443 research outputs found
Grand unification through gravitational effects
We systematically study the unification of gauge couplings in the presence of
(one or more) effective dimension-5 operators cHGG/4MPl, induced into the grand
unified theory by gravitational interactions at the Planck scale MPl. These
operators alter the usual condition for gauge coupling unification, which can,
depending on the Higgs content H and vacuum expectation value, result in
unification at scales MX significantly different than naively expected. We find
non-supersymmetric models of SU(5) and SO(10) unification, with natural Wilson
coefficients c, that easily satisfy the constraints from proton decay.
Furthermore, gauge coupling unification at scales as high as the Planck scale
seems feasible, possibly hinting at simultaneous unification of gauge and
gravitational interactions. In the Appendix we work out the group theoretical
aspects of this scenario for SU(5) and SO(10) unified groups in detail; this
material is also relevant in the analysis of non-universal gaugino masses
obtained from supergravity.Comment: 27 pages, 5 figures, 8 tables, 1 appendix, revtex; v2: introduction
and conclusion expanded, references added, minor changes, version published
in PR
Monsters, black holes and the statistical mechanics of gravity
We review the construction of monsters in classical general relativity.
Monsters have finite ADM mass and surface area, but potentially unbounded
entropy. From the curved space perspective they are objects with large proper
volume that can be glued on to an asymptotically flat space. At no point is the
curvature or energy density required to be large in Planck units, and quantum
gravitational effects are, in the conventional effective field theory
framework, small everywhere. Since they can have more entropy than a black hole
of equal mass, monsters are problematic for certain interpretations of black
hole entropy and the AdS/CFT duality.
In the second part of the paper we review recent developments in the
foundations of statistical mechanics which make use of properties of
high-dimensional (Hilbert) spaces. These results primarily depend on kinematics
-- essentially, the geometry of Hilbert space -- and are relatively insensitive
to dynamics. We discuss how this approach might be adopted as a basis for the
statistical mechanics of gravity. Interestingly, monsters and other highly
entropic configurations play an important role.Comment: 9 pages, 4 figures, revtex; invited Brief Review to be published in
Modern Physics Letters
Enhancing the Psychology Curriculum Through Service Learning
Educators in psychology should aspire to encourage students’ holistic growth in academic, personal, and civic domains. We propose that service learning is the most potent pedagogy for developing well-rounded, psychologically literate citizens capable of meeting the goals for the undergraduate psychology major. This article defines service learning, delineates the rationales for service learning, and summarizes research demonstrating the efficacy of this pedagogical approach. The article also describes the learning objectives derived from the American Psychological Association Guidelines for the Undergraduate Major (Version 2.0, 2013), with an emphasis on the ways in which service learning contributes to academic learning, civic learning, and personal growth. Finally, the article illustrates the four types of service learning, and it provides a concrete example for structuring reflection in order to connect community experiences with course content in a service learning psychology course
Dark radiation as a signature of dark energy
We propose a simple dark energy model with the following properties: the
model predicts a late-time dark radiation component that is not ruled out by
current observational data, but which produces a distinctive time-dependent
equation of state w(z) for z < 3. The dark energy field can be coupled strongly
enough to Standard Model particles to be detected in colliders, and the model
requires only modest additional particle content and little or no fine-tuning
other than a new energy scale of order milli-electron volts.Comment: 6 pages, 5 figures, revtex; v2: footnote 3 added, minor changes,
published versio
Topological Methods for Exploring Low-density States in Biomolecular Folding Pathways
Characterization of transient intermediate or transition states is crucial
for the description of biomolecular folding pathways, which is however
difficult in both experiments and computer simulations. Such transient states
are typically of low population in simulation samples. Even for simple systems
such as RNA hairpins, recently there are mounting debates over the existence of
multiple intermediate states. In this paper, we develop a computational
approach to explore the relatively low populated transition or intermediate
states in biomolecular folding pathways, based on a topological data analysis
tool, Mapper, with simulation data from large-scale distributed computing. The
method is inspired by the classical Morse theory in mathematics which
characterizes the topology of high dimensional shapes via some functional level
sets. In this paper we exploit a conditional density filter which enables us to
focus on the structures on pathways, followed by clustering analysis on its
level sets, which helps separate low populated intermediates from high
populated uninteresting structures. A successful application of this method is
given on a motivating example, a RNA hairpin with GCAA tetraloop, where we are
able to provide structural evidence from computer simulations on the multiple
intermediate states and exhibit different pictures about unfolding and
refolding pathways. The method is effective in dealing with high degree of
heterogeneity in distribution, capturing structural features in multiple
pathways, and being less sensitive to the distance metric than nonlinear
dimensionality reduction or geometric embedding methods. It provides us a
systematic tool to explore the low density intermediate states in complex
biomolecular folding systems.Comment: 23 pages, 6 figure
Coordinated Crowd Simulation With Topological Scene Analysis
This paper proposes a new algorithm to produce globally coordinated crowds in an environment with multiple paths and obstacles. Simple greedy crowd control methods easily lead to congestion at bottlenecks within scenes, as the characters do not cooperate with one another. In computer animation, this problem degrades crowd quality especially when ordered behaviour is needed, such as soldiers marching towards a castle. Similarly, in applications such as real-time strategy games, this often causes player frustration, as the crowd will not move as efficiently as it should. Also, planning of building would usually require visualization of ordered evacuation to maximize the flow. Planning such globally coordinated crowd movement is usually labour intensive. Here, we propose a simple solution that is easy to use and efficient in computation. First, we compute the harmonic field of the environment, taking into account the starting points, goals and obstacles. Based on the field, we represent the topology of the environment using a Reeb Graph, and calculate the maximum capacity for each path in the graph. With the harmonic field and the Reeb Graph, path planning of crowd can be performed using a lightweight algorithm, such that any blocking of one another's paths is minimized. Comparing to previous methods, our system can synthesize globally coordinated crowd with smooth and efficient movement. It also enables control of the crowd with high-level parameters such as the degree of cooperation and congestion. Finally, the method is scalable to thousands of characters with minimal impact to computation time. It is best applied in interactive crowd synthesis systems such as animation designs and real-time strategy games
Social competitiveness and plasticity of neuroendocrine function in old age: influence of neonatal novelty exposure and maternal care reliability
Abstract Early experience is known to have a profound impact on brain and behavioral function later in life. Relatively few studies, however, have examined whether the effects of early experience remain detectable in the aging animal. Here, we examined the effects of neonatal novelty exposure, an early stimulation procedure, on late senescent rats' ability to win in social competition. During the first 3 weeks of life, half of each litter received daily 3-min exposures to a novel environment while the other half stayed in the home cage. At 24 months of age, pairs of rats competed against each other for exclusive access to chocolate rewards. We found that novelty-exposed rats won more rewards than home-staying rats, indicating that early experience exerts a life-long effect on this aspect of social dominance. Furthermore, novelty-exposed but not home-staying rats exhibited habituation of corticosterone release across repeated days of social competition testing, suggesting that early experience permanently enhances plasticity of the stress response system. Finally, we report a surprising finding that across individual rat families, greater effects of neonatal novelty exposure on stress response plasticity were found among families whose dams provided more reliable, instead of a greater total quantity of, maternal care
Evaluation of Warm Season Annual Forages for Livestock: Biomass and Cost of Production
Seventeen warm season annual forage options were evaluated as livestock feed to be grazed, hayed, ensiled, or left as a cover crop. Treatments were planted in mid-May and terminated in late September with one harvest for silage, two hay cuttings, and three grazing rotations. One additional treatment was unharvested to serve as a cover crop. Biomass production and cost to produce final outputs were determined. Even with restricted rainfall during the summer months in 2020, the growth for the chosen forage options was at least 1,500 lb of dry matter (DM) per acre, with the exception of sunÂflowers that had the lowest biomass production. Biomass production was the greatest for the forages that were left in the field as cover crop, followed by hay, then grazed, with the lowest biomass measured for the silage harvest. Monocultures of grass and sunn hemp produced as much biomass as multi-species blends that included grass or sunn hemp. Adding a high-producing grass species to sunflower and cowpeas increased biomass production compared to the respective monoculture. Regardless of harvest method, monocultures of cowpea and the blend of pearl millet + cowpea cost the most per unit of production. The lowest costs per unit of production for all harvest methods were found in three treatments: a monoculture of sorghum-sudan, the low seeding rate of pearl millet, and the blend of sorghum-sudan + sunn hemp
Molecular and morphometric variation in European populations of the articulate brachiopod <i>Terebeatulina retusa</i>
Molecular and morphometric variation within and between population samples of the articulate brachiopod <i>Terebratulina</i> spp., collected in 1985-1987 from a Norwegian fjord, sea lochs and costal sites in western Scotland, the southern English Channel (Brittany) and the western Mediterranean, were measured by the analysis of variation in the lengths of mitochondrial DNA (mtDNA) fragments produced by digestion with nine restriction endonucleases and by multivariate statistical analysis of six selected morphometric parameters. Nucleotide difference within each population sample was high. Nucleotide difference between population samples from the Scottish sites, both those that are tidally contiguous and those that appear to be geographically isolated, were not significantly different from zero. Nucleotide differences between the populations samples from Norway, Brittany, Scotland and the western Mediterranean were also very low. Morphometric analysis confirmed the absence of substantial differentiation
- …