Soliton-like solutions based on geometrically nonlinear Cosserat micropolar elasticity

The Cosserat model generalises an elastic material taking into account the possible microstructure of the elements of the material continuum. In particular, within the Cosserat model the structured material point is rigid and can only experience microrotations, which is also known as micropolar elasticity. We present the geometrically nonlinear theory taking into account all possible interaction terms between the elastic and microelastic structures. This is achieved by considering the irreducible pieces of the deformation gradient and of the dislocation curvature tensor. In addition we also consider the so-called Cosserat coupling term. In this setting we seek soliton type solutions assuming small elastic displacements, however, we allow the material points to experience full rotations which are not assumed to be small. By choosing a particular ansatz we are able to reduce the system of equations to a sine–Gordon type equation which is known to have soliton solutions

Space-time evolution induced by spinor fields with canonical and non-canonical kinetic terms

We study spinor field theories as an origin to induce space-time evolution. Self-interacting spinor fields with canonical and non-canonical kinetic terms are considered in a Friedman-Robertson-Walker universe. The deceleration parameter is calculated by solving the equation of motion and the Friedman equation, simultaneously. It is shown that the spinor fields can accelerate and decelerate the universe expansion. To construct realistic models we discuss the contributions from the dynamical symmetry breaking.Comment: 16 pages, 19 figure

Dark spinor models in gravitation and cosmology

We introduce and carefully define an entire class of field theories based on non-standard spinors. Their dominant interaction is via the gravitational field which makes them naturally dark; we refer to them as Dark Spinors. We provide a critical analysis of previous proposals for dark spinors noting that they violate Lorentz invariance. As a working assumption we restrict our analysis to non-standard spinors which preserve Lorentz invariance, whilst being non-local and explicitly construct such a theory. We construct the complete energy-momentum tensor and derive its components explicitly by assuming a specific projection operator. It is natural to next consider dark spinors in a cosmological setting. We find various interesting solutions where the spinor field leads to slow roll and fast roll de Sitter solutions. We also analyse models where the spinor is coupled conformally to gravity, and consider the perturbations and stability of the spinor.Comment: 43 pages. Several new sections and details added. JHEP in prin

Cancer Survivors’ Health Behaviors and Outcomes: A Population-Based Study of Sexual and Gender Minorities

BACKGROUND: Most case-control studies compare cancer survivors with general population controls without considering sexual orientation or gender identity. This case-control analysis compared health risk behaviors and health outcomes among sexual and gender minority cancer survivors to those of matched sexual and gender minority participants without cancer (controls). METHODS: Using data from the 2014-2021 Behavioral Risk Factor Surveillance System, a population-based sample of 4507 cancer survivors who self-identified as transgender, gay men, bisexual men, lesbian women, or bisexual women were 1:1 propensity score matched, using age at survey, race and ethnicity, marital status, education, access to health care, and US census region. Within each sexual and gender minority group, behaviors and outcomes were compared between survivors and participants without cancer, and survivors\u27 odds ratios and 95% confidence intervals calculated. RESULTS: Gay male survivors had higher odds of depression, poor mental health, limited usual activities, difficulty concentrating, and fair or poor health. Few differences were observed between bisexual male survivors and participants without cancer. Compared with controls, lesbian female survivors had greater odds of overweight-obese status, depression, poor physical health, and fair or poor health. Bisexual female survivors had the highest rates of current smoking, depression, poor mental health, and difficulty concentrating across all sexual and gender minority groups. Statistically significantly different from transgender controls, transgender survivors had greater odds of heavy alcohol use, physical inactivity, and fair or poor health. CONCLUSIONS: This analysis revealed an urgent need to address the high prevalence of engaging in multiple health risk behaviors and not following guidelines to avoid second cancers, additional adverse outcomes, and cancer recurrences among sexual and gender minority cancer survivors

Sharing Fear via Facebook: A Lesson in Political Public Relations

Our study compared the use of fear messages on Facebook by Barack Obama and Mitt Romney during the 2012 U.S. presidential elections. Results show that written fear messages embedded in photographs posted on Facebook by both candidates affected the degree to which those photographs were shared. More specifically, photographs containing written fear messages were shared more often than photographs not containing written fear messages. Furthermore, while the challenging candidate, Mitt Romney, used more photographs containing fear messages, the increase in shares was consistent across candidates. Implications regarding information distribution within communities, public relations practitioners specializing in political campaigning and society as a whole are discusse

Phenomenological covariant approach to gravity

We covariantly modify the Einstein-Hilbert action such that the modified action perturbatively resolves the flat rotational velocity curve of the spiral galaxies and gives rise to the Tully-Fisher relation, and dynamically generates the cosmological constant. This modification requires introducing just a single new universal parameter.Comment: v6: a mistake in deriving the equation of the cosmological constant corrected, refs adde

Negative selection, not receptor editing, is a physiological response of autoreactive thymocytes

Antigen receptor editing—a process of secondary rearrangements of antigen receptor genes in autoreactive lymphocytes—is a well-established tolerance mechanism in B cells, whereas its role in T cells remains controversial. Here, we investigated this issue using a novel Tcra knock-in locus, which ensured appropriate timing of TCRα expression and allowed secondary rearrangements. Under these conditions the only response to self-antigen that could be unambiguously identified was negative selection of CD4/CD8 double positive thymocytes. No evidence could be obtained for antigen-induced TCR editing, whereas replacement of the transgenic TCRα chain by ongoing gene rearrangement occurred in some cells irrespective of the presence or absence of self-antigen

Inflating wormholes in the braneworld models

The braneworld model, in which our Universe is a three-brane embedded in a five-dimensional bulk, allows the existence of wormholes, without any violation of the energy conditions. A fundamental ingredient of traversable wormholes is the violation of the null energy condition (NEC). However, in the brane world models, the stress energy tensor confined on the brane, threading the wormhole, satisfies the NEC. In conventional general relativity, wormholes existing before inflation can be significantly enlarged by the expanding spacetime. We investigate the evolution of an inflating wormhole in the brane world scenario, in which the wormhole is supported by the nonlocal brane world effects. As a first step in our study we consider the possibility of embedding a four-dimensional brane world wormhole into a five dimensional bulk. The conditions for the embedding are obtained by studying the junction conditions for the wormhole geometry, as well as the full set of the five dimensional bulk field equations. For the description of the inflation we adopt the chaotic inflation model. We study the dynamics of the brane world wormholes during the exponential inflation stage, and in the stage of the oscillating scalar field. A particular exact solution corresponding to a zero redshift wormhole is also obtained. The resulting evolution shows that while the physical and geometrical parameters of a zero redshift wormhole decay naturally, a wormhole satisfying some very general initial conditions could turn into a black hole, and exist forever.Comment: 30 pages, no figures, accepted for publication in CQ