Bosonic string - Kaluza Klein theory exact solutions using 5D-6D dualities

We present the explicit formulae which allow to transform the general solution of the 6D Kaluza--Klein theory on a 3--torus into the special solution of the 6D bosonic string theory on a 3--torus as well as into the general solution of the 5D bosonic string theory on a 2--torus. We construct a new family of the extremal solutions of the 3D chiral equation for the SL(4,R)/SO(4) coset matrix and interpret it in terms of the component fields of these three duality related theories.Comment: 13 pages in LaTe

Breakdown of the linear approximation in the perturbative analysis of heat conduction in relativistic systems

We analyze the effects of thermal conduction in a relativistic fluid just after its departure from spherical symmetry, on a time scale of the order of relaxation time. Using first order perturbation theory, it is shown that, as in spherical systems, at a critical point the effective inertial mass density of a fluid element vanishes and becomes negative beyond that point. The impact of this effect on the reliability of causality conditions is discussed.Comment: 11 pages (Latex2.09) To appear in Physics Letters

Amor y Apoyo: Lecciones de Latinx Families in Nourishing Resilience to First and Second-Generation College Students

The present qualitative study aims to understand how Latino/Hispanic herea er referred to as Latinx, parent involvement is different or similar among first- and second-generation college students in how they experience higher education and how parental education impacts the use of student support services. Hence, supporting Latinx student retention by developing university and parental relationships. Second-generation college students and Latinx parents were unable to be included in the study because of their scarcity or hesitation of participating. Therefore, participants included a convenience sample of six first-generation undergraduate students from a 4-year institution. Semi-structured interviews were conducted to obtain their stories of parental involvement and student involvement. Results suggest that (1) first-generation college students experience a hands-off involvement from parents, however, they enjoyed the freedom this brought, (2) Latinx parents might have a misunderstanding of college student identity, and (3) students expressed a desire to have their parents learn about and understand mental health. Implications of findings include universities creating more resources to support Latinx students’ mental health, as well as earlier school outreach for Latinx parent involvement to better inform them about the college lifestyle

Relativistic gravitational collapse in comoving coordinates: The post-quasistatic approximation

A general iterative method proposed some years ago for the description of relativistic collapse, is presented here in comoving coordinates. For doing that we redefine the basic concepts required for the implementation of the method for comoving coordinates. In particular the definition of the post-quasistatic approximation in comoving coordinates is given. We write the field equations, the boundary conditions and a set of ordinary differential equations (the surface equations) which play a fundamental role in the algorithm. As an illustration of the method, we show how to build up a model inspired in the well known Schwarzschild interior solution. Both, the adiabatic and non adiabatic, cases are considered.Comment: 14 pages, 11 figures; updated version to appear in Int. J. Modern Phys.

Collapsing Spheres Satisfying An "Euclidean Condition"

We study the general properties of fluid spheres satisfying the heuristic assumption that their areas and proper radius are equal (the Euclidean condition). Dissipative and non-dissipative models are considered. In the latter case, all models are necessarily geodesic and a subclass of the Lemaitre-Tolman-Bondi solution is obtained. In the dissipative case solutions are non-geodesic and are characterized by the fact that all non-gravitational forces acting on any fluid element produces a radial three-acceleration independent on its inertial mass.Comment: 1o pages, Latex. Title changed and text shortened to fit the version to appear in Gen.Rel.Grav

Charging Interacting Rotating Black Holes in Heterotic String Theory

We present a formulation of the stationary bosonic string sector of the whole toroidally compactified effective field theory of the heterotic string as a double Ernst system which, in the framework of General Relativity describes, in particular, a pair of interacting spinning black holes; however, in the framework of low--energy string theory the double Ernst system can be particularly interpreted as the rotating field configuration of two interacting sources of black hole type coupled to dilaton and Kalb--Ramond fields. We clarify the rotating character of the $B_{t\phi}$--component of the antisymmetric tensor field of Kalb--Ramond and discuss on its possible torsion nature. We also recall the fact that the double Ernst system possesses a discrete symmetry which is used to relate physically different string vacua. Therefore we apply the normalized Harrison transformation (a charging symmetry which acts on the target space of the low--energy heterotic string theory preserving the asymptotics of the transformed fields and endowing them with multiple electromagnetic charges) on a generic solution of the double Ernst system and compute the generated field configurations for the 4D effective field theory of the heterotic string. This transformation generates the $U(1)^n$ vector field content of the whole low--energy heterotic string spectrum and gives rise to a pair of interacting rotating black holes endowed with dilaton, Kalb--Ramond and multiple electromagnetic fields where the charge vectors are orthogonal to each other.Comment: 15 pages in latex, revised versio