516 research outputs found
Classical and quantum exact solutions for a FRW multi-scalar field cosmology with an exponential potential driven inflation
A flat Fiedmann-Robertson-Walker (FRW) multi-scalar field cosmology is
studied with a particular potential of the form , which emerges as a relation between the
time derivatives of the scalars field momenta. Classically, by employing the
Hamiltonian formalism of two scalar fields with standard
kinetic energy, exact solutions are found for the Einstein-Klein-Gordon (EKG)
system for different scenarios specified by the parameter
, as well as the e-folding function which is also computed. For the quantum scheme of this model, the
corresponding Wheeler-DeWitt (WDW) equation is solved by applying an
appropriate change of variables.Comment: Latex file, accepted in Advances and Mathematical physics, Hindawi.
arXiv admin note: text overlap with arXiv:1806.0119
Las habilidad cientÃficas en los libros de texto
El trabajo trata de analizar si los libros de texto contribuyen al desarrollo de habilidades cientÃficas en los estudiantes de Educación Secundaria Obligatoria. La investigación se ha centrado en tres aspectos: los tipos de actividades que predominan, las habilidades cientÃficas que se ponen en práctica y los criterios que siguen para secuenciarlas a lo largo de la etapa. Los resultados muestran que las actividades de los libros de texto están orientadas fundamentalmente al aprendizaje conceptual y que los trabajos prácticos que incluyen no permiten desarrollar la mayorÃa de las habilidades cientÃficas que deberÃan alcanzar los estudiantes de la ESO; asà mismo se comprueba que no siguen criterios coherentes para secuenciar las actividades en los diferentes cursos de la etapa
Strong enhancement of superconductivity at high pressures within the charge-density-wave states of 2H-TaS 2 and 2H-TaSe 2
We present measurements of the superconducting and charge density wave
critical temperatures (Tc and TCDW) as a function of pressure in the transition
metal dichalchogenides 2H-TaSe2 and 2H-TaS2. Resistance and susceptibility
measurements show that Tc increases from temperatures below 1 K up to 8.5 K at
9.5 GPa in 2H-TaS2 and 8.2 K at 23 GPa in 2H-TaSe2. We observe a kink in the
pressure dependence of TCDW at about 4 GPa that we attribute to the lock-in
transition from incommensurate CDW to commensurate CDW. Above this pressure,
the commensurate TCDW slowly decreases coexisting with superconductivity within
our full pressure range.Comment: Published in Phys. Rev B 93, 184512 (2016
Bernstein-Sato functional equations, -filtrations, and multiplier ideals of direct summands
This paper investigates the existence and properties of a Bernstein-Sato
functional equation in nonregular settings. In particular, we construct
-modules in which such formal equations can be studied. The existence of the
Bernstein-Sato polynomial for a direct summand of a polynomial over a field is
proved in this context. It is observed that this polynomial can have zero as a
root, or even positive roots. Moreover, a theory of -filtrations is
introduced for nonregular rings, and the existence of these objects is
established for what we call differentially extensible summands. This family of
rings includes toric, determinantal, and other invariant rings. This new theory
is applied to the study of multiplier ideals and Hodge ideals of singular
varieties. Finally, we extend known relations among the objects of interest in
the smooth case to the setting of singular direct summands of polynomial rings.Comment: 42 pages. A new section on Hodge ideals is included. Comments welcom
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