Fracture toughness in fibrous materials

In the present paper, a fiber bundle model in (1+1)-dimensions that simulates the rupture process of a fibrous material pulled by an uniaxial force F is analyzed. In this model the load of a broken fiber is shifted in equal portions onto the nearest unbroken fibers. The force-displacement diagram is obtained for several traction velocities v and temperatures t. Also, it is shown how the fracture toughness $K_c$ changes with the traction velocity v and with the temperature t. In this paper it is shown that the rupture process is strongly dependent on temperature t and on velocity v.Comment: 4 pages, 4 figures.eps, Revte

Cuscuton kinks and branes

In this paper, we study a peculiar model for the scalar field. We add the cuscuton term in a standard model and investigate how this inclusion modifies the usual behavior of kinks. We find the first order equations and calculate the energy density and the total energy of the system. Also, we investigate the linear stability of the model, which is governed by a Sturm-Liouville eigenvalue equation that can be transformed in an equation of the Shcr\"odinger type. The model is also investigated in the braneworld scenario, where a first order formalism is also obtained and the linear stability is investigated.Comment: 21 pages, 9 figures; content added; to appear in NP

Experimental Realization of the Fuse Model of Crack Formation

In this work, we present an experimental investigation of the fuse model. Our main goal was to study the influence of the disorder on the fracture process. The experimental apparatus used consisted of an $L\times L$ square lattice with fuses placed on each bond of the lattice. Two types of materials were used as fuses: copper and steel wool wires. The lattice composed only by copper wires varied from a weakly disordered system to a strongly disordered one. The lattice formed only by steel wool wires corresponded to a strongly disordered one. The experimental procedure consisted of applying a potential difference V to the lattice and measuring the respective current I. The characteristic function $I(V)$ obtained was investigated in order to find the scaling law dependence of the voltage and the current on the system size $L$ when the disorder was changed. Our results show that the scaling laws are only verified for the disordered regime.Comment: 4 pages, 8 figures.ep

Compact Vortices

We study a family of Maxwell-Higgs models, described by the inclusion of a function of the scalar field that represent generalized magnetic permeability. We search for vortex configurations which obey first-order differential equations that solve the equations of motion. We first deal with the asymptotic behavior of the field configurations, and then implement a numerical study of the solutions, the energy density and the magnetic field. We work with the generalized permeability having distinct profiles, giving rise to new models, and we investigate how the vortices behave, compared with the solutions of the corresponding standard models. In particular, we show how to build compact vortices, that is, vortex solutions with the energy density and magnetic field vanishing outside a compact region of the plane.Comment: 9 pages, 12 figures; v2, motivation and references adde

First Order Formalism for Generalized Vortices

This work develops a procedure to find classes of Lagrangian densities that describe generalizations of the Abelian Maxwell-Higgs, the Chern-Simons-Higgs and the Maxwell-Chern-Simons-Higgs models. The investigation focuses on the construction of models that support vortices that obey the stressless condition and lead to first order differential equations which are compatible with the equations of motion. The results induce the appearance of constraints that restrict the choice of the Lagrangian densities, but help us to introduce an auxiliary function that allows to calculate the energy without knowing the explicit form of the solutions.Comment: 36 pages, 10 figures; new version, to appear in NP

Fake news: a technological approach to proving the origins of content, using blockchains

In this paper, we introduce a prototype of an innovative technology for proving the origins of captured digital media. In an era of fake news, when someone shows us a video or picture of some event, how can we trust its authenticity? It seems the public no longer believe that traditional media is a reliable reference of fact, perhaps due, in part, to the onset of many diverse sources of conflicting information, via social media. Indeed, the issue of ‘fake’ reached a crescendo during the 2016 US Presidential Election, when the winner, Donald Trump, claimed that the New York Times was trying to discredit him by pushing disinformation. Current research into overcoming the problem of fake news does not focus on establishing the ownership of media resources used in such stories - the blockchain-based application introduced in this article is technology that is capable of indicating the authenticity of digital media. Put simply; by using the trust mechanisms of blockchain technology, the tool can show, beyond doubt, the provenance of any source of digital media, including images used out of context in attempts to mislead. Although the application is an early prototype and its capability to find fake resources is Peer Review Only/Not for Distributionsomewhat limited, we outline future improvements that would overcome such limitations. Furthermore, we believe our application (and its use of blockchain technology and standardised metadata), introduces a novel approach to overcoming falsities in news reporting and the provenance of media resources used therein. However, while our application has the potential to be able to verify the originality of media resources, we believe technology is only capable of providing a partial solution to fake news. That is because it is incapable of proving the authenticity of a news story as a whole. We believe that takes human skills

The importance of the mixed phase in hybrid stars built with the Nambu-Jona-Lasinio model

We investigate the structure of hybrid stars based on two different constructions: one is based on the Gibbs condition for phase coexistence and considers the existence of a mixed phase (MP), and the other is based on the Maxwell construction and no mixed phase is obtained. The hadron phase is described by the non-linear Walecka model (NLW) and the quark phase by the Nambu-Jona-Lasinio model (NJL). We conclude that the masses and radii obtained are model dependent but not significantly different for both constructions.Comment: 8 pages, 7 figures, 3 table

Vortices in Maxwell-Higgs models with a global factor

This paper deals with planar vortices in a generalized model that presents a global factor which depends on the scalar field in the Nielsen-Olesen Lagrange density. We show that the system supports a first order framework. Contrary to what occurs with kinks in the line, planar vortices require the presence of constraints that brings modifications into the first order equations. Novel features are unveiled, such as finite energy configurations with infinite energy density at the origin and the presence of parameters that modifies the energy, keeping the solutions unchanged.Comment: 6 pages, 4 figure