Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GAUGE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Dark left-right gauge model: SU(2){sub R} phenomenology

In the recently proposed dark left-right gauge model of particle interactions, the left-handed fermion doublet ({nu},e){sub L} is connected to its right-handed counterpart (n,e){sub R} through a scalar bidoublet, but {nu}{sub L} couples to n{sub R} only through {phi}{sub 1}{sup 0} which has no vacuum expectation value. The usual R parity, i.e. R=(-){sup 3B+L+2j}, can be defined for this nonsupersymmetric model so that both n and {Phi}{sub 1} are odd together with W{sub R}{sup {+-}.} The lightest n is thus a viable dark-matter candidate (scotino). Here we explore the phenomenology associated with the SU(2){sub R} gauge group of this model, which allows it to appear at the TeV energy scale. The exciting possibility of Z{sup '{yields}}8 charged leptons is discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Gauge symmetry breaking in ten-dimensional Yang-Mills theory dynamically compactified on S{sup 6}

We study fluctuation modes in ten-dimensional Yang-Mills theory with a higher derivative term for the gauge field. We consider the ten-dimensional space-time to be a product of a four-dimensional space-time and six-dimensional sphere which exhibits dynamical compactification. Because of the isometry on S{sup 6}, there are flat directions corresponding to the Nambu-Goldstone zero modes in the effective theory on the solution. The zero modes are absorbed into gauge fields and form massive vector fields as a consequence of the Higgs-Kibble mechanism. The mass of the vector fields is proportional to the inverse of the radius of the sphere and larger than the mass scale set by the radius because of the higher derivative term.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Gauge-invariant and infrared-improved variational analysis of the Yang-Mills vacuum wave functional

We study a gauge-invariant variational framework for the Yang-Mills vacuum wave functional. Our approach is built on gauge-averaged Gaussian trial functionals which substantially extend previously used trial bases in the infrared by implementing a general low-momentum expansion for the vacuum-field dispersion (which is taken to be analytic at zero momentum). When completed by the perturbative Yang-Mills dispersion at high momenta, this results in a significantly enlarged trial-functional space which incorporates both dynamical mass generation and asymptotic freedom. After casting the dynamics associated with these wave functionals into an effective action for collections of soft vacuum-field orbits, the leading infrared improvements manifest themselves as four-gradient interactions. Those turn out to significantly lower the minimal vacuum energy density, thus indicating a clear overall improvement of the vacuum description. The dimensional transmutation mechanism and the dynamically generated mass scale remain almost quantitatively robust, however, which ensures that our prediction for the gluon condensate is consistent with standard values. Further results include a finite group velocity for the soft gluonic modes due to the higher-gradient corrections and indications for a negative differential color resistance of the Yang-Mills vacuum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

keV sterile neutrino dark matter in gauge extensions of the standard model

It is known, that a keV scale sterile neutrino is a good warm dark matter candidate. We study how this possibility could be realized in the context of gauge extensions of the standard model. The naieve expectation leads to large thermal overproduction of sterile neutrinos in this setup. However, we find that it is possible to use out-of-equilibrium decay of the other right-handed neutrinos of the model to dilute the present density of the keV sterile neutrinos and achieve the observed dark matter density. We present the universal requirements that should be satisfied by the gauge extensions of the standard model, containing right-handed neutrinos, to be viable models of warm dark matter, and provide a simple example in the context of the left-right symmetric model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Infrared singularities in Landau gauge Yang-Mills theory

We present a more detailed picture of the infrared regime of Landau-gauge Yang-Mills theory. This is done within a novel framework that allows one to take into account the influence of finite scales within an infrared power counting analysis. We find that there are two qualitatively different infrared fixed points of the full system of Dyson-Schwinger equations. The first extends the known scaling solution, where the ghost dynamics is dominant and gluon propagation is strongly suppressed. It features in addition to the strong divergences of gluonic vertex functions in the previously considered uniform scaling limit, when all external momenta tend to zero, also weaker kinematic divergences, when only some of the external momenta vanish. The second solution represents the recently proposed decoupling scenario where the gluons become massive and the ghosts remain bare. In this case we find that none of the vertex functions is enhanced, so that the infrared dynamics is entirely suppressed. Our analysis also provides a strict argument why the Landau-gauge gluon dressing function cannot be infrared divergent.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Infrared evolution and phase structure of a gauge theory containing different fermion representations

We study the evolution of an asymptotically free vectorial SU(N) gauge theory from the ultraviolet to the infrared and the resultant phase structure in the general case in which the theory contains fermions transforming according to several different representations of the gauge group. We discuss the sequential fermion condensation and dynamical mass generation that occur, and comment on the effect of bare fermion mass terms.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Localizing gauge fields on a topological Abelian string and the Coulomb law

The confinement of electromagnetic field is studied in axial symmetrical, warped, six-dimensional brane world, using a recently proposed topological Abelian string-vortex solution as background. It was found, that the massless gauge field fluctuations follow four-dimensional Maxwell equations in the Lorenz gauge. The massless zero mode is localized when the thickness of the string vortex is less than 5{beta}/4{pi}e{sup 2}v{sup 2} and there are no other localized massless modes. There is also an infinite of nonlocalized massive Fourier modes, that follow four-dimensional Proca equations with a continuous spectrum. To compute the corrections to the Coulomb potential, a radial cutoff was introduced, in order to achieve a discrete mass spectrum. As a main result, a (R{sub o}/{beta}R{sup 2}) correction was found for the four-dimensional effective Coulomb law; the result is in correspondence with the observed behavior of the Coulomb potential at today's measurable distances.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

General gauge mediation in five dimensions

We use the ''general gauge mediation'' (GGM) formalism to describe a five-dimensional setup with an S{sup 1}/Z{sub 2} orbifold. We first consider a model independent supersymmetry breaking hidden sector on one boundary and generic chiral matter on another. Using the definition of GGM, the effects of the hidden sector are contained in a set of global symmetry current correlator functions and is mediated through the bulk. We find the gaugino, sfermion and hyperscalar mass formulas for minimal and generalized messengers in different regimes of a large, small and intermediate extra dimension. Then we use the five-dimensional GGM formalism to construct a model in which an SU(5) Intriligator, Seiberg and Shih (ISS) model is located on the hidden boundary. We weakly gauge a global symmetry of the ISS model and associate it with the bulk vector superfield. Compared to four-dimensional GGM, there is a natural way to adjust the gaugino versus sfermion mass ratio by a factor (Ml){sup 2}, where M is a characteristic mass scale of the supersymmetry breaking sector and l is the length of the extra dimension.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions

We have measured the running coupling constant of SU(3) gauge theory coupled to N{sub f}=2 flavors of symmetric representation fermions, using the Schroedinger functional scheme. Our lattice action is defined with hypercubic smeared links which, along with the larger lattice sizes, bring us closer to the continuum limit than in our previous study. We observe that the coupling runs more slowly than predicted by asymptotic freedom, but we are unable to observe fixed point behavior before encountering a first order transition to a strong coupling phase. This indicates that the infrared fixed point found with the thin-link action is a lattice artifact. The slow running of the gauge coupling permits an accurate determination of the mass anomalous dimension for this theory, which we observe to be small, {gamma}{sub m} < or approx. 0.6, over the range of couplings we can reach. We also study the bulk and finite-temperature phase transitions in the strong coupling region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Heavy quark free energy in QCD and in gauge theories with gravity duals

Recent lattice results in pure glue SU(3) theory at high temperatures have shown that the expectation value of the renormalized Polyakov loop approaches its asymptotic limit at high temperatures from above. We show that this implies that the 'heavy quark free energy' obtained from the renormalized loop computed on the lattice does not behave like a true thermodynamic free energy. While this should be expected to occur in asymptotically free gauge theories such as QCD, we use the gauge/string duality to show that in a large class of strongly coupled gauge theories with nontrivial UV fixed points the Polyakov loop reaches its asymptotic value from above only if the dimension of the relevant operator used to deform the conformal field theory is greater than or equal to 3.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Direct gauge mediation of uplifted metastable supersymmetry breaking in supergravity

We propose a direct gauge mediation model based on an uplifted metastable supersymmetry (SUSY) breaking coupled to supergravity. A constant superpotential plays an essential role to fix the moduli as well as breaking SUSY and R symmetry and the cancellation of the cosmological constant. Gaugino masses are generated at leading order of SUSY breaking scale, and comparable to the sfermion masses as in the ordinary gauge mediation. The Landau pole problem for QCD coupling can be easily solved since more than half of messengers become superheavy, which are heavier than the grand unified theory (GUT) scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Constraints on realistic Gauge-Higgs unified models

We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the standard model gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T parameter at tree level. We show that none of the resulting models can have |s{sub w}|{approx}1/2 (the sine of the weak-mixing angle) at tree level and briefly discuss possible solutions to this problem.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

A note on charged black holes in AdS space and the dual gauge theories

We study the thermodynamics and the phase structures of Reissner-Nordstroem and Born-Infeld black holes in AdS space by constructing ''off-shell'' free energies using thermodynamic quantities derived directly from the action. We then use these results to propose ''off-shell'' effective potentials for the respective boundary gauge theories. The saddle points of the potentials describe all the equilibrium phases of the gauge theories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Viable axion from gauged flavor symmetries

We consider a string-inspired nonsupersymmetric extension of the standard model with gauged anomalous U(1) flavor symmetries. Consistency requires the Green-Schwarz (GS) mechanism to cancel mixed anomalies. The additional required scalars provide Stueckelberg masses for the Z{sup '} particles associated to the gauged flavor symmetry, so they decouple at low energies. Our models also include a complex scalar field {phi} to generate Froggatt-Nielsen mass terms for light particles, giving a partial solution to the fermion mass problem. A residual approximate (anomalous) global symmetry survives at low energies. The associated pseudo-Goldstone mode is the phase of the {phi} scalar field, and it becomes the dominant contribution to the physical axion. An effective field theory analysis that includes neutrino masses gives a prediction for the axion decay constant. We find a simple model where the axion decay constant is in the center of the allowed window.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Conservative corrections to the innermost stable circular orbit (ISCO) of a Kerr black hole: A new gauge-invariant post-Newtonian ISCO condition, and the ISCO shift due to test-particle spin and the gravitational self-force

The innermost stable circular orbit (ISCO) delimits the transition from circular orbits to those that plunge into a black hole. In the test-mass limit, well-defined ISCO conditions exist for the Kerr and Schwarzschild spacetimes. In the finite-mass case, there are a large variety of ways to define an ISCO in a post-Newtonian (PN) context. Here I generalize the gauge-invariant ISCO condition of Blanchet and Iyer [Classical Quantum Gravity 20, 755 (2003)] to the case of spinning (nonprecessing) binaries. The Blanchet-Iyer ISCO condition has two desirable and unexpected properties: (1) it exactly reproduces the Schwarzschild ISCO in the test-mass limit, and (2) it accurately approximates the recently calculated shift in the Schwarzschild ISCO frequency due to the conservative-piece of the gravitational self-force [L. Barack and N. Sago, Phys. Rev. Lett. 102, 191101 (2009)]. The generalization of this ISCO condition to spinning binaries has the property that it also exactly reproduces the Kerr ISCO in the test-mass limit (up to the order at which PN spin corrections are currently known). The shift in the ISCO due to the spin of the test-particle is also calculated. Remarkably, the gauge-invariant PN ISCO condition exactly reproduces the ISCO shift predicted by the Papapetrou equations for a fully relativistic spinning particle. It is surprising that an analysis of the stability of the standard PN equations of motion is able (without any form of 'resummation') to accurately describe strong-field effects of the Kerr spacetime. The ISCO frequency shift due to the conservative self-force in Kerr is also calculated from this new ISCO condition, as well as from the effective-one-body Hamiltonian of Barausse and Buonanno [Phys. Rev. D 81, 084024 (2010)]. These results serve as a useful point of comparison for future gravitational self-force calculations in the Kerr spacetime.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Dark discrete gauge symmetries

We investigate scenarios in which dark matter is stabilized by an Abelian Z{sub N} discrete gauge symmetry. Models are surveyed according to symmetries and matter content. Multicomponent dark matter arises when N is not prime and Z{sub N} contains one or more subgroups. The dark sector interacts with the visible sector through the renormalizable kinetic mixing and Higgs portal operators, and we highlight the basic phenomenology in these scenarios. In particular, multiple species of dark matter can lead to an unconventional nuclear recoil spectrum in direct detection experiments, while the presence of new light states in the dark sector can dramatically affect the decays of the Higgs at the Tevatron and LHC, thus providing a window into the gauge origin of the stability of dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Spontaneously broken topological SL(5,R) gauge theory with standard gravity emerging

A completely metric-free sl(5,R) gauge framework is developed in four dimensions. After spontaneous symmetry breaking of the corresponding topological BF scheme, Einstein spaces with a tiny cosmological constant emerge, similarly as in (anti-)de Sitter gauge theories of gravity. The induced {Lambda} is related to the scale of the symmetry breaking. A ''background'' metric surfaces from a Higgs-like mechanism. The finiteness of such a topological scheme converts into asymptotic safeness after quantization of the spontaneously broken model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Higher-derivative gauge interactions of Bagger-Lambert-Gustavsson theory in N=1 superspace

We study the structure of the gauge sector of the Bagger-Lambert-Gustavsson theory in the form proposed by van Raamsdonk, adapted to three dimensions, N=1 superspace. By using the novel Higgs mechanism proposed by Mukhi and Papageorgakis, we derive the manifestly N=1 supersymmetric higher-order terms (beyond the supersymmetric Yang-Mills action) that follow from the Bagger-Lambert-Gustavsson theory in its expansion with respect to the inverse gauge coupling constant squared. We find that all those terms have at least one anticommutator of the super-Yang-Mills field strength superfields as a factor, and thus are reducible to the supersymmetric Yang-Mills terms with the higher (spacetime) derivatives.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗