194 research outputs found
Spontaneous Symmetry Breakdown and Critical Perspectives of Higgs Mechanism
The foundations of the mass generation mechanism of particles are reviewed.
The Spontaneous Symmetry Breaking (SSB) process within the standard model (SM)
and the minimal supersymmetric standard model (MSSM) is used to explore the
present status of the Higgs Mechanism along with the constraints in detecting
the Higgs particles in experiments. The possible explanations and
generalizations for the case that the Higgs particles should not appear or to
couple the Higgs Mechanism (because of their gravitational nature of
interaction) are also iscussed in detail in view of the Higgs field gravity.Comment: 13 pages, no figures. Final version based on original to appear in
the Indian Journal of Physic
Black Hole Solutions and Pressure Terms in Induced Gravity with Higgs Potential
We study the quintessential properties of the Black Hole solutions in a
scalar--tensor theory of gravity with Higgs potential in view of the static and
spherically symmetric line element. In view of our earlier results,
Reissner--Nordstr\"om-like and Schwarzschild Black Hole solutions are derived
with the introduction of a series-expansion method to solve the field equations
without and with Higgs field mass. The physical consequences of the Black Hole
solutions and the solutions obtained in the weak field limit are discussed in
detail by the virtue of the equation-of-state parameter, the scalar-field
excitations and the geodesic motion. The appearance of naked singularities is
also discussed together with the dependence of Black Hole horizons on the field
excitations, which are themselves dependent on pressure terms which effectively
screen the mass terms. A possible connection to flat rotation curves following
the interaction with the scalar field is also presented in the weak field limit
of gravity, together with a discussion of dynamical effects of scalar fields
and pressure terms on mass.Comment: 28 pages, 4 figures, contents and figures modified, major revision,
results are unchanged, published in Classical and Quantum Gravit
The well-posedness of the Cauchy problem for self-interacting vector fields
We point out that the initial-value (Cauchy) problem for self-interactingvector fields presents the same well-posedness issues as for first-orderderivative self-interacting scalar fields (often referred to as -essence).For the latter, suitable strategies have been employed in the last few years tosuccessfully evolve the Cauchy problem at the level of the infrared theory,without the need for an explicit ultraviolet completion. We argue that the verysame techniques can also be applied to self-interacting vector fields, avoidinga number of issues and "pathologies" recently found in the literature.<br
Well-posed evolution of field theories with anisotropic scaling: the Lifshitz scalar field in a black hole space-time
Partial differential equations exhibiting an anisotropic scaling between
space and time -- such as those of Horava-Lifshitz gravity -- have a dispersive
nature. They contain higher-order spatial derivatives, but remain second order
in time. This is inconvenient for performing long-time numerical evolutions, as
standard explicit schemes fail to maintain convergence unless the time step is
chosen to be very small. In this work, we develop an implicit evolution scheme
that does not suffer from this drawback, and which is stable and second-order
accurate. As a proof of concept, we study the numerical evolution of a Lifshitz
scalar field on top of a spherically symmetric black hole space-time. We
explore the evolution of a static pulse and an (approximately) ingoing
wave-packet for different strengths of the Lorentz-breaking terms, accounting
also for the effect of the angular momentum eigenvalue and the resulting
effective centrifugal barrier. Our results indicate that the dispersive terms
produce a cascade of modes that accumulate in the region in between the Killing
and universal horizons, indicating a possible instability of the latter.Comment: 22 pages, 8 figures, 1 table, comments are welcome
A serial multiplex immunogold labeling method for identifying peptidergic neurons in connectomes.
This is the final version of the article.Available from eLife Sciences Publications via the DOI in this record.Electron microscopy-based connectomics aims to comprehensively map synaptic connections in neural tissue. However, current approaches are limited in their capacity to directly assign molecular identities to neurons. Here, we use serial multiplex immunogold labeling (siGOLD) and serial-section transmission electron microscopy (ssTEM) to identify multiple peptidergic neurons in a connectome. The high immunogenicity of neuropeptides and their broad distribution along axons, allowed us to identify distinct neurons by immunolabeling small subsets of sections within larger series. We demonstrate the scalability of siGOLD by using 11 neuropeptide antibodies on a full-body larval ssTEM dataset of the annelid Platynereis. We also reconstruct a peptidergic circuitry comprising the sensory nuchal organs, found by siGOLD to express pigment-dispersing factor, a circadian neuropeptide. Our approach enables the direct overlaying of chemical neuromodulatory maps onto synaptic connectomic maps in the study of nervous systems.The research leading to these results received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/European Research Council Grant Agreement 260821. This project is supported by the Marie Curie ITN "Neptune", GA 317172, funded under the FP7, PEOPLE Work Programme of the European Commission
Neuronal connectome of a sensory-motor circuit for visual navigation.
This is the final version of the article. Available from eLife Sciences Publications via the DOI in this record.Animals use spatial differences in environmental light levels for visual navigation; however, how light inputs are translated into coordinated motor outputs remains poorly understood. Here we reconstruct the neuronal connectome of a four-eye visual circuit in the larva of the annelid Platynereis using serial-section transmission electron microscopy. In this 71-neuron circuit, photoreceptors connect via three layers of interneurons to motorneurons, which innervate trunk muscles. By combining eye ablations with behavioral experiments, we show that the circuit compares light on either side of the body and stimulates body bending upon left-right light imbalance during visual phototaxis. We also identified an interneuron motif that enhances sensitivity to different light intensity contrasts. The Platynereis eye circuit has the hallmarks of a visual system, including spatial light detection and contrast modulation, illustrating how image-forming eyes may have evolved via intermediate stages contrasting only a light and a dark field during a simple visual task.The research leading to these results received
funding from the European Research Council under the European Union's Seventh Framework
Programme (FP7/2007-2013)/European Research Council Grant Agreement 260821
Scalar-field Pressure in Induced Gravity with Higgs Potential and Dark Matter
A model of induced gravity with a Higgs potential is investigated in detail
in view of the pressure components related to the scalar-field excitations. The
physical consequences emerging as an artifact due to the presence of these
pressure terms are analysed in terms of the constraints parting from energy
density, solar-relativistic effects and galactic dynamics along with the dark
matter halos.Comment: 26 pages, 3 figures, Minor revision, Published in JHE
Harmonized Soil Database of Ecuador (HESD): data from 2009 to 2015
One of the largest challenges with soil information
around the world is how to harmonize archived soil data from different
sources and how to make it accessible to soil scientist. In Ecuador, there
have been two major projects that have provided soil information, but the
methodology of these projects, although comparable, did not coincide, especially with respect to how
information was reported. Here, we present a new soil database for Ecuador,
comprising 13 542 soil profiles with 51 713 measured soil horizons, including
92 different edaphic variables. The original data were in a non-editable format
(i.e., PDF), which made it difficult to access and process the information. Our
study provides an integrated framework that combines multiple analytic tools for
automatically converting legacy soil information from an analog format into
usable digital soil mapping inputs across Ecuador. This framework allowed us
to incorporate quantitative information on a broad set of soil properties
and retrieve qualitative information on soil morphological properties
collected in the profile description phase, which is rarely included in soil
databases. We present a new harmonized national soil database using a
specific methodology to preserve relevant information. The national
representativeness of soil information has been enhanced compared with other
international databases, and this new database contributes to filling the
gaps in publicly available soil information across the country. The database
is freely available at
https://doi.org/10.6073/pasta/1560e803953c839e7aedef78ff7d3f6c (Armas
et al., 2022).</p
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