48,617 research outputs found
Relic gravitational waves and the cosmic accelerated expansion
The possibility of reconstructing the whole history of the scale factor of
the Universe from the power spectrum of relic gravitational waves (RGWs) makes
the study of these waves quite interesting. First, we explore the impact of a
hypothetical era -right after reheating- dominated by mini black holes and
radiation that may lower the spectrum several orders of magnitude. Next, we
calculate the power spectrum of the RGWs taking into account the present stage
of accelerated expansion and an hypothetical second dust era. Finally, we study
the generalized second law of gravitational thermodynamics applied to the
present era of accelerated expansion of the Universe.Comment: 4 pages, 2 figures. Uses AIP style. To be published in the AIP
Proceedings of the XXVIII Spanish Relativity Meetin
One-loop kink mass shifts: a computational approach
In this paper we develop a procedure to compute the one-loop quantum
correction to the kink masses in generic (1+1)-dimensional one-component scalar
field theoretical models. The procedure uses the generalized zeta function
regularization method helped by the Gilkey-de Witt asymptotic expansion of the
heat function via Mellin's transform. We find a formula for the one-loop kink
mass shift that depends only on the part of the energy density with no field
derivatives, evaluated by means of a symbolic software algorithm that automates
the computation. The improved algorithm with respect to earlier work in this
subject has been tested in the sine-Gordon and models. The
quantum corrections of the sG-soliton and -kink masses have
been estimated with a relative error of 0.00006% and 0.00007% respectively.
Thereafter, the algorithm is applied to other models. In particular, an
interesting one-parametric family of double sine-Gordon models interpolating
between the ordinary sine-Gordon and a re-scaled sine-Gordon model is
addressed. Another one-parametric family, in this case of models, is
analyzed. The main virtue of our procedure is its versatility: it can be
applied to practically any type of relativistic scalar field models supporting
kinks.Comment: 35 pages, 6 figures, to be published in Nuclear Physics
Asymmetric kink scattering in a two-component scalar field theory model
ProducciĂłn CientĂficaIn this paper the kink scattering in a two-component scalar field theory model in (1+1)-Minkowskian
space-time is addressed. The potential term U(fi_1; fi_2) is given by a polynomial of fourth degree in the
first field component and of sixth degree in the second one. The novel characteristic of this model is
that the kink variety describes two different types of extended particles. These particles are characterized
by its topological charge but also by a new feature determined by a discrete charge L = 0,1,-1.
For this reason, the kink scattering involves a very rich variety of processes, which comprises kink
annihilation, reflection, charge exchange, transmutation, etc. It has been found that not only the final
velocity of the scattered kinks, but also the final nature of the emerging lumps after the collision are
very sensitive on the initial velocities. Asymmetric scattering processes arise when Type I and Type
II particles are obliged to collide. In this case, ten different final scenarios are possible. Symmetric
scattering events are also discussed.In this paper the kink scattering in a two-component scalar field theory model in (1+1)-Minkowskian space-time is addressed. The potential term U(Ď•1, Ď•2) is given by a polynomial of fourth degree in the first field component and of sixth degree in the second one. The novel characteristic of this model is that the kink variety describes two different types of extended particles. These particles are characterized by its topological charge but also by a new feature determined by a discrete charge . For this reason, the kink scattering involves a very rich variety of processes, which comprises kink annihilation, reflection, charge exchange, transmutation, etc. It has been found that not only the final velocity of the scattered kinks, but also the final nature of the emerging lumps after the collision are very sensitive on the initial velocities. Asymmetric scattering processes arise when Type I and Type II particles are obliged to collide. In this case, ten different final scenarios are possible. Symmetric scattering events are also discussed.Ministerio de EconomĂa, Ciencia y Competitividad (grant MTM2014-57129-C2-1-P)Junta de Castilla y Leon (grant VA057U16
Free differential algebras and generic 2D dilatonic (super)gravities
The field equations for both generic bosonic and generic locally
supersymmetric 2D dilatonic gravity theories in the absence of matter are
written as free differential algebras. This constitutes a generalization of the
gauge theoretic formulation. Moreover, it is shown that the condition of free
differential algebra can be used to obtain the equations in the locally
supersymmetric case. Using this formulation, the general solution of the field
equations is found in the language of differential forms. The relation with the
ordinary formulation and the coupling to supersymmetric conformal matter are
also studied.Comment: 19 pages, Late
Management of human resources in the physical activity and sport: concepts and perspectives
The management proper of human resources in organizations of physical activity and sport is essential to ensure the quality, efficiency and professionalism of service offered and even, if not done the right way can produce the benefits become a nuisance and risks to health, safety and education of citizens and for society as such. The perspective of management and organization of human resources in the states of physical activity and sport should be comprehensive, integrated and cross, which means that as human resources are critical in these organizations and the service itself, it extends to each of the processes, actions and decisions throughout the organization and is therefore the responsibility of all managers, not to mention that there will be bodies that address only specific aspects of human resources
Kink dynamics in the MSTB model
ProducciĂłn CientĂficaIn this paper kink scattering processes are investigated in the Montonen–Sarker–Trullinger–Bishop (MSTB) model. The MSTB model is in fact a one-parametric family of relativistic scalar field theories living in a one-time one-space Minkowski space-time which encompasses two coupled scalar fields. Among the static solutions of the model two kinds of topological kinks are distinguished in a precise range of the family parameter. In that regime there exists one unstable kink exhibiting only one non-null component of the scalar field. Another type of topological kink solutions, stable in this case, includes two different kinks for which the two components of the scalar field are non-null. Both one-component and two-component topological kinks are accompanied by their antikink partners. The decay of the unstable kink to one of the stable solutions plus radiation is numerically computed. The pair of stable two-component kinks living
respectively on upper and lower semi-ellipses in the field space belongs to the same topological sector in the configuration space and provides an ideal playground to address several scattering events involving one kink and either its own antikink or the antikink of the other stable kink. By means of numerical analysis we shall find and describe interesting physical phenomena. Bion (kink–antikink oscillations) formation, kink reflection, kink–antikink annihilation, kink transmutation and resonances are examples of these types of events. The appearance of these phenomena emerging in the kink–antikink scattering depends critically on the initial collision velocity and the chosen value of the coupling constant parametrizing the family of MSTB models.MINDECO grant MTM2014-57129-C2-1-P and Junta de Castilla y León grants VA057U16 and BU229P18
Egyptian blue and/or atacamite in an ancient egyptian coffin
This work deals with the composition of the blue and green pigments used in the wooden sarcophagus studied by Abdelaal et al. and published in 2014 in this journal. From the published data, a degradation of the originally used Egyptian blue pigment is proposed. The presence of chlorine in the pigment deduced from SEM-EDS analyses and the greenish hue observed point to the formation of a certain amount of atacamite (or one of its polymorphs, paratacamite or clionoatacamite) because of the Egyptian blue degradation process named copper chloride cancer.Postprint (author's final draft
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