122661013
MULTIMONOPOLE–ANTIMONOPOLE SOLUTIONS OF THE SU(2) YANG–MILLS–HIGGS FIELD THEORY
In this paper we constructed exact static multimonopole–antimonopole solutions of the YMH field theory. By labelling these solutions as A1, A2, B1, and B2, we notice that the exact axially symmetric 1-monopole — two antimonopoles solution is actually a special case of the A1 solution when the topological index parameter m=1. Also the B1 solution will reduce to a spherically symmetric Wu–Yang type monopole of unit charge when m=0. All these exact solutions satisfy the first order Bogomol'nyi equations and possess infinite energy. Hence they are a different type of the BPS solution. Except for the A1 solution when m=1 and the B1 solution when m=0, these solutions in general do not possess axial symmetry. They represent different combinations of monopoles, multimonopole, and antimonopoles, symmetrically arranged about the z-axis.
119199675
Comments on the Monopole-Antimonopole Pair Solutions
Recently, the monopole-antimonopole pair and monopole-antimonopole chain solutions are solved with internal space coordinate system of -winding number m greater than one. However, we notice that it is also possible to solve these solutions numerically in terms of -winding number m = 1 instead. When m = 1, the exact asymptotic solutions at small and large distances are parameterized by a single integer parameter s. Here we once again study the monopole-antimonopole pair solution of the SU(2) YangMills-Higgs theory which belongs to the topological trivial sector numerically in its new form. This solution with -winding and -winding number one is parameterized by s = 0 at small r and s = 1 at large r.
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
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.
118505849
GENERALIZED JACOBI ELLIPTIC ONE-MONOPOLE: TYPE A
We present a new classical generalized one-monopole solution of the SU(2) Yang–Mills–Higgs theory with the Higgs field in the adjoint representation. We show that this generalized solution with θ-winding number m = 1 and ϕ-winding number n = 1 is an axially symmetric Jacobi elliptic generalization of the 't Hooft–Polyakov one-monopole. We construct this axially symmetric one-monopole solution by generalizing the large distance asymptotic solution of the 't Hooft–Polyakov one-monopole to the Jacobi elliptic functions and solving the second-order equations of motion numerically when the Higgs potential is vanishing and nonvanishing. These solutions are regular non-BPS finite energy solutions.
18491679
Galaxy Number Counts and Implications for Strong Lensing
We compare galaxy number counts in Advanced Camera for Surveys (ACS) fields containing moderate-redshift (0.2 <z <1.0) strong gravitational lenses with those in two control samples: (1) the first square degree of the COSMOS survey, comprising 259 ACS fields and (2) 20 ‘pure-parallel’ fields randomly located on the sky. Through a Bayesian analysis we determine the expectation values (μ0) and confidence levels of the underlying number counts for a range of apertures and magnitude bins. Our analysis has produced the following results: (i) we infer that our control samples are not consistent, with the number counts in the COSMOS sample being significantly higher than in the pure-parallel sample for 21 ≤F814W≤ 23. This result matches those found in previous analyses of COSMOS data using different techniques. (ii) We find that small-sized apertures, centred on strong lenses, are overdense compared with randomly placed apertures in the control samples, even compared to the COSMOS sample. Correcting for the local clustering of elliptical galaxies, based on the average two-point correlation function, reduces this overdensity to the 1-2σ level. Thus, the overdensity of galaxies seen along a typical line of sight to a lens can be explained mostly by the natural clustering of galaxies, rather than being due to lenses lying along otherwise biased lines of sight. However, a larger sample of lenses is needed to see if the remaining bias persists when the lens-field uncertainties are smaller. (iii) There is considerable scatter in the lines of sight to individual lens systems, but quantities that are linearly dependent on the external convergence (e.g. H0) should become unbiased if the extra galaxies that cause the bias can be accounted for in the lens models either through direct modelling or via an informed prior on the external convergence. The number counts can be used to set such an informed prior.
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.
119217335
PRIMUS: ENHANCED SPECIFIC STAR FORMATION RATES IN CLOSE GALAXY PAIRS
Tidal interactions between galaxies can trigger star formation, which contributes to the global star formation rate (SFR) density of the universe and could be a factor in the transformation of blue, star-forming galaxies to red, quiescent galaxies over cosmic time. We investigate tidally triggered star formation in isolated close galaxy pairs drawn from the Prism Multi-Object Survey (PRIMUS), a low-dispersion prism redshift survey that has measured ∼ 120,000 robust galaxy redshifts over 9.1 deg 2 out to z ∼ 1. We select a sample of galaxies in isolated galaxy pairs at redshifts 0.25 ≤ z ≤ 0.75, with no other objects within a projected separation of 300 h ―1 kpc and Δz/(1 + z) = 0.01, and compare them to a control sample of isolated galaxies to test for systematic differences in their rest-frame FUV - r and NUV - r colors as a proxy for relative specific star formation rates (SSFRs). We find that galaxies in r p ≤ 50 h ―1 kpc pairs have bluer dust-corrected UV - r colors on average than the control galaxies by ―0.134 ± 0.045 mag in FUV - r and ―0.075 ± 0.038 mag in NUV - r, corresponding to an ∼ 15%―20% increase in SSFR. This indicates an enhancement in SSFR due to tidal interactions. We also find that this relative enhancement is greater for a subset of r p ≤ 30 h ―1 kpc pair galaxies, for which the average color offsets are ―0.193 ± 0.065 mag in FUV - r and ―0.159 ± 0.048 mag in NUV - r, corresponding to an ∼25%―30% increase in SSFR. We test for evolution in the enhancement of tidally triggered star formation with redshift across our sample redshift range and find marginal evidence for a decrease in SSFR enhancement from 0.25 ≤ z ≤ 0.5 to 0.5 ≤ z ≤ 0.75. This indicates that a change in enhanced star formation triggered by tidal interactions in low-density environments is not a contributor to the decline in the global SFR density across this redshift range.
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.
118580751
Weyl fluid dark matter model tested on the galactic scale by weak gravitational lensing
The higher-dimensional Weyl curvature induces on the brane a new source of gravity. This Weyl fluid of geometrical origin (reducing in the spherically symmetric, static configuration to a dark radiation and dark pressure) modifies spacetime geometry around galaxies and has been shown to explain the flatness of galactic rotation curves. Independent observations for discerning between the Weyl fluid and other dark matter models are necessary. Gravitational lensing could provide such a test. Therefore we study null geodesics and weak gravitational lensing in the dark radiation dominated region of galaxies in a class of spherically symmetric braneworld metrics. We find that the lensing profile in the braneworld scenario is distinguishable from dark matter lensing, despite both the braneworld scenario and dark matter models fitting the rotation curve data. In particular, in the asymptotic regions, light deflection is 18% enhanced as compared to dark matter halo predictions. For a linear equation of state of the Weyl fluid, we further find a critical radius below which braneworld effects reduce, while above it they amplify light deflection. This is in contrast to any dark matter model, the addition of which always increases the deflection angle.