2,444 research outputs found
Orbital Debris Modeling and Applications at Kyushu University
AbstractThe orbital debris modeling can build evolutionary models as essential tools to predict the current or future orbital debris populations, and also to discuss what and how to do for orbital debris mitigation and environmental remediation. The orbital debris modeling can also devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Another application of the orbital debris modeling is to estimate attitude motion of space objects to be removed for environmental remediation. This paper briefly introduces efforts into orbital debris modeling and applications at Kyushu University
An anisotropic hybrid non-perturbative formulation for 4D N = 2 supersymmetric Yang-Mills theories
We provide a simple non-perturbative formulation for non-commutative
four-dimensional N = 2 supersymmetric Yang-Mills theories. The formulation is
constructed by a combination of deconstruction (orbifold projection), momentum
cut-off and matrix model techniques. We also propose a moduli fixing term that
preserves lattice supersymmetry on the deconstruction formulation. Although the
analogous formulation for four-dimensional N = 2 supersymmetric Yang-Mills
theories is proposed also in Nucl.Phys.B857(2012), our action is simpler and
better suited for computer simulations. Moreover, not only for the
non-commutative theories, our formulation has a potential to be a
non-perturbative tool also for the commutative four-dimensional N = 2
supersymmetric Yang-Mills theories.Comment: 32 pages, final version accepted in JHE
Thermal phases of D1-branes on a circle from lattice super Yang-Mills
We report on the results of numerical simulations of 1+1 dimensional SU(N)
Yang-Mills theory with maximal supersymmetry at finite temperature and
compactified on a circle. For large N this system is thought to provide a dual
description of the decoupling limit of N coincident D1-branes on a circle. It
has been proposed that at large N there is a phase transition at strong
coupling related to the Gregory-Laflamme (GL) phase transition in the
holographic gravity dual. In a high temperature limit there was argued to be a
deconfinement transition associated to the spatial Polyakov loop, and it has
been proposed that this is the continuation of the strong coupling GL
transition. Investigating the theory on the lattice for SU(3) and SU(4) and
studying the time and space Polyakov loops we find evidence supporting this. In
particular at strong coupling we see the transition has the parametric
dependence on coupling predicted by gravity. We estimate the GL phase
transition temperature from the lattice data which, interestingly, is not yet
known directly in the gravity dual. Fine tuning in the lattice theory is
avoided by the use of a lattice action with exact supersymmetry.Comment: 21 pages, 8 figures. v2: References added, two figures were modified
for clarity. v3: Normalisation of lattice coupling corrected by factor of two
resulting in change of estimate for c_cri
Lattice formulation of two-dimensional N=(2,2) super Yang-Mills with SU(N) gauge group
We propose a lattice model for two-dimensional SU(N) N=(2,2) super Yang-Mills
model. We start from the CKKU model for this system, which is valid only for
U(N) gauge group. We give a reduction of U(1) part keeping a part of
supersymmetry. In order to suppress artifact vacua, we use an admissibility
condition.Comment: 16 pages, 3 figures; v2: typo crrected; v3: 18 pages, a version to
appear in JHE
Absence of sign problem in two-dimensional N=(2,2) super Yang-Mills on lattice
We show that N=(2,2) SU(N) super Yang-Mills theory on lattice does not have
sign problem in the continuum limit, that is, under the phase-quenched
simulation phase of the determinant localizes to 1 and hence the phase-quench
approximation becomes exact. Among several formulations, we study models by
Cohen-Kaplan-Katz-Unsal (CKKU) and by Sugino. We confirm that the sign problem
is absent in both models and that they converge to the identical continuum
limit without fine tuning. We provide a simple explanation why previous works
by other authors, which claim an existence of the sign problem, do not capture
the continuum physics.Comment: 27 pages, 24 figures; v2: comments and references added; v3: figures
on U(1) mass independence and references added, to appear in JHE
Classical and Quantum Cosmology of Multigravity
Recently, a multigraviton theory on a simple closed circuit graph
corresponding to the discretization of compactification of the
Kaluza-Klein (KK) theory has been considered. In the present paper, we extend
this theory to that on a general graph and study what modes of particles are
included. Furthermore, we generalize it in a possible nonlinear theory based on
the vierbein formalism and study classical and quantum cosmological solutions
in the theory. We found that scale factors in a solution for this theory repeat
acceleration and deceleration.Comment: 17 pages, 15 figures, RevTeX4.1, revised versio
On the shape of a D-brane bound state and its topology change
As is well known, coordinates of D-branes are described by NxN matrices. From
generic non-commuting matrices, it is difficult to extract physics, for
example, the shape of the distribution of positions of D-branes. To overcome
this problem, we generalize and elaborate on a simple prescription, first
introduced by Hotta, Nishimura and Tsuchiya, which determines the most
appropriate gauge to make the separation between diagonal components (D-brane
positions) and off-diagonal components. This prescription makes it possible to
extract the distribution of D-branes directly from matrices. We verify the
power of it by applying it to Monte-Carlo simulations for various lower
dimensional Yang-Mills matrix models. In particular, we detect the topology
change of the D-brane bound state for a phase transition of a matrix model; the
existence of this phase transition is expected from the gauge/gravity duality,
and the pattern of the topology change is strikingly similar to the counterpart
in the gravity side, the black hole/black string transition. We also propose a
criterion, based on the behavior of the off-diagonal components, which
determines when our prescription gives a sensible definition of D-brane
positions. We provide numerical evidence that our criterion is satisfied for
the typical distance between D-branes. For a supersymmetric model, positions of
D-branes can be defined even at a shorter distance scale. The behavior of
off-diagonal elements found in this analysis gives some support for previous
studies of D-brane bound states.Comment: 29 pages, 16 figure
Arabic Language Arts Standards: Revolution or Disruption?
© The Author(s) 2018. Textbooks are major organizers of Arabic language instruction in most Arab countries (Faour, 2012). Textbooks approved by ministries of education have traditionally guided teaching of content knowledge, skills, and values to be taught at each grade level (Faour, 2012; Sabella, 2014; Taha-Thomure, 2008). This research is a foundation study into the use of Arabic Language Arts (ALA) standards in six schools in three countries in the Arabian Gulf region (Bahrain, Saudi Arabia, and United Arab Emirates). Fifty-eight teachers used the ALA standards adapted from the Ohio English Language Arts standards (Taha, 2017a) for at least one year. Results of the online survey indicated that 83.5% of teachers found the standards had a positive effect on their teaching, while 94.9% of teachers found that the standards helped them collaborate with each other in planning and finding suitable resources to use. This suggests that well-supported innovations can lead to teachers being aware of and using ALA to improve student learning and instruction. Results also highlight some of the challenges teachers faced to find the necessary Arab language resources that will help them implement a standards-based approach, in addition to the amount of time they needed to put into preparing for the lessons
Robertsonian chromosome polymorphism found in a local herd of the Japanese Black cattle
International audienc
Phase structure of twisted Eguchi-Kawai model
We study the phase structure of the four-dimensional twisted Eguchi-Kawai
model using numerical simulations. This model is an effective tool for studying
SU(N) gauge theory in the large-N limit and provides a nonperturbative
formulation of the gauge theory on noncommutative spaces. Recently it was found
that its Z_N^4 symmetry, which is crucial for the validity of this model, can
break spontaneously in the intermediate coupling region. We investigate in
detail the symmetry breaking point from the weak coupling side. Our simulation
results show that the continuum limit of this model cannot be taken.Comment: 7 pages, 4 figures, talk presented at the XXV International Symposium
on Lattice Field Theory, July 30 - August 4, 2007, Regensburg, German
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