15,765 research outputs found
Loop algebras, gauge invariants and a new completely integrable system
One fruitful motivating principle of much research on the family of
integrable systems known as ``Toda lattices'' has been the heuristic assumption
that the periodic Toda lattice in an affine Lie algebra is directly analogous
to the nonperiodic Toda lattice in a finite-dimensional Lie algebra. This paper
shows that the analogy is not perfect. A discrepancy arises because the natural
generalization of the structure theory of finite-dimensional simple Lie
algebras is not the structure theory of loop algebras but the structure theory
of affine Kac-Moody algebras. In this paper we use this natural generalization
to construct the natural analog of the nonperiodic Toda lattice. Surprisingly,
the result is not the periodic Toda lattice but a new completely integrable
system on the periodic Toda lattice phase space. This integrable system is
prescribed purely in terms of Lie-theoretic data. The commuting functions are
precisely the gauge-invariant functions one obtains by viewing elements of the
loop algebra as connections on a bundle over
Extremal metrics on blow ups
Given a compact Kahler manifold with an extremal metric (M,\omega), we give
sufficient conditions on finite sets points p_1,...,p_n and weights a_1,...a_n
for which the blow up of M at p_1,...,p_n has an extremal metric in the Kahler
class \pi^*[\omega] - \epsilon (a_1 PD[E_1] + .. + a_n PD[E_n]) for all
\epsilon sufficiently small. In particular our result implies that if
(M,\omega) is a toric manifold and p_1,...,p_n is any subset of the fixed locus
of the torus action, then such metrics exist for any choice of the weights. The
relationship with previous constructions of the first two authors for Kahler
constant scalar curvature metrics is discussed.Comment: 39 page
What has NMR taught us about stripes and inhomogeneity?
The purpose of this brief invited paper is to summarize what we have (not)
learned from NMR on stripes and inhomogeneity in La{2-x}Sr{x}CuO{4}. We explain
that the reality is far more complicated than generally accepted.Comment: Accepted for publication in the Proceedings of the LT-23 Conference
(invited
The HPV cellular transactivator Brn-3a can be used to predict cervical adenocarcinoma and squamous carcinoma precancer lesions in the developed and developing worlds
The cellular transactivator Brn-3a has previously been shown to be expressed at elevated levels in the cervix of women with squamous cell carcinoma of the cervix (SCC) and to activate the expression of HPV E6 mRNA. In this study, we show that common and rare cervical precancer lesions, including those of adenocarcinoma (AC), which are usually difficult to diagnose using classical procedures, also expressed high levels of Brn-3a and can be diagnosed by measuring the levels of Brn-3a and E6 mRNAs
Focusing a deterministic single-ion beam
We focus down an ion beam consisting of single 40Ca+ ions to a spot size of a
few mum using an einzel-lens. Starting from a segmented linear Paul trap, we
have implemented a procedure which allows us to deterministically load a
predetermined number of ions by using the potential shaping capabilities of our
segmented ion trap. For single-ion loading, an efficiency of 96.7(7)% has been
achieved. These ions are then deterministically extracted out of the trap and
focused down to a 1sigma-spot radius of (4.6 \pm 1.3)mum at a distance of 257mm
from the trap center. Compared to former measurements without ion optics, the
einzel-lens is focusing down the single-ion beam by a factor of 12. Due to the
small beam divergence and narrow velocity distribution of our ion source,
chromatic and spherical aberration at the einzel-lens is vastly reduced,
presenting a promising starting point for focusing single ions on their way to
a substrate.Comment: 16 pages, 7 figure
Spectral asymmetry and Riemannian geometry. III
In Parts I and II of this paper ((4),(5)) we studied the 'spectral asymmetry' of certain elliptic self-adjoint operators arising in Riemannian geometry. More precisely, for any elliptic self-adjoint operator A on a compact manifold we defined ηA(s)=Σλ+0signλ|λ|-8, where λ runs over the eigenvalues of A. For the particular operators of interest in Riemannian geometry we showed that ηA(s) had an analytic continuation to the whole complex s-plane, with simple poles, and that s=0 was not a pole. The real number ηA(0), which is a measure of 'spectral asymmetry', was studied in detail particularly in relation to representations of the fundamental group
Uso do SOC na análise de curvas de crescimento.
bitstream/item/76084/1/CNPTIA-COM.TEC.-8901-89.pd
The strong-CP question in SU(3)_c X SU(3)_L X U(1)_N models
We analyze two recent models based on the gauge group
SU(3)SU(3)U(1) where each generation is not
anomaly-free, but anomaly cancels when three generations are taken into
account. We show that the most general Yukawa couplings of these models admit
of a Peccei-Quinn symmetry. This symmetry can be extended to the entire
Lagrangian by using extra fields in a very elegant way so that the resulting
axion can be made invisible.Comment: Latex, 8 pages, no figure
Controlling fast transport of cold trapped ions
We realize fast transport of ions in a segmented micro-structured Paul trap.
The ion is shuttled over a distance of more than 10^4 times its groundstate
wavefunction size during only 5 motional cycles of the trap (280 micro meter in
3.6 micro seconds). Starting from a ground-state-cooled ion, we find an
optimized transport such that the energy increase is as low as 0.10 0.01
motional quanta. In addition, we demonstrate that quantum information stored in
a spin-motion entangled state is preserved throughout the transport. Shuttling
operations are concatenated, as a proof-of-principle for the shuttling-based
architecture to scalable ion trap quantum computing.Comment: 5 pages, 4 figure
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