549 research outputs found
Towards Mixed Gr{\"o}bner Basis Algorithms: the Multihomogeneous and Sparse Case
One of the biggest open problems in computational algebra is the design of
efficient algorithms for Gr{\"o}bner basis computations that take into account
the sparsity of the input polynomials. We can perform such computations in the
case of unmixed polynomial systems, that is systems with polynomials having the
same support, using the approach of Faug{\`e}re, Spaenlehauer, and Svartz
[ISSAC'14]. We present two algorithms for sparse Gr{\"o}bner bases computations
for mixed systems. The first one computes with mixed sparse systems and
exploits the supports of the polynomials. Under regularity assumptions, it
performs no reductions to zero. For mixed, square, and 0-dimensional
multihomogeneous polynomial systems, we present a dedicated, and potentially
more efficient, algorithm that exploits different algebraic properties that
performs no reduction to zero. We give an explicit bound for the maximal degree
appearing in the computations
The fundamental solution and Strichartz estimates for the Schr\"odinger equation on flat euclidean cones
We study the Schr\"odinger equation on a flat euclidean cone of cross-sectional radius , developing
asymptotics for the fundamental solution both in the regime near the cone point
and at radial infinity. These asymptotic expansions remain uniform while
approaching the intersection of the "geometric front", the part of the solution
coming from formal application of the method of images, and the "diffractive
front" emerging from the cone tip. As an application, we prove Strichartz
estimates for the Schr\"odinger propagator on this class of cones.Comment: 21 pages, 4 figures. Minor typos corrected. To be published in Comm.
Math. Phy
Evaluation of plasma‐spray and magnetron‐sputter Ca‐P‐coated implants: An in vivo experiment using rabbits
Uniqueness of collinear solutions for the relativistic three-body problem
Continuing work initiated in an earlier publication [Yamada, Asada, Phys.
Rev. D 82, 104019 (2010)], we investigate collinear solutions to the general
relativistic three-body problem. We prove the uniqueness of the configuration
for given system parameters (the masses and the end-to-end length). First, we
show that the equation determining the distance ratio among the three masses,
which has been obtained as a seventh-order polynomial in the previous paper,
has at most three positive roots, which apparently provide three cases of the
distance ratio. It is found, however, that, even for such cases, there exists
one physically reasonable root and only one, because the remaining two positive
roots do not satisfy the slow motion assumption in the post-Newtonian
approximation and are thus discarded. This means that, especially for the
restricted three-body problem, exactly three positions of a third body are true
even at the post-Newtonian order. They are relativistic counterparts of the
Newtonian Lagrange points L1, L2 and L3. We show also that, for the same masses
and full length, the angular velocity of the post-Newtonian collinear
configuration is smaller than that for the Newtonian case. Provided that the
masses and angular rate are fixed, the relativistic end-to-end length is
shorter than the Newtonian one.Comment: 18 pages, 1 figure; typos corrected, text improved; accepted by PR
Melnikov theory to all orders and Puiseux series for subharmonic solutions
We study the problem of subharmonic bifurcations for analytic systems in the
plane with perturbations depending periodically on time, in the case in which
we only assume that the subharmonic Melnikov function has at least one zero. If
the order of zero is odd, then there is always at least one subharmonic
solution, whereas if the order is even in general other conditions have to be
assumed to guarantee the existence of subharmonic solutions. Even when such
solutions exist, in general they are not analytic in the perturbation
parameter. We show that they are analytic in a fractional power of the
perturbation parameter. To obtain a fully constructive algorithm which allows
us not only to prove existence but also to obtain bounds on the radius of
analyticity and to approximate the solutions within any fixed accuracy, we need
further assumptions. The method we use to construct the solution -- when this
is possible -- is based on a combination of the Newton-Puiseux algorithm and
the tree formalism. This leads to a graphical representation of the solution in
terms of diagrams. Finally, if the subharmonic Melnikov function is identically
zero, we show that it is possible to introduce higher order generalisations,
for which the same kind of analysis can be carried out.Comment: 30 pages, 6 figure
A histological and histomorphometrical evaluation of the application of screw‐designed calciumphosphate (Ca‐P)‐coated implants in the cancellous maxillary bone of the goat
Mechanical and histologic evaluation of Ca‐P plasma‐spray and magnetron sputter‐coated implants in trabecular bone of the goat
Origin of Complex Quantum Amplitudes and Feynman's Rules
Complex numbers are an intrinsic part of the mathematical formalism of
quantum theory, and are perhaps its most mysterious feature. In this paper, we
show that the complex nature of the quantum formalism can be derived directly
from the assumption that a pair of real numbers is associated with each
sequence of measurement outcomes, with the probability of this sequence being a
real-valued function of this number pair. By making use of elementary symmetry
conditions, and without assuming that these real number pairs have any other
algebraic structure, we show that these pairs must be manipulated according to
the rules of complex arithmetic. We demonstrate that these complex numbers
combine according to Feynman's sum and product rules, with the modulus-squared
yielding the probability of a sequence of outcomes.Comment: v2: Clarifications, and minor corrections and modifications. Results
unchanged. v3: Minor changes to introduction and conclusio
Decoherence-free quantum information in Markovian systems
Decoherence in Markovian systems can result indirectly from the action of a
system Hamiltonian which is usually fixed and unavoidable. Here, we show that
in general in Markovian systems, because of the system Hamiltonian, quantum
information decoheres. We give conditions for the system Hamiltonian that must
be satisfied if coherence is to be preserved. Finally, we show how to construct
robust subspaces for quantum information processing.Comment: 4 pages, published versio
The effect of Ca-P plasma-sprayed coatings on the initial bone healing of oral implants: An experimental study in the goat
- …