longcope, D W
2012-01-01
In the present work we study evolution of magnetic helicity in the solar corona. We compare the rate of change of a quantity related to the magnetic helicity in the corona to the flux of magnetic helicity through the photosphere and find that the two rates are similar. This gives observational evidence that helicity flux across the photosphere is indeed what drives helicity changes in solar corona during emergence. For the purposes of estimating coronal helicity we neither assume a strictly linear force-free field, nor attempt to construct a non-linear force-free field. For each coronal loop evident in Extreme Ultraviolet (EUV) we find a best-matching line of a linear force-free field and allow the twist parameter alpha to be different for each line. This method was introduced and its applicability was discussed in Malanushenko et. al. (2009). The object of the study is emerging and rapidly rotating AR 9004 over about 80 hours. As a proxy for coronal helicity we use the quantity averaged over many reconstruc...
Saturation of Zeldovich Stretch-Twist-Fold Map Dynamos
Seta, Amit; Subramanian, Kandaswamy
2014-01-01
Zeldovich's stretch-twist fold (STF) dynamo provided a breakthrough in conceptual understanding of fast dynamos, including fluctuation or small scale dynamos. We study the evolution and saturation behaviour of two types of Baker's map dynamos, which have been used to model Zeldovich's STF dynamo process. Using such maps allows one to analyze dynamos at much higher magnetic Reynolds numbers $R_M$ as compared to direct numerical simulations. In the 2-strip map dynamo there is constant constructive folding while the 4-strip map dynamo also allows the possibility of field reversal. Incorporating a diffusive step parameterised by $R_M$, we find that the magnetic field $B(x)$ is amplified only above a critical $R_M=R_{crit} \\sim 4$ for both types of dynamos. We explore the saturation of these dynamos in 3 ways; by a renormalized decrease of the effective $R_M$ (Case I) or due to a decrease in the efficiency of field amplification by stretching (Case II), or a combination of both effects (Case III). For Case I, we s...
Twist1 activity thresholds define multiple functions in limb development.
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson C; Costantini, Frank; Behringer, Richard R; Laufer, Ed
2010-11-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1(-/-) embryos die at midgestation. However, studies on early limb buds found that Twist1(-/-) mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional alleles to generate a Twist1 allelic series that survives to birth. As Twist1 activity is reduced, limb skeletal defects progress from preaxial polydactyly to girdle reduction combined with hypoplasia, aplasia or mirror symmetry of all limb segments. With reduced Twist1 activity there is striking and progressive upregulation of ectopic Shh expression in the anterior of the limb, combined with an anterior shift in the posterior Shh domain, which is expressed at normal intensity, and loss of the posterior AER. Consequently limb outgrowth is initially impaired, before an ectopic anterior Shh domain expands the AER, promoting additional growth and repatterning. Reducing the dosage of FGF targets of the Etv gene family, which are known repressors of Shh expression in anterior limb mesenchyme, strongly enhances the anterior skeletal phenotype. Conversely this and other phenotypes are suppressed by reducing the dosage of the Twist1 antagonist Hand2. Our data support a model whereby multiple Twist1 activity thresholds contribute to early limb bud patterning, and suggest how particular combinations of skeletal defects result from differing amounts of Twist1 activity.
Aeromechanical Evaluation of Smart-Twisting Active Rotor
Lim, Joon W.; Boyd, D. Douglas, Jr.; Hoffman, Frauke; van der Wall, Berend G.; Kim, Do-Hyung; Jung, Sung N.; You, Young H.; Tanabe, Yasutada; Bailly, Joelle; Lienard, Caroline; Delrieux, Yves
2014-01-01
An investigation of Smart-Twisting Active Rotor (STAR) was made to assess potential benefits of the current active twist rotor concept for performance improvement, vibration reduction, and noise alleviation. The STAR rotor is a 40% Mach-scaled, Bo105 rotor with an articulated flap-lag hinge at 3.5%R and no pre-cone. The 0-5 per rev active twist harmonic inputs were applied for various flight conditions including hover, descent, moderate to high speed level flights, and slowed rotor high advance ratio. For the analysis, the STAR partners used multiple codes including CAMRAD II, S4, HOST, rFlow3D, elsA, and their associated software. At the high thrust level in hover, the 0 per rev active twist with 80% amplitude increased figure of merit (FM) by 0.01-0.02 relative to the baseline. In descent, the largest BVI noise reduction was on the order of 2 to 5 dB at the 3 per rev active twist. In the high speed case (mu = 0.35), the 2 per rev actuation was found to be the most effective in achieving a power reduction as well as a vibration reduction. At the 2 per rev active twist, total power was reduced by 0.65% at the 60 deg active twist phase, and vibration was reduced by 47.6% at the 45 deg active twist phase. The use of the 2 per rev active twist appears effective for vibration reduction. In the high advance ratio case (mu = 0.70), the 0 per rev actuation appeared to have negligible impact on performance improvement. In summary, computational simulations successfully demonstrated that the current active twist concept provided a significant reduction of the maximum BVI noise in descent, a significant reduction of the vibration in the high speed case, a small improvement on rotor performance in hover, and a negligible impact on rotor performance in forward flight.
Quantum mechanics of many particles defined on twisted N-enlarged Newton-Hooke space-times
Daszkiewicz, Marcin
2013-01-01
We provide the quantum mechanics of many particles moving in twisted N-enlarged Newton-Hooke space-time. In particular, we consider the example of such noncommutative system - the set of M particles moving in Coulomb field of external point-like source and interacting each other also by Coulomb potential.
Twist-joints and double twist-joints in RNA structure.
Boutorine, Yury I; Steinberg, Sergey V
2012-12-01
Analysis of available RNA crystal structures has allowed us to identify a new family of RNA arrangements that we call double twist-joints, or DTJs. Each DTJ is composed of a double helix that contains two bulges incorporated into different strands and separated from each other by 2 or 3 bp. At each bulge, the double helix is over-twisted, while the unpaired nucleotides of both bulges form a complex network of stacking and hydrogen-bonding with nucleotides of helical regions. In total, we identified 14 DTJ cases, which can be combined in three groups based on common structural characteristics. One DTJ is found in a functional center of the ribosome, another DTJ mediates binding of the pre-tRNA to the RNase P, and two more DTJs form the sensing domains in the glycine riboswitch.
Optical Twist Induced by Plasmonic Resonance
Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack
2016-06-01
Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster.
Twisted Light Transmission over 143 kilometers
Krenn, Mario; Fink, Matthias; Fickler, Robert; Ursin, Rupert; Malik, Mehul; Zeilinger, Anton
2016-01-01
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, while free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here we show the transmission of orbital angular momentum modes of light over a distance of 143 kilometers between two Canary Islands, which is 50 times greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order, and decode the transmitted message with an error rate of 8.33%....
Twisted Polynomials and Forgery Attacks on GCM
DEFF Research Database (Denmark)
Abdelraheem, Mohamed Ahmed A. M. A.; Beelen, Peter; Bogdanov, Andrey;
2015-01-01
nonce misuse resistance, such as POET. The algebraic structure of polynomial hashing has given rise to security concerns: At CRYPTO 2008, Handschuh and Preneel describe key recovery attacks, and at FSE 2013, Procter and Cid provide a comprehensive framework for forgery attacks. Both approaches rely...... heavily on the ability to construct forgery polynomials having disjoint sets of roots, with many roots (“weak keys”) each. Constructing such polynomials beyond naïve approaches is crucial for these attacks, but still an open problem. In this paper, we comprehensively address this issue. We propose to use...... in an improved key recovery algorithm. As cryptanalytic applications of our twisted polynomials, we develop the first universal forgery attacks on GCM in the weak-key model that do not require nonce reuse. Moreover, we present universal weak-key forgeries for the nonce-misuse resistant AE scheme POET, which...
A Solvable Twisted One-Plaquette Model
Billó, M.; D'Adda, A.
We solve a hot twisted Eguchi-Kawai model with only timelike plaquettes in the deconfined phase, by computing the quadratic quantum fluctuations around the classical vacuum. The solution of the model has some novel features: the eigenvalues of the timelike link variable are separated in L bunches, if L is the number of links of the original lattice in the time direction, and each bunch obeys a Wigner semicircular distribution of eigenvalues. This solution becomes unstable at a critical value of the coupling constant, where it is argued that a condensation of classical solutions takes place. This can be inferred by comparison with the heat-kernel model in the Hamiltonian limit, and the related Douglas-Kazakov phase transition in QCD2. As a byproduct of our solution, we can reproduce the dependence of the coupling constant from the parameter describing the asymmetry of the lattice, and compare it to previous results by Karsch.
Twisted and Nontwisted Bifurcations Induced by Diffusion
Lin, X B
1996-01-01
We discuss a diffusively perturbed predator-prey system. Freedman and Wolkowicz showed that the corresponding ODE can have a periodic solution that bifurcates from a homoclinic loop. When the diffusion coefficients are large, this solution represents a stable, spatially homogeneous time-periodic solution of the PDE. We show that when the diffusion coefficients become small, the spatially homogeneous periodic solution becomes unstable and bifurcates into spatially nonhomogeneous periodic solutions. The nature of the bifurcation is determined by the twistedness of an equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients decrease. In the nontwisted case two spatially nonhomogeneous simple periodic solutions of equal period are generated, while in the twisted case a unique spatially nonhomogeneous double periodic solution is generated through period-doubling. Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic bifurcations; periodic solutions.
Twisted accretion discs: Pt. 5; Viscous evolution
Energy Technology Data Exchange (ETDEWEB)
Kumar, S. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.). Inst. fuer Astrophysik)
1990-08-15
The time-dependence of accretion discs with orbits tilted out of the symmetry plane is studied. The effects of mass inflow modulation, and tilt variation at the disc outer edge, are examined for both circumbinary discs and for discs around compact objects. The appendices extend the numerical work to some analytic examples of tilt diffusion and external forcing effects. It is also shown that the disc must not be treated as a rigid tilted object if global angular momentum is to be conserved. These results are relevant to the problem of long-term periodicities of the light curves in Her X1 and {epsilon} Aur, the S-type symmetry of radio jets, warped gas discs in galaxies and polar rings in Neptune. Twisted discs may also arise in star-forming regions. (author).
Unusual presentation of twisted ovarian cyst
Directory of Open Access Journals (Sweden)
Vineet V Mishra
2016-01-01
Full Text Available Ovarian torsion (also termed as adnexal torsion refers to partial or complete rotation of the ovary and a portion of fallopian tube along its supplying vascular pedicle. It occurs commonly in reproductive age group; more on the right side (60% and often presents with acute lower abdominal pain lasting for few hours and up to 24 h, accounting for 2.7% of acute gynecological conditions. It is one of the devastating conditions, hampering blood supply of ovary which may lead to total necrosis of ovarian tissue and complications, if not diagnosed and managed in time. Hence, we present a case on a twisted ovarian cyst in postmenopausal woman with unusual symptomatology leading to delayed diagnosis and loss of an ovary.
Twisted Spectral Triple for the Standard Model and Spontaneous Breaking of the Grand Symmetry
Energy Technology Data Exchange (ETDEWEB)
Devastato, Agostino, E-mail: agostino.devastato@na.infn.it; Martinetti, Pierre, E-mail: martinetti@dima.unige.it [Università di Napoli Federico II, Dipartimento di Fisica (Italy)
2017-03-15
Grand symmetry models in noncommutative geometry, characterized by a non-trivial action of functions on spinors, have been introduced to generate minimally (i.e. without adding new fermions) and in agreement with the first order condition an extra scalar field beyond the standard model, which both stabilizes the electroweak vacuum and makes the computation of the mass of the Higgs compatible with its experimental value. In this paper, we use a twist in the sense of Connes-Moscovici to cure a technical problem due to the non-trivial action on spinors, that is the appearance together with the extra scalar field of unbounded vectorial terms. The twist makes these terms bounded and - thanks to a twisted version of the first-order condition that we introduce here - also permits to understand the breaking to the standard model as a dynamical process induced by the spectral action, as conjectured in [24]. This is a spontaneous breaking from a pre-geometric Pati-Salam model to the almost-commutativegeometryofthestandardmodel,withtwoHiggs-likefields: scalar and vector.
Twisted Spectral Triple for the Standard Model and Spontaneous Breaking of the Grand Symmetry
Devastato, Agostino; Martinetti, Pierre
2017-03-01
Grand symmetry models in noncommutative geometry, characterized by a non-trivial action of functions on spinors, have been introduced to generate minimally (i.e. without adding new fermions) and in agreement with the first order condition an extra scalar field beyond the standard model, which both stabilizes the electroweak vacuum and makes the computation of the mass of the Higgs compatible with its experimental value. In this paper, we use a twist in the sense of Connes-Moscovici to cure a technical problem due to the non-trivial action on spinors, that is the appearance together with the extra scalar field of unbounded vectorial terms. The twist makes these terms bounded and - thanks to a twisted version of the first-order condition that we introduce here - also permits to understand the breaking to the standard model as a dynamical process induced by the spectral action, as conjectured in [24]. This is a spontaneous breaking from a pre-geometric Pati-Salam model to the almost-commutativegeometryofthestandardmodel,withtwoHiggs-likefields: scalar and vector.
Cosmic strings with twisted magnetic flux lines and wound-strings in extra dimensions
Lake, Matthew
2012-01-01
We consider a generalization of the Nielsen-Olesen ansatz, in the abelian-Higgs model, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra- dimensional effects for F-strings may be mimicked by field-theoretic structure in topological defects.
Effect of the twist operator in the D1D5 CFT
Carson, Zaq; Mathur, Samir D; Turton, David
2014-01-01
The D1D5 CFT has been very useful in the study of black holes. The interaction in this theory involves a twist operator, which links together different copies of a free CFT. For the bosonic fields, we examine the action of this twist when it links together CFT copies with winding numbers M and N to produce a copy with winding M+N. Starting with the vacuum state generates a squeezed state, which we compute. Starting with an initial excitation on one of the copies gives a linear combination of excitations on the final state, which we also compute. These results generalize earlier computations where these quantities were computed for the special case M=N=1. Our results should help in understanding the thermalization process in the D1D5 CFT, which gives the dual of black hole formation in the bulk.
Geodesic dynamo chaotic flows and non-Anosov maps in twisted magnetic flux tubes
de Andrade, Garcia
2008-01-01
Recently Tang and Boozer [{\\textbf{Phys. Plasmas (2000)}}], have investigated the anisotropies in magnetic field dynamo evolution, from local Lyapunov exponents, giving rise to a metric tensor, in the Alfven twist in magnetic flux tubes (MFTs). Thiffeault and Boozer [\\textbf{Chaos}(2001)] have investigated the how the vanishing of Riemann curvature constrained the Lyapunov exponential stretching of chaotic flows. In this paper, Tang-Boozer-Thiffeault differential geometric framework is used to investigate effects of twisted magnetic flux tube filled with helical chaotic flows on the Riemann curvature tensor. When Frenet torsion is positive, the Riemann curvature is unstable, while the negative torsion induces an stability when time $t\\to{\\infty}$. This enhances the dynamo action inside the MFTs. The Riemann metric, depends on the radial random flows along the poloidal and toroidal directions. The Anosov flows has been applied by Arnold, Zeldovich, Ruzmaikin and Sokoloff [\\textbf{JETP (1982)}] to build a unifo...
Effect of pump depletion and cross-focusing on twisted terahertz radiation generation
Sobhani, Hassan; Dehghan, Mehdi; Dadar, Elham
2017-02-01
In this paper, the pump depletion and cross-focusing effects on the generation of twisted terahertz radiation are investigated. Based on the beating of two Laguerre-Gaussian lasers in a radial plasma channel, a twisted terahertz radiation can be produced. In the presence of pump depletion, the lasers power is consumed. So, the ponderomotive force nonlinearity decreases and the output terahertz field approaches to a saturation value. Under competition between the diffraction and nonlinearity effects, the amplitude of laser beam width oscillation grows. When the incident laser beams have non-similar topological charge numbers, the normalized generated terahertz amplitude is low and the pump depletion effect on the laser beam width evolution is ignorable.
Constructing a polynomial whose nodal set is the three-twist knot 52
Dennis, Mark R.; Bode, Benjamin
2017-06-01
We describe a procedure that creates an explicit complex-valued polynomial function of three-dimensional space, whose nodal lines are the three-twist knot 52. The construction generalizes a similar approach for lemniscate knots: a braid representation is engineered from finite Fourier series and then considered as the nodal set of a certain complex polynomial which depends on an additional parameter. For sufficiently small values of this parameter, the nodal lines form the three-twist knot. Further mathematical properties of this map are explored, including the relationship of the phase critical points with the Morse-Novikov number, which is nonzero as this knot is not fibred. We also find analogous functions for other simple knots and links. The particular function we find, and the general procedure, should be useful for designing knotted fields of particular knot types in various physical systems.
Heat Transfers Enhancement with Different Square Jagged Twisted Tapes
Directory of Open Access Journals (Sweden)
Mr. A.V.Gawandare
2014-03-01
Full Text Available The present experimental work are carried out with copper twisted tape inserts 3mm with 5.2,4.2 and 3.2 twists respectively. The inserts when placed in the path of the flow of the fluid, create a high degree of turbulence resulting in an increase in the heat transfer rate and the pressure drop. The work includes the determination of friction factor and heat transfer coefficient for various twisted wire inserts with varying twists and different materials. The Reynolds number is varied from 5000 to 16000. Correlations for Nusselt number and friction factor are developed for the twisted wire inserts from the obtained results. The results of varying twists in square jagged tape with different pitches have been compared with the values for the smooth tube. The 3mm thick with 3.2 twists copper insert shows increase in Nusselt number values by 76% however there is increase in friction factor by only 19.5% as compared to the smooth tube values.
Quantum spin Hall effect in twisted bilayer graphene
Finocchiaro, F.; Guinea, F.; San-Jose, P.
2017-06-01
Motivated by a recent experiment (Sanchez-Yamagishi et al 2016 Nat. Nanotechnol. 214) reporting evidence of helical spin-polarized edge states in layer-biased twisted bilayer graphene under a magnetic flux, we study the possibility of stabilising a quantum spin Hall (QSH) phase in such a system, without Zeeman or spin-orbit couplings, and with a QSH gap induced instead by electronic interactions. We analyse how magnetic flux, electric field, interlayer rotation angle, and interactions (treated at a mean field level) combine to produce a pseudo-QSH with broken time-reversal symmetry, and spin-polarized helical edge states. The effect is a consequence of a robust interaction-induced ferrimagnetic ordering of the quantum Hall ground state under an interlayer bias, provided the two rotated layers are effectively decoupled at low energies. We discuss in detail the electronic structure and the constraints on system parameters, such as the angle, interactions and magnetic flux, required to reach the pseudo-QSH phase. We find, in particular, that purely local electronic interactions are not sufficient to account for the experimental observations, which demand at least nearest-neighbour interactions to be included.
Sun, Tong; Fu, Junjiang; Shen, Tao; Lin, Xia; Liao, Lan; Feng, Xin-Hua; Xu, Jianming
2016-05-27
Twist1 is a basic helix-loop-helix transcription factor that strongly promotes epithelial-to-mesenchymal transition, migration, invasion, and metastasis of cancer cells. The MAPK-phosphorylated Twist1 on its serine 68 (Ser(P)(68)-Twist1) has a significantly enhanced stability and function to drive cancer cell invasion and metastasis. However, the phosphatase that dephosphorylates Ser(P)(68)-Twist1 and destabilizes Twist1 has not been identified and characterized. In this study, we screened a serine/threonine phosphatase cDNA expression library in HEK293T cells with ectopically coexpressed Twist1. We found that the small C-terminal domain phosphatase 1 (SCP1) specifically dephosphorylates Ser(P)(68)-Twist1 in both cell-free reactions and living cells. SCP1 uses its amino acid residues 43-63 to interact with the N terminus of Twist1. Increased SCP1 expression in cells decreased Ser(P)(68)-Twist1 and total Twist1 proteins, whereas knockdown of SCP1 increased Ser(P)(68)-Twist1 and total Twist1 proteins. Furthermore, the levels of SCP1 are negatively correlated with Twist1 protein levels in several cancer cell lines. SCP1-dephosphorylated Twist1 undergoes fast degradation via the ubiquitin-proteasome pathway. Importantly, an increase in SCP1 expression in breast cancer cells with either endogenous or ectopically expressed Twist1 largely inhibits the Twist1-induced epithelial-to-mesenchymal transition phenotype and the migration and invasion capabilities of these cells. These results indicate that SCP1 is the phosphatase that counterregulates the MAPK-mediated phosphorylation of Ser(68)-Twist1. Thus, an increase in SCP1 expression and activity may be a useful strategy for eliminating the detrimental roles of Twist1 in cancer cells.
Tri-bimaximal mixing from twisted Friedberg-Lee symmetry
Energy Technology Data Exchange (ETDEWEB)
Araki, Takeshi [National Tsing Hua University, Department of Physics, Hsinchu (China); Takahashi, Ryo [Osaka University, Department of Physics, Graduate School of Science, Osaka (Japan)
2009-10-15
We investigate the Friedberg-Lee (FL) symmetry and its promotion to include the {mu}-{tau} symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation of the FL symmetry. The second one is based on the S{sub 3} permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each scheme are also presented. (orig.)
Tri-bimaximal mixing from twisted Friedberg-Lee symmetry
Araki, Takeshi; Takahashi, Ryo
2009-10-01
We investigate the Friedberg-Lee (FL) symmetry and its promotion to include the μ- τ symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation of the FL symmetry. The second one is based on the S 3 permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each scheme are also presented.
Assembly and Folding of Twisted Baskets in Organic Solvents.
Pratumyot, Yaowalak; Chen, Shigui; Hu, Lei; Polen, Shane M; Hadad, Christopher M; Badjić, Jovica D
2016-09-02
A synthetic method for obtaining enantiopure and twisted baskets of type (P)-3 is described. These chiral cavitands were found to fold quinoline gates, at the rim of their twisted platform, in acetonitrile and give molecular capsules that assemble into large unilamellar vesicles. In a less polar dichloromethane, however, cup-shaped (P)-3 packed into vesicles but with the quinoline gates in an unfolded orientation. The ability of twisted baskets to form functional nanostructured materials could be of interest for building stereoselective sensors and catalysts.
TWIST1 promotes invasion through mesenchymal change in human glioblastoma
Directory of Open Access Journals (Sweden)
Wakimoto Hiroaki
2010-07-01
Full Text Available Abstract Background Tumor cell invasion into adjacent normal brain is a mesenchymal feature of GBM and a major factor contributing to their dismal outcomes. Therefore, better understandings of mechanisms that promote mesenchymal change in GBM are of great clinical importance to address invasion. We previously showed that the bHLH transcription factor TWIST1 which orchestrates carcinoma metastasis through an epithelial mesenchymal transition (EMT is upregulated in GBM and promotes invasion of the SF767 GBM cell line in vitro. Results To further define TWIST1 functions in GBM we tested the impact of TWIST1 over-expression on invasion in vivo and its impact on gene expression. We found that TWIST1 significantly increased SNB19 and T98G cell line invasion in orthotopic xenotransplants and increased expression of genes in functional categories associated with adhesion, extracellular matrix proteins, cell motility and locomotion, cell migration and actin cytoskeleton organization. Consistent with this TWIST1 reduced cell aggregation, promoted actin cytoskeletal re-organization and enhanced migration and adhesion to fibronectin substrates. Individual genes upregulated by TWIST1 known to promote EMT and/or GBM invasion included SNAI2, MMP2, HGF, FAP and FN1. Distinct from carcinoma EMT, TWIST1 did not generate an E- to N-cadherin "switch" in GBM cell lines. The clinical relevance of putative TWIST target genes SNAI2 and fibroblast activation protein alpha (FAP identified in vitro was confirmed by their highly correlated expression with TWIST1 in 39 human tumors. The potential therapeutic importance of inhibiting TWIST1 was also shown through a decrease in cell invasion in vitro and growth of GBM stem cells. Conclusions Together these studies demonstrated that TWIST1 enhances GBM invasion in concert with mesenchymal change not involving the canonical cadherin switch of carcinoma EMT. Given the recent recognition that mesenchymal change in GBMs is
Topological duality twist and brane instantons in F-theory
Energy Technology Data Exchange (ETDEWEB)
Martucci, Luca [Dipartimento di Fisica ed Astronomia “Galileo Galilei”, Università di Padova andINFN - Sezione di Padova,Via Marzolo 8, I-35131 Padova (Italy)
2014-06-30
A variant of the topological twist, involving SL(2,ℤ) dualities and hence named topological duality twist, is introduced and explicitly applied to describe a U(1) N=4 super Yang-Mills theory on a Kähler space with holomorphically space-dependent coupling. Three-dimensional duality walls and two-dimensional chiral theories naturally enter the formulation of the duality twisted theory. Appropriately generalized, this theory is relevant for the study of Euclidean D3-brane instantons in F-theory compactifications. Some of its properties and implications are discussed.
Twist Neutrality and the Diameter of the Nucleosome Core Particle
DEFF Research Database (Denmark)
Bohr, Jakob; Olsen, Kasper
2012-01-01
The diameter of the nucleosome core particle is the same for all the eukaryotes. Here we discuss the possibility that this selectiveness is consistent with a propensity for twist neutrality, in particular, for the double helical DNA to stay rotationally neutral when strained. Reorganization of DNA...... cannot be done without some level of temporal tensile stress, and as a consequence chiral molecules, such as helices, will twist under strain. The requirement that the nucleosome, constituting the nucleosome core particle and linker DNA, has a vanishing strain-twist coupling leads to a requirement...
Differential forms and {kappa}-Minkowski spacetime from extended twist
Energy Technology Data Exchange (ETDEWEB)
Juric, Tajron; Meljanac, Stjepan [Rudjer Boskovic Institute, Zagreb (Croatia); Strajn, Rina [Jacobs University Bremen, Bremen (Germany)
2013-07-15
We analyze bicovariant differential calculus on {kappa}-Minkowski spacetime. It is shown that corresponding Lorentz generators and noncommutative coordinates compatible with bicovariant calculus cannot be realized in terms of commutative coordinates and momenta. Furthermore, {kappa}-Minkowski space and NC forms are constructed by twist related to a bicrossproduct basis. It is pointed out that the consistency condition is not satisfied. We present the construction of {kappa}-deformed coordinates and forms (super-Heisenberg algebra) using extended twist. It is compatible with bicovariant differential calculus with {kappa}-deformed igl(4)-Hopf algebra. The extended twist leading to {kappa}-Poincare-Hopf algebra is also discussed. (orig.)
Robles-Hernández, Beatriz; Sebastián, Nerea; de la Fuente, M. Rosario; López, David O.; Diez-Berart, Sergio; Salud, Josep; Ros, M. Blanca; Dunmur, David A.; Luckhurst, Geoffrey R.; Timimi, Bakir A.
2015-12-01
The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and 2H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and 2H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. 2H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.
Electron-phonon scattering and in-plane electric conductivity in twisted bilayer graphene
Ray, N.; Fleischmann, M.; Weckbecker, D.; Sharma, S.; Pankratov, O.; Shallcross, S.
2016-12-01
We have surveyed the in-plane transport properties of the graphene twist bilayer using (i) a low-energy effective Hamiltonian for the underlying electronic structure, (ii) an isotropic elastic phonon model, and (iii) the linear Boltzmann equation for elastic electron-phonon scattering. We find that transport in the twist bilayer is profoundly sensitive to the rotation angle of the constituent layers. Similar to the electronic structure of the twist bilayer, the transport is qualitatively different in three distinct angle regimes. At large angles (θ >≈10∘ ) and at temperatures below an interlayer Bloch-Grüneisen temperature of ≈10 K, the conductivity is independent of the twist angle, i.e., the layers are fully decoupled. Above this temperature the layers, even though decoupled in the ground state, are recoupled by electron-phonon scattering and the transport is different both from single-layer graphene as well as the Bernal bilayer. In the small-angle regime θ <≈2∘ , the conductivity drops by two orders of magnitude and develops a rich energy dependence, reflecting the complexity of the underlying topological changes (Lifshitz transitions) of the Fermi surface. At intermediate angles, the conductivity decreases continuously as the twist angle is reduced, while the energy dependence of the conductivity presents two sharp transitions, that occur at specific angle-dependent energies, and that may be related to (i) the well-studied van Hove singularity of the twist bilayer and (ii) a Lifshitz transition that occurs when trigonally placed electron pockets decorate the strongly warped Dirac cone. Interestingly, we find that, while the electron-phonon scattering is dominated by layer symmetric flexural phonons in the small-angle limit, at large angles, in contrast, it is the layer antisymmetric flexural mode that is most important. We examine the role of a layer perpendicular electric field finding that it affects the conductivity strongly at low temperatures
Testing mixed action approaches to meson spectroscopy with twisted mass sea quarks
Berlin, Joshua; Wagner, Marc
2013-01-01
We explore and compare three mixed action setups with Wilson twisted mass sea quarks and different valence quark actions: (1) Wilson twisted mass, (2) Wilson twisted mass + clover and (3) Wilson + clover. Our main goal is to reduce lattice discretization errors in mesonic spectral quantities, in particular to reduce twisted mass parity and isospin breaking.
Directory of Open Access Journals (Sweden)
Laurent Jacqueroud
2016-05-01
Full Text Available The TWIST1 embryonic transcription factor displays biphasic functions during the course of carcinogenesis. It facilitates the escape of cells from oncogene-induced fail-safe programs (senescence, apoptosis and their consequent neoplastic transformation. Additionally, it promotes the epithelial-to-mesenchymal transition and the initiation of the metastatic spread of cancer cells. Interestingly, cancer cells recurrently remain dependent on TWIST1 for their survival and/or proliferation, making TWIST1 their Achilles’ heel. TWIST1 has been reported to form either homodimeric or heterodimeric complexes mainly in association with the E bHLH class I proteins. These complexes display distinct, sometimes even antagonistic, functions during development and unequal prometastatic functions in prostate cancer cells. Using a tethered dimer strategy, we successively assessed the ability of TWIST1 dimers to cooperate with an activated version of RAS in human mammary epithelial cell transformation, to provide mice with the ability to spontaneously develop breast tumors, and lastly to maintain a senescence program at a latent state in several breast cancer cell lines. We demonstrate that the TWIST1-E12 complex, unlike the homodimer, is an oncogenic form of TWIST1 in mammary epithelial cells and that efficient binding of both partners is a prerequisite for its activity. The detection of the heterodimer in human premalignant lesions by a proximity ligation assay, at a stage preceding the initiation of the metastatic cascade, is coherent with such an oncogenic function. TWIST1-E protein heterodimeric complexes may thus constitute the main active forms of TWIST1 with regard to senescence inhibition over the time course of breast tumorigenesis.
Let's Twist Again: N=2 Super Yang Mills Theory Coupled To Matter
Maggiore, Nicola
2010-01-01
We give the twisted version of N=2 Super Yang Mills theory coupled to matter, including quantum fields, supersymmetry transformations, action and algebraic structure. We show that the whole action, coupled to matter, can be written as the variation of a nilpotent operator, modulo field equations. An extended Slavnov-Taylor identity, collecting gauge symmetry and supersymmetry, is written, which allows to define the web of algebraic constraints, in view of the algebraic renormalization and of the extension of the non-renormalization theorems holding for N=2 SYM theory without matter.
Particle-in-cell simulations of the twisted magnetospheres of magnetars
Chen, Alexander Y
2016-01-01
The magnetospheres of magnetars are believed to be filled with electron-positron plasma generated by electric discharge. We present a first direct numerical experiment showing how the plasma is created in an axisymmetric closed magnetosphere. The $e^\\pm$ discharge occurs in response to twisting of the magnetic field lines by a shear deformation of the magnetar surface, which launches electric currents into the magnetosphere. The simulation shows the formation of an electric "gap" with unscreened electric field ($\\mathbf{E}\\cdot \\mathbf{B}\
Shadow casted by a twisted and rotating black hole
Chen, Songbai
2016-01-01
Zhang have obtained recently a twisted rotating black hole metric, which is a vacuum solution in four-dimensional Einstein gravity. This black hole solution has a rotation parameter, but without the total angular moment. Here, we have investigated the shadow casted by a twisted rotating black hole. Our results show that the shape of the shadow of the twisted rotating black hole is a standard round disk and does not depend on the inclination angle of the observer. It means that although the twisted rotating black hole has a rotation parameter, its shadow possesses the same behaviors as the common static black hole rather than the usual Kerr-like black holes. Moreover, we find that the marginally circular orbit radius of photon is independent of the direction of photon around the black hole. The value of the marginally circular orbit radius of photon and the size of shadow increase monotonously with the rotation parameter.
Cayley-Dickson and Clifford Algebras as Twisted Group Algebras
Bales, John W
2011-01-01
The effect of some properties of twisted groups on the associated algebras, particularly Cayley-Dickson and Clifford algebras. It is conjectured that the Hilbert space of square-summable sequences is a Cayley-Dickson algebra.
Determination of Elastic Twist in Horizontal Axis Wind Turbines (HAWTs)
Energy Technology Data Exchange (ETDEWEB)
Stoddard, F.; Nelson, V.; Starcher, K.; Andrews, B.
2006-06-01
This report presents the results of a project at the Alternative Energy Institute (AEI) which measured and calculated the elastic twist of three representative composite horizontal-axis blades: Carter 300, Gougeon ESI 54, and UTRC 8 kW.
Spectrum of a duality-twisted Ising quantum chain
Grimm, U
2002-01-01
The Ising quantum chain with a peculiar twisted boundary condition is considered. This boundary condition, first introduced in the framework of the spin-1/2 XXZ Heisenberg quantum chain, is related to the duality transformation, which becomes a symmetry of the model at the critical point. Thus, at the critical point, the Ising quantum chain with the duality-twisted boundary is translationally invariant, similar as in the case of the usual periodic or antiperiodic boundary conditions. The complete energy spectrum of the Ising quantum chain is calculated analytically for finite systems, and the conformal properties of the scaling limit are investigated. This provides an explicit example of a conformal twisted boundary condition and a corresponding generalised twisted partition function.
The Kostant partition functions for twisted Kac-Moody algebras
Directory of Open Access Journals (Sweden)
Ranabir Chakrabarti
2000-01-01
Full Text Available Employing the method of generating functions and making use of some infinite product identities like Euler, Jacobi's triple product and pentagon identities we derive recursion relations for Kostant's partition functions for the twisted Kac-Moody algebras.
Polanski lavastas filmi "Oliver Twist" oma lastele / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm "Oliver Twist" Charles Dickensi romaani ainetel esilinastus Prahas, kus toimusid ka filmivõtted. Tšehhi, Suurbritannia, Prantsusmaa ja Itaalia koostöös valminud filmi lavastas Roman Polanski
Õnnetu saatusega Oliver Twist Polanski meelevallas / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm Charles Dickensi romaani järgi "Oliver Twist" : stsenarist Ronald Harwood : režissöör Roman Polanski : nimiosas Barney Clark, Fagin - Ben Kingsley : Suurbritannia - Tšehhi - Prantsusmaa - Itaalia 2005
Polarisation of microwave emission from reconnecting twisted coronal loops
Gordovskyy, Mykola; Kontar, Eduard
2016-01-01
Magnetic reconnection and particle acceleration due to the kink instability in twisted coronal loops can be a viable scenario for confined solar flares. Detailed investigation of this phenomenon requires reliable methods for observational detection of magnetic twist in solar flares, which may not be possible solely through extreme UV and soft X-ray thermal emission. The gradient of microwave polarisation across flaring loops can serve as one of the detection criteria. The aim of this study is to investigate the effect of magnetic twist in flaring coronal loops on the polarisation of gyro-synchrotron microwave emission, and determine whether microwave emission polarisation could provide a means for observational detection. We use time-dependent magnetohydrodynamic and test-particle models, developed using LARE3D and GCA codes to investigate twisted coronal loops relaxing following the kink-instability, and calculate synthetic microwave emission maps (I and V Stokes components) using GX simulator. It is found t...
Twistted ξ-(α,β expansive mappings in metric spaces
Directory of Open Access Journals (Sweden)
Poonam Nagpal
2016-04-01
Full Text Available In this paper, we introduce a pair of twisted ζ-(α,β expansive mappings in metric spaces and prove fixed point theorems for these mappings. Some examples are also provided to support our main results.
Polanski lavastas filmi "Oliver Twist" oma lastele / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm "Oliver Twist" Charles Dickensi romaani ainetel esilinastus Prahas, kus toimusid ka filmivõtted. Tšehhi, Suurbritannia, Prantsusmaa ja Itaalia koostöös valminud filmi lavastas Roman Polanski
Õnnetu saatusega Oliver Twist Polanski meelevallas / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm Charles Dickensi romaani järgi "Oliver Twist" : stsenarist Ronald Harwood : režissöör Roman Polanski : nimiosas Barney Clark, Fagin - Ben Kingsley : Suurbritannia - Tšehhi - Prantsusmaa - Itaalia 2005
Radiative Capture of Twisted Electrons by Bare Ions
Matula, Oliver; Serbo, Valeriy G; Surzhykov, Andrey; Fritzsche, Stephan
2014-01-01
Recent advances in the production of twisted electron beams with a subnanometer spot size offer unique opportunities to explore the role of orbital angular momentum (OAM) in basic atomic processes. In the present work, we address one of these processes: radiative recombination of twisted electrons with bare ions. Based on the density matrix formalism and the non-relativistic Schr\\"odinger theory, analytical expressions are derived for the angular distribution and the linear polarization of photons emitted due to the capture of twisted electrons into the ground state of (hydrogen-like) ions. We show that these angular and polarization distributions are sensitive to both, the transverse momentum and the topological charge of the electron beam. To observe in particular the value of this charge, we propose an experiment that makes use of the coherent superposition of two twisted beams.
A Stylistic Analysis of Register Theory in Oliver Twist
Institute of Scientific and Technical Information of China (English)
刘鑫
2015-01-01
Stylistic analysis refers to the linguistic approach to literature.Stylistics will mainly focus on the register theory,taking Charles Dickens' masterpiece Oliver Twist as a good example to demonstrate how the register theory is embodied in the work.
The Kostant partition functions for twisted Kac-Moody algebras
Ranabir Chakrabarti; Santhanam, Thalanayar S.
2000-01-01
Employing the method of generating functions and making use of some infinite product identities like Euler, Jacobi's triple product and pentagon identities we derive recursion relations for Kostant's partition functions for the twisted Kac-Moody algebras.
Applying Twisted Boundary Conditions for Few-body Nuclear Systems
Körber, Christopher
2015-01-01
We describe and implement twisted boundary conditions for the deuteron and triton systems within finite-volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twists angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length $L\\approx8-14$ fm. Of particular importance is our derivation and numerical verification of three-body analogue of `i-periodic' twist angles that eliminate the leading order finite-volume effects to the three-body binding energy.
Double twist helical nanofilaments in bent-core liquid crystals
Zhang, Cuiyu; Diorio, Nicholas; Lavrentovich, Oleg D.; Jakli, Antal
2014-03-01
Cryo-TEM observations on 40-150 nm films of four bent-core liquid crystal materials in their helical nanofilament (HNF) phase show that the filaments get deformed near the substrate, and the subsequent arrays of nanofilaments are not parallel, but twisted with respect to each other. The effect can explain the mysterious properties of the HNF materials, such as structural color and ambidextrous optical activity. The observed double twist structure was not expected in the previous models of this phase. Being principally different from the packing of molecules in the twist grain boundary (TGB) and blue (BP) phases, the double-twist structure of HNF expands the rich word of nanostructured organic materials. This work was financially supported by NSF DMR-0964765 and DMR 1104850. The cryo-TEM facility was supported by the Ohio Research Scholars Program. We are grateful for Prof. G. Heppke and Dr. D. Lotsch for providing the PnOPIMB materials for us.
A Stylistic Analysis of Register Theory in Oliver Twist
Institute of Scientific and Technical Information of China (English)
刘鑫
2015-01-01
Stylistic analysis refers to the linguistic approach to literature.Stylistics will mainly focus on the register theory,taking Charles Dickens’ masterpiece Oliver Twist as a good example to demonstrate how the register theory is embodied in the work.
Representations of Knot Groups and Twisted Alexander Polynomials
Institute of Scientific and Technical Information of China (English)
Xiao Song LIN
2001-01-01
We present a twisted version of the Alexander polynomial associated with a matrix representation of the knot group. Examples of two knots with the same Alexander module but differenttwisted Alexander polynomials are given.
Magnetic Twist and Writhe of Active Regions: On the Origin of Deformed Flux Tubes
Fuentes, M López; Mandrini, C H; Pevtsov, A A; van Driel-Gesztelyi, L
2014-01-01
We study the long term evolution of a set of 22 bipolar active regions (ARs) in which the main photospheric polarities are seen to rotate one around the other during several solar rotations. We first show that differential rotation is not at the origin of this large change in the tilt angle. A possible origin of this distortion is the nonlinear development of a kink-instability at the base of the convective zone; this would imply the formation of a non-planar flux tube which, while emerging across the photosphere, would show a rotation of its photospheric polarities as observed. A characteristic of the flux tubes deformed by this mechanism is that their magnetic twist and writhe should have the same sign. From the observed evolution of the tilt of the bipoles, we derive the sign of the writhe of the flux tube forming each AR; while we compute the sign of the twist from transverse field measurements. Comparing the handedness of the magnetic twist and writhe, we find that the presence of kink-unstable flux tube...
Computational Investigation of Swirling Supersonic Jets Generated Through a Nozzle-Twisted Lance
Li, Mingming; Li, Qiang; Zou, Zongshu; An, Xizhong
2017-02-01
The dynamic characteristics of supersonic swirling jets generated through a nozzle-twisted lance are numerically studied. The essential features of the swirling jets are identified by defining a deviation angle. The effects of nozzle twist angle (NTA) on swirling flow intensity, coalescence characteristics, and dynamic parameter distributions of the jets are discussed. The rotational flow characteristics are revealed. The results show that the jets from the nozzle-twisted lance are imparted to a circumferential rotating movement around the lance axis, and such swirling flow is enhanced by increasing NTA. The enhanced swirling flow causes weaker coalescence of the jets, faster attenuations of the axial velocity, and higher heat transfer rate between the jets and surroundings. The supersonic core length, however, is found to be less sensitive to the swirling flow intensity. The radial spreading of the jets, changing non-monotonically with NTA, arrives at its maximum at 5 deg of NTA. Furthermore, the swirling flow induces a considerable tangential velocity component, and as a result, a holistic and effective horizontal swirling flow field develops. The y-vorticity distribution range and the corresponding magnitude turn larger with increasing NTA, which promote the vortex motion of the local fluid element and thus intensify the local mixing.
Twisted compactifications of 3d N = 4 theories and conformal blocks
Gaiotto, Davide
2016-01-01
Three-dimensional N = 4 supersymmetric quantum field theories admit two topological twists, the Rozansky-Witten twist and its mirror. Either twist can be used to define a supersymmetric compactification on a Riemann surface and a corre- sponding space of supersymmetric ground states. These spaces of ground states can play an interesting role in the Geometric Langlands program. We propose a description of these spaces as conformal blocks for certain non-unitary Vertex Operator Algebras and test our conjecture in some important examples. The two VOAs can be constructed respectively from a UV Lagrangian description of the N = 4 theory or of its mirror. We further conjecture that the VOAs associated to an N = 4 SQFT inherit properties of the theory which only emerge in the IR, such as enhanced global symmetries. Thus knowledge of the VOAs should allow one to compute the spaces of supersymmetric ground states for a theory coupled to supersymmetric background connections for the full symmetry group of the IR SCFT. ...
Coherent nonlinear electromagnetic response in twisted bilayer and few-layer graphene
Indian Academy of Sciences (India)
Vipin Kumar; Enamullah; Upendra Kumar; Girish S Setlur
2014-10-01
The phenomenon of Rabi oscillations far from resonance is described in bilayer and few-layer graphene. These oscillations in the population and polarization at the Dirac point in -layer graphene are seen in the nth harmonic termin the external driving frequency. The underlying reason behind these oscillations is attributable to the pseudospin degree of freedom possessed by all these systems. Conventional Rabi oscillations, which occur only near resonance, are seen in multiple harmonics in multilayer graphene. However, the experimentally measurable current density exhibits anomalous behaviour only in the first harmonic in all the graphene systems. A fully numerical solution of the optical Bloch equations is in complete agreement with the analytical results, thereby justifying the approximation schemes used in the latter. The same phenomena are also described in twisted bilayer graphene with and without an electric potential difference between the layers. It is found that the anomalous Rabi frequency is strongly dependent on twist angle for weak applied fields – a feature absent in single-layer graphene, whereas the conventional Rabi frequency is relatively independent of the twist angle.
Quark mass anomalous dimension from the twisted mass Dirac operator spectrum
Energy Technology Data Exchange (ETDEWEB)
Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics
2013-12-15
We investigate whether it is possible to extract the quark mass anomalous dimension and its scale dependence from the spectrum of the twisted mass Dirac operator in Lattice QCD. The answer to this question appears to be positive, provided that one goes to large enough eigenvalues, sufficiently above the non-perturbative regime. The obtained results are compared to continuum perturbation theory. By analyzing possible sources of systematic effects, we find the domain of applicability of the approach, extending from an energy scale of around 1.5 to 4 GeV. The lower limit is dictated by physics (non-perturbative effects at low energies), while the upper bound is set by the ultraviolet cut-off of present-day lattice simulations. We use gauge field configuration ensembles generated by the European Twisted Mass Collaboration (ETMC) with 2 flavours of dynamical twisted mass quarks, at 4 lattice spacings in the range between around 0.04 and 0.08 fm.
The Algebra of Formal Twisted Pseudodifferential Symbols and a Noncommutative Residue
Zadeh, Farzad Fathi; Khalkhali, Masoud
2010-10-01
Motivated by Connes-Moscovici’s notion of a twisted spectral triple, we define an algebra of formal twisted pseudodifferential symbols with respect to a twisting of the base algebra. We extend the Adler-Manin trace and the logarithmic cocycle on the algebra of pseudodifferential symbols to our twisted setting. We also give a general method to construct twisted pseudodifferential symbols on crossed product algebras.
A super-twisted Dirac operator and Novikov inequalities
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A super-twisted Dirac operator is constructed and deformed suitably.Following Shubin's approach to Novikov inequalities associated to the deformed de Rham-Hodge operator,we give a formula for the index of the super-twisted Dirac operator,and Novikov type inequalities for the deformed operator.In particular,we obtain a purely analytic proof of the Hopf index theorem for general vector bundles.
A super-twisted Dirac operator and Novikov inequalities
Institute of Scientific and Technical Information of China (English)
冯惠涛; 郭恩力
2000-01-01
A s黳er-twisted Dirac operator is constructed and deformed suitably. Following Shubin’s approach to Novikov inequalities associated to the deformed de Rham-Hodge operator, we give a for-mula for the index of the super-twisted Dirac operator, and Novikov type inequalities for the deformed operator, In particular, we obtain a purely analytic proof of the Hopf index theorem for general vector bundles.
Dehn twists and free subgroups of symplectic mapping class groups
Keating, Ailsa
2012-01-01
Given two Lagrangian spheres in an exact symplectic manifold, we find conditions under which the Dehn twists about them generate a free non-abelian subgroup of the symplectic mapping class group. This extends a result of Ishida for Riemann surfaces. The proof generalises the categorical version of Seidel's long exact sequence to arbitrary powers of a fixed Dehn twist. We also show that the Milnor fibre of any isolated degenerate hypersurface singularity contains such pairs of spheres.
Blade tip vortex measurements on actively twisted rotor blades
Bauknecht, André; Ewers, Benjamin; Schneider, Oliver; Raffel, Markus
2017-05-01
Active rotor control concepts, such as active twist actuation, have the potential to effectively reduce the noise and vibrations of helicopter rotors. The present study focuses on the experimental investigation of active twist for the reduction of blade-vortex interaction (BVI) effects on a model rotor. Results of a large-scale smart-twisting active rotor test under hover conditions are described. This test investigated the effects of individual blade twist control on the blade tip vortices. The rotor blades were actuated with peak torsion amplitudes of up to 2° and harmonic frequencies of 1-5/rev with different phase angles. Time-resolved stereoscopic particle image velocimetry was carried out to study the effects of active twist on the strength and trajectories of the tip vortices between ψ _ {v}= 3.6° and 45.7° of vortex age. The analysis of the vortex trajectories revealed that the 1/rev active twist actuation mainly caused a vertical deflection of the blade tip and the corresponding vortex trajectories of up to 1.3% of the rotor radius R above and -1%R below the unactuated condition. An actuation with frequencies of 2 and 3/rev significantly affected the shapes of the vortex trajectories and caused negative vertical displacements of the vortices relative to the unactuated case of up to 2%R within the first 35° of wake age. The 2 and 3/rev actuation also had the most significant effects on the vortex strength and altered the initial peak swirl velocity by up to -34 and +31% relative to the unactuated value. The present aerodynamic investigation reveals a high control authority of the active twist actuation on the strength and trajectories of the trailing blade tip vortices. The magnitude of the evoked changes indicates that the active twist actuation constitutes an effective measure for the mitigation of BVI-induced noise on helicopters.
Twisted Bundle on Noncommutative Space and U(1) Instanton
Ho, P M
2000-01-01
We study the notion of twisted bundles on noncommutative space. Due to theexistence of projective operators in the algebra of functions on thenoncommutative space, there are twisted bundles with non-constant dimension.The U(1) instanton solution of Nekrasov and Schwarz is such an example. As amathematical motivation for not excluding such bundles, we find gaugetransformations by which a bundle with constant dimension can be equivalent toa bundle with non-constant dimension.
Helicity and internal twist within the vortex filament model
Hietala, N; Salman, H
2016-01-01
For ideal fluids, besides energy, kinetic helicity is the only other known quadratic invariant of the Euler equations besides energy and is understood to be inherently linked to the degree of knotting of vortex lines within the fluid. For vortices arising in superfluid $^4$He, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in a helicity that does not retain its key attribute as a quadratic invariant. By defining the spanwise vector to coincide with the Seifert framing, we are able to introduce twist and henceforth recover the key properties of helicity. Through a detailed analysis of the velocity field induced in the vicinity of the superfluid vortices we are able to express our choice of the spanwise vector in terms of the tangential component of velocity along the filament. Since adding an arbitrary tangential velocity does not alter the configuration ...
Two-cylinder entanglement entropy under a twist
Chen, Xiao; Witczak-Krempa, William; Faulkner, Thomas; Fradkin, Eduardo
2017-04-01
We study the von Neumann and Rényi entanglement entropy (EE) of the scale-invariant theories defined on the tori in 2 + 1 and 3 + 1 spacetime dimensions. We focus on the spatial bi-partitions of the torus into two cylinders, and allow for twisted boundary conditions along the non-contractible cycles. Various analytical and numerical results are obtained for the universal EE of the relativistic boson and Dirac fermion conformal field theories (CFTs), the fermionic quadratic band touching and the boson with z = 2 Lifshitz scaling. The shape dependence of the EE clearly distinguishes these theories, although intriguing similarities are found in certain limits. We also study the evolution of the EE when a mass is introduced to detune the system from its scale-invariant point, by employing a renormalized EE that goes beyond a naive subtraction of the area law. In certain cases we find the non-monotonic behavior of the torus EE under RG flow, which distinguishes it from the EE of a disk.
Twisting/Rolling Motions and Chirality in Filament Eruptions
McKillop, S.; Murphy, N. A.; Miralles, M. P.; McCauley, P.; Su, Y.
2015-12-01
Panasenco et al. [1] report observations of several CMEs that display a rolling motion about the axis of the erupting prominence. Murphy et al. [2] present simulations of line-tied asymmetric magnetic reconnection that make a falsifiable prediction regarding the handedness of rolling motions of flux ropes during solar eruptions. Mass motions in prominence eruptions tend to be complicated, and characterizing these motions is a challenge. We use the AIA filament eruption catalog [3] as a source for finding events. If rolling motions are detected then we will investigate the handedness prediction. We use magnetograms from HMI to determine the strength and asymmetric properties of the photospheric magnetic field in the regions of interest and will use AIA observations to determine the handedness of the rolling motions. We then compare the photospheric magnetic information with the handedness to determine if there is a relationship between the two. The AIA filament eruption catalog is a great source for finding events, but it lacks a chirality determination. We aim to add these determinations and then compare the chirality with the directionality of the twisting/rolling motions. [1] O. Panasenco, S. Martin, A. D. Joshi, & N. Srivastava, J. Atmos. Sol.-Terr. Phys., 73, 1129 (2011) [2] N. A. Murphy, M. P. Miralles, C. L. Pope, J. C. Raymond, H. D. Winter, K. K. Reeves, D. B. Seaton, A. A. van Ballegooijen, & J. Lin, ApJ, 751, 56 (2012) [3] http://aia.cfa.harvard.edu/filament/
Twisting, Rolling Motions, and Helicity in Prominence Eruptions
McKillop, Sean; Miralles, Mari Paz; Murphy, Nicholas A.; McCauley, Patrick; Su, Yingna
2015-04-01
Panasenco et al. [1] report observations of several CMEs that display a rolling motion about the axis of the erupting prominence. Murphy et al. [2] present simulations of line-tied asymmetric magnetic reconnection that make a falsifiable prediction regarding the handedness of rolling motions of flux ropes during solar eruptions. Mass motions in prominence eruptions tend to be complicated and characterizing these motions is a challenge. We use the AIA filament eruption catalog [3] as a source for finding events. If rolling motions are detected then we will investigate the handedness prediction. We use magnetograms from HMI to determine the strength and asymmetric properties of the photospheric magnetic field in the regions of interest and will use AIA observations to determine the handedness of the rolling motions. We then compare the photospheric magnetic information with the handedness to determine if there is a relationship between the two. We also determine the chirality of the prominences to see if there is any interesting relationship to the twist, rolling motion and/or handedness of the roll.[1] O. Panasenco, S. Martin, A. D. Joshi, & N. Srivastava, J. Atmos. Sol.-Terr. Phys., 73, 1129 (2011)[2] N. A. Murphy, M. P. Miralles, C. L. Pope, J. C. Raymond, H. D. Winter, K. K. Reeves, D. B. Seaton, A. A. van Ballegooijen, & J. Lin, ApJ, 751, 56 (2012)[3] http://aia.cfa.harvard.edu/filament/
Rigidly connected magnetic lines: twisting and winding of magnetic lines
Prasad, G.
2017-10-01
The dynamical process of magnetic flux variation in a fluid's stream tube is described by constructing 1+1+ (2) decomposition of the gradient of fluid's 4-velocity. The necessary and sufficient conditions are obtained for a spacelike congruence to be a congruence of rigidly connected spacelike curves. The evolution of magnetic flux in a magnetic tube is explored under the assumptions that magnetic lines are rigidly connected and the chemical potential of the fluid is constant along a magnetic tube. The interplay between magnetic and stream tubes is demonstrated. It is shown that the growth of magnetic energy in a magnetic tube cannot exceed to that of a stream tube. It is found that the proper time variation of twist of magnetic lines is caused by gravitation inside a neutron star if magnetic lines are rigidly connected and charge neutrality condition holds. Helmholtz-like magnetic vorticity flux conservation in a magnetic tube constituted by rigidly connected geodetic magnetic lines is derived under the assumption that the charge neutrality condition holds. It is shown that the winding of frozen-in poloidal magnetic field due to differential rotation requires meridional circulation in an axisymmetric stationary hydromagnetic configuration.
Two-cylinder entanglement entropy under a twist
Chen, Xiao; Faulkner, Thomas; Fradkin, Eduardo
2016-01-01
We study the von Neumann and R\\'enyi entanglement entropy (EE) of scale-invariant theories defined on tori in 2+1 and 3+1 spacetime dimensions. We focus on spatial bi-partitions of the torus into two cylinders, and allow for twisted boundary conditions along the non-contractible cycles. Various analytical and numerical results are obtained for the universal EE of the relativistic boson and Dirac fermion conformal field theories (CFTs), and for the fermionic quadratic band touching and the boson with $z=2$ Lifshitz scaling. The shape dependence of the EE clearly distinguishes these theories, although intriguing similarities are found in certain limits. We also study the evolution of the EE when a mass is introduced to detune the system from its scale-invariant point, by employing a renormalized EE that goes beyond a naive subtraction of the area law. In certain cases we find non-monotonic behavior of the torus EE under RG flow, which distinguishes it from the EE of a disk.
Twist decomposition of Drell-Yan structure functions: phenomenological implications
Brzemiński, Dawid; Motyka, Leszek; Sadzikowski, Mariusz; Stebel, Tomasz
2017-01-01
The forward Drell-Yan process in pp scattering at the LHC at √{S} = 14 TeV is considered. We analyze the Drell-Yan structure functions assuming the dominance of a Compton-like emission of a virtual photon from a fast quark scattering off the small x gluons. The color dipole framework is applied to perform quantitatively the twist decomposition of all the Drell-Yan structure functions. Two models of the color dipole scattering are applied: the Golec-Biernat-Wüsthoff model and the dipole cross section obtained from the Balitsky-Fadin-Kuraev-Lipatov evolution equation. The two models have essentially different higher twist content and the gluon transverse momentum distribution and lead to different significant effects beyond the collinear leading twist description. It is found that the gluon transverse momentum effects are significant in the Drell-Yan structure functions for all Drell-Yan pair masses M, and the higher twist effects become important for M ≲ 10GeV. It is found that the structure function W TT related to the A 2 angular coefficient and the Lam-Tung observable A 0 - A 2 are particularly sensitive to the gluon k T effects and to the higher twist effects. A procedure is suggested how to disentangle the higher twist effects from the gluon transverse momentum effects.
DNA packaging in bacteriophage: is twist important?
Spakowitz, Andrew James; Wang, Zhen-Gang
2005-06-01
We study the packaging of DNA into a bacteriophage capsid using computer simulation, specifically focusing on the potential impact of twist on the final packaged conformation. We perform two dynamic simulations of packaging a polymer chain into a spherical confinement: one where the chain end is rotated as it is fed, and one where the chain is fed without end rotation. The final packaged conformation exhibits distinct differences in these two cases: the packaged conformation from feeding with rotation exhibits a spool-like character that is consistent with experimental and previous theoretical work, whereas feeding without rotation results in a folded conformation inconsistent with a spool conformation. The chain segment density shows a layered structure, which is more pronounced for packaging with rotation. However, in both cases, the conformation is marked by frequent jumps of the polymer chain from layer to layer, potentially influencing the ability to disentangle during subsequent ejection. Ejection simulations with and without Brownian forces show that Brownian forces are necessary to achieve complete ejection of the polymer chain in the absence of external forces.
Twisted light transmission over 143 km
Krenn, Mario; Handsteiner, Johannes; Fink, Matthias; Fickler, Robert; Ursin, Rupert; Malik, Mehul; Zeilinger, Anton
2016-11-01
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, whereas free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here, we show the transmission of orbital angular momentum modes of light over a distance of 143 km between two Canary Islands, which is 50× greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order and decode the transmitted message with an error rate of 8.33%. Using our data, we estimate that the distribution of orbital angular momentum entanglement over more than 100 km of free space is feasible. Moreover, the quality of our free-space link can be further improved by the use of state-of-the-art adaptive optics systems.
Roots of Dehn twists about separating curves
Rajeevsarathy, Kashyap
2011-01-01
Let $C$ be a curve in a closed orientable surface $F$ of genus $g \\geq 2$ that separates $F$ into subsurfaces $\\widetilde {F_i}$ of genera $g_i$, for $i = 1,2$. We study the set of roots in $\\Mod(F)$ of the Dehn twist $t_C$ about $C$. All roots arise from pairs of $C_{n_i}$-actions on the $\\widetilde{F_i}$, where $n=\\lcm(n_1,n_2)$ is the degree of the root, that satisfy a certain compatibility condition. The $C_{n_i}$ actions are of a kind that we call nestled actions, and we classify them using tuples that we call data sets. The compatibility condition can be expressed by a simple formula, allowing a classification of all roots of $t_C$ by compatible pairs of data sets. We use these data set pairs to classify all roots for $g = 2$ and $g = 3$. We show that there is always a root of degree at least $2g^2+2g$, while $n \\leq 4g^2+2g$. We also give some additional applications.
Baryon masses with dynamical twisted mass fermions
Alexandrou, C; Koutsou, G; Baron, R; Guichon, P; Brinet, M; Carbonell, J; Drach, V; Liu, Z; Pène, O; Urbach, C
2007-01-01
We present results on the mass of the nucleon and the $\\Delta$ using two dynamical degenerate twisted mass quarks. The evaluation is performed at four quark masses corresponding to a pion mass in the range of 690-300 MeV on lattices of size 2.1 fm and 2.7 fm. We check for cutoff effects by evaluating these baryon masses on lattices of spatial size 2.1 fm with lattice spacings $a(\\beta=3.9)=0.0855(6)$ fm and $a(\\beta=4.05)=0.0666(6)$ fm, determined from the pion sector and find them to be within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. The nucleon mass at the physical point provides a determination of the lattice spacing. Using heavy baryon chiral perturbation theory at ${\\cal O}(p^3)$ we find $a(\\beta=3.9)=0.0879(12)$ fm, with a systematic error due to the chiral extrapolation estimated to be about the same as the statistical error. This value of the lattice spacing is in good agreement with the value determined from the pion se...
Dark Matter in a twisted bottle
Arbey, Alexandre; Deandrea, Aldo; Kubik, Bogna
2013-01-01
The real projective plane is a compact, non-orientable orbifold of Euler characteristic 1 without boundaries, which can be described as a twisted Klein bottle. We shortly review the motivations for choosing such a geometry among all possible two-dimensional orbifolds, while the main part of the study will be devoted to dark matter study and limits in Universal Extra Dimensional (UED) models based on this peculiar geometry. In the following we consider such a UED construction based on the direct product of the real projective plane with the standard four-dimensional Minkowski space-time and discuss its relevance as a model of a weakly interacting Dark Matter candidate. One important difference with other typical UED models is the origin of the symmetry leading to the stability of the dark matter particle. This symmetry in our case is a remnant of the six-dimensional Minkowski space-time symmetry partially broken by the compactification. Another important difference is the very small mass splitting between the ...
Dark Matter in a twisted bottle
Arbey, Alexandre; Cacciapaglia, Giacomo; Deandrea, Aldo; Kubik, Bogna
2013-01-01
The real projective plane is a compact, non-orientable orbifold of Euler characteristic 1 without boundaries, which can be described as a twisted Klein bottle. We shortly review the motivations for choosing such a geometry among all possible two-dimensional orbifolds, while the main part of the study will be devoted to dark matter study and limits in Universal Extra Dimensional (UED) models based on this peculiar geometry. In the following we consider such a UED construction based on the direct product of the real projective plane with the standard four-dimensional Minkowski space-time and discuss its relevance as a model of a weakly interacting Dark Matter candidate. One important difference with other typical UED models is the origin of the symmetry leading to the stability of the dark matter particle. This symmetry in our case is a remnant of the six-dimensional Minkowski space-time symmetry partially broken by the compactification. Another important difference is the very small mass splitting between the particles of a given Kaluza-Klein tier, which gives a very important role to co-annihilation effects. Finally the role of higher Kaluza-Klein tiers is also important and is discussed together with a detailed numerical description of the influence of the resonances.
Formation of Solar Delta Active Regions:Twist and Writhe of Magnetic Ropes
Institute of Scientific and Technical Information of China (English)
Hong-Qi Zhang
2004-01-01
We analyze the process of formation of delta configuration in some well-known super active regions based on photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows a potential-like configuration in the solar atmosphere,the magnetic shear develops mainly near the magnetic neutral line with magnetic islands of opposite polarities, and the large-scale photospheric twisted field forming gradually later. Some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, supposed to be generated in the subatmosphere,is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and not entirely consistent with the relationship with magnetic shear in some delta active regions. (3) The proposition is that the large-scale delta active regions are formed from contribution by small-scale non-potential magnetic flux bundles generated in the subatmosphere.
Mujika, Jon I; Formoso, Elena; Mercero, Jose M; Lopez, Xabier
2006-08-03
We present an ab initio study of the acid hydrolysis of a highly twisted amide and a planar amide analogue. The aim of these studies is to investigate the effect that the twist of the amide bond has on the reaction barriers and mechanism of acid hydrolysis. Concerted and stepwise mechanisms were investigated using density functional theory and polarizable continuum model calculations. Remarkable differences were observed between the mechanism of twisted and planar amide, due mainly to the preference for N-protonation of the former and O-protonation of the latter. In addition, we were also able to determine that the hydrolytic mechanism of the twisted amide will be pH dependent. Thus, there is a preference for a stepwise mechanism with formation of an intermediate in the acid hydrolysis, whereas the neutral hydrolysis undergoes a concerted-type mechanism. There is a nice agreement between the characterized intermediate and available X-ray data and a good agreement with the kinetically estimated rate acceleration of hydrolysis with respect to analogous undistorted amide compounds. This work, along with previous ab initio calculations, describes a complex and rich chemistry for the hydrolysis of highly twisted amides as a function of pH. The theoretical data provided will allow for a better understanding of the available kinetic data of the rate acceleration of amides upon twisting and the relation of the observed rate acceleration with intrinsic differential reactivity upon loss of amide bond resonance.
Performance of twist-coupled blades on variable speed rotors
Energy Technology Data Exchange (ETDEWEB)
Lobitz, D.W.; Veers, P.S.; Laino, D.J.
1999-12-07
The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.
Homozygous Nonsense Mutations in TWIST2 Cause Setleis Syndrome
Tukel, Turgut; Šošić, Dražen; Al-Gazali, Lihadh I.; Erazo, Mónica; Casasnovas, Jose; Franco, Hector L.; Richardson, James A.; Olson, Eric N.; Cadilla, Carmen L.; Desnick, Robert J.
2010-01-01
The focal facial dermal dysplasias (FFDDs) are a group of inherited developmental disorders in which the characteristic diagnostic feature is bitemporal scar-like lesions that resemble forceps marks. To date, the genetic defects underlying these ectodermal dysplasias have not been determined. To identify the gene defect causing autosomal-recessive Setleis syndrome (type III FFDD), homozygosity mapping was performed with genomic DNAs from five affected individuals and 26 members of the consanguineous Puerto Rican (PR) family originally described by Setleis and colleagues. Microsatellites D2S1397 and D2S2968 were homozygous in all affected individuals, mapping the disease locus to 2q37.3. Haplotype analyses of additional markers in the PR family and a consanguineous Arab family further limited the disease locus to ∼3 Mb between D2S2949 and D2S2253. Of the 29 candidate genes in this region, the bHLH transcription factor, TWIST2, was initially sequenced on the basis of its known involvement in murine facial development. Homozygous TWIST2 nonsense mutations, c.324C>T and c.486C>T, were identified in the affected members of the Arab and PR families, respectively. Characterization of the expressed mutant proteins, p.Q65X and p.Q119X, by electrophoretic mobility shift assays and immunoblot analyses indicated that they were truncated and unstable. Notably, Setleis syndrome patients and Twist2 knockout mice have similar facial features, indicating the gene's conserved role in mammalian development. Although human TWIST2 and TWIST1 encode highly homologous bHLH transcription factors, the finding that TWIST2 recessive mutations cause an FFDD and dominant TWIST1 mutations cause Saethre-Chotzen craniocynostosis suggests that they function independently in skin and bone development. PMID:20691403
Extension-twist coupling optimization in composite rotor blades
Ozbay, Serkan
2005-07-01
For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different. Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass. A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept
Investigation of Shielding Properties of Yarns, Twisted with Metal Wire
Directory of Open Access Journals (Sweden)
Sandra VARNAITĖ-ŽURAVLIOVA
2014-04-01
Full Text Available The development level of the modern techniques and information technologies creates diverse nature electromagnetic fields and electric field accumulations in the human environment. Electrically conductive textiles that protect against electromagnetic waves and electric charge accumulations can be usable as protective covers for work in computer equipment rooms, measuring stands, air and gas filters and so on. One of the methods used in increase of electrical conductivity in textiles is the development of their specific structures (including the development of threads with the metal component. In this paper, unlike the currently used in the world conductive material production method, where different metal fibres are used as an additives to the main fibre composition in order to create a variety of fibres and yarns, a spun yarn with metal wire was prototyped as samples for this research and the parameters of protective properties of these samples were investigated (such as surface resistivity, vertical resistance, etc.. The protective and shielding properties of woven network with prototyped twisted electro conductive thread with a wire (metal wire diameter of 15 microns were investigated. During the investigation the influence of the following factors, such as conductive fibre composition, electrically conductive thread distribution frequency of the longitudinal and transverse direction, on the protective shielding properties of conductive network were analyzed. The research enabled the assessment of influence of electrically conductive fibre yarn composition and its distribution in the woven mesh on protective shielding properties. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.2492
Investigation of Shielding Properties of Yarns, Twisted with Metal Wire
Directory of Open Access Journals (Sweden)
Sandra VARNAITĖ-ŽURAVLIOVA
2014-04-01
Full Text Available The development level of the modern techniques and information technologies creates diverse nature electromagnetic fields and electric field accumulations in the human environment. Electrically conductive textiles that protect against electromagnetic waves and electric charge accumulations can be usable as protective covers for work in computer equipment rooms, measuring stands, air and gas filters and so on. One of the methods used in increase of electrical conductivity in textiles is the development of their specific structures (including the development of threads with the metal component. In this paper, unlike the currently used in the world conductive material production method, where different metal fibres are used as an additives to the main fibre composition in order to create a variety of fibres and yarns, a spun yarn with metal wire was prototyped as samples for this research and the parameters of protective properties of these samples were investigated (such as surface resistivity, vertical resistance, etc.. The protective and shielding properties of woven network with prototyped twisted electro conductive thread with a wire (metal wire diameter of 15 microns were investigated. During the investigation the influence of the following factors, such as conductive fibre composition, electrically conductive thread distribution frequency of the longitudinal and transverse direction, on the protective shielding properties of conductive network were analyzed. The research enabled the assessment of influence of electrically conductive fibre yarn composition and its distribution in the woven mesh on protective shielding properties. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.2492
Structure, Stability, and Evolution of Magnetic Flux Ropes from the Perspective of Magnetic Twist
Liu, Rui; Titov, Viacheslav S; Chen, Jun; Wang, Yuming; Wang, Haimin; Liu, Chang; Xu, Yan; Wiegelmann, Thomas
2015-01-01
We investigate the evolution of NOAA Active Region 11817 during 2013 August 10--12, when it developed a complex field configuration and produced four confined, followed by two eruptive, flares. These C-and-above flares are all associated with a magnetic flux rope (MFR) located along the major polarity inversion line, where shearing and converging photospheric flows are present. Aided by the nonlinear force-free field modeling, we identify the MFR through mapping magnetic connectivities and computing the twist number $\\mathcal{T}_w$ for each individual field line. The MFR is moderately twisted ($|\\mathcal{T}_w| < 2$) and has a well-defined boundary of high squashing factor $Q$. We found that the field line with the extremum $|\\mathcal{T}_w|$ is a reliable proxy of the rope axis, and that the MFR's peak $|\\mathcal{T}_w|$ temporarily increases within half an hour before each flare while it decreases after the flare peak for both confined and eruptive flares. This pre-flare increase in $|\\mathcal{T}_w|$ has li...
New class of LRS spacetimes with simultaneous rotation and spatial twist
Singh, Sayuri; Goswami, Rituparno; Maharaj, Sunil D
2016-01-01
We establish the existence and find the necessary and sufficient conditions for a new class of solutions of Locally Rotationally Symmetric spacetimes that have non vanishing rotation and spatial twist simultaneously. We transparently show that the existence of such solutions demand non vanishing and bounded heat flux and these solutions are self similar. We provide a brief algorithm indicating how to solve the system of field equations with the given Cauchy data on an initial spacelike Cauchy surface. Finally we argue that these solutions can be used as a first approximation from spherical symmetry to study rotating, inhomogeneous, dynamic and radiating astrophysical stars.
An ultra-thin waveguide twist constructed using fish-scale metallic wires
Han, Jin; Fan, Yuancheng; Wei, Zeyong; Wu, Chao; Cao, Yang; Yu, Xing; Li, Fang; Wang, Zhanshan
2011-01-01
This study theoretically and experimentally investigates the transmission properties of a metamaterial slab comprised of two layers of metallic fish-scale structure arrays and a sandwiched dielectric layer. Calculations show that the asymmetric transmission can be tuned by varying the slab thickness, due to evanescent interlayer coupling. The spatial evolution of the local field inside the structure indicates that the slab functions as a perfect polarization transformer at certain frequencies in the manner of a waveguide twist. Measured transmission spectra are in good agreement with calculated results when material dissipation is considered.
On one-loop entanglement entropy of two short intervals from OPE of twist operators
Li, Zhibin
2016-01-01
We investigate the one-loop entanglement entropy of two short intervals with small cross ratio $x$ on a complex plane in two-dimensional conformal field theory (CFT) using operator product expansion of twist operators. We focus on the one-loop entanglement entropy instead of the general order $n$ R\\'enyi entropy, and this makes the calculation much easier. We consider the contributions of stress tensor to order $x^{10}$, contributions of $W_3$ operator to order $x^{12}$, and contributions of $W_4$ operator to order $x^{14}$. The CFT results agree with the ones in gravity.
Real space renormalization group for twisted lattice N=4 super Yang-Mills
Catterall, Simon
2014-01-01
A necessary ingredient for our previous results on the form of the long distance effective action of the twisted lattice N=4 super Yang-Mills theory is the existence of a real space renormalization group which preserves the lattice structure, both the symmetries and the geometric interpretation of the fields. In this brief article we provide an explicit example of such a blocking scheme and illustrate its practicality in the context of a small scale Monte Carlo renormalization group calculation. We also discuss the implications of this result, and the possible ways in which to use it in order to obtain further information about the long distance theory.
Equivalent forces in Newton equation from twist deformations and noninertial coordinate frames
Daszkiewicz, Marcin
2013-01-01
We compare two ways of force terms generating in the model of nonrelativistic particle moving in the presence of constant field force $\\vec{F}$. First of them uses the twist-deformed N-enlarged Newton-Hooke quantum space-times while the second one incorporates the Coriolis transformations of classical space. Particularly, we find the conditions for which the both treatments provide the same force terms. The presented investigations are performed by analogy to the schemes and ideas proposed in paper [1].
BKM Lie superalgebras from counting twisted CHL dyons
Govindarajan, Suresh
2010-01-01
Following Sen[arXiv:0911.1563], we study the counting of (`twisted') BPS states that contribute to twisted helicity trace indices in four-dimensional CHL models with N=4 supersymmetry. The generating functions of half-BPS states, twisted as well as untwisted, are given in terms of multiplicative eta products with the Mathieu group, M_{24}, playing an important role. These multiplicative eta products enable us to construct Siegel modular forms that count twisted quarter-BPS states. The square-roots of these Siegel modular forms turn out be precisely a special class of Siegel modular forms, the dd-modular forms, that have been classified by Clery and Gritsenko[arXiv:0812.3962]. We show that each one of these dd-modular forms arise as the Weyl-Kac-Borcherds denominator formula of a rank-three Borcherds-Kac-Moody Lie superalgebra. The walls of the Weyl chamber are in one-to-one correspondence with the walls of marginal stability in the corresponding CHL model for twisted dyons as well as untwisted ones. This lead...
THE NONLINEAR EVOLUTION OF A TWIST IN A MAGNETIC SHOCKTUBE
Energy Technology Data Exchange (ETDEWEB)
Williams, Thomas; Taroyan, Youra [Department of Physics, IMPACS, Aberystwyth University, Aberystwyth (United Kingdom); Fedun, Viktor [Space Systems Laboratory, Department of Automatic Control and Systems Engineering, The University of Sheffield, Sheffield (United Kingdom)
2016-02-01
The interaction between a small twist and a horizontal chromospheric shocktube is investigated. The magnetic flux tube is modeled using 1.5-D magnetohydrodynamics. The presence of a supersonic yet sub-Alfvénic flow along the flux tube allows the Alfvénic pulse driven at the photospheric boundary to become trapped and amplified between the stationary shock front and photosphere. The amplification of the twist leads to the formation of slow and fast shocks. The pre-existing stationary shock is destabilized and pushed forward as it merges with the slow shock. The propagating fast shock extracts the kinetic energy of the flow and launches rapid twists of 10–15 km s{sup −1} upon each reflection. A cavity is formed between the slow and fast shocks where the flux tube becomes globally twisted within less than an hour. The resultant highly twisted magnetic flux tube is similar to those prone to kink instabilities, which may be responsible for solar eruptions. The generated torsional flux is calculated.
Probing Viscoelasticity of Cholesteric Liquid Crystals in a Twisting Cell
Angelo, Joseph; Moheghi, Alireza; Diorio, Nick; Jakli, Antal
2013-03-01
Viscoelastic properties of liquid crystals are typically studied either using Poiseuille flow, which can be produced by a pressure gradient in a capillary tube,[2] or Couette flow, which can be generated by a shear between concentric cylinders.[3] We use a different method in which we twist the liquid crystal sandwiched between two cylindrical glass plates, one of which can rotate about its center, the other of which is fixed. When the cell is twisted, there is a force proportional to the twist angle and the twist elastic constant, and inversely proportional to the pitch and sample thickness, normal to the substrates due to the change in pitch in the cholesteric liquid crystal (CLC). Measuring this force on various CLCs with known pitch we could obtain the twist elastic constants. In addition to the equilibrium force, we observed a transient force during the rotation, which is related to the flow of the material, thus allowing us to determine the Leslie viscosity component α1, which typically cannot be assessed by other methods. We expect this apparatus to be a useful tool to study the visco-elastic properties of liquid crystals. The authors acknowledge support from NSF grant DMR-0907055.
Higher twist effects in deeply virtual Compton scattering
Energy Technology Data Exchange (ETDEWEB)
Pirnay, Bjoern Michael
2016-08-01
In this work we explore the effects of higher twist power corrections on the deeply virtual Compton scattering process. The calculation of the helicity amplitudes for all possible polarization combinations is performed within the framework of QCD operator product expansion. As a result the known accuracy of the amplitudes is improved to include the (kinematic) twist-4 contributions. For the most part the analysis focuses on spin-1/2 targets, the answers for scalar targets conveniently emerge as a byproduct. We investigate the analytical structure of these corrections and prove consistency with QCD factorization. We give an estimation of the numerical impact of the sub-leading twist contributions for proton targets with the help of a phenomenological model for the nonperturbative proton generalized parton distributions. We compare different twist approximations and relate predictions for physical observables to experiments performed by the Hall A, CLAS, HERMES, H1 and ZEUS collaborations. The estimate also includes a numerical study for planned COMPASS-II runs. Throughout the analysis special emphasis is put on the convention dependence induced by finite twist truncation of scattering amplitudes.
"Twisted Beam" SEE Observations of Ionospheric Heating from HAARP
Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.; Han, S.-M.; Pedersen, T. R.; Scales, W. A.
2015-10-01
Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world's largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP experiments using a "twisted beam" excitation mode. Analysis of twisted beam heating shows that the SEE results obtained are identical to more traditional patterns. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional "solid spot" region from a pencil beam. The ring heating pattern may be more conducive to the creation of stable artificial airglow layers because of the horizontal structure of the ring. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.
BKM Lie superalgebras from counting twisted CHL dyons
Govindarajan, Suresh
2011-05-01
Following Sen, we study the counting of (`twisted') BPS states that contribute to twisted helicity trace indices in four-dimensional CHL models with mathcal{N} = 4 supersymmetry. The generating functions of half-BPS states, twisted as well as untwisted, are given in terms of multiplicative eta products with the Mathieu group, M 24, playing an important role. These multiplicative eta products enable us to construct Siegel modular forms that count twisted quarter-BPS states. The square-roots of these Siegel modular forms turn out be precisely a special class of Siegel modular forms, the dd-modular forms, that have been classified by Clery and Gritsenko. We show that each one of these dd-modular forms arise as the Weyl-Kac-Borcherds denominator formula of a rank-three Borcherds-Kac-Moody Lie superalgebra. The walls of the Weyl chamber are in one-to-one correspondence with the walls of marginal stability in the corresponding CHL model for twisted dyons as well as untwisted ones. This leads to a periodic table of BKM Lie superalgebras with properties that are consistent with physical expectations.
Curvature regulation of the ciliary beat through axonemal twist
Sartori, Pablo; Geyer, Veikko F.; Howard, Jonathon; Jülicher, Frank
2016-10-01
Cilia and flagella are hairlike organelles that propel cells through fluid. The active motion of the axoneme, the motile structure inside cilia and flagella, is powered by molecular motors of the axonemal dynein family. These motors generate forces and torques that slide and bend the microtubule doublets within the axoneme. To create regular waveforms, the activities of the dyneins must be coordinated. It is thought that coordination is mediated by stresses due to radial, transverse, or sliding deformations, and which build up within the moving axoneme and feed back on dynein activity. However, which particular components of the stress regulate the motors to produce the observed waveforms of the many different types of flagella remains an open question. To address this question, we describe the axoneme as a three-dimensional bundle of filaments and characterize its mechanics. We show that regulation of the motors by radial and transverse stresses can lead to a coordinated flagellar motion only in the presence of twist. We show that twist, which could arise from torque produced by the dyneins, couples curvature to transverse and radial stresses. We calculate emergent beating patterns in twisted axonemes resulting from regulation by transverse stresses. The resulting waveforms are similar to those observed in flagella of Chlamydomonas and sperm. Due to the twist, the waveform has nonplanar components, which result in swimming trajectories such as twisted ribbons and helices, which agree with observations.
The epsilon regime with twisted mass Wilson fermions
Bar, Oliver; Shindler, Andrea
2010-01-01
We investigate the leading lattice spacing effects in mesonic two-point correlators computed with twisted mass Wilson fermions in the epsilon-regime. By generalizing the procedure already introduced for the untwisted Wilson chiral effective theory, we extend the continuum chiral epsilon expansion to twisted mass WChPT. We define different regimes, depending on the relative power counting for the quark masses and the lattice spacing. We explicitly compute, for arbitrary twist angle, the leading O(a^2) corrections appearing at NLO in the so-called GSM^* regime. As in untwisted WChPT, we find that in this situation the impact of explicit chiral symmetry breaking due to lattice artefacts is strongly suppressed. Of particular interest is the case of maximal twist, which corresponds to the setup usually adopted in lattice simulations with twisted mass Wilson fermions. The formulae we obtain can be matched to lattice data to extract physical low energy couplings, and to estimate systematic uncertainties coming from ...
Comments on twisted indices in 3d supersymmetric gauge theories
Energy Technology Data Exchange (ETDEWEB)
Closset, Cyril [Simons Center for Geometry and PhysicsState University of New York, Stony Brook, NY 11794 (United States); Kim, Heeyeon [Perimeter Institute for Theoretical Physics31 Caroline Street North, Waterloo, N2L 2Y5, Ontario (Canada)
2016-08-09
We study three-dimensional N=2 supersymmetric gauge theories on Σ{sub g}×S{sup 1} with a topological twist along Σ{sub g}, a genus-g Riemann surface. The twisted supersymmetric index at genus g and the correlation functions of half-BPS loop operators on S{sup 1} can be computed exactly by supersymmetric localization. For g=1, this gives a simple UV computation of the 3d Witten index. Twisted indices provide us with a clean derivation of the quantum algebra of supersymmetric Wilson loops, for any Yang-Mills-Chern-Simons-matter theory, in terms of the associated Bethe equations for the theory on ℝ{sup 2}×S{sup 1}. This also provides a powerful and simple tool to study 3d N=2 Seiberg dualities. Finally, we study A- and B-twisted indices for N=4 supersymmetric gauge theories, which turns out to be very useful for quantitative studies of three-dimensional mirror symmetry. We also briefly comment on a relation between the S{sup 2}×S{sup 1} twisted indices and the Hilbert series of N=4 moduli spaces.
Iterative methods for overlap and twisted mass fermions
Energy Technology Data Exchange (ETDEWEB)
Chiarappa, T. [Univ. di Milano Bicocca (Italy); Jansen, K.; Shindler, A.; Wetzorke, I. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Nagai, K.I. [Wuppertal Univ. (Gesamthochschule) (Germany). Fachbereich Physik; Papinutto, M. [INFN Sezione di Roma Tre, Rome (Italy); Scorzato, L. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT), Villazzano (Italy); Urbach, C. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Wenger, U. [ETH Zuerich (Switzerland). Inst. fuer Theoretische Physik
2006-09-15
We present a comparison of a number of iterative solvers of linear systems of equations for obtaining the fermion propagator in lattice QCD. In particular, we consider chirally invariant overlap and chirally improved Wilson (maximally) twisted mass fermions. The comparison of both formulations of lattice QCD is performed at four fixed values of the pion mass between 230 MeV and 720 MeV. For overlap fermions we address adaptive precision and low mode preconditioning while for twisted mass fermions we discuss even/odd preconditioning. Taking the best available algorithms in each case we find that calculations with the overlap operator are by a factor of 30-120 more expensive than with the twisted mass operator. (orig.)
Adaptive dual-layer super-twisting control and observation
Edwards, Christopher; Shtessel, Yuri
2016-09-01
In this paper, a super-twisting-like structure with adaptive gains is proposed. The structure is parameterised by two scalar gains, both of which adapt, and by an additional time-varying term. The magnitudes of the adaptive terms are allowed to both increase and decrease as appropriate so that they are as small as possible, in the sense that they do not unnecessarily over-bound the uncertainty, and yet are large enough to sustain a sliding motion. In the paper, a new time varying gain is incorporated into the traditional super-twisting architecture. The proposed adaption law has a dual-layer structure which is formally analyzed using Lyapunov techniques. The additional term has the effect of simplifying the stability analysis whilst guaranteeing the second-order sliding mode properties of the traditional super-twisting scheme.
Template preparation of twisted nanoparticles of mesoporous silica
Institute of Scientific and Technical Information of China (English)
Kui Niu; Zhongbin Ni; Chengwu Fu; Tatsuo Kaneko; Mingqing Chen
2011-01-01
Optical isomers of N-lauroyl-L-(or-D-) alanine sodium salt {C12-L-(or-D-)AlaS} surfactants were used for the preparation of mesoporous silica nanoparticles with a twisted hexagonal rod-like morphology. Thermogravimetric analysis (TGA) was used to determine the temperature for template removal. Circular dichroism (CD) spectra of the surfactant solution with various compositions illustrated the formation and supramolecular assembly of protein-like molecular architecture leading to formation of twisted nanoparticles. Scanning electron microscopy (SEM),high-resolution transmission electron microscopy (HRTEM)and X-ray powder diffraction (XRD) patterns of these as-synthesized mesoporous silica confirmed that the twisted morphology of these nanoparticles was closely related to the supramolecular-assembled complex of amino acid surfactants.
Twisted Conjugacy Classes in Abelian Extensions of Certain Linear Groups
Mubeena, T
2011-01-01
Given an automorphism $\\phi:\\Gamma\\lr \\Gamma$, one has an action of $\\Gamma$ on itself by $\\phi$-twisted conjugacy, namely, $g.x=gx\\phi(g^{-1})$. The orbits of this action are called $\\phi$-twisted conjugacy classes. One says that $\\Gamma$ has the $R_\\infty$-property if there are infinitely many $\\phi$-twisted conjugacy classes for every automorphism $\\phi$ of $\\Gamma$. In this paper we show that $\\SL(n,\\bz)$ and its congruence subgroups have the $R_\\infty$-property. Further we show that any (countable) abelian extension of $\\Gamma$ has the $R_\\infty$-property where $\\Gamma$ is a torsion free non-elementary hyperbolic group, or $\\SL(n,\\bz), \\Sp(2n,\\bz)$ or a principal congruence subgroup of $\\SL(n,\\bz)$ or the fundamental group of a complete Riemannian manifold of constant negative curvature.
Twists of Pl\\"ucker coordinates as dimer partition functions
Scott, Jeanne
2013-01-01
The homogeneous coordinate ring of the Grassmannian Gr(k,n) has a cluster structure defined in terms of planar diagrams known as Postnikov diagrams. The cluster corresponding to such a diagram consists entirely of Pl\\"ucker coordinates. We introduce a twist map on Gr(k,n) related to the BZ-twist, and give an explicit Laurent expansion for the twist of an arbitrary Pl\\"ucker coordinate, in terms of the cluster variables associated with a fixed Postnikov diagram. The expansion arises as a (scaled) dimer partition function of a weighted version of the bipartite graph dual to the Postnikov diagram, modified by a boundary condition determined by the Pl\\"ucker coordinate.
On the Stern sequence and its twisted version
Allouche, Jean-Paul
2012-01-01
In a recent preprint on ArXiv, Bacher introduced a twisted version of the Stern sequence. His paper contains in particular three conjectures relating the generating series for the Stern sequence and for the twisted Stern sequence. Soon afterwards Coons published two papers in {\\it Integers}: first he proved these conjectures, second he used his result to obtain a correlation-type identity for the Stern sequence. We recall here a simple result of Reznick and we state a similar result for the twisted Stern sequence. We deduce an easy proof of Coons' identity, and a simple proof of Bacher's conjectures. Furthermore we prove identities similar to Coons' for variations on the Stern sequence that include Bacher's sequence.
Iterative methods for overlap and twisted mass fermions
Energy Technology Data Exchange (ETDEWEB)
Chiarappa, T. [Univ. di Milano Bicocca (Italy); Jansen, K.; Shindler, A.; Wetzorke, I. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Nagai, K.I. [Wuppertal Univ. (Gesamthochschule) (Germany). Fachbereich Physik; Papinutto, M. [INFN Sezione di Roma Tre, Rome (Italy); Scorzato, L. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT), Villazzano (Italy); Urbach, C. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Wenger, U. [ETH Zuerich (Switzerland). Inst. fuer Theoretische Physik
2006-09-15
We present a comparison of a number of iterative solvers of linear systems of equations for obtaining the fermion propagator in lattice QCD. In particular, we consider chirally invariant overlap and chirally improved Wilson (maximally) twisted mass fermions. The comparison of both formulations of lattice QCD is performed at four fixed values of the pion mass between 230 MeV and 720 MeV. For overlap fermions we address adaptive precision and low mode preconditioning while for twisted mass fermions we discuss even/odd preconditioning. Taking the best available algorithms in each case we find that calculations with the overlap operator are by a factor of 30-120 more expensive than with the twisted mass operator. (orig.)
A Topological Approach to Bend-Twist Maps with Applications
Directory of Open Access Journals (Sweden)
Anna Pascoletti
2011-01-01
Full Text Available In this paper we reconsider, in a purely topological framework, the concept of bend-twist map previously studied in the analytic setting by Tongren Ding in (2007. We obtain some results about the existence and multiplicity of fixed points which are related to the classical Poincaré-Birkhoff twist theorem for area-preserving maps of the annulus; however, in our approach, like in Ding (2007, we do not require measure-preserving conditions. This makes our theorems in principle applicable to nonconservative planar systems. Some of our results are also stable for small perturbations. Possible applications of the fixed point theorems for topological bend-twist maps are outlined in the last section.
Group dualities, T-dualities, and twisted K-theory
Mathai, Varghese
2016-01-01
This paper explores further the connection between Langlands duality and T-duality for compact simple Lie groups, which appeared in work of Daenzer-Van Erp and Bunke-Nikolaus. We show that Langlands duality gives rise to isomorphisms of twisted K-groups, but that these K-groups are trivial except in the simplest case of SU(2) and SO(3). Along the way we compute explicitly the map on $H^3$ induced by a covering of compact simple Lie groups, which is either 1 or 2 depending in a complicated way on the type of the groups involved. We also give a new method for computing twisted K-theory using the Segal spectral sequence, giving simpler computations of certain twisted K-theory groups of compact Lie groups relevant for D-brane charges in WZW theories and rank-level dualities. Finally we study a duality for orientifolds based on complex Lie groups with an involution.
Ham, J.-Y.; Lee, J.
2016-09-01
We calculate the Chern-Simons invariants of twist-knot orbifolds using the Schläfli formula for the generalized Chern-Simons function on the family of twist knot cone-manifold structures. Following the general instruction of Hilden, Lozano, and Montesinos-Amilibia, we here present concrete formulae and calculations. We use the Pythagorean Theorem, which was used by Ham, Mednykh and Petrov, to relate the complex length of the longitude and the complex distance between the two axes fixed by two generators. As an application, we calculate the Chern-Simons invariants of cyclic coverings of the hyperbolic twist-knot orbifolds. We also derive some interesting results. The explicit formulae of the A-polynomials of twist knots are obtained from the complex distance polynomials. Hence the edge polynomials corresponding to the edges of the Newton polygons of the A-polynomials of twist knots can be obtained. In particular, the number of boundary components of every incompressible surface corresponding to slope -4n+2 turns out to be 2. Bibliography: 39 titles.
Leading-twist distribution amplitudes of scalar and vector mesons
Li, B.-L.; Chang, L.; Ding, M.; Roberts, C. D.; Zong, H.-S.
2016-11-01
A symmetry-preserving truncation of the two-body light-quark bound-state problem in relativistic quantum field theory is used to calculate the leading-twist parton distribution amplitudes (PDAs) of scalar systems, both ground-state and radial excitations, and the radial excitations of vector mesons. Owing to the fact that the scale-independent leptonic decay constant of a scalar meson constituted from equal-mass valence constituents vanishes, it is found that the PDA of a given scalar system possesses one more zero than that of an analogous vector meson. Consequently, whereas the mean light-front relative momentum of the valence constituents within a vector meson is zero, that within a scalar meson is large, an outcome which hints at a greater role for light-front angular momentum in systems classified as P -wave in quantum mechanical models. Values for the scale-dependent decay constants of ground-state scalar and vector systems are a by-product of this analysis, and they turn out to be roughly equal, viz. ≃0.2 GeV at an hadronic scale. In addition, it is confirmed that the dilation characterizing ground-state PDAs is manifest in the PDAs of radial excitations too. The impact of S U (3 )-flavor symmetry breaking is also considered. When compared with pseudoscalar states, it is a little stronger in scalar systems, but the size is nevertheless determined by the flavor dependence of dynamical chiral symmetry breaking and the PDAs are still skewed toward the heavier valence quark in asymmetric systems.
Anomalous phase shift in a twisted quantum loop
Energy Technology Data Exchange (ETDEWEB)
Taira, Hisao [Division of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan); Shima, Hiroyuki, E-mail: taira@eng.hokudai.ac.j [Department of Applied Mathematics 3, LaCaN, Universitat Politecnica de Catalunya (UPC), Barcelona 08034 (Spain)
2010-09-03
The coherent motion of electrons in a twisted quantum ring is considered to explore the effect of torsion inherent to the ring. Internal torsion of the ring composed of helical atomic configuration yields a non-trivial quantum phase shift in the electrons' eigenstates. This torsion-induced phase shift causes novel kinds of persistent current flow and an Aharonov-Bohm-like conductance oscillation. The two phenomena can occur even when no magnetic flux penetrates inside the twisted ring, thus being in complete contrast with the counterparts observed in untwisted rings.
Folding DNA into twisted and curved nanoscale shapes.
Dietz, Hendrik; Douglas, Shawn M; Shih, William M
2009-08-01
We demonstrate the ability to engineer complex shapes that twist and curve at the nanoscale from DNA. Through programmable self-assembly, strands of DNA are directed to form a custom-shaped bundle of tightly cross-linked double helices, arrayed in parallel to their helical axes. Targeted insertions and deletions of base pairs cause the DNA bundles to develop twist of either handedness or to curve. The degree of curvature could be quantitatively controlled, and a radius of curvature as tight as 6 nanometers was achieved. We also combined multiple curved elements to build several different types of intricate nanostructures, such as a wireframe beach ball or square-toothed gears.
Exponential reduction of finite volume effects with twisted boundary conditions
Cherman, Aleksey; Wagman, Michael L; Yaffe, Laurence G
2016-01-01
Flavor-twisted boundary conditions can be used for exponential reduction of finite volume artifacts in flavor-averaged observables in lattice QCD calculations with $SU(N_f)$ light quark flavor symmetry. Finite volume artifact reduction arises from destructive interference effects in a manner closely related to the phase averaging which leads to large $N_c$ volume independence. With a particular choice of flavor-twisted boundary conditions, finite volume artifacts for flavor-singlet observables in a hypercubic spacetime volume are reduced to the size of finite volume artifacts in a spacetime volume with periodic boundary conditions that is four times larger.
Duality and conformal twisted boundaries in the Ising model
Grimm, U
2002-01-01
There has been recent interest in conformal twisted boundary conditions and their realisations in solvable lattice models. For the Ising and Potts quantum chains, these amount to boundary terms that are related to duality, which is a proper symmetry of the model at criticality. Thus, at criticality, the duality-twisted Ising model is translationally invariant, similar to the more familiar cases of periodic and antiperiodic boundary conditions. The complete finite-size spectrum of the Ising quantum chain with this peculiar boundary condition is obtained.
Moments of meson distribution functions with dynamical twisted mass fermions
Baron, R; Carbonell, J; Jansen, K; Liu, Z; Pène, O; Urbach, C
2007-01-01
We present our preliminary results on the lowest moment of quark distribution functions of the pion using two flavor dynamical simulations with Wilson twisted mass fermions at maximal twist. The calculation is done in a range of pion masses from 300 to 500 MeV. A stochastic source method is used to reduce inversions in calculating propagators. Finite volume effects at the lowest quark mass are examined by using two different lattice volumes. Our results show that we achieve statistical errors of only a few percent. We plan to compute renormalization constants non-perturbatively and extend the calculation to two more lattice spacings and to the nucleons.
Note on twisted elliptic genus of K3 surface
Energy Technology Data Exchange (ETDEWEB)
Eguchi, Tohru, E-mail: eguchi@yukawa.kyoto-u.ac.j [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Hikami, Kazuhiro, E-mail: KHikami@gmail.co [Department of Mathematics, Naruto University of Education, Tokushima 772-8502 (Japan)
2011-01-03
We discuss the possibility of Mathieu group M{sub 24} acting as symmetry group on the K3 elliptic genus as proposed recently by Ooguri, Tachikawa and one of the present authors. One way of testing this proposal is to derive the twisted elliptic genera for all conjugacy classes of M{sub 24} so that we can determine the unique decomposition of expansion coefficients of K3 elliptic genus into irreducible representations of M{sub 24}. In this Letter we obtain all the hitherto unknown twisted elliptic genera and find a strong evidence of Mathieu moonshine.
Brief Analysis of the Semantic Deviation in Oliver Twist
Institute of Scientific and Technical Information of China (English)
黄二靓
2016-01-01
As one of the foremost critical realist writers of the Victorian era, Charles Dickens is adept at using language to create all kinds of characters in a humorous or ironic tone. Therefore he received massive popularity for his unique style in storytelling. Oliver Twist is one of Charles Dickens's masterpieces and also the most appropriate choice for the stylistic study on Charles Dickens. This thesis endeavors to explore the aesthetic effect of semantic deviation appearing in Oliver Twist so that we can have a better comprehension about the excellent writing skill of Charles Dickens.
A universal coefficient theorem for twisted K-theory
Khorami, Mehdi
2010-01-01
In this paper, we recall the definition of twisted K-theory in various settings. We prove that for a twist $\\tau$ corresponding to a three dimensional integral cohomology class of a space X, there exist a "universal coefficient" isomorphism K_{*}^{\\tau}(X)\\cong K_{*}(P_{\\tau})\\otimes_{K_{*}(\\mathbb{C}P^{\\infty})} \\hat{K}_{*} where $P_\\tau$ is the total space of the principal $\\mathbb{C}P^{\\infty}$-bundle induced over X by $\\tau$ and $\\hat K_*$ is obtained form the action of $\\mathbb{C}P^{\\infty}$ on K-theory.
Simulating QCD at the physical point with N{sub f}=2 Wilson twisted mass fermions at maximal twist
Energy Technology Data Exchange (ETDEWEB)
Abdel-Rehim, A. [The Cyprus Institute, Nicosia (Cyprus). CaSToRC; Alexandrou, C. [The Cyprus Institute, Nicosia (Cyprus). CaSToRC; Cyprus Univ. Nicosia (Cyprus). Dept. of Physics; Burger, F. [DESY Zeuthen (Germany). NIC; Collaboration: European Twisted Mass Collaboration; and others
2015-12-15
We present simulations of QCD using N{sub f}=2 dynamical Wilson twisted mass lattice QCD with physical value of the pion mass and at one value of the lattice spacing. Such simulations at a∼0.09 fm became possible by adding the clover term to the action. While O(a) improvement is still guaranteed by Wilson twisted mass fermions at maximal twist, the introduction of the clover term reduces O(a{sup 2}) cutoff effects related to isospin symmetry breaking. We give results for a set of phenomenologically interesting observables like pseudo-scalar masses and decay constants, quark masses and the anomalous magnetic moments of leptons. We mostly find remarkably good agreement with phenomenology, even though we cannot take the continuum and thermodynamic limits.
Simulating QCD at the Physical Point with $N_f=2$ Wilson Twisted Mass Fermions at Maximal Twist
Abdel-Rehim, A; Burger, F; Constantinou, M; Dimopoulos, P; Frezzotti, R; Hadjiyiannakou, K; Jansen, K; Kallidonis, C; Kostrzewa, B; Koutsou, G; Mangin-Brinet, M; Petschlies, M; Pientka, G; Rossi, G C; Urbach, C; Wenger, U
2015-01-01
We present simulations of QCD using Nf=2 dynamical Wilson twisted mass lattice QCD with physical value of the pion mass and at one value of the lattice spacing. Such simulations at ~0.09 fm became possible by adding the clover term to the action. While O(a) improvement is still guaranteed by Wilson twisted mass fermions at maximal twist, the introduction of the clover term reduces cutoff effects related to isospin symmetry breaking. We give results for a set of phenomenologically interesting observables like pseudo-scalar masses and decay constants, quark masses and the anomalous magnetic moments of leptons. We mostly find remarkably good agreement with phenomenology, even though we cannot take the continuum and thermodynamic limits.
Motion Analysis of Fiber Band in Compact Field of Compact Spinning
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The technological process of compact spinning and the compact procedure of fiber band in compact field are briefly illustrated. The motions of fiber band in compact field are discussed theoretically from which tilting angle of suction slot in profile tube, additional twists created by fiber band's rotating around its own axis and ultimate twists in compact yarn are deduced accordingly. The existence of additional twists is also verified through experiments.
Sanabria, Charlie; Lee, Peter J.; Starch, William; Devred, Arnaud; Larbalestier, David C.
2016-07-01
As part of the ITER conductor qualification process, 3 m long cable-in-conduit conductors (CICCs) were tested at the SULTAN facility under conditions simulating ITER operation so as to establish the current-sharing temperature, T cs, as a function of multiple full Lorentz force loading cycles. After a comprehensive evaluation of both the toroidal field (TF) and the central solenoid (CS) conductors, it was found that T cs degradation was common in long twist pitch TF conductors while short twist pitch CS conductors showed some T cs increase. However, one kind of TF conductors containing superconducting strand fabricated by the Bochvar Institute of Inorganic Materials (VNIINM) avoided T cs degradation despite having long twist pitch. In our earlier metallographic autopsies of long and short twist pitch CS conductors, we observed a substantially greater transverse strand movement under Lorentz force loading for long twist pitch conductors, while short twist pitch conductors had negligible transverse movement. With help from the literature, we concluded that the transverse movement was not the source of T cs degradation but rather an increase of the compressive strain in the Nb3Sn filaments possibly induced by longitudinal movement of the wires. Like all TF conductors this TF VNIINM conductor showed large transverse motions under Lorentz force loading, but T cs actually increased, as in all short twist pitch CS conductors. We here propose that the high surface roughness of the VNIINM strand may be responsible for the suppression of the compressive strain enhancement (characteristic of long twist pitch conductors). It appears that increasing strand surface roughness could improve the performance of long twist pitch CICCs.
Curvatures and potential of M-theory in D=4 with fluxes and twist
D'Auria, R; Trigiante, M
2005-01-01
We give the curvatures of the free differential algebra (FDA) of M--theory compactified to D=4 on a twisted seven--torus with the 4--form flux switched on. Two formulations are given, depending on whether the 1--form field strengths of the scalar fields (originating from the 3--form gauge field $\\hat{A}^{(3)}$) are included or not in the FDA. We also give the bosonic equations of motion and discuss at length the scalar potential which emerges in this type of compactifications. For flat groups we show the equivalence of this potential with a dual formulation of the theory which has the full $\\rE_{7(7)}$ symmetry.
Twisted toroidal vortex-solitons in inhomogeneous media with repulsive nonlinearity
Kartashov, Y V; Shnir, Y; Torner, L
2014-01-01
Toroidal modes in the form of so-called Hopfions, with two independent winding numbers, a hidden one (twist, s), which characterizes a circular vortex thread embedded into a three-dimensional soliton, and the vorticity around the vertical axis m, appear in many fields, including the field theory, ferromagnetics, and semi- and superconductors. Such topological states are normally generated in multi-component systems, or as trapped quasi-linear modes in toroidal potentials. We uncover that stable solitons with this structure can be created, without any linear potential, in the single-component setting with the strength of repulsive nonlinearity growing fast enough from the center to the periphery, for both steep and smooth modulation profiles. Toroidal modes with s=1 and vorticity m=0,1,2 are produced. They are stable for m1. An approximate analytical solution is obtained for the twisted ring with s=1, m=0. Under the application of an external torque, it rotates like a solid ring. The setting can be implemented...
On the space of connections having non-trivial twisted harmonic spinors
Energy Technology Data Exchange (ETDEWEB)
Bei, Francesco, E-mail: bei@math.hu-berlin.de [Institut für Mathematik, Humboldt Universität zu Berlin, Unter den Linden 6, 10099 Berlin (Germany); Waterstraat, Nils, E-mail: n.waterstraat@kent.ac.uk [School of Mathematics, Statistics & Actuarial Science, University of Kent, Canterbury, Kent CT2 7NF (United Kingdom)
2015-09-15
We consider Dirac operators on odd-dimensional compact spin manifolds which are twisted by a product bundle. We show that the space of connections on the twisting bundle which yields an invertible operator has infinitely many connected components if the untwisted Dirac operator is invertible and the dimension of the twisting bundle is sufficiently large.
Effect and mechanism of the Twist gene on invasion and metastasis of gastric carcinoma cells
Institute of Scientific and Technical Information of China (English)
Geng-Qiu Luo; Jing-He Li; Ji-Fang Wen; Yan-Hong Zhou; Yong-Bin Hu; Jian-Hua Zhou
2008-01-01
AIM: To study the effect of the transfected Twist gene on invasion and metastasis of gastric carcinoma cells and the possible mechanisms involved.METHODS: Human gastric carcinoma MKN28 cells were stably transfected with Twist sense plasmid, and MKN45 cells were stably transfected with Twist antisense plasmid using the lipofectamine transfection technique.RT-PCR,Western blotting, ENSA, gelatin zymography assay, and in vitro invasion and migration assays were performed.Nude mice metastasis models were established by the abdominal cavity transfer method.RESULTS: Cell models (TwistS-MKN28) that steadily expressed high Twist protein were obtained.Compared with MKN28 and pcDNA3-MKN28 cells, adherence,migration and invasion ability of TwistS-MKN28 cells were clearly raised.The number of cancer nodules was increased significantly in the abdominal cavity and liver of nude mice inoculated with TwistS-MKN28 cells.Overexpression of Twist in MKN28 cells increased Tcf-4/Lef DNA binding activity, and promoted expression of Tcf-4's downstream target genes cyclin Dt and HMP-2.However, suppression of Twist (TwistAS-NKN45) inhibited MKN45 cell invasion and the expression of cyclin D1 was reduced.The activity of MMP-2 was also decreased.CONCLUSION: These results indicate that Twist promotes gastric cancer cell migration, invasion and metastasis, and Twist may play an important role in Wnt/Tcf-4 signaling.
Gauge theory on twisted kappa-Minkowski: old problems and possible solutions
Dimitrijevic, Marija; Pachol, Anna
2014-01-01
We review the application of twist deformation formalism and the construction of noncommutative gauge theory on kappa-Minkowski space-time. We compare two different types of twists: the Abelian and the Jordanian one. In each case we provide the twisted differential calculus and consider U(1) gauge theory. Different methods of obtaining a gauge invariant action and related problems are thoroughly discussed.
Gauge Theory on Twisted kappa-Minkowski: Old Problems and Possible Solutions
Dimitrijević, Marija; Jonke, Larisa; Pachoł, Anna
2014-06-01
We review the application of twist deformation formalism and the construction of noncommutative gauge theory on κ-Minkowski space-time. We compare two different types of twists: the Abelian and the Jordanian one. In each case we provide the twisted differential calculus and consider {U}(1) gauge theory. Different methods of obtaining a gauge invariant action and related problems are thoroughly discussed.
Twist decomposition of Drell-Yan structure functions: phenomenological implications
Brzeminski, Dawid; Sadzikowski, Mariusz; Stebel, Tomasz
2016-01-01
The forward Drell--Yan process in $pp$ scattering at the LHC at $\\sqrt{S}=14$ TeV is considered. We analyze the Drell--Yan structure functions assuming the dominance of a Compton-like emission of a virtual photon from a fast quark scattering off the small $x$ gluons. The color dipole framework is applied to perform quantitatively the twist decomposition of all the Drell--Yan structure functions. Two models of the color dipole scattering are applied: the Golec-Biernat--W\\"{u}sthoff model and the dipole cross section obtained from the Balitsky--Fadin--Kuraev--Lipatov evolution equation. The two models have essentially different higher twist content and the gluon transverse momentum distribution and lead to different significant effects beyond the collinear leading twist description. It is found that the gluon transverse momentum effects are significant in the Drell--Yan structure functions for all Drell--Yan pair masses $M$, and the higher twist effects become important for $M \\lesssim 10$ GeV. It is found that...
Twisting singular solutions of Betheʼs equations
Nepomechie, Rafael I.; Wang, Chunguang
2014-12-01
The Bethe equations for the periodic XXX and XXZ spin chains admit singular solutions, for which the corresponding eigenvalues and eigenvectors are ill-defined. We use a twist regularization to derive conditions for such singular solutions to be physical, in which case they correspond to genuine eigenvalues and eigenvectors of the Hamiltonian.
DVCS on the nucleon to the twist-3 accuracy
Kivel, N A
2001-01-01
The amplitude of the deeply virtual Compton scattering off nucleon is computed to the twist-3 accuracy in the Wandzura-Wilczek (WW) approximation. The result is presented in the form which can be easily used for analysis of DVCS observables.
Renormalization of four-fermion operators for higher twist calculations
Capitani, S; Horsley, R; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A
1999-01-01
The evaluation of the higher twist contributions to Deep Inelastic Scattering amplitudes involves a non trivial choice of operator bases for the higher orders of the OPE expansion of the two hadronic currents. In this talk we discuss the perturbative renormalization of the four-fermion operators that appear in the above bases.
Photoelectric Effect for Twist-deformed Space-time
Daszkiewicz, M.
In this article, we investigate the impact of twisted space-time on the photoelectric effect, i.e., we derive the $\\theta$-deformed threshold frequency. In such a way we indicate that the space-time noncommutativity strongly enhances the photoelectric process.
Exploring the epsilon regime with twisted mass fermions
Jansen, K; Shindler, A; Urbach, C; Wenger, U
2007-01-01
In this proceeding contribution we report on a first study in order to explore the so called epsilon regime with Wilson twisted mass (Wtm) fermions. To show the potential of this approach we give a preliminary determination of the chiral condensate.
A mod 2 index theorem for the twisted Signature operator
Institute of Scientific and Technical Information of China (English)
张伟平
1999-01-01
A mod 2 index theorem for the twisted Signature operator on 4q+1 dimensional manifolds is established. This result generalizes a result of Farber and Turaev, which was proved for the case of orthogonal flat bundles, to arbitrary real vector bundles. It also provides an analytic interpretation of the sign of the Poincar(?)-Reidemeister scalar product defined by Farber and Turaev.
Action of the cork twist on Floer homology
Akbulut, Selman
2011-01-01
We utilize the Ozsvath-Szabo contact invariant to detect the action of involutions on certain homology spheres that are surgeries on symmetric links, generalizing a previous result of Akbulut and Durusoy. Potentially this may be useful to detect different smooth structures on 4-manifolds by cork twisting operation.
Twist-related locomotion of a snake-like robot
Institute of Scientific and Technical Information of China (English)
Ye Changlong; Ma Shugen; Li Bin; Wang Yuechao; Jing Tao
2006-01-01
As a hyper-redundant robot, a 3D snake-like robot can perform many other configurations and types of locomotion adapted to environment except for mimicking the natural snake locomotion. The natural snake locomotion usually limits locomotion capability of the robot because of inadequacy in the mechanism and actuation to imitate characters of natural snake such as the too many DOFs and the characteristics of the muscle. In order to apply snake-like robots to the unstructured environment, the researchers have designed many gaits for increasing the adaptability to a variety of surroundings. The twist-related locomotion is an effective gait achieved by jointly driving the pitching-DOF and yawing-DOF, with which the snakelike robot can move on rough ground and even climb up some obstacles. In this paper, the twist-related locomotion function is firstly solved, and simplified to be expressible by sine or cosine function. The 2D locomotion such as V-shape and U-shape is achieved. Also by applying it to the serpentine locomotion or other types of locomotion, the snake-like robot can complete composite locomotion that combines the serpentine locomotion or others with twist-related locomotion. Then we extend the twist-related locomotion to 3D space. Finally, the experimental results are presented to validate all above analyses.
Twist and its effect on ACL graft forces.
Arnold, M.P.; Blankevoort, L.; Ham, A. ten; Verdonschot, N.J.J.; Kampen, A. van
2004-01-01
Graft tension is a controversial topic in anterior cruciate ligament (ACL) surgery. Evidence suggests a narrow range of graft tensions, which allow the graft to remodel to a stable and mature neoligament. In previous cadaver experiments, we showed that twisting the graft could modulate the graft for
Higher-Twist Dynamics in Large Transverse Momentum Hadron Production
Energy Technology Data Exchange (ETDEWEB)
Arleo, Francois; /Annecy, LAPTH; Brodsky, Stanley J.; /SLAC; Hwang, Dae Sung; /Sejong U.; Sickles, Anne M.; /Brookhaven
2009-12-17
A scaling law analysis of the world data on inclusive large-p{sub {perpendicular}} hadron production in hadronic collisions is carried out. A significant deviation from leading-twist perturbative QCD predictions at next-to-leading order is reported. The observed discrepancy is largest at high values of x{sub {perpendicular}} = 2p{sub {perpendicular}}/{radical}s. In contrast, the production of prompt photons and jets exhibits the scaling behavior which is close to the conformal limit, in agreement with the leading-twist expectation. These results bring evidence for a non-negligible contribution of higher-twist processes in large-p{sub {perpendicular}} hadron production in hadronic collisions, where the hadron is produced directly in the hard subprocess rather than by gluon or quark jet fragmentation. Predictions for scaling exponents at RHIC and LHC are given, and it is suggested to trigger the isolated large-p{sub {perpendicular}} hadron production to enhance higher-twist processes.
Twisted Conformal Algebra and Quantum Statistics of Harmonic Oscillators
Directory of Open Access Journals (Sweden)
J. Naji
2014-01-01
Full Text Available We consider noncommutative two-dimensional quantum harmonic oscillators and extend them to the case of twisted algebra. We obtained modified raising and lowering operators. Also we study statistical mechanics and thermodynamics and calculated partition function which yields the free energy of the system.
Determinant of twisted chiral Dirac Operator on the Lattice
Fosco, C. D.; Randjbar-Daemi, S.
1995-01-01
Using the overlap formulation, we calculate the fermionic determinant on the lattice for chiral fermions with twisted boundary conditions in two dimensions. When the lattice spacing tends to zero we recover the results of the usual string-theory continuum calculations.
Twisted accretion discs. Pt. 3. Application to Epsilon Aurigae
Energy Technology Data Exchange (ETDEWEB)
Kumar, S.
1987-04-15
Twisting and alignment in a steady-state circumbinary accretion disc is studied. It is then used to account for observed features in the scenario of Epsilon Aurigae as a triple. The alignment depends on viscosity in the disc, but it is always substantial and leads to a tilted slab-like profile when viewed edge-on.
Design studies for twist-coupled wind turbine blades.
Energy Technology Data Exchange (ETDEWEB)
Valencia, Ulyses (Wichita State University, Wichita, KS); Locke, James (Wichita State University, Wichita, KS)
2004-06-01
This study presents results obtained for four hybrid designs of the Northern Power Systems (NPS) 9.2-meter prototype version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with {+-}45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with and without twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Linear and nonlinear buckling loads were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads to the e-glass baseline.
Real bundle gerbes, orientifolds and twisted KR-homology
Hekmati, Pedram; Szabo, Richard J; Vozzo, Raymond F
2016-01-01
We introduce a notion of Real bundle gerbes on manifolds equipped with an involution. We elucidate their relation to Jandl gerbes and prove that they are classified by their Real Dixmier-Douady class in Grothendieck's equivariant sheaf cohomology. We show that the Grothendieck group of Real bundle gerbe modules is isomorphic to twisted KR-theory for a torsion Real Dixmier-Douady class. Building on the Baum-Douglas model for K-homology and the orientifold construction in string theory, we introduce geometric cycles for twisted KR-homology groups using Real bundle gerbe modules. We prove that this defines a real-oriented generalised homology theory dual to twisted KR-theory for Real closed manifolds, and more generally for Real finite CW-complexes, for any Real Dixmier-Douady class. This is achieved by defining an explicit natural transformation to analytic twisted KR-homology and proving that it is an isomorphism. Our constructions give a new framework for the classification of orientifolds in string theory, p...
Twist and its effect on ACL graft forces
Arnold, MP; Blankevoort, L; ten Ham, A; Verdonschot, N; van Kampen, A
2004-01-01
Graft tension is a controversial topic in anterior cruciate ligament (ACL) surgery. Evidence suggests a narrow range of graft tensions, which allow the graft to remodel to a stable and mature neoligament. In previous cadaver experiments, we showed that twisting the graft could modulate the graft for
Nucleon Structure in Lattice QCD using twisted mass fermions
Alexandrou, C; Korzec, T; Carbonell, J; Harraud, P A; Papinutto, M; Guichon, P; Jansen, K
2010-01-01
We present results on the nucleon form factors and moments of generalized parton distributions obtained within the twisted mass formulation of lattice QCD. We include a discussion of lattice artifacts by examining results at different volumes and lattice spacings. We compare our results with those obtained using different discretization schemes and to experiment.
Nucleon form factors with dynamical twisted mass fermions
Alexandrou, C; Brinet, M; Carbonell, J; Drach, V; Harraud, P A; Korzec, T; Koutsou, G
2008-01-01
The electromagnetic and axial form factors of the nucleon are evaluated in twisted mass QCD with two degenerate flavors of light, dynamical quarks. The axial charge g_A, magnetic moment and the Dirac and Pauli radii are determined for pion masses in the range 300 MeV to 500 MeV.
Static-light meson masses from twisted mass lattice QCD
Jansen, K; Shindler, A; Wagner, M
2008-01-01
We compute the static-light meson spectrum using two-flavor Wilson twisted mass lattice QCD. We have considered five different values for the light quark mass corresponding to 300 MeV < m_PS < 600 MeV. We have extrapolated our results, to make predictions regarding the spectrum of B and B_s mesons.
Photoelectric effect for twist-deformed space-time
Daszkiewicz, Marcin
2016-01-01
In this article, we investigate the impact of twisted space-time on the photoelectric effect, i.e., we derive the $\\theta$-deformed threshold frequency. In such a way we indicate that the space-time noncommutativity strongly enhances the photoelectric process.
Modulated liquid-crystal phases induced by polarity: Twist-bend, splay-bend, and blue phases
Selinger, Jonathan; Shamid, Shaikh; Allender, David
2014-03-01
Nematic liquid crystals exhibit flexoelectric couplings between polar order and gradients in the director field. When the couplings become strong enough, the uniform nematic phase can become unstable to the formation of a modulated polar phase. The question is then: What is the structure of the modulated polar phase? Classic work by Meyer and further studies by Dozov predicted two possible structures, known as twist-bend and splay-bend. One of these predictions, the twist-bend phase, has recently been identified in experiments on bent-core liquid crystals. Here, we investigate modulated polar phases through a combination of Landau theory and lattice simulations. We find a range of possibilities, including the twist-bend and splay-bend phases as well as polar blue phases, with 2D or 3D modulations of the director field and the polar order. We compare these polar blue phases with chiral blue phases, and discuss opportunities for observing them experimentally. Supported by NSF DMR-1106014.
Small x behavior of parton distributions. A study of higher twist effects
Illarionov, A Yu; Parente, G; Illarionov, Alexei Yu.; Kotikov, Anatoly V.; Parente, Gonzalo
2004-01-01
Higher twist corrections to the structure function F_2 at small x are studied for the case of a flat initial condition for the twist-two QCD evolution in the next-to-leading order approximation. We present an analytical parameterization of the contributions from the twist-two and higher twist operators of the Wilson operator product expansion. Higher twist terms are evaluated using two different approaches, one motivated by BFKL and the other motivated by the renormalon formalism. The results of the latter approach are in very good agreement with deep inelastic scattering data from HERA.
Automatic O(a) improvement for twisted mass QCD in the presence of spontaneous symmetry breaking
Aoki, Sinya; Bär, Oliver
2006-08-01
In this paper we present a proof for automatic O(a) improvement in twisted mass lattice QCD at maximal twist, which uses only the symmetries of the leading part in the Symanzik effective action. In the process of the proof we clarify that the twist angle is dynamically determined by vacuum expectation values in the Symanzik theory. For maximal twist according to this definition, we show that scaling violations of all quantities which have nonzero values in the continuum limit are even in a. In addition, using Wilson chiral perturbation theory, we investigate this definition for maximal twist and compare it to other definitions which were already employed in actual simulations.
Influence of twisting and bending on the Jc and n-value of multifilamentary MgB2 strands
Yang, Y.; Li, G.; Susner, M.; Sumption, M. D.; Rindfleisch, M.; Tomsic, M.; Collings, E. W.
2015-12-01
The influences of strand twisting and bending (applied at room temperature) on the critical current densities, Jc, and n-values of MgB2 multifilamentary strands were evaluated at 4.2 K as function of applied field strength, B. Three types of MgB2 strand were evaluated: (i) advanced internal magnesium infiltration (AIMI)-processed strands with 18 filaments (AIMI-18), (ii) powder-in-tube (PIT) strands processed using a continuous tube forming and filling (CTFF) technique with 36 filaments (PIT-36) and (iii) CTFF processed PIT strands with 54 filaments (PIT-54). Transport measurements of Jc(B) and n-value at 4.2 K in fields of up to 10 T were made on: (i) PIT-54 after it was twisted (at room temperature) to twist pitch values, Lp, of 10-100 mm. Transport measurements of Jc(B) and n-value were performed at 4.2 K; (ii) PIT-36 and AIMI-18 after applying bending strains up to 0.6% at room temperature. PIT-54 twisted to pitches of 100 mm down to 10 mm exhibited no degradation in Jc(B) and only small changes in n-value. Both the Jc(B) and n-value of PIT-36 were seen to be tolerant to bending strain of up to 0.4%. On the other hand, AIMI-18 showed ±10% changes in Jc(B) and significant scatter in n-value over the bending strain range of 0-0.6%.
Nightingale, R. W.; Ma, G.; Ji, E.
2009-12-01
In our previous studies of rotating sunspots about their umbral centers over the past decade, we have been measuring the rotation at the photosphere of the cross sections of large, twisted magnetic flux tubes passing through from below. Many such rotating sunspots have been found and reported in the literature and at earlier meetings [e.g., Brown et al., Sol. Phys. 216, 79, 2003; Yan et al., ApJ 682, L65, 2008; Nightingale et al., Fall AGU Mtg. 2007]. Here we are attempting to measure the rotation of 1 million degree K EUV loops seen in TRACE 171A images emerging from what may be a large 6000 deg K magnetic flux tube (invisible at EUV), which may be the extension of the associated rotating sunspot up in the corona, for active region 9114 on August 8 - 10, 2000. These nonpotential EUV loops appear to be attached at their other end to nonrotating opposite polarity magnetic flux regions and also appear to be flipping around like a twisted jump rope that is attached to a wall at one end. In movies of these twisted coronal loop fans the rotation appears obvious, but is difficult to measure, because of the constant motion and change of intensity of the fans, which tend to obscure each other and the apparent tube center. We will show movies over the 3 days of the twisted loop fans, and details and first results of our measurements, which appear to be similar to those previously found for the associated rotating sunspot down at the photosphere. We will discuss how the twisted magnetic flux tube energizes the corona, carrying energy up from beneath the photosphere. This work was supported by NASA under the TRACE contract NAS5-38099.
Turbulent ${\\alpha}$-effect in twisted magnetic flux tubes dynamos in Riemannian space
de Andrade, Garcia
2007-01-01
Analytical solution of first order torsion ${\\alpha}$-effect in twisted magnetic flux tubes representing a flux tube dynamo in Riemannian space is presented. Toroidal and poloidal component of the magnetic field decays as $r^{-1}$, while grow exponentially in time. The rate of speed of the helical dynamo depends upon the value of Frenet curvature of the tube. The $\\alpha$ factor possesses a fundamental contribution from constant torsion tube approximation. It is also assumed that the curvature of the magnetic axis of the tube is constant. Though ${\\alpha}$-effect dynamo equations are rather more complex in Riemann flux tube coordinates, a simple solution assuming force-free magnetic fields is shown to be possible. Dynamo solutions are possible if the dynamo action is able to change the signs of torsion and curvature of the dynamo flux tube simultaneously.
Colloidal membranes of hard rods: unified theory of free edge structure and twist walls.
Kaplan, C Nadir; Meyer, Robert B
2014-07-14
Monodisperse suspensions of rod like chiral fd viruses are condensed into a rod-length thick colloidal monolayers of aligned rods by depletion forces. Twist deformations of the molecules are expelled to the monolayer edge as in a chiral smectic A liquid crystal, and a cholesteric band forms at the edge. Coalescence of two such isolated membranes results in a twist wall sandwiched between two regions of aligned rods, dubbed π-walls. By modeling the membrane as a binary fluid of coexisting cholesteric and chiral smectic A liquid-crystalline regions, we develop a unified theory of the π-walls and the monolayer edge. The mean-field analysis of our model yields the molecular tilt profiles, the local thickness change, and the crossover from smectic to cholesteric behavior at the monolayer edge and across the π-wall. Furthermore, we calculate the line tension associated with the formation of these interfaces. Our model offers insights regarding the stability and the detailed structure of the π-wall and the monolayer edge.
Supersymmetric partition functions and the three-dimensional A-twist arXiv
Closset, Cyril; Willett, Brian
We study three-dimensional $\\mathcal{N}=2$ supersymmetric gauge theories on $\\mathcal{M}_{g,p}$, an oriented circle bundle of degree $p$ over a closed Riemann surface, $\\Sigma_g$. We compute the $\\mathcal{M}_{g,p}$ supersymmetric partition function and correlation functions of supersymmetric loop operators. This uncovers interesting relations between observables on manifolds of different topologies. In particular, the familiar supersymmetric partition function on the round $S^3$ can be understood as the expectation value of a so-called "fibering operator" on $S^2 \\times S^1$ with a topological twist. More generally, we show that the 3d $\\mathcal{N}=2$ supersymmetric partition functions (and supersymmetric Wilson loop correlation functions) on $\\mathcal{M}_{g,p}$ are fully determined by the two-dimensional A-twisted topological field theory obtained by compactifying the 3d theory on a circle. We give two complementary derivations of the result. We also discuss applications to F-maximization and to three-dimens...
(3+1)D Anomalous Twisted Gauge Theories with Global Symmetry
Ye, Peng
2016-01-01
In (3+1)D twisted gauge theories, global symmetry may be imposed on topological currents $\\star\\frac{1}{2\\pi}db^I$ in a hydrodynamical way ($I=1,2,\\cdots$, $\\{b^I\\}$ is a set of Kalb-Ramond gauge fields). This methodology has been applied before in the Chern-Simons theory of fractional quantum Hall liquids. We find that, in some twisted gauge theories (with discrete Abelian gauge group $G_g$), implementing a global symmetry (denoted by $G_s$) is always inconsistent. There are two consequences. First, the symmetry-enriched topological order (SET) of the ground state is anomalous, which cannot exist in (3+1)D system alone. It can exist as a boundary of 4+1D topological phases. Second, if $G_s$ is fully gauged, the resulting new gauge theory has gauge anomaly. A (4+1)D topological phase is required to cancel this anomaly. We elaborate this phenomenon via a concrete example.
Stretch-Twist-Fold and slow filamentary dynamos in liquid sodium Madison Dynamo Experiments
de Andrade, Garcia
2009-01-01
Recently Ricca and Maggione [MHD (2008)] have presented a very simple and interesting model of stretch-twist-fold dynamo in diffusive media based on numerical simulations of Riemannian flux tubes. In this paper we present a yet simpler way of analytically obtaining fast and slow dynamo, generated by by the curvature energy of magnetic filaments in diffusive media. geometrical model for the galactic or accretion disk dynamo in shear flows is presented. In the fast dynamo case it is shown that the absence of stretching leads to the absence of fast dynamos and when torsion of filaments vanishes the dynamo action cannot be support as well. This is the Cowling-Zeldovich theorem for planar flows. Isotropy of the magnetic fields hypothesis is used to compute the fast nature of dynamo. A similar result using non-holonomic Frenet frame has been recently obtained for filamentary dynamos [Garcia de Andrade, AN (2008)]. The stretch-twist-fold (STF) filamented models discussed here may serve to formulate future experiment...
Singular dimensions of the N=2 superconformal algebras; 2, the twisted N=2 algebra
Dörrzapf, M; Doerrzapf, Matthias; Gato-Rivera, Beatriz
1999-01-01
We introduce a suitable adapted ordering for the twisted N=2 superconformal algebra (i.e. with mixed boundary conditions for the fermionic fields). We show that the ordering kernels for complete Verma modules have two elements and the ordering kernels for G-closed Verma modules just one. Therefore, spaces of singular vectors may be two-dimensional for complete Verma modules whilst for G-closed Verma modules they can only be one-dimensional. We give all singular vectors for the levels 1/2, 1, and 3/2 for both complete Verma modules and G-closed Verma modules. We also give explicit examples of degenerate cases with two-dimensional singular vector spaces in complete Verma modules. General expressions are conjectured for the relevant terms of all (primitive) singular vectors, i.e. for the coefficients with respect to the ordering kernel. These expressions allow to identify all degenerate cases as well as all G-closed singular vectors. They also lead to the discovery of subsingular vectors for the twisted N=2 supe...
Pseudo-scalar meson form factors with maximally twisted Wilson fermions at Nf = 2
Simula, S
2007-01-01
We present preliminary results for various electroweak form factors of pseudo-scalar mesons using the tree-level improved Symanzik gauge action and the maximally twisted mass fermionic action with Nf = 2 dynamical flavors. Our results, obtained for both light and heavy quark masses at a single lattice spacing (a ~ 0.09 fm) and at a single lattice volume (V * T = 24**3 * 48), exhibit a quite remarkable statistical precision thanks to the use of all-to-all quark propagators computed with a stochastic method. Moreover very low values of the four-momentum transfer are achieved by making use of twisted boundary conditions on the valence quark fields. The mass dependence of the pion charge radius is analyzed using Chiral Perturbation Theory, obtaining clear evidence of relevant two-loop contributions. The universal Isgur-Wise function is computed from heavy-to-heavy electromagnetic transitions and its slope in the case of $u(d)$ spectator quarks is found to be rho(IW)**2 = 0.77 +/- 0.28, where the error is statisti...
The Flow and Heat and Mass Transfer on a Twisted and Fluted Tube
Conlisk, A. T.; Mei, Ning
1999-11-01
Absorption heat pumps often employ falling liquid films to transfer heat and mass both to and from the liquid. Generally, smooth vertical tubes are not efficient enough to provide the required amount of heat and mass transfer and more complex tube geometries must be used. In this paper we extend the work of Conlisk (AIChE Journal, Vol. 40, no. 5, 1994) for a vertical fluted tube to the case of a vertically twisted tube in which the flow channels are inclined at a fixed angle to the gravity vector. We consider single-component condensation and evaporation as well as binary absorption and desorption of a LiBr-water mixture. In certain parameter regimes, the equations governing the flow field and the heat and mass transfer may be solved in closed form. The film profile is shown to driven by surface tension which drives fluid into the grooves, thus thinning the film on the crests of the flutes. Results for the twisted tube are compared with the vertically fluted tube and with the smooth tube in terms of heat and mass transfer rates.
Nair, Anitha S.; Sudeep Kumar, V. P.; Joe, Hubert
2014-09-01
Twist sensitivity of cladding-mode resonances in a mechanically induced long-period fiber grating formed over a single-mode fiber is experimentally demonstrated and theoretically analyzed. Of the two usual cladding-mode resonances corresponding to LP11 and LP12, higher-order mode LP12 is more sensitive to twist in comparison with the lower-order mode LP11. The extent of down-shifting of resonant wavelengths depends on twist-induced circular birefringence and the modal field distribution of the cladding-modes inside the fiber. When the fiber is severely twisted to 3.5 rad/cm, a shift sensitivity is observed of 1 nm/(rad/cm) for the LP11 mode and 4.23 nm/(rad/cm) for the LP12 mode. The fiber breaks when the twist rate exceeds 3.5 rad/cm. In comparison with LP12, the LP11 resonance is almost independent of the axial strain variation with an ultra-low sensitivity of 0.18 pm/με, and it is also almost insensitive to the temperature variation with a coefficient of 35 pm/°C. Forming the LP11 resonance far away from its cut-off wavelength, a widely tunable band-pass filter is also demonstrated with a very high twist sensitivity of 8.75 nm/(rad/cm) and negligible cross-sensitivity to strain and temperature. The experimental and theoretical results are very useful in selecting sensitive and stable cladding-mode resonances in the design of new mechanically induced long-period fiber gratings based torsion sensors and tunable band-pass filters.
Deformations of Fell bundles and twisted graph algebras
Raeburn, Iain
2016-11-01
We consider Fell bundles over discrete groups, and the C*-algebra which is universal for representations of the bundle. We define deformations of Fell bundles, which are new Fell bundles with the same underlying Banach bundle but with the multiplication deformed by a two-cocycle on the group. Every graph algebra can be viewed as the C*-algebra of a Fell bundle, and there are are many cocycles of interest with which to deform them. We thus obtain many of the twisted graph algebras of Kumjian, Pask and Sims. We demonstate the utility of our approach to these twisted graph algebras by proving that the deformations associated to different cocycles can be assembled as the fibres of a C*-bundle.
Progress in the Determination of Polarized PDFs and Higher Twist
Leader, Elliot; Stamenov, Dimiter B
2007-01-01
The impact of the recent very precise CLAS and COMPASS g1/F1 data on polarized parton densities and higher twist effects is discussed. It is demonstrated that the low Q^2 CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function g1, while the large Q^2 COMPASS data influence mainly the strange quark and gluon polarizations. It is also shown that the uncertainties in the determination of the polarized parton densities are significantly reduced. We find also that the present inclusive DIS data cannot rule out a negative polarized and changing in sign gluon densities. The present status of the proton spin sum rule is discussed.
Twisted inhomogeneous Diophantine approximation and badly approximable sets
Harrap, Stephen
2010-01-01
For any real pair i, j geq 0 with i+j=1 let Bad(i, j) denote the set of (i, j)-badly approximable pairs. That is, Bad(i, j) consists of irrational vectors x:=(x_1, x_2) in R^2 for which there exists a positive constant c(x) such that max {||qx_1||^(-i), ||qx_2||^(-j)} > c(x)/q for all q in N. Building on a result of Kurzweil, a new characterization of the set Bad(i, j) in terms of `well-approximable' vectors in the area of `twisted' inhomogeneous Diophantine approximation is established. In addition, it is shown that Bad^x(i, j), the `twisted' inhomogeneous analogue of Bad(i, j), has full Hausdorff dimension 2 when x is chosen from the set Bad(i, j).
Higher twist effects in DIS: an outline of diquark contributions
Energy Technology Data Exchange (ETDEWEB)
Anselmino, M. [Turin Univ. (Italy). Dipt. di Fisica Teorica]|[Istituto Nazionale di Fisica Nucleare, Turin (Italy); Caruso, F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Universidade do Estado, Rio de Janeiro, RJ (Brazil). Inst. de Fisica
1996-12-01
A quark-diquark picture of the nucleon, previously introduced in the description of a several exclusive and inclusive processes at intermediate Q{sup 2} values, is found to accurately model the higher-twist data on the unpolarized proton structure function F{sub 2}{sup p}(x,Q{sup 2}). The main results of the model are summarized. The emerging set of parameters is consistent with the diquark properties suggested by other experimental and theoretical analyses. Higher-twist corrections to the Bjorken and Gottfried sum rule are also estimated in the framework of the same quark-diquark model. The resulting corrections to both sum rules turn out to be negligible. (author). 23 refs.; Contribution to the Diquark III Conference, Torino, Italy.
Twisted optical metamaterials for planarized ultrathin broadband circular polarizers.
Zhao, Y; Belkin, M A; Alù, A
2012-05-29
Optical metamaterials are usually based on planarized, complex-shaped, resonant nano-inclusions. Three-dimensional geometries may provide a wider set of functionalities, including broadband chirality to manipulate circular polarization at the nanoscale, but their fabrication becomes challenging as their dimensions get smaller. Here we introduce a new paradigm for the realization of optical metamaterials, showing that three-dimensional effects may be obtained without complicated inclusions, but instead by tailoring the relative orientation within the lattice. We apply this concept to realize planarized, broadband bianisotropic metamaterials as stacked nanorod arrays with a tailored rotational twist. Because of the coupling among closely spaced twisted plasmonic metasurfaces, metamaterials realized with conventional lithography may effectively operate as three-dimensional helical structures with broadband bianisotropic optical response. The proposed concept is also shown to relax alignment requirements common in three-dimensional metamaterial designs. The realized sample constitutes an ultrathin, broadband circular polarizer that may be directly integrated within nanophotonic systems.
Twist-three at five loops, Bethe Ansatz and wrapping
Beccaria, M; Lukowski, T; Zieme, S
2009-01-01
We present a formula for the five-loop anomalous dimension of N=4 SYM twist-three operators in the sl(2) sector. We obtain its asymptotic part from the Bethe Ansatz and finite volume corrections from the generalized Luescher formalism, considering scattering processes of spin chain magnons with virtual particles that travel along the cylinder. The complete result respects the expected large spin scaling properties and passes non-trivial tests including reciprocity constraints. We analyze the pole structure and find agreement with a conjectured resummation formula. In analogy with the twist-two anomalous dimension at four-loops, wrapping effects are of order log^2 M/M^2 for large values of the spin.
A twisted generalization of Lie-Yamaguti algebras
Gaparayi, Donatien
2010-01-01
A twisted generalization of Lie-Yamaguti algebras, called Hom-Lie-Yamaguti algebras, is defined. Hom-Lie-Yamaguti algebras generalize Hom-Lie triple systems (and susequently ternary Hom-Nambu algebras) and Hom-Lie algebras in the same way as Lie-Yamaguti algebras generalize Lie triple systems and Lie algebras. It is shown that the category of Hom-Lie-Yamaguti algebras is closed under twisting by self-morphisms. Constructions of Hom-Lie-Yamaguti algebras from classical Lie-Yamaguti algebras and Malcev algebras are given. It is observed that, when the ternary operation of a Hom-Lie-Yamaguti algebra expresses through its binary one in a specific way, then such a Hom-Lie-Yamaguti algebra is a Hom-Malcev algebra.
Small gaps between zeros of twisted L-functions
Conrey, J B; Soundararajan, K
2012-01-01
We use the asymptotic large sieve, developed by the authors, to prove that if the Generalized Riemann Hypothesis is true, then there exist many Dirichlet L-functions that have a pair of consecutive zeros closer together than 0.37 times their average spacing. More generally, we investigate zero spacings within the family of twists by Dirichlet characters of a fixed L-function and give precise bounds for small gaps which depend only on the degree of the L-function.
Photoswitching of helical twisting power by chiral photochromic diarylethene dopants
Yamaguchi, Tadatsugu; Irie, Masahiro
2002-12-01
Two kinds of chiral diarylethene derivatives were synthesized and used as dopants for photoresponsive liquid crystals. Both derivatives underwent thermally irreversible and fatigue resistant photochromic reactions and exhibited reversible circular diochroism (CD) spectral changes. Large photostimulated pitch chances of chiral nematic K-15 liquid crystals were observed by the addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.
Twisted Hamiltonian Lie Algebras and Their Multiplicity-Free Representations
Institute of Scientific and Technical Information of China (English)
Ling CHEN
2011-01-01
We construct a class of new Lie algebras by generalizing the one-variable Lie algebras generated by the quadratic conformal algebras (or corresponding Hamiltonian operators) associated with Poisson algebras and a quasi-derivation found by Xu. These algebras can be viewed as certain twists of Xu's generalized Hamiltonian Lie algebras. The simplicity of these algebras is completely determined. Moreover, we construct a family of multiplicity-free representations of these Lie algebras and prove their irreducibility.
Spin Squeezing of One-Axis Twisting Model
Li, Song-Song
2017-09-01
We investigate spin squeezing of the one-axis twisting model. By using short-time approximation solutions of the angular momentum operators, we analytically and numerically calculate the spin squeezing parameter. It is shown that smaller linear interaction can produce a stronger spin squeezing and maintain a longer time interval. It is also shown that the stronger spin squeezing can be achieved by increasing the number of particles.
Leading Twist Parton Distribution Amplitudes in Heavy Vector Mesons
Directory of Open Access Journals (Sweden)
Gao Fei
2016-01-01
Full Text Available We employed QCD’s Dyson-Schwinger equations (DSEs for heavy quarks and obtained the leading twist parton distribution amplitudes (PDAs in heavy vector mesons J/Ψ and ϒ. We found that all of the amplitudes are narrower than the asymptotic form, while they deviate from δ function. This indicates that the interaction between the two continent quarks are still important in the mesons consisted of charm and bottom quarks.
Mass of nonrelativistic meson from leading twist distribution amplitudes
Energy Technology Data Exchange (ETDEWEB)
Braguta, V. V., E-mail: braguta@mail.ru [Institute for High Energy Physics (Russian Federation)
2011-01-15
In this paper distribution amplitudes of pseudoscalar and vector nonrelativistic mesons are considered. Using equations of motion for the distribution amplitudes, relations are derived which allow one to calculate the masses of nonrelativistic pseudoscalar and vector meson if the leading twist distribution amplitudes are known. These relations can be also rewritten as relations between the masses of nonrelativistic mesons and infinite series of QCD operators, what can be considered as an exact version of Gremm-Kapustin relation in NRQCD.
The XXZ model with anti-periodic twisted boundary conditions
Niekamp, Sönke; Frahm, Holger
2009-01-01
We derive functional equations for the eigenvalues of the XXZ model subject to anti-diagonal twisted boundary conditions by means of fusion of transfer matrices and by Sklyanin's method of separation of variables. Our findings coincide with those obtained using Baxter's method and are compared to the recent solution of Galleas. As an application we study the finite size scaling of the ground state energy of the model in the critical regime.
The XXZ model with anti-periodic twisted boundary conditions
Energy Technology Data Exchange (ETDEWEB)
Niekamp, Soenke; Wirth, Tobias; Frahm, Holger [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, 30167 Hannover (Germany)
2009-05-15
We derive functional equations for the eigenvalues of the XXZ model subject to anti-diagonal twisted boundary conditions by means of fusion of transfer matrices and by Sklyanin's method of separation of variables. Our findings coincide with those obtained using Baxter's method and are compared to the recent solution of Galleas. As an application we study the finite size scaling of the ground-state energy of the model in the critical regime.
The Importance of Higher Twist Corrections in Polarized DIS
Leader, Elliot; Stamenov, D B
2003-01-01
The higher twist corrections $h^N(x)/Q^2$ to the spin dependent proton and neutron $g_1$ structure functions are extracted from the world data on $g_1(x,Q^2)$ in a model independent way and found to be non-negligible. Their role in determining the polarized parton densities in the nucleon is discussed. It is also considered how the results are influenced by the recent JLab and HERMES/d inclusive DIS data.
Some new quasi-twisted ternary linear codes
Directory of Open Access Journals (Sweden)
Rumen Daskalov
2015-09-01
Full Text Available Let [n, k, d]_q code be a linear code of length n, dimension k and minimum Hamming distance d over GF(q. One of the basic and most important problems in coding theory is to construct codes with best possible minimum distances. In this paper seven quasi-twisted ternary linear codes are constructed. These codes are new and improve the best known lower bounds on the minimum distance in [6].
Neutral mesons and disconnected diagrams in Twisted Mass QCD
Michael, C
2007-01-01
We evaluate properties of neutral mesons in Nf=2 dynamical simulations of TMQCD at maximal twist. The pion is explored - establishing the size of the isospin splitting (an order a^2 effect). We investigate the eta' (the Nf=2 flavour singlet pseudoscalar meson) and neutral rho and scalar mesons. We show that disconnected diagrams can be evaluated very efficiently in TMQCD using variance reduction methods.