Showing papers on "Symmetry (physics) published in 2008"
TL;DR: In this paper, the nonrelativistic conformal group (the Schroedinger group) is realized holographically as the symmetry of a spacetime, and a toy model in which this geometry is a solution to field equations is presented.
Abstract: We discuss a realization of the nonrelativistic conformal group (the Schroedinger group) as the symmetry of a spacetime. We write down a toy model in which this geometry is a solution to field equations. We discuss various issues related to nonrelativistic holography. In particular, we argue that free fermions and fermions at unitarity correspond to the same bulk theory with different choices for the near-boundary asymptotics corresponding to the source and the expectation value of one operator. We describe an extended version of nonrelativistic general coordinate invariance which is realized holographically.
1,154 citations
TL;DR: In this paper, the S-matrix for the su(2|3) dynamic spin chain and for planar N = 4 super Yang-Mills was derived and investigated.
Abstract: We derive and investigate the S-matrix for the su(2|3) dynamic spin chain and for planar N = 4 super Yang–Mills. Due to the large amount of residual symmetry in the excitation picture, the S-matrix turns out to be fully constrained up to an overall phase. We carry on by diagonalizing it and obtain Bethe equations for periodic states. This proves an earlier proposal for the asymptotic Bethe equations for the su(2|3) dynamic spin chain and for N = 4 SYM.
857 citations
TL;DR: It is shown that with an appropriate periodic potential of triangular symmetry, there exists an energy window over which the only available states are these quasiparticles, thus providing a good system to probe experimentally the new massless Dirac fermions.
Abstract: We show that new massless Dirac fermions are generated when a slowly varying periodic potential is applied to graphene. These quasiparticles, generated near the supercell Brillouin zone boundaries with anisotropic group velocity, are different from the original massless Dirac fermions. The quasiparticle wave vector (measured from the new Dirac point), the generalized pseudospin vector, and the group velocity are not collinear. We further show that with an appropriate periodic potential of triangular symmetry, there exists an energy window over which the only available states are these quasiparticles, thus providing a good system to probe experimentally the new massless Dirac fermions. The required parameters of external potentials are within the realm of laboratory conditions.
364 citations
TL;DR: In this article, a tree level superstring theory on certain supersymmetric backgrounds admits a symmetry which we call ''fermionic T-duality'' which is a non-local redefinition of the fermionic worldsheet fields similar to the redefinition we perform on bosonic variables when we do an ordinary Tduality.
Abstract: We show that tree level superstring theories on certain supersymmetric backgrounds admit a symmetry which we call ``fermionic T-duality''. This is a non-local redefinition of the fermionic worldsheet fields similar to the redefinition we perform on bosonic variables when we do an ordinary T-duality. This duality maps a supersymmetric background to another supersymmetric background with different RR fields and a different dilaton. We show that a certain combination of bosonic and fermionic T-dualities maps the full superstring theory on AdS5 × S5 back to itself in such a way that gluon scattering amplitudes in the original theory map to something very close to Wilson loops in the dual theory. This duality maps the ``dual superconformal symmetry'' of the original theory to the ordinary superconformal symmetry of the dual model. This explains the dual superconformal invariance of planar scattering amplitudes of N = 4 super Yang Mills and also sheds some light on the connection between amplitudes and Wilson loops. In the appendix, we propose a simple prescription for open superstring MHV tree amplitudes in a flat background.
273 citations
TL;DR: The results showed that, when using the symmetry index, the interpretation of asymmetry can be highly affected by the choice of reference value, and that the symmetry angle does not require a reference value and is not prone to the same limitations.
246 citations
TL;DR: It is shown that the only finite group capable of yielding the tribimaximal mixing for all Yukawa couplings is S4, or any group containing it, and that the best way to determine horizontal symmetry is from neutrino mixing.
Abstract: We argue that the best way to determine horizontal symmetry is from neutrino mixing and proceed to show that the only finite group capable of yielding the tribimaximal mixing for all Yukawa couplings is S{sub 4}, or any group containing it. The method used is largely group theoretical, but it can be implemented by dynamical schemes in which the Higgs expectation values introduced to break S{sub 4} spontaneously are uniquely determined up to an unknown scale for each.
228 citations
TL;DR: In this article, a stabilized method based on the difference between a consistent and an under-integrated mass matrix of the pressure for the Stokes equations approximated by the lowest equal-order finite element pairs was proposed.
197 citations
TL;DR: In this article, it was shown that two stationary, asymptotically flat vacuum black holes in 5 dimensions with two commuting axial symmetries are identical if and only if their masses, angular momenta, and their "interval structures" coincide.
Abstract: We show that two stationary, asymptotically flat vacuum black holes in 5 dimensions with two commuting axial symmetries are identical if and only if their masses, angular momenta, and their “interval structures” coincide. We also show that the horizon must be topologically either a 3-sphere, a ring, or a Lens-space. Our argument is a generalization of constructions of Morisawa and Ida (based in turn on key work of Maison) who considered the spherical case, combined with basic arguments concerning the nature of the factor manifold of symmetry orbits.
195 citations
TL;DR: In this article, a general approach for finding exact cosmological solutions in f(R) gravity is discussed, where instead of taking into account phenomenological models, the authors assume, as a physical criterion, the existence of Noether symmetries in the Cosmological Lagrangian, leading to the selection of viable models and allowing us to solve the equations of motion.
Abstract: A general approach for finding exact cosmological solutions in f(R) gravity is discussed. Instead of taking into account phenomenological models, we assume, as a physical criterion, the existence of Noether symmetries in the cosmological f(R) Lagrangian. As a result, the presence of such symmetries leads to the selection of viable models and allows us to solve the equations of motion. We discuss also the case in which no Noether charge is present but general criteria can be used to achieve solutions.
178 citations
TL;DR: In this paper, the authors derived the Onsager-Casimir relations in the linear transport regime and universal relations among nonlinear transport coefficients for a two-terminal noncentrosymmetric system.
Abstract: We study the full counting statistics of electron transport through multiterminal interacting quantum dots under a finite magnetic field. Microscopic reversibility leads to a symmetry of the cumulant generating function, which generalizes the fluctuation theorem in the context of the quantum transport. Using the symmetry, we derive the Onsager-Casimir relations in the linear transport regime and universal relations among nonlinear transport coefficients. One of the measurable relations is that the nonlinear conductance, the second-order coefficient with respect to the bias voltage, is connected to the third current cumulant in equilibrium, which can be a finite and uneven function of the magnetic field for two-terminal noncentrosymmetric system.
173 citations
TL;DR: In this paper, the massless Nambu-Goldstone modes of bumblebee models with spontaneous local Lorentz and diffeomorphism violation have been studied in both local and spacetime frames.
Abstract: Theories with spontaneous local Lorentz and diffeomorphism violation contain massless NambuGoldstone modes, which arise as field excitations in the minimum of the symmetry-breaking potential. If the shape of the potential also allows excitations above the minimum, then an alternative gravitational Higgs mechanism can occur in which massive modes involving the metric appear. The origin and basic properties of the massive modes are addressed in the general context involving an arbitrary tensor vacuum value. Special attention is given to the case of bumblebee models, which are gravitationally coupled vector theories with spontaneous local Lorentz and diffeomorphism violation. Mode expansions are presented in both local and spacetime frames, revealing the Nambu-Goldstone and massive modes via decomposition of the metric and bumblebee fields, and the associated symmetry properties and gauge fixing are discussed. The class of bumblebee models with kinetic terms of the Maxwell form is used as a focus for more detailed study. The nature of the associated conservation laws and the interpretation as a candidate alternative to Einstein-Maxwell theory are investigated. Explicit examples involving smooth and Lagrange-multiplier potentials are studied to illustrate features of the massive modes, including their origin, nature, dispersion laws, and effects on gravitational interactions. In the weak static limit, the massive mode and Lagrange-multiplier fields are found to modify the Newton and Coulomb potentials. The nature and implications of these modifications are examined.
TL;DR: In this paper, the authors analyzed the vacuum structure of SU(2) QCD with multiple massless adjoint representation fermions formulated on a small spatial S{sup 1}xR{sup 3}.
Abstract: We analyze the vacuum structure of SU(2) QCD with multiple massless adjoint representation fermions formulated on a small spatial S{sup 1}xR{sup 3}. The absence of thermal fluctuations, and the fact that quantum fluctuations favor the vacuum with unbroken center symmetry in a weakly coupled regime, renders the interesting dynamics of these theories analytically calculable. Confinement and the generation of the mass gap in the gluonic sector are shown analytically. In this regime, theory exhibits confinement without continuous chiral-symmetry breaking. However, a flavor singlet chiral condensate (which breaks a discrete chiral symmetry) persists at arbitrarily small S{sup 1}. Under certain reasonable assumptions, we show that the theory exhibits a zero temperature chiral phase transition in the absence of any change in spatial center symmetry realizations.
TL;DR: In this article, the authors consider the generic problem of wake instabilities past fixed axisymmetric bodies, and focus on the extreme cases of a sphere and a flat disk.
Abstract: We consider the generic problem of wake instabilities past fixed axisymmetric bodies, and focus on the extreme cases of a sphere and a flat disk. Numerical results reveal that the wakes of these two bodies evolve differently as the Reynolds number is increased. Especially, two new vortex shedding modes are identified behind a disk. To interpret these results, we introduce a model based on the theory of mode interactions in presence of O(2) symmetry. This model, which was initially developed for the Taylor-Couette system, allows us to explain the structural differences observed in the evolution of the two types of wakes and to accurately predict the evolution of the lift force.
TL;DR: In this article, the equivalence principle is used to explain the non-relativistic conformal "Schroedinger" symmetry of some gravity backgrounds proposed recently in the AdS/CFT context.
Abstract: The non-relativistic conformal "Schroedinger" symmetry of some gravity backgrounds proposed recently in the AdS/CFT context, is explained in the "Bargmann framework". The formalism incorporates the Equivalence Principle. Newton-Hooke conformal symmetries, which are analogs of those of Schroedinger in the presence of a negative cosmological constant, are discussed in a similar way. Further examples include topologically massive gravity with negative cosmological constant and the Madelung hydrodynamical description.
TL;DR: In this article, the twisted flip operator is shown to be compatible with the action of the symmetry group, which is relevant for describing particle statistics in the presence of noncommutativity.
Abstract: We consider the issue of statistics for identical particles or fields in {kappa}-deformed spaces, where the system admits a symmetry group G. We obtain the twisted flip operator compatible with the action of the symmetry group, which is relevant for describing particle statistics in the presence of the noncommutativity. It is shown that for a special class of realizations, the twisted flip operator is independent of the ordering prescription.
TL;DR: In this paper, the authors examined the three-dimensional Script N = 6 superconformal Chern-Simons theory with U(N) × U(n) gauge symmetry, which was constructed by Aharony, Bergman, Jafferis, and Maldacena (ABJM).
Abstract: We examine the three-dimensional Script N = 6 superconformal Chern-Simons theory with U(N) × U(N) gauge symmetry, which was recently constructed by Aharony, Bergman, Jafferis, and Maldacena (ABJM). Using a formulation with manifest SU(4) R-symmetry and no auxiliary fields, we verify in complete detail both the Poincare supersymmetry and the conformal supersymmetry of the action. Together, these imply the complete OSp(6|4) superconformal symmetry of the theory. The potential, which is sixth order in scalar fields, is recast as a sum of squares.
Posted Content•
TL;DR: In this paper, the formation of black holes in pure general relativity by the focusing of incoming gravitational waves was studied, where the initial data are no longer confined to a suitably small neighborhood of Minkowskian data.
Abstract: The subject of this work is the formation of black holes in pure general relativity, by the focusing of incoming gravitational waves. The theorems established in this monograph constitute the first foray into the long time dynamics of general relativity in the large, that is, when the initial data are no longer confined to a suitably small neighborhood of Minkowskian data. The theorems are general, no symmetry conditions on the initial data being imposed.
TL;DR: In this article, the authors present two ways of introducing elements with reduced symmetry, one based on Stokes problems, and the other based on the nice property of several interpolation operators, which allows to prove the convergence of the Arnold-Falk-Winther element with simple and standard arguments, without the use of the============Berstein-Gelfand Gelfand resolution.
Abstract: In continuum mechanics problems, we have to work in most cases with symmetric tensors,
symmetry expressing the conservation of angular momentum. Discretization of symmetric
tensors is however difficult and a classical solution is to employ some form of reduced symmetry.
We present two ways of introducing elements with reduced symmetry.
The first one is based on Stokes problems, and in the two-dimensional case allows to
recover practically all interesting elements on the market. This however is
(definitely) not true in three dimensions. On the other hand the second approach (based on a very
nice property of several interpolation operators) works for three-dimensional problems as well,
and allows, in particular, to prove the convergence of the
Arnold-Falk-Winther element with simple and standard arguments, without the use of the
Berstein-Gelfand-Gelfand resolution.
TL;DR: For any variational symmetry of the problem of the calculus of variations on time scales, there exists a conserved quantity along the respective Euler-Lagrange extremals as discussed by the authors.
TL;DR: In this paper, the authors consider the metastable N = 1 QCD model of Intriligator, Seiberg and Shih (ISS), deformed by adding a baryon term to the superpotential.
TL;DR: In this article, the authors examined the three-dimensional N = 6 superconformal Chern-Simons theory with U(N) X U (N) gauge symmetry, which was recently constructed by Aharony, Bergman, Jafferis, and Maldacena (ABJM).
Abstract: We examine the three-dimensional N = 6 superconformal Chern--Simons theory with U(N) X U(N) gauge symmetry, which was recently constructed by Aharony, Bergman, Jafferis, and Maldacena (ABJM). Using a formulation with manifest SU(4) R-symmetry and no auxiliary fields, we verify in complete detail both the Poincare supersymmetry and the conformal supersymmetry of the action. Together, these imply the complete OSp(6|4) superconformal symmetry of the theory. The potential, which is sixth order in scalar fields, is recast as a sum of squares.
TL;DR: In this article, the authors show that the recent string theory embedding of a spacetime with nonrelativistic Schrodinger symmetry can be generalised to a twenty one dimensional family of solutions with that symmetry.
Abstract: We show that the recent string theory embedding of a spacetime with nonrelativistic Schrodinger symmetry can be generalised to a twenty one dimensional family of solutions with that symmetry. Our solutions include IIB backgrounds with no three form flux turned on, and arise as near horizon limits of branewave spacetimes. We show that there is a hypersurface in the space of these theories where an instability appears in the gravitational description, indicating a phase transition in the nonrelativistic field theory dual. We also present simple embeddings of duals for nonrelativistic critical points where the dynamical critical exponent can take many values z ≠ 2.
TL;DR: In this paper, the spectrum of short multiplets around the extremum of N=8 gauged supergravity potential was calculated using group theoretic methods, and it was shown that the monopole operators have a number of desired properties, such as supersymmetry and SU(3) global symmetry.
Abstract: We use group theoretic methods to calculate the spectrum of short multiplets around the extremum of N=8 gauged supergravity potential which possesses N=2 supersymmetry and SU(3) global symmetry. Upon uplifting to M-theory, it describes a warped product of AdS_4 and a certain squashed and stretched 7-sphere. We find quantum numbers in agreement with those of the gauge invariant operators in the N=2 superconformal Chern-Simons theory recently proposed to be the dual of this M-theory background. This theory is obtained from the U(N)xU(N) theory through deforming the superpotential by a term quadratic in one of the superfields. To construct this model explicitly, one needs to employ monopole operators whose complete understanding is still lacking. However, for the U(2)xU(2) gauge theory we make a proposal for the form of the monopole operators which has a number of desired properties. In particular, this proposal implies enhanced symmetry of the U(2)xU(2) ABJM theory for k=1,2; it makes its similarity to and subtle difference from the BLG theory quite explicit.
TL;DR: The symmetry principles of NMR pulse-sequence design are summarized and the selection rules associated with symmetrical pulse sequences are discussed using average Hamiltonian theory.
Abstract: The symmetry principles of NMR pulse-sequence design are summarized. The discussion is guided by an analogy with tiling schemes in the decorative arts. The symmetry operations for NMR pulse sequences are discussed in terms of excitation field modifiers and temporal modifiers. The quantum operators which describe the effect of these modifiers on the excitation field spin Hamiltonian are provided. The symmetry transformations of spin propagators, and the different types of pulse-sequence elements are discussed. The common types of symmetry expansion are treated using the propagator transformations and the Euler angles for the excitation field propagators. The selection rules associated with symmetrical pulse sequences are discussed using average Hamiltonian theory.
TL;DR: A spin-adapted density matrix renormalization group (DMRG) algorithm designed to target spin and spatial symmetry states that can be difficult to obtain while using a non-spin- Adapted algorithm is presented.
Abstract: We present a spin-adapted density matrix renormalization group (DMRG) algorithm designed to target spin and spatial symmetry states that can be difficult to obtain while using a non-spin-adapted algorithm. The algorithmic modifications that have to be introduced into the usual density matrix renormalization group scheme in order to spin adapt it are discussed, and it is demonstrated that the introduced modifications do not change the overall scaling of the method. The new approach is tested on HNCO, a model system, that has a singlet-triplet curve crossing between states of the same symmetry. The advantages of the spin-adapted DMRG scheme are discussed, and it is concluded that the spin-adapted DMRG method converges better in almost all cases and gives more parallel curves to the full configuration interaction result than the non-spin-adapted method. It is shown that the spin-adapted DMRG energies can be lower than the ones obtained from the non-spin-adapted scheme. Such a counterintuitive result is explained by noting that the spin-adapted method is not a special case of the non-spin-adapted one; consequently, the spin-adapted result is not an upper bound for the non-spin-adapted energy.
TL;DR: In this article, the Noether symmetry of a generic f(R) cosmological model is investigated by utilizing the behavior of the corresponding Lagrangian under the infinitesimal generators of the desired symmetry.
TL;DR: In this paper, the authors study the dynamic stability of the 3D axisymmetric Navier-Stokes Equations with swirl and propose a new one-dimensional model that approximates the Navier Stokes equations along the symmetry axis.
Abstract: In this paper, we study the dynamic stability of the three-dimensional axisymmetric Navier-Stokes Equations with swirl. To this purpose, we propose a new one-dimensional model that approximates the Navier-Stokes equations along the symmetry axis. An important property of this one-dimensional model is that one can construct from its solutions a family of exact solutions of the three-dimensionaFinal Navier-Stokes equations. The nonlinear structure of the one-dimensional model has some very interesting properties. On one hand, it can lead to tremendous dynamic growth of the solution within a short time. On the other hand, it has a surprising dynamic depletion mechanism that prevents the solution from blowing up in finite time. By exploiting this special nonlinear structure, we prove the global regularity of the three-dimensional Navier-Stokes equations for a family of initial data, whose solutions can lead to large dynamic growth, but yet have global smooth solutions.
TL;DR: In this article, a new phase of SU(N) gauge theories is found which exhibits spontaneous symmetry breaking of Z(4) to Z(2), representing a partially-confined phase in which quarks are confined, but diquarks are not.
Abstract: The addition of an adjoint Polyakov loop term to the action of a pure gauge theory at finite temperature leads to new phases of SU(N) gauge theories. For SU(3), a new phase is found which breaks Z(3) symmetry in a novel way; for SU(4), the new phase exhibits spontaneous symmetry breaking of Z(4) to Z(2), representing a partially-confined phase in which quarks are confined, but diquarks are not. The overall phase structure and thermodynamics is consistent with a theoretical model of the effective potential for the Polyakov loop based on perturbation theory.
Journal Article•
TL;DR: Oscillations of P_{DeltaE}(lambda) on a fine lambda scale are shown to have a quantum origin, involving threshold phenomena within a system of interacting ionization and HG channels, and to be sensitive to the bound state wave function's symmetry.
Abstract: Describing harmonic generation (HG) in terms of a system's complex quasienergy, the harmonic power P_{DeltaE}(lambda) (over a fixed interval, DeltaE, of harmonic energies) is shown to reproduce the wavelength scaling predicted recently by two groups of authors based on solutions of the time-dependent Schrödinger equation: P_{DeltaE}(lambda) approximately lambda;{-x}, where x approximately 5-6. Oscillations of P_{DeltaE}(lambda) on a fine lambda scale are then shown to have a quantum origin, involving threshold phenomena within a system of interacting ionization and HG channels, and to be sensitive to the bound state wave function's symmetry.
TL;DR: In this paper, the effect of an external magnetic field on the dynamics of fundamental flavors in both the confined and deconfined phases of a large Nc gauge theory was studied using the Sakai-Sugimoto model.
Abstract: Using the Sakai–Sugimoto model we study the effect of an external magnetic field on the dynamics of fundamental flavours in both the confined and deconfined phases of a large Nc gauge theory. We find that an external magnetic field promotes chiral symmetry breaking, consistent with the ``magnetic catalysis'' observed in the field theory literature, and seen in other studies using holographic duals. The external field increases the separation between the deconfinement temperature and the chiral symmetry restoring temperature. In the deconfined phase we investigate the temperature-magnetic field phase diagram and observe, for example, there exists a maximum critical temperature (at which symmetry is restored) for very large magnetic field. We find that this and certain other phenomena persist for the Sakai–Sugimoto type models with probe branes of diverse dimensions. We comment briefly on the dynamics in the presence of an external electric field.