121227608
Vortex Ring Dyons of the SU(2) Yang‐Mills‐Higgs Model
We present an axially symmetric vortex ring dyons solutions of the SU(2) Yang‐Mills‐Higgs theory. These vortex rings carry electric charges that are determined by a parameter, −1⩽η⩽1. They possess vanishing magnetic charge and are located at a ring centered around the z‐axis where the Higgs field vanishes. These stationary vortex ring dyon solutions possess finite energy but they do not satisfy the first order Bogomol’nyi equations. In the Bogomol’nyi‐Prasad‐Sommerfield (BPS) limit where the Higgs field potential is zero, the time component of the gauge field is parallel to the Higgs field in isospace. The total energy, net electric charge and diameter of the vortex ring increase exponentially to infinity when η approaches ±1. On the contrary, when λ = 1, all these three values reach their critical value as η approaches ±1.
118395102
One Monopole-Antimonopole Pair Solutions
We present new classical generalized one monopole-antimonopole pair solutions of the SU(2) Yang-Mills-Higgs theory with the Higgs field in the adjoint representation. We show that in general the one monopole-antimonopole solution need not be solved by imposing mtheta-winding number to be integer greater than one. We also show that this solution can be solved when m = 1 by transforming the large distance asymptotic solutions to general solutions that depend on a parameter p. Secondly we show that these large distance asymptotic solutions can be further generalized to the Jacobi elliptic functions. We focus our numerical calculation on the Jacobi elliptic functions solution when the nphi-winding number is one and show that this generalized Jacobi elliptic 1-MAP solution possesses lower energy. All these solutions are numerical finite energy non-BPS solutions of the Yang-Mills-Higgs field theory.
119564127
Exact Solutions of the Abelian Decomposed Restricted Gauge Potential
We construct new exact solution of the SU(2) Yang‐Mills‐Higgs model by considering Abelian decomposition of the gauge potential. The solution is obtained by considering only the restricted part of the decomposition, where the unrestricted valence part is switched off. The solutions possess free parameters c1, c2 and q that correspond to different physical system of monopoles. Under the limit of c1 = 0, c2 = 1, and q = 1, the solution is that of the Wu‐Yang‐like monopole.
119481039
STATIC MONOPOLES AND THEIR ANTICONFIGURATIONS
Recently, we have reported on the existence of some monopoles, multimonopole, and antimonopoles configurations. In this paper we would like to present more monopoles, multimonopole, and antimonopoles configurations of the magnetic ansatz of Ref. 9 when the parameters p and b of the solutions takes different serial values. These exact solutions are a different kind of BPS solution. They satisfy the first order Bogomol'nyi equation but possess infinite energy. They can have radial, axial, or rotational symmetry about the z-axis. We classified these serial solutions as (i) the multimonopole at the origin; (ii) the finitely separated 1-monopoles; (iii) the screening solutions of multimonopole and (iv) the axially symmetric monopole solutions. We also give a construction of their anticonfigurations with all the magnetic charges of poles in the configurations reversed. Half-integer topological magnetic charge multimonopole also exist in some of these series of solutions.
118381576
Particles of One-Half Topological Charge
We would like to show the existence of nite energy SU(2) Yang-MillsHiggs particles of one-half topological charge. The ’t Hooft Abelian magnetic elds of these solutions at spatial innity correspond to the magnetic eld
8117211
Monopole-antimonopole and vortex rings
The SU(2) Yang-Mills-Higgs theory supports the existence of monopoles, antimonopoles, and vortex rings. In this paper, we would like to present new exact static antimonopole-monopole-antimonopole (A-M-A) configurations. The net magnetic charge of these configurations is always −1, while the net magnetic charge at the origin is always +1 for all positive integer values of the solution’s parameter m. However, when m increases beyond 1, vortex rings appear coexisting with these AMA configurations. The number of vortex rings increases proportionally with the value of m. They are located in space where the Higgs field vanishes along rings. We also show that a single-point singularity in the Higgs field does not necessarily correspond to a structureless 1-monopole at the origin but to a zero-size monopole-antimonopole-monopole (MAM) structure when the solution’s parameter m is odd. This monopole is the Wu-Yang-type monopole and it possesses the Dirac string potential in the Abelian gauge. These exact solutions ...
118343376
Inflation and late-time acceleration in braneworld cosmological models with varying brane tension
Braneworld models with variable brane tension λ introduce a new degree of freedom that allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We consider a thermodynamic interpretation of the varying brane tension models, by showing that the field equations with variable λ can be interpreted as describing matter creation in a cosmological framework. The particle creation rate is determined by the variation rate of the brane tension, as well as by the brane–bulk energy-matter transfer rate. We investigate the effect of a variable brane tension on the cosmological evolution of the Universe, in the framework of a particular model in which the brane tension is an exponentially dependent function of the scale factor. The resulting cosmology shows the presence of an initial inflationary expansion, followed by a decelerating phase, and by a smooth transition towards a late accelerated de Sitter type expansion. The varying brane tension is also responsible for the generation of the matter in the Universe (reheating period). The physical constraints on the model parameters, resulting from the observational cosmological data, are also investigated.
971110
Static potential and local color fields in unquenched three-dimensional lattice QCD
Abstract String breaking by dynamical quarks in (2+1)-d lattice QCD is demonstrated in this project, by measuring the static potential and the local color-electric field strength between a heavy quark and antiquark pair at large separations. Simulations are done for unquenched SU(2) color with two flavors of staggered quarks. An improved gluon action is used which allows simulations to be done on coarse lattices, providing an extremely efficient means to access the quark separations and propagation times at which string breaking occurs. The static quark potential is extracted using only Wilson loop operators and hence no valence quarks are present in the trial states. Results give unambiguous evidence for string breaking as the static quark potential completely saturates at twice the heavy-light meson mass at large separations. It is also shown that the local color-electric field strength between the quark pair tends toward vacuum values at large separations. Implications of these results for unquenched simulations of QCD in 4-d are drawn.
119230920
Reheating the Universe in Braneworld Cosmological Models with bulk-brane energy transfer
The emergence of the cosmological composition (the reheating era) after the inflationary period is analyzed in the framework of the braneworld models, in which our Universe is a three-brane embedded in a five-dimensional bulk, by assuming the possibility of the brane-bulk energy exchange. The inflaton field is assumed to decay into normal matter only, while the dark matter is injected into the brane from the bulk. To describe the reheating process we adopt a phenomenological approach, by describing the decay of the inflaton field by a friction term proportional to the energy density of the field. After the radiation dominated epoch the model reduces to the standard four dimensional cosmological model. The modified field equations are analyzed analytically and numerically in both the extra-dimensions dominate reheating phase (when the quadratic terms in energy density dominate the dynamics), and in the general case. The evolution profiles of the matter, of the scalar field and of the scale factor of the universe are obtained for different values of the parameters of the model, and of the equations of state of the normal and dark matter, respectively. The equation describing the time evolution of the ratio of the energy density of the dark and of the normal matter is also obtained. The ratio depends on the rate of the energy flow between the bulk and the brane. The observational constraint of an approximately constant ratio of the dark and of the baryonic matter requires that the dark matter must be non-relativistic (cold). The model predicts a reheating temperature of the order of 3 × 10 6 GeV, a brane tension of the order of 10 25 GeV 4 , and the obtained composition of the universe is consistent with the observational data.
118337254
QCD TOPOLOGY AND LATTICE PERTURBATION THEORY FROM MONTE CARL0 SIMULATIONS WITH IMPROVED STAGGERED FERMIONS
The staggered quark formulation is one of many ways to include fermions on the lattice. Dynamical simulations are now routinely done with improved staggered quark actions which are more efficient than other popular formalisms. In this thesis two research works on improved staggered fermions are presented. A systematic study of the staggered Dirac operator's spectral properties is first presented. It is a long standing belief that staggered fermions do not feel gauge field topology because of the lack of zero eigenvalues of the operator at finite lattice spacing. The existence of fermionic zero modes in topological nontrivial background gauge fields is required by the Atiyah-Singer index theorem. In this study we observe that eigenmodes with very small eigenvalue and large chirality appear if improved staggered operators are used. These small eigenmodes can be identified as the "zero modes" associated with the topology of the gauge fields. We have also compared the distribution of the remaining nonchiral modes with the predictions of Random Matrix Theory. Satisfactory agreement is obtained. In the second project perturbative expansions of Wilson loops are computed in full QCD from Monte Carlo simulations with improved staggered fermions. This approach provides a much simpler alternative to diagrammatic perturbation theory, and has previously been shown to be successful in reproducing the perturbation series in pure gauge theory. This method is applied here for the first time to unquenched QCD. Twisted boundary conditions are used to eliminate effects of zero momentum modes and to suppress tunneling between the degenerate Z3 vaccua. A new simulation algorithm, the rational hybrid Monte Carlo algorithm, with no finite step size error is also employed. This is the first time this algorithm has been used in a numerical application. Results are in excellent agreement with analytic perturbation theory; this provides an important cross-check of the perturbation theory input to a recent determination of the strong coupling am(MZ) by the HPQCD collaboration.
119254962
PRIMUS: THE DEPENDENCE OF AGN ACCRETION ON HOST STELLAR MASS AND COLOR
We present evidence that the incidence of active galactic nuclei (AGNs) and the distribution of their accretion rates do not depend on the stellar masses of their host galaxies, contrary to previous studies. We use hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS, COSMOS, and ELAIS-S1) with redshifts from the Prism Multi-object Survey to identify 242 AGNs with L{sub 2-10keV} = 10{sup 42-44} erg s{sup -1} within a parent sample of {approx}25,000 galaxies at 0.2 < z < 1.0 over {approx}3.4 deg{sup 2} and to i {approx} 23. We find that although the fraction of galaxies hosting an AGN at fixed X-ray luminosity rises strongly with stellar mass, the distribution of X-ray luminosities is independent of mass. Furthermore, we show that the probability that a galaxy will host an AGN can be defined by a universal Eddington ratio distribution that is independent of the host galaxy stellar mass and has a power-law shape with slope -0.65. These results demonstrate that AGNs are prevalent at all stellar masses in the range 9.5< log M{sub *}/M{sub sun}<12 and that the same physical processes regulate AGN activity in all galaxies in this stellar mass range. While a higher AGN fraction maymore » be observed in massive galaxies, this is a selection effect related to the underlying Eddington ratio distribution. We also find that the AGN fraction drops rapidly between z {approx} 1 and the present day and is moderately enhanced (factor {approx}2) in galaxies with blue or green optical colors. Consequently, while AGN activity and star formation appear to be globally correlated, we do not find evidence that the presence of an AGN is related to the quenching of star formation or the color transformation of galaxies.« less