Constraining the Break of Spatial Diffeomorphism Invariance with Planck Data

The current most accepted paradigm for the early universe cosmology, the inflationary scenario, shows a good agreement with the recent Cosmic Microwave Background (CMB) and polarization data. However, when the inflation consistency relation is relaxed, these observational data exclude a larger range of red tensor tilt values, prevailing the blue ones which are not predicted by the minimal inflationary models. Recently, it has been shown that the assumption of spatial diffeomorphism invariance breaking (SDB) in the context of an effective field theory of inflation leads to interesting observational consequences. Among them, the possibility of generating a blue tensor spectrum, which can recover the specific consistency relation of the String Gas Cosmology, for a certain choice of parameters. We use the most recent CMB data to constrain the SDB model and test its observational viability through a Bayesian analysis assuming as reference an extended LCDM+tensor perturbation model, which considers a power-law tensor spectrum parametrized in terms of the tensor-to-scalar ratio, r, and the tensor spectral index, n_t. If the inflation consistency relation is imposed, r = -8n_t, we obtain a strong evidence in favor of the reference model whereas if such relation is relaxed, a weak evidence in favor of the model with diffeomorphism breaking is found. We also use the same CMB data set to make an observational comparison between the SDB model, standard inflation and String Gas Cosmology

Particle Production in Ekpyrotic Scenarios

We consider Parker particle production in the Ekpyrotic scenario (in particular in the New Ekpyrotic model) and show that the density of particles produced by the end of the phase of Ekpyrotic contraction is sufficient to lead to a hot state of matter after the bounce. Hence, no separate reheating mechanism is necessary.Comment: 8 page

Nonresonance impulsive higher order functional nonconvex-valued differential inclusions

In this paper, the authors investigate the existence of solutions for nonresonance impulsive higher order functional differential inclusions in Banach spaces with nonconvex valued right hand side. They present two results. In the first one, they rely on a fixed point theorem for contraction multivalued maps due to Covitz and Nadler, and for the second one, they use Schaefer's fixed point theorem combined with lower semi-continuous multivalued operators with decomposable values

Magnetic transitions and magnetodielectric effect in the antiferromagnet SrNdFeO4_4

We investigated the magnetic phase diagram of single crystals of SrNdFeO$_{4}$ by measuring the magnetic properties, the specific heat and the dielectric permittivity. The system has two magnetically active ions, Fe$^{3+}$ and Nd$^{3+}$. The Fe$^{3+}$ spins are antiferromagnetically ordered below 360 K with the moments lying in the ab-plane, and undergo a reorientation transition at about 35-37 K to an antiferromagnetic order with the moments along the c-axis. A short-range, antiferromagnetic ordering of Nd$^{3+}$ along the c-axis was attributed to the reorientation of Fe$^{3+}$ followed by a long-range ordering at lower temperature [S. Oyama {\it et al.} J. Phys.: Condens. Matter. {\bf 16}, 1823 (2004)]. At low temperatures and magnetic fields above 8 T, the Nd$^{3+}$ moments are completely spin-polarized. The dielectric permittivity also shows anomalies associated with spin configuration changes, indicating that this compound has considerable coupling between spin and lattice. A possible magnetic structure is proposed to explain the results.Comment: 8 pages, 10 figures, submitted to PR

Quantum noise of non-ideal Sagnac speed meter interferometer with asymmetries

The speed meter concept has been identified as a technique that can potentially provide laser-interferometric measurements at a sensitivity level which surpasses the Standard Quantum Limit (SQL) over a broad frequency range. As with other sub-SQL measurement techniques, losses play a central role in speed meter interferometers and they ultimately determine the quantum noise limited sensitivity that can be achieved. So far in the literature, the quantum noise limited sensitivity has only been derived for lossless or lossy cases using certain approximations (for instance that the arm cavity round trip loss is small compared to the arm cavity mirror transmission). In this article we present a generalised, analytical treatment of losses in speed meters that allows accurate calculation of the quantum noise limited sensitivity of Sagnac speed meters with arm cavities. In addition, our analysis allows us to take into account potential imperfections in the interferometer such as an asymmetric beam splitter or differences of the reflectivities of the two arm cavity input mirrors. Finally,we use the examples of the proof-of-concept Sagnac speed meter currently under construction in Glasgow and a potential implementation of a Sagnac speed meter in the Einstein Telescope (ET) to illustrate how our findings affect Sagnac speed meters with meter- and kilometre-long baselines.Comment: 22 pages, 8 figures, 1 table, (minor corrections and changes made to text and figures in version 2

On the oscillatory behavior of even order neutral delay dynamic equations on time-scales

We establish some new criteria for the oscillation of the even order neutral dynamic equation \begin{equation*} \left( a(t)\left( \left( x(t)-p(t)x(\tau (t))\right) ^{\Delta^{n-1}}\right) ^{\alpha }\right) ^{\Delta }+q(t)\left( x^{\sigma}(g(t))\right) ^{\lambda }=0 \end{equation*} on a time scale $\mathbb{T}$, where $n \geq 2$ is even, $\alpha$ and $\lambda$ are ratios of odd positive integers, $a$, $p$ and $q$ are real valued positive rd-continuous functions defined on $\mathbb{T}$, and $g$ and $\tau$ are real valued rd-continuous functions on $\mathbb{T}$. Examples illustrating the results are included

Dissipationless Spin Current between Two Coupled Ferromagnets

We demonstrate the general principle which states that a dissipationless spin current flows between two coupled ferromagnets if their magnetic orders are misaligned. This principle applies regardless the two ferromagnets are metallic or insulating, and also generally applies to bulk magnetic insulators. On a phenomenological level, this principle is analogous to Josephson effect, and yields a dissipationless spin current that is independent from scattering. The microscopic mechanisms for the dissipationless spin current depend on the systems, which are elaborated in details. A uniform, static magnetic field is further proposed to be an efficient handle to create the misaligned configuration and stabilize the dissipationless spin current.Comment: 10 pages, 5 figure

Magnetic Tweed Contrast In Ferromagnetic Shape Memory Alloys

Recently, ferromagnetic martensite, specifically ferromagnetic shape memory alloys (FMSMAs), have received renewed attention because of their large domain motion induced magnetostrictive strains. In the low temperature phase of these alloys, 90◦ magnetic domain walls are simultaneously elastic twin boundaries. Above the temperature at which these alloys undergo a near second order martensitic transformation, their microstructure as observed by two-beam TEM methods, consists of the well known tweed contrast. This structure represents a random mixture of incipient twins of the martensitic phase. The transformation hysteresis of Co-Ni-Ga FMSMAs is quite small. In addition, the alloy is elastically soft similar to others that undergo a near second order martensitic transformation. Therefore, it is possible that magnetic tweed be observed in this alloy. This paper reports on its observation by conventional TEM, electron diffraction and Lorentz microscopy