Twisted semilocal strings in the MSSM

The standard electroweak model is extended by means of a second Brout-Englert-Higgs-doublet. The symmetry breaking potential is chosen is such a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a stationary, axially symmetric ansatz of the bosonic fields consistently reduces the Euler-Lagrange equations to a set of differential equations. The potential involves, in particular, a direct interaction between the two doublets. Stationary, axially-symmetric solutions of the classical equations are constructed. Some of them can be assimilated to embedded Nielsen-Olesen strings. From these solutions there are bifurcations and new solutions appear which exhibit the characteristics of the recently constructed twisted semilocal strings. A special emphasis is set on "doubly-twisted" solutions for which the two doublets present different time-dependent phase factors. They are regular and have a finite energy which can be lower than the energy of the embedded twisted solution. Electric-type solutions, such that the fields oscillate asymptotically far from the symmetry-axis, are also reported.Comment: 17 pages, 11 figures, discussion extended, new solutions obtaine

Exotic composites: the decay of deficit angles in global-local monopoles

We study static, spherically symmetric, composite global-local monopoles with a direct interaction term between the two sectors in the regime where the interaction potential is large. At some critical coupling the global defect disappears and with it the deficit angle of the space-time. We find new solutions which represent local monopoles in an Anti-de-Sitter spacetime. In another parameter range the magnetic monopole, or even both, disappear. The decay of the magnetic monopole is accompanied by a dynamical transition from the higgsed phase to the gauge-symmetric phase. We comment on the applications to cosmology, topological inflation and braneworlds.Comment: 17 pages, 11 figures; Minor corrections, matches published versio

Numerical Solutions of Matrix Differential Models using Cubic Matrix Splines II

This paper presents the non-linear generalization of a previous work on matrix differential models. It focusses on the construction of approximate solutions of first-order matrix differential equations Y'(x)=f(x,Y(x)) using matrix-cubic splines. An estimation of the approximation error, an algorithm for its implementation and illustrative examples for Sylvester and Riccati matrix differential equations are given.Comment: 14 pages; submitted to Math. Comp. Modellin

Chandra Spectroscopy Of The Hot Star β Crucis And The Discovery Of A Pre-Main-Sequence Companion

In order to test the O star wind-shock scenario for X-ray production in less luminous stars with weaker winds, we made a pointed 74-ks observation of the nearby early B giant, beta Crucis (beta Cru; B0.5 III), with the Chandra High Energy Transmission Grating Spectrometer. We find that the X-ray spectrum is quite soft, with a dominant thermal component near 3 million K, and that the emission lines are resolved but quite narrow, with half widths of 150 km s(-1). The forbidden-to-intercombination line ratios of Ne IX and Mg XI indicate that the hot plasma is distributed in the wind, rather than confined near the photosphere. It is difficult to understand the X-ray data in the context of the standard wind-shock paradigm for OB stars, primarily because of the narrow lines, but also because of the high X-ray production efficiency. A scenario in which the bulk of the outer wind is shock heated is broadly consistent with the data, but not very well motivated theoretically. It is possible that magnetic channelling could explain the X-ray properties, although no field has been detected on beta Cru. We detected periodic variability in the hard (h nu \u3e 1 keV) X-rays, modulated on the known optical period of 4.58 h, which is the period of the primary beta Cephei pulsation mode for this star. We also have detected, for the first time, an apparent companion to beta Cru at a projected separation of 4 arcsec. This companion was likely never seen in optical images because of the presumed very high contrast between it and beta Cru in the optical. However, the brightness contrast in the X-ray is only 3:1, which is consistent with the companion being an X-ray active low-mass pre-main-sequence star. The companion\u27s X-ray spectrum is relatively hard and variable, as would be expected from a post-T Tauri star. The age of the beta Cru system (between 8 and 10 Myr) is consistent with this interpretation which, if correct, would add beta Cru to the roster of Lindroos binaries - B stars with low-mass pre-main-sequence companions

Chandra Spectroscopy Of The Hot Star β Crucis And The Discovery Of A Pre-Main-Sequence Companion

In order to test the O star wind-shock scenario for X-ray production in less luminous stars with weaker winds, we made a pointed 74-ks observation of the nearby early B giant, beta Crucis (beta Cru; B0.5 III), with the Chandra High Energy Transmission Grating Spectrometer. We find that the X-ray spectrum is quite soft, with a dominant thermal component near 3 million K, and that the emission lines are resolved but quite narrow, with half widths of 150 km s(-1). The forbidden-to-intercombination line ratios of Ne IX and Mg XI indicate that the hot plasma is distributed in the wind, rather than confined near the photosphere. It is difficult to understand the X-ray data in the context of the standard wind-shock paradigm for OB stars, primarily because of the narrow lines, but also because of the high X-ray production efficiency. A scenario in which the bulk of the outer wind is shock heated is broadly consistent with the data, but not very well motivated theoretically. It is possible that magnetic channelling could explain the X-ray properties, although no field has been detected on beta Cru. We detected periodic variability in the hard (h nu \u3e 1 keV) X-rays, modulated on the known optical period of 4.58 h, which is the period of the primary beta Cephei pulsation mode for this star. We also have detected, for the first time, an apparent companion to beta Cru at a projected separation of 4 arcsec. This companion was likely never seen in optical images because of the presumed very high contrast between it and beta Cru in the optical. However, the brightness contrast in the X-ray is only 3:1, which is consistent with the companion being an X-ray active low-mass pre-main-sequence star. The companion\u27s X-ray spectrum is relatively hard and variable, as would be expected from a post-T Tauri star. The age of the beta Cru system (between 8 and 10 Myr) is consistent with this interpretation which, if correct, would add beta Cru to the roster of Lindroos binaries - B stars with low-mass pre-main-sequence companions

Einstein-Yang-Mills solutions in higher dimensional de Sitter spacetime

We consider particle-like and black holes solutions of the Einstein-Yang-Mills system with positive cosmological constant in d>4 spacetime dimensions. These configurations are spherically symmetric and present a cosmological horizon for a finite value of the radial coordinate, approaching asymptotically the de Sitter background. In the usual Yang--Mills case we find that the mass of these solutions, evaluated outside the cosmological horizon at future/past infinity generically diverges for d>4. Solutions with finite mass are found by adding to the action higher order gauge field terms belonging to the Yang--Mills hierarchy. A discussion of the main properties of these solutions and their differences from those to the usual Yang-Mills model, both in four and higher dimensions is presented.Comment: 17 pages, 8 figure

An Academic Library-Biotech Industry Partnership: Defining a Collaboration

New York Medical College opened BioInc@NYMC, a multimillion-dollar government-funded biotechnology incubator, in October 2014. To spur medical innovation and economic development, the public and private sectors collaborated to provide biotech start-ups with state-of-the-art facilities. By April 2015 four start-up companies had joined the incubator. The Health Sciences Library was given a unique opportunity to interface with the private biotechnology industry and define an academic library-biotechnology industry partnership

Spherically symmetric Yang-Mills solutions in a (4+n)- dimensional space-time

We consider the Einstein-Yang-Mills Lagrangian in a (4+n)-dimensional space-time. Assuming the matter and metric fields to be independent of the n extra coordinates, a spherical symmetric Ansatz for the fields leads to a set of coupled ordinary differential equations. We find that for n > 1 only solutions with either one non-zero Higgs field or with all Higgs fields constant exist. We construct the analytic solutions which fulfill this conditions for arbitrary n, namely the Einstein-Maxwell-dilaton solutions. We also present generic solutions of the effective 4-dimensional Einstein-Yang-Mills-Higgs-dilaton model, which possesses n Higgs triplets coupled in a specific way to n independent dilaton fields. These solutions are the abelian Einstein-Maxwell- dilaton solutions and analytic non-abelian solutions, which have diverging Higgs fields. In addition, we construct numerically asymptotically flat and finite energy solutions for n=2.Comment: 15 Latex pages, 4 eps figures; v2: discussion of results revisite

Fast iterative solution of reaction-diffusion control problems arising from chemical processes

PDE-constrained optimization problems, and the development of preconditioned iterative methods for the efficient solution of the arising matrix system, is a field of numerical analysis that has recently been attracting much attention. In this paper, we analyze and develop preconditioners for matrix systems that arise from the optimal control of reaction-diffusion equations, which themselves result from chemical processes. Important aspects in our solvers are saddle point theory, mass matrix representation and effective Schur complement approximation, as well as the outer (Newton) iteration to take account of the nonlinearity of the underlying PDEs