1,090 research outputs found
On the capture of dark matter by neutron stars
We calculate the number of dark matter particles that a neutron star
accumulates over its lifetime as it rotates around the center of a galaxy, when
the dark matter particle is a self-interacting boson but does not
self-annihilate. We take into account dark matter interactions with baryonic
matter and the time evolution of the dark matter sphere as it collapses within
the neutron star. We show that dark matter self-interactions play an important
role in the rapid accumulation of dark matter in the core of the neutron star.
We consider the possibility of determining an exclusion region of the parameter
space for dark matter mass and dark matter interaction cross sections based on
the observation of old neutron stars with strong dark matter self-interactions.
We show that for a dark matter density of GeV/cm and dark matter
mass less than approximately 10 GeV, there is a potential exclusion
region for dark matter interactions with nucleons that is three orders of
magnitude more stringent than without self-interactions. The potential
exclusion region for dark matter self-interaction cross sections is many orders
of magnitude stronger than the current Bullet Cluster limit. For example, for
high dark matter density regions, we find that for GeV when the
dark matter interaction cross section with the nucleons ranges from
cm to cm, the dark matter
self-interaction cross section limit is cm,
which is about ten orders of magnitude stronger than the Bullet Cluster limit.Comment: 12 pages, 9 figures, v2. change in treatment of dark matter collapse
in neutron star, conclusions changed; v3. minor revisions of text for
clarification, added references, v4. version accepted for publication in JCA
Researcher as Artist/Artist as Researcher
This is a postmodern article that is nontraditional in its form, content, and mode of representation. Upon recognizing that we share interests and common experiences as artists, we decided to collect life history information from each other about our artistic experiences. Thus we have become, simultaneously, "the researched" and "the re searcher." In these conversations, we explore the ways in which we were each guided by our past, very strong aesthetic and artistic experiences. We also include the voices of other researchers and artists in our conversations as we explore the influences of art in the formation of our worldviews.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68774/2/10.1177_107780049500100107.pd
Standard Model baryogenesis through four-fermion operators in braneworlds
We study a new baryogenesis scenario in a class of braneworld models with low
fundamental scale, which typically have difficulty with baryogenesis. The
scenario is characterized by its minimal nature: the field content is that of
the Standard Model and all interactions consistent with the gauge symmetry are
admitted. Baryon number is violated via a dimension-6 proton decay operator,
suppressed today by the mechanism of quark-lepton separation in extra
dimensions; we assume that this operator was unsuppressed in the early Universe
due to a time-dependent quark-lepton separation. The source of CP violation is
the CKM matrix, in combination with the dimension-6 operators. We find that
almost independently of cosmology, sufficient baryogenesis is nearly impossible
in such a scenario if the fundamental scale is above 100 TeV, as required by an
unsuppressed neutron-antineutron oscillation operator. The only exception
producing sufficient baryon asymmetry is a scenario involving
out-of-equilibrium c quarks interacting with equilibrium b quarks.Comment: 39 pages, 5 figures v2: typos, presentational changes, references and
acknowledgments adde
The Middle Way: East Asian masters students’ perceptions of critical argumentation in U.K. universities.
The paper explores the learning experiences of East Asian masters students in dealing with Western academic norms of critical thinking in classroom debate and assignment writing. The research takes a cultural approach, and employs grounded theory and case study methodology, the aims being for students to explain their perceptions of their personal learning journeys. The data suggest that the majority of students interviewed rejected full academic acculturation into Western norms of argumentation. They instead opted for a ‘Middle Way’ that synergizes the traditional cultural academic values held by many East Asian students with those elements of Western academic norms that are perceived to be aligned with these. This is a relatively new area of research which represents a challenge for British lecturers and students
Waterfowl recently infected with low pathogenic avian influenza exhibit reduced local movement and delayed migration
Understanding relationships between infection and wildlife movement patterns is important for predicting pathogen spread, especially for multispecies pathogens and those that can spread to humans and domestic animals, such as avian influenza viruses (AIVs). Although infection with low pathogenic AIVs is generally considered asymptomatic in wild birds, prior work has shown that influenza-infected birds occasionally delay migration and/or reduce local movements relative to their uninfected counterparts. However, most observational research to date has focused on a few species in northern Europe; given that influenza viruses are widespread globally and outbreaks of highly pathogenic strains are increasingly common, it is important to explore influenza–movement relationships across more species and regions. Here, we used telemetry data to investigate relationships between influenza infection and movement behavior in 165 individuals from four species of North American waterfowl that overwinter in California, USA. We studied both large-scale migratory and local overwintering movements and found that relationships between influenza infection and movement patterns varied among species. Northern pintails (Anas acuta) with antibodies to avian influenza, indicating prior infection, made migratory stopovers that averaged 12 days longer than those with no influenza antibodies. In contrast, greater white-fronted geese (Anser albifrons) with antibodies to avian influenza made migratory stopovers that averaged 15 days shorter than those with no antibodies. Canvasbacks (Aythya valisineria) that were actively infected with influenza upon capture in the winter delayed spring migration by an average of 28 days relative to birds that were uninfected at the time of capture. At the local scale, northern pintails and canvasbacks that were actively infected with influenza used areas that were 7.6 and 4.9 times smaller than those of uninfected ducks, respectively, during the period of presumed active influenza infection. We found no evidence for an influence of active influenza infection on local movements of mallards (Anas platyrhynchos). These results suggest that avian influenza can influence waterfowl movements and illustrate that the relationships between avian influenza infection and wild bird movements are context- and species-dependent. More generally, understanding and predicting the spread of multihost pathogens requires studying multiple taxa across space and time
Minimal Composite Higgs Model with Light Bosons
We analyze a composite Higgs model with the minimal content that allows a
light Standard-Model-like Higgs boson, potentially just above the current LEP
limit. The Higgs boson is a bound state made up of the top quark and a heavy
vector-like quark. The model predicts that only one other bound state may be
lighter than the electroweak scale, namely a CP-odd neutral scalar. Several
other composite scalars are expected to have masses in the TeV range. If the
Higgs decay into a pair of CP-odd scalars is kinematically open, then this
decay mode is dominant, with important implications for Higgs searches. The
lower bound on the CP-odd scalar mass is loose, in some cases as low as
100 MeV, being set only by astrophysical constraints.Comment: 33 pages, latex. Corrections in eqs. 3.21, 3.23, 4.1, 4.5-10. One
figure adde
Special Supplemental Nutrition Program for Women, Infants, and Children Participant Grocery Store Purchases during the COVID-19 Pandemic in North Carolina
Background: Families participating in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) experienced barriers to accessing healthy food during the COVID-19 pandemic, but we do not yet understand how WIC participant food purchases shifted during the pandemic. Objectives: We aimed to describe the association between the initial shock of the pandemic in March 2020 and WIC shoppers’ food purchases and changes in purchases before and during the pandemic at a top grocery chain and examine differences in these relationships by duration of WIC use. Methods: We used longitudinal food transaction data from WIC shoppers (n = 2,989,116 shopper-month observations from 175,081 unique WIC shoppers) from 496 stores in a top grocery store chain in North Carolina between October 2019 and May 2021. We used an interrupted time series design to describe the following: 1) the relationship between the initial shock of the pandemic and WIC shopper food purchases and 2) differences in purchases before and during the pandemic. To assess differences in purchases between shoppers consistently using WIC electronic benefit transfer (EBT) cards and shoppers starting or stopping WIC EBT use during the pandemic, we used models stratified by WIC group. Primary outcomes were share (%) of total calories purchased from fruits, vegetables, nuts, and legumes (FV), processed foods, and sugar-sweetened beverages (SSBs). Results: We observed small decreases in the share of total calories from FV (−0.4%) and small increases in the share of calories from processed food (1.1%) and SSBs (0.5%) purchased at this retailer when comparing the pre and post March 2020 periods. Compared with shoppers that started or stopped using WIC benefits during the pandemic, shoppers that used WIC benefits consistently had slightly higher FV and lower processed food and SSB purchases at this retailer. Conclusions: Future studies should examine whether additional supports for nutrient-dense food choices may be needed for families with low incomes in public health emergencies
On the Spontaneous CP Breaking at Finite Temperature in a Nonminimal Supersymmetric Standard Model
We study the spontaneous CP breaking at finite temperature in the Higgs
sector in the Minimal Supersymmetric Standard Model with a gauge singlet. We
consider the contribution of the standard model particles and that of stops,
charginos, neutralinos, charged and neutral Higgs boson to the one-loop
effective potential. Plasma effects for all bosons are also included. Assuming
CP conservation at zero temperature, so that experimental constraints coming
from, {\it e.g.}, the electric dipole moment of the neutron are avoided, and
the electroweak phase transition to be of the first order and proceeding via
bubble nucleation, we show that spontaneous CP breaking cannot occur inside the
bubble mainly due to large effects coming from the Higgs sector. However,
spontaneous CP breaking can be present in the region of interest for the
generation of the baryon asymmetry, namely inside the bubble wall. The
important presence of very tiny explicit CP violating phases is also commented.Comment: 28 pages, 4 figures available upon request, DFPD 94/TH/38 and SISSA
94/81-A preprint
Supernova Bounds on Majoron-emitting decays of light neutrinos
Neutrino masses arising from the spontaneous violation of ungauged
lepton-number are accompanied by a physical Goldstone boson, generically called
Majoron. In the high-density supernova medium the effects of Majoron-emitting
neutrino decays are important even if they are suppressed in vacuo by small
neutrino masses and/or small off-diagonal couplings. We reconsider the
influence of these decays on the neutrino signal of supernovae in the light of
recent Super-Kamiokande data on solar and atmospheric neutrinos. We find that
majoron-neutrino coupling constants in the range 3\times 10^{-7}\lsim g\lsim
2\times 10^{-5} or g \gsim 3 \times 10^{-4} are excluded by the observation
of SN1987A. Then we discuss the potential of Superkamiokande and the Sudbury
Neutrino Observatory to detect majoron neutrino interactions in the case of a
future galactic supernova. We find that these experiments could probe majoron
neutrino interactions with improved sensitivity.Comment: 28 pages, 5 figure
Group Formation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68807/2/10.1177_104649647300400206.pd
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