34,480 research outputs found
A Comparison of Continuously Controlled and Controlled K-theory
We define an unreduced version of the e-controlled lower -theoretic groups
of Ranicki and Yamasaki, and Quinn. We show that the reduced versions of our
groups coincide (in the inverse limit and its first derived, ) with
those of Ranicki and Yamasaki. We also relate the controlled groups to the
continuously controlled groups of Anderson and Munkholm, and to the Quinn
homology groups of Quinn
Some neutron and gamma radiation characteristics of plutonium cermet fuel for isotopic power sources
Gamma and neutron measurements on various types of plutonium sources are presented in order to show the effects of O-17, O-18 F-19, Pu-236, age of the fuel, and size of the source on the gamma and neutron spectra. Analysis of the radiation measurements shows that fluorine is the main contributor to the neutron yields from present plutonium-molybdenum cermet fuel, while both fluorine and Pu-236 daughters contribute significantly to the gamma ray intensities
Gaussian pulse dynamics in gain media with Kerr nonlinearity
Using the Kantorovitch method in combination with a Gaussian ansatz, we
derive the equations of motion for spatial, temporal and spatiotemporal optical
propagation in a dispersive Kerr medium with a general transverse and spectral
gain profile. By rewriting the variational equations as differential equations
for the temporal and spatial Gaussian q parameters, optical ABCD matrices for
the Kerr effect, a general transverse gain profile and nonparabolic spectral
gain filtering are obtained. Further effects can easily be taken into account
by adding the corresponding ABCD matrices. Applications include the temporal
pulse dynamics in gain fibers and the beam propagation or spatiotemporal pulse
evolution in bulk gain media. As an example, the steady-state spatiotemporal
Gaussian pulse dynamics in a Kerr-lens mode-locked laser resonator is studied
Exotic order in simple models of bosonic systems
We show that simple Bose Hubbard models with unfrustrated hopping and short
range two-body repulsive interactions can support stable fractionalized phases
in two and higher dimensions, and in zero magnetic field. The simplicity of the
constructed models advances the possibility of a controlled experimental
realization and novel applications of such unconventional states.Comment: 4 pages, 4 figure
A Divergent Synthetic Route to the Vallesamidine and Schizozygine Alkaloids: Total Synthesis of (+)‐Vallesamidine and (+)‐14,15‐Dehydrostrempeliopine
The total synthesis of representative members of the schizozygine alkaloids, (+)‐vallesamidine and (+)‐14,15‐dehydrostrempeliopine, were completed from a late‐stage divergent intermediate. The synthesis took advantage of efficient nitro‐group reactions with the A/B/C ring skeleton constructed concisely on a gram scale through an asymmetric Michael addition, nitro‐Mannich/lactamisation, Tsuji–Trost allylation, and intramolecular C−N coupling reaction. Other key features of the synthesis are a novel [1,4] hydride transfer/Mannich‐type cyclisation to build ring E and a diastereoselective ring‐closing metathesis reaction to construct ring D. This approach gave access to a late‐stage C14,C15 alkene divergent intermediate that could be simply transformed into (+)‐vallesamidine, (+)‐14,15‐dehydrostrempeliopine, and potentially other schizozygine alkaloids and unnatural derivatives
A Divergent Synthetic Route to the Vallesamidine, Strempeliopine and Schizozygine Alkaloids: Total Synthesis of (+)-Vallesamidine and (+)-14,15-Dehydrostrempeliopine
The total synthesis of representative members of the schizozygine alkaloids, (+)‐vallesamidine and (+)‐14,15‐dehydrostrempeliopine, were completed from a late‐stage divergent intermediate. The synthesis took advantage of efficient nitro‐group reactions with the A/B/C ring skeleton constructed concisely on a gram scale through an asymmetric Michael addition, nitro‐Mannich/lactamisation, Tsuji–Trost allylation, and intramolecular C−N coupling reaction. Other key features of the synthesis are a novel [1,4] hydride transfer/Mannich‐type cyclisation to build ring E and a diastereoselective ring‐closing metathesis reaction to construct ring D. This approach gave access to a late‐stage C14,C15 alkene divergent intermediate that could be simply transformed into (+)‐vallesamidine, (+)‐14,15‐dehydrostrempeliopine, and potentially other schizozygine alkaloids and unnatural derivatives
Non-unique factorization of polynomials over residue class rings of the integers
We investigate non-unique factorization of polynomials in Z_{p^n}[x] into
irreducibles. As a Noetherian ring whose zero-divisors are contained in the
Jacobson radical, Z_{p^n}[x] is atomic. We reduce the question of factoring
arbitrary non-zero polynomials into irreducibles to the problem of factoring
monic polynomials into monic irreducibles. The multiplicative monoid of monic
polynomials of Z_{p^n}[x] is a direct sum of monoids corresponding to
irreducible polynomials in Z_p[x], and we show that each of these monoids has
infinite elasticity. Moreover, for every positive integer m, there exists in
each of these monoids a product of 2 irreducibles that can also be represented
as a product of m irreducibles.Comment: 11 page
Three-Dimensional Spin-Orbit Coupling in a Trap
We investigate the properties of an atom under the influence of a synthetic
three-dimensional spin-orbit coupling (Weyl coupling) in the presence of a
harmonic trap. The conservation of total angular momentum provides a
numerically efficient scheme for finding the spectrum and eigenfunctions of the
system. We show that at large spin-orbit coupling the system undergoes
dimensional reduction from three to one dimension at low energies, and the
spectrum is approximately Landau level-like. At high energies, the spectrum is
approximately given by the three-dimensional isotropic harmonic oscillator. We
explore the properties of the ground state in both position and momentum space.
We find the ground state has spin textures with oscillations set by the
spin-orbit length scale
Quasi-adiabatic Continuation of Quantum States: The Stability of Topological Ground State Degeneracy and Emergent Gauge Invariance
We define for quantum many-body systems a quasi-adiabatic continuation of
quantum states. The continuation is valid when the Hamiltonian has a gap, or
else has a sufficiently small low-energy density of states, and thus is away
from a quantum phase transition. This continuation takes local operators into
local operators, while approximately preserving the ground state expectation
values. We apply this continuation to the problem of gauge theories coupled to
matter, and propose a new distinction, perimeter law versus "zero law" to
identify confinement. We also apply the continuation to local bosonic models
with emergent gauge theories. We show that local gauge invariance is
topological and cannot be broken by any local perturbations in the bosonic
models in either continuous or discrete gauge groups. We show that the ground
state degeneracy in emergent discrete gauge theories is a robust property of
the bosonic model, and we argue that the robustness of local gauge invariance
in the continuous case protects the gapless gauge boson.Comment: 15 pages, 6 figure
Schema Independent Relational Learning
Learning novel concepts and relations from relational databases is an
important problem with many applications in database systems and machine
learning. Relational learning algorithms learn the definition of a new relation
in terms of existing relations in the database. Nevertheless, the same data set
may be represented under different schemas for various reasons, such as
efficiency, data quality, and usability. Unfortunately, the output of current
relational learning algorithms tends to vary quite substantially over the
choice of schema, both in terms of learning accuracy and efficiency. This
variation complicates their off-the-shelf application. In this paper, we
introduce and formalize the property of schema independence of relational
learning algorithms, and study both the theoretical and empirical dependence of
existing algorithms on the common class of (de) composition schema
transformations. We study both sample-based learning algorithms, which learn
from sets of labeled examples, and query-based algorithms, which learn by
asking queries to an oracle. We prove that current relational learning
algorithms are generally not schema independent. For query-based learning
algorithms we show that the (de) composition transformations influence their
query complexity. We propose Castor, a sample-based relational learning
algorithm that achieves schema independence by leveraging data dependencies. We
support the theoretical results with an empirical study that demonstrates the
schema dependence/independence of several algorithms on existing benchmark and
real-world datasets under (de) compositions
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