16,558 research outputs found
Azimuthal correlations of forward di-hadrons in d+Au collisions at RHIC in the Color Glass Condensate
We present a good description of recent experimental data on forward
di-hadron azimuthal correlations measured in deuteron-gold collisions at RHIC,
where monojet production has been observed. Our approach is based on the Color
Glass Condensate effective theory for the small-x degrees of freedom of the
nuclear wave function, including the use of non-linear evolution equations with
running QCD coupling. Our analysis provides further evidence for the presence
of saturation effects in RHIC data.Comment: 4 pages, 2 figures, version to appear in PR
Vortex pinning by meandering line defects in planar superconductors
To better understand vortex pinning in thin superconducting slabs, we study
the interaction of a single fluctuating vortex filament with a curved line
defect in (1+1) dimensions. This problem is also relevant to the interaction of
scratches with wandering step edges in vicinal surfaces. The equilibrium
probability density for a fluctuating line attracted to a particular fixed
defect trajectory is derived analytically by mapping the problem to a straight
line defect in the presence of a space and time-varying external tilt field.
The consequences of both rapid and slow changes in the frozen defect
trajectory, as well as finite size effects are discussed. A sudden change in
the defect direction leads to a delocalization transition, accompanied by a
divergence in the trapping length, near a critical angle.Comment: 9 pages, 9 figure
Triply Special Relativity
We describe an extension of special relativity characterized by {\it three}
invariant scales, the speed of light, , a mass, and a length .
This is defined by a non-linear extension of the Poincare algerbra, ,
which we describe here. For , becomes the Snyder
presentation of the -Poincare algebra, while for it
becomes the phase space algebra of a particle in deSitter spacetime. We
conjecture that the algebra is relevant for the low energy behavior of quantum
gravity, with taken to be the Planck mass, for the case of a nonzero
cosmological constant . We study the modifications of
particle motion which follow if the algebra is taken to define the Poisson
structure of the phase space of a relativistic particle.Comment: 13 page
Range Extension of the Endangered Gray Bat, Myotis grisescens, into the Arkansas River Valley
Optometric applications of programmable calculators
Optometric applications of programmable calculator
A radiological assessment of nuclear power and propulsion operations near Space Station Freedom
Scenarios were identified which involve the use of nuclear power systems in the vicinity of Space Station Freedom (SSF) and their radiological impact on the SSF crew was quantified. Several of the developed scenarios relate to the use of SSF as an evolutionary transportation node for lunar and Mars missions. In particular, radiation doses delivered to SSF crew were calculated for both the launch and subsequent return of a Nuclear Electric Propulsion (NEP) cargo vehicle and a Nuclear Thermal Rocket (NTR) personnel vehicle to low earth orbit. The use of nuclear power on co-orbiting platforms and the storage and handling issues associated with radioisotope power systems were also explored as they relate to SSF. A central philosophy in these analyses was the utilization of a radiation dose budget, defined as the difference between recommended dose limits from all radiation sources and estimated doses received by crew members from natural space radiations. Consequently, for each scenario examined, the dose budget concept was used to identify and quantify constraints on operational parameters such as launch separation distances, returned vehicle parking distances, and reactor shutdown times prior to vehicle approach. The results indicate that realistic scenarios do not exist which would preclude the use of nuclear power sources in the vicinity of SSF. The radiation dose to the SSF crew can be maintained at safe levels solely by implementing proper and reasonable operating procedures
Conditions for the occurrence of mean-motion resonances in a low mass planetary system
The dynamical interactions that occur in newly formed planetary systems may
reflect the conditions occurring in the protoplanetary disk out of which they
formed. With this in mind, we explore the attainment and maintenance of orbital
resonances by migrating planets in the terrestrial mass range. Migration time
scales varying between millions of years and thousands of years are considered.
In the former case, for which the migration time is comparable to the lifetime
of the protoplanetary gas disk, a 2:1 resonance may be formed. In the latter,
relatively rapid migration regime commensurabilities of high degree such as 8:7
or 11:10 may be formed. However, in any one large-scale migration several
different commensurabilities may be formed sequentially, each being associated
with significant orbital evolution. We also use a simple analytic theory to
develop conditions for first order commensurabilities to be formed. These
depend on the degree of the commensurability, the imposed migration and
circularization rates, and the planet mass ratios. These conditions are found
to be consistent with the results of our simulations.Comment: 11 pages with 4 figures, pdflatex, to appear in the proceedings of
the conference "Extra-solar Planets in Multi-body Systems: Theory and
Observations"; eds. K. Gozdziewski, A. Niedzielski and J. Schneider, EAS
Publication Serie
Phase diagram of the restricted solid-on-solid model coupled to the Ising model
We study the phase transitions of a restricted solid-on-solid model coupled
to an Ising model, which can be derived from the coupled XY-Ising model. There
are two kinds of phase transition lines. One is a Ising transition line and the
other is surface roughening transition line. The latter is a KT transition line
from the viewpoint of the XY model. Using a microcanonical Monte Carlo
technique, we obtain a very accurate two dimensional phase diagram. The two
transition lines are separate in all the parameter space we study. This result
is strong evidence that the fully frustrated XY model orders by two separate
transitions and that roughening and reconstruction transitions of crystal
surfaces occur separately.Comment: 17 pages, source RevTeX file and 8 PS figures are tarred and
compressed via uufile
A Composite Little Higgs Model
We describe a natural UV complete theory with a composite little Higgs. Below
a TeV we have the minimal Standard Model with a light Higgs, and an extra
neutral scalar. At the TeV scale there are additional scalars, gauge bosons,
and vector-like charge 2/3 quarks, whose couplings to the Higgs greatly reduce
the UV sensitivity of the Higgs potential. Stabilization of the Higgs mass
squared parameter, without finetuning, occurs due to a softly broken shift
symmetry--the Higgs is a pseudo Nambu-Goldstone boson. Above the 10 TeV scale
the theory has new strongly coupled interactions. A perturbatively
renormalizable UV completion, with softly broken supersymmetry at 10 TeV is
explicitly worked out. Our theory contains new particles which are odd under an
exact "dark matter parity", (-1)^{(2S+3B+L)}. We argue that such a parity is
likely to be a feature of many theories of new TeV scale physics. The lightest
parity odd particle, or "LPOP", is most likely a neutral fermion, and may make
a good dark matter candidate, with similar experimental signatures to the
neutralino of the MSSM. We give a general effective field theory analysis of
the calculation of corrections to precision electroweak observables.Comment: 28 page
Preparing CySat-1: A look at Iowa State University’s first CubeSat
In this paper, an overview of the scientific mission of CySat-1, the derived vehicle requirements, impact on system design, and the educational opportunities presented by these challenges. CySat-1, previously scheduled for launch on the SpaceX-21 and awaiting further details following the COVID-19 pandemic, is a CubeSat designed and built by students at Iowa State University. The primary mission of CySat-1 is to provide hands-on experience to undergraduate students in designing, building, and testing a space system. CySat-1 also hosts a scientific payload, a software-defined radio (SDR) radiometer, to survey soil moisture content on Earth from Low Earth Orbit. This mission further reinforces the affordability of CubeSats for future research missions. The Iowa State University CubeSat, CySat-1, was selected for NASA’s CubeSat launch initiative (CSLI) program and will be launched with a future ELaNa mission. The operation will be for three to six months after the deployment from the International Space Station.
We will discuss the overall function of the payload and how we integrated the payload into the CubeSat. This discussion will include the student-initiative design and fabrication of critical components, including the payload and CubeSat structures. CySat-1 augments in-house, student designs with commercial off-the-shelf (COTS) components, creating a real-world integration challenge. Iowa State University’s first CubeSat program spurred the installation of facilities such as a clean room with the anti-static capability to support building, testing, and integration of delicate space hardware. Through this process, students acquired experience with industrial level integration and testing procedures.
Undergraduate teams working on CySat-1 lead the design and fabrication of the payload, structure, and system integration, providing experience with systems engineering, technical writing, and various cross-disciplinary applications. Over sixty undergraduate students, several graduate students, and four faculty members from multiple departments worked on the development of this CubeSat under the Make to Innovate program at Iowa State University, which engages students in various projects to augment their understanding of engineering fundamentals
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