5,992 research outputs found
Canonical decomposition of linear differential operators with selected differential Galois groups
We revisit an order-six linear differential operator having a solution which
is a diagonal of a rational function of three variables. Its exterior square
has a rational solution, indicating that it has a selected differential Galois
group, and is actually homomorphic to its adjoint. We obtain the two
corresponding intertwiners giving this homomorphism to the adjoint. We show
that these intertwiners are also homomorphic to their adjoint and have a simple
decomposition, already underlined in a previous paper, in terms of order-two
self-adjoint operators. From these results, we deduce a new form of
decomposition of operators for this selected order-six linear differential
operator in terms of three order-two self-adjoint operators. We then generalize
the previous decomposition to decompositions in terms of an arbitrary number of
self-adjoint operators of the same parity order. This yields an infinite family
of linear differential operators homomorphic to their adjoint, and, thus, with
a selected differential Galois group. We show that the equivalence of such
operators is compatible with these canonical decompositions. The rational
solutions of the symmetric, or exterior, squares of these selected operators
are, noticeably, seen to depend only on the rightmost self-adjoint operator in
the decomposition. These results, and tools, are applied on operators of large
orders. For instance, it is seen that a large set of (quite massive) operators,
associated with reflexive 4-polytopes defining Calabi-Yau 3-folds, obtained
recently by P. Lairez, correspond to a particular form of the decomposition
detailed in this paper.Comment: 40 page
Globally nilpotent differential operators and the square Ising model
We recall various multiple integrals related to the isotropic square Ising
model, and corresponding, respectively, to the n-particle contributions of the
magnetic susceptibility, to the (lattice) form factors, to the two-point
correlation functions and to their lambda-extensions. These integrals are
holonomic and even G-functions: they satisfy Fuchsian linear differential
equations with polynomial coefficients and have some arithmetic properties. We
recall the explicit forms, found in previous work, of these Fuchsian equations.
These differential operators are very selected Fuchsian linear differential
operators, and their remarkable properties have a deep geometrical origin: they
are all globally nilpotent, or, sometimes, even have zero p-curvature. Focusing
on the factorised parts of all these operators, we find out that the global
nilpotence of the factors corresponds to a set of selected structures of
algebraic geometry: elliptic curves, modular curves, and even a remarkable
weight-1 modular form emerging in the three-particle contribution
of the magnetic susceptibility of the square Ising model. In the case where we
do not have G-functions, but Hamburger functions (one irregular singularity at
0 or ) that correspond to the confluence of singularities in the
scaling limit, the p-curvature is also found to verify new structures
associated with simple deformations of the nilpotent property.Comment: 55 page
Lateral-directional control of the x-15 airplane
Lateral directional control and stability characteristics of X-15 aircraf
A-infinity algebra of an elliptic curve and Eisenstein series
We compute explicitly the A-infinity structure on the Ext-algebra of the
collection , where is a line bundle of degree 1 on an
elliptic curve . The answer involves higher derivatives of Eisenstein
series.Comment: 13 pages, 3 figures; v3: added remark on the limit at the cus
Renormalization, isogenies and rational symmetries of differential equations
We give an example of infinite order rational transformation that leaves a
linear differential equation covariant. This example can be seen as a
non-trivial but still simple illustration of an exact representation of the
renormalization group.Comment: 36 page
Painleve versus Fuchs
The sigma form of the Painlev{\'e} VI equation contains four arbitrary
parameters and generically the solutions can be said to be genuinely
``nonlinear'' because they do not satisfy linear differential equations of
finite order. However, when there are certain restrictions on the four
parameters there exist one parameter families of solutions which do satisfy
(Fuchsian) differential equations of finite order. We here study this phenomena
of Fuchsian solutions to the Painlev{\'e} equation with a focus on the
particular PVI equation which is satisfied by the diagonal correlation function
C(N,N) of the Ising model. We obtain Fuchsian equations of order for
C(N,N) and show that the equation for C(N,N) is equivalent to the
symmetric power of the equation for the elliptic integral .
We show that these Fuchsian equations correspond to rational algebraic curves
with an additional Riccati structure and we show that the Malmquist Hamiltonian
variables are rational functions in complete elliptic integrals. Fuchsian
equations for off diagonal correlations are given which extend our
considerations to discrete generalizations of Painlev{\'e}.Comment: 18 pages, Dedicated to the centenary of the publication of the
Painleve VI equation in the Comptes Rendus de l'Academie des Sciences de
Paris by Richard Fuchs in 190
Angular Momentum Profiles of Warm Dark Matter Halos
We compare the specific angular momentum profiles of virialized dark halos in
cold dark matter (CDM) and warm dark matter (WDM) models using high-resolution
dissipationless simulations. The simulations were initialized using the same
set of modes, except on small scales, where the power was suppressed in WDM
below the filtering length. Remarkably, WDM as well as CDM halos are
well-described by the two-parameter angular momentum profile of Bullock et al.
(2001), even though the halo masses are below the filtering scale of the WDM.
Although the best-fit shape parameters change quantitatively for individual
halos in the two simulations, we find no systematic variation in profile shapes
as a function of the dark matter type. The scatter in shape parameters is
significantly smaller for the WDM halos, suggesting that substructure and/or
merging history plays a role producing scatter about the mean angular momentum
distribution, but that the average angular momentum profiles of halos originate
from larger-scale phenomena or a mechanism associated with the virialization
process. The known mismatch between the angular momentum distributions of dark
halos and disk galaxies is therefore present in WDM as well as CDM models. Our
WDM halos tend to have a less coherent (more misaligned) angular momentum
structure and smaller spin parameters than do their CDM counterparts, although
we caution that this result is based on a small number of halos.Comment: 5 pages, 1 figure, Submitted to ApJ
Study of the local field distribution on a single-molecule magnet-by a single paramagnetic crystal; a DPPH crystal on the surface of an Mn12-acetate crystal
The local magnetic field distribution on the subsurface of a single-molecule
magnet crystal, SMM, above blocking temperature (T >> Tb) detected for a very
short time interval (~ 10-10 s), has been investigated. Electron Paramagnetic
Resonance (EPR) spectroscopy using a local paramagnetic probe was employed as a
simple alternative detection method. An SMM crystal of
[Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O (Mn12-acetate) and a crystal of 2,2-
diphenyl-1-picrylhydrazyl (DPPH) as the paramagnetic probe were chosen for this
study. The EPR spectra of DPPH deposited on Mn12-acetate show additional
broadening and shifting in the magnetic field in comparison to the spectra of
the DPPH in the absence of the SMM crystal. The additional broadening of the
DPPH linewidth was considered in terms of the two dominant electron spin
interactions (dipolar and exchange) and the local magnetic field distribution
on the crystal surface. The temperature dependence of the linewidth of the
Gaussian distribution of local fields at the SMM surface was extrapolated for
the low temperature interval (70-5 K)
Distribution of localized states from fine analysis of electron spin resonance spectra of organic semiconductors: Physical meaning and methodology
We develop an analytical method for the processing of electron spin resonance
(ESR) spectra. The goal is to obtain the distributions of trapped carriers over
both their degree of localization and their binding energy in semiconductor
crystals or films composed of regularly aligned organic molecules [Phys. Rev.
Lett. v. 104, 056602 (2010)]. Our method has two steps. We first carry out a
fine analysis of the shape of the ESR spectra due to the trapped carriers; this
reveals the distribution of the trap density of the states over the degree of
localization. This analysis is based on the reasonable assumption that the
linewidth of the trapped carriers is predetermined by their degree of
localization because of the hyperfine mechanism. We then transform the
distribution over the degree of localization into a distribution over the
binding energies. The transformation uses the relationships between the binding
energies and the localization parameters of the trapped carriers. The
particular relation for the system under study is obtained by the Holstein
model for trapped polarons using a diagrammatic Monte Carlo analysis. We
illustrate the application of the method to pentacene organic thin-film
transistors.Comment: 14 pages, 11 figure
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