1,255 research outputs found
Mentoring as a Statistical Educator in a Christian College
In this paper, I present principles based on more than thirty years of intentional mentoring as a statistical educator in a Christian college. I believe this mentoring has been enhanced due to the setting- a Christian college, and the discipline - statistics. I discuss distinctives of the Christian college setting that positively impact mentoring in any discipline with respect to the mentor, the mentee, and the pervading campus atmosphere. I focus on mentoring as a statistical educator by specifically considering the following: attracting students to the discipline of statistics, preparing students for careers using statistics, and preparing students for graduate study in a statistics related field. For each, I consider principles of successful mentoring in statistics at the undergraduate level regardless of the type of institution and how these principles can be expanded within the context of a Christian college
QCD Axion Star Collapse with the Chiral Potential
In a previous work, we analyzed collapsing axion stars using the low-energy
instanton potential, showing that the total energy is always bounded and that
collapsing axion stars do not form black holes. In this paper, we provide a
proof that the conclusions are unchanged when using instead the more general
chiral potential for QCD axions.Comment: 11 page
Decay of Ultralight Axion Condensates
Axion particles can form macroscopic condensates, whose size can be galactic
in scale for models with very small axion masses eV, and which
are sometimes referred to under the name of Fuzzy Dark Matter. Many analyses of
these condensates are done in the non-interacting limit, due to the weakness of
the self-interaction coupling of axions. We investigate here how certain
results change upon inclusion of these interactions, finding a decreased
maximum mass and a modified mass-radius relationship. Further, these
condensates are, in general, unstable to decay through number-changing
interactions. We analyze the stability of galaxy-sized condensates of
axion-like particles, and sketch the parameter space of stable configurations
as a function of a binding energy parameter. We find a strong lower bound on
the size of Fuzzy Dark Matter condensates which are stable to decay, with
lifetimes longer than the age of the universe.Comment: 24 pages, 2 figures. v2: Added brief discussion of angular momentum;
extended Appendix A; typos correcte
Boson Stars from Self-Interacting Dark Matter
We study the possibility that self-interacting bosonic dark matter forms
star-like objects. We study both the case of attractive and repulsive
self-interactions, and we focus particularly in the parameter phase space where
self-interactions can solve well standing problems of the collisionless dark
matter paradigm. We find the mass radius relations for these dark matter
bosonic stars, their density profile as well as the maximum mass they can
support.Comment: 12 pages, 6 figures; references adde
An On-the-Road Comparison of In-Vehicle Navigation Assistance Systems
We compared system performance and driver opinion of 3 in-vehicle navigation aids - two advanced traveler information systems (ATISs; Ali-Scout and TetraStar) and written instructions - when used on the road concurrently under identical conditions. Few drivers in the study had difficulty finding initial routes or became lost. Users of Ali-Scout, an ATIS that utilizes traffic information in routing, drove longer-distance routes, got lost more frequently, and gave their system less positive ratings than did TetraStar users. Users of the 2 ATISs traversed routes that were significantly shorter in duration than those driven by users of written instructions. The time savings benefit of the advanced technology systems over written instructions was greatest during peak traffic conditions. Drivers who were familiar with the road network, overall, had less difficulty finding destinations and drove shorter-duration routes than drivers who were unfamiliar with the road network. Actual or potential applications of this research include improving the design of technologies that provide navigation assistance to travelers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67382/2/10.1518_001872099779591222.pd
Collisions of Dark Matter Axion Stars with Astrophysical Sources
If QCD axions form a large fraction of the total mass of dark matter, then
axion stars could be very abundant in galaxies. As a result, collisions with
each other, and with other astrophysical bodies, can occur. We calculate the
rate and analyze the consequences of three classes of collisions, those
occurring between a dilute axion star and: another dilute axion star, an
ordinary star, or a neutron star. In all cases we attempt to quantify the most
important astrophysical uncertainties; we also pay particular attention to
scenarios in which collisions lead to collapse of otherwise stable axion stars,
and possible subsequent decay through number changing interactions. Collisions
between two axion stars can occur with a high total rate, but the low relative
velocity required for collapse to occur leads to a very low total rate of
collapses. On the other hand, collisions between an axion star and an ordinary
star have a large rate, collisions/year/galaxy, and
for sufficiently heavy axion stars, it is plausible that most or all such
collisions lead to collapse. We identify in this case a parameter space which
has a stable region and a region in which collision triggers collapse, which
depend on the axion number () in the axion star, and a ratio of mass to
radius cubed characterizing the ordinary star (). Finally, we
revisit the calculation of collision rates between axion stars and neutron
stars, improving on previous estimates by taking cylindrical symmetry of the
neutron star distribution into account. Collapse and subsequent decay through
collision processes, if occurring with a significant rate, can affect dark
matter phenomenology and the axion star mass distribution.Comment: 19 pages, 5 figures. v2: References added, typos correcte
Classical Nonrelativistic Effective Field Theory and the Role of Gravitational Interactions
Coherent oscillation of axions or axion-like particles may give rise to
long-lived clumps, called axion stars, because of the attractive gravitational
force or its self-interaction. Such a kind of configuration has been
extensively studied in the context of oscillons without the effect of gravity,
and its stability can be understood by an approximate conservation of particle
number in a non-relativistic effective field theory (EFT). We extend this
analysis to the case with gravity to discuss the longevity of axion stars and
clarify the EFT expansion scheme in terms of gradient energy and Newton's
constant. Our EFT is useful to calculate the axion star configuration and its
classical lifetime without any ad hoc assumption. In addition, we derive a
simple stability condition against small perturbations. Finally, we discuss the
consistency of other non-relativistic effective field theories proposed in the
literature.Comment: 37 pages, 3 figure
Christian Endeavor
Title onlyhttps://scholarsjunction.msstate.edu/cht-sheet-music/4209/thumbnail.jp
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