Solitonic excitations in the Haldane phase of a S=1 chain

We study low-lying excitations in the 1D $S=1$ antiferromagnetic valence-bond-solid (VBS) model. In a numerical calculation on finite systems the lowest excitations are found to form a discrete triplet branch, separated from the higher-lying continuum. The dispersion of these triplet excitations can be satisfactorily reproduced by assuming approximate wave functions. These wave functions are shown to correspond to moving hidden domain walls, i.e. to one-soliton excitations.Comment: RevTex 3.0, 24 pages, 2 figures on request by fax or mai

Proximal 21q deletion as a result of a <i>de novo </i>unbalanced t(12;21) translocation in a patient with dysmorphic features, hepatomegaly, thick myocardium and delayed psychomotor development

BACKGROUND: IInterstitial 21q deletions can cause a wide spectrum of symptoms depending on the size and the location of the deletion. It has previously been suggested that the long arm of chromosome 21 can be divided into three regions based on the clinical severity of the patients and deletion of the region from 32.3 Mb to 37.1 Mb was more crucial than the deletion of other regions. CASE PRESENTATION: In this study we describe a female patient with dysmorphic features, hepatomegaly, thick myocardium and psychomotor delay. Conventional karyotyping was initially interpreted as full monosomy 21, but subsequent chromosome microarray analysis suggested an approximately 18 Mb partial monosomy. Re-evaluation of the karyotype and fluorescence in situ hybridization revealed deletion of the proximal 21q11.2-q22.11 segment and insertion of 21q22.11-qter to 12qter. The deletion of the present case overlaps with two of the proposed regions including part of the proposed crucial region. CONCLUSIONS: This report emphasizes the relevance of investigating suspected full monosomies with high resolution methods and FISH in order to investigate the extent of the deletion and the presence of more complex rearrangements

Using the Hadamard and related transforms for simplifying the spectrum of the quantum baker's map

We rationalize the somewhat surprising efficacy of the Hadamard transform in simplifying the eigenstates of the quantum baker's map, a paradigmatic model of quantum chaos. This allows us to construct closely related, but new, transforms that do significantly better, thus nearly solving for many states of the quantum baker's map. These new transforms, which combine the standard Fourier and Hadamard transforms in an interesting manner, are constructed from eigenvectors of the shift permutation operator that are also simultaneous eigenvectors of bit-flip (parity) and possess bit-reversal (time-reversal) symmetry.Comment: Version to appear in J. Phys. A. Added discussions; modified title; corrected minor error

Excitation Spectrum of the Spin-1/2 Ferromagnetic-Antiferromagnetic Alternating Heisenberg Chain:

The natural explanation of the excitation spectrum of the spin-1 antiferromagnetic Heisenberg chain is given from the viewpoint of the spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain. The energy spectrum of the latter is calculated with fixed momentum $k$ by numerical diagonalization of finite size systems. It consists of a branch of propagating triplet pair (triplet wave) and the continuum of multiple triplet waves for weak ferromagnetic coupling. As the ferromagnetic coupling increases, the triplet wave branch is absorbed in the continuum for small $k$, reproducing the characteristics of the spin-1 antiferromagnetic Heisenberg chain.Comment: 12 Pages REVTEX, Postscript file for the figures included. SKPH-94-C00

Nuclear Magnetic Relaxation in the Haldane-Gap Antiferromagnet Ni(C_2_H_8_N_2_)_2_NO_2_(ClO_4_)

A new theory is proposed to interpret nuclear spin-lattice relaxation-time (T_1_) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C_2_H_8_N_2_)_2_NO_2_(ClO_4_) (NENP). While Sagi and Affleck pioneeringly discussed this subject in terms of field-theoretical languages, there is no theoretical attempt yet to explicitly simulate the novel observations of 1/T_1_ reported by Fujiwara et al.. By means of modified spin waves, we solve the minimum of 1/T_1_ as a function of an applied field, pending for the past decade.Comment: to be published in J. Phys. Soc. Jpn. 73, No. 4 (2004

An extended massless phase and the Haldane phase in a spin-1 isotropic antiferromagnetic chain

We study the phase transition of isotropic spin-1 models in the vicinity of the Uimin-Lai-Sutherland model by using the SU(3)_1 WZW model with certain marginal perturbations. The unstable RG trajectory by a marginally relevant perturbation generates a mass gap for the Haldane phase, and thus the universality class of the transition from the massless phase to the Haldane phase at ULS point becomes the BKT type. Our results support recent numerical studies by F\'ath and S\'olyom. In the massless phase, we calculate logarithmic finite-size corrections of the energy for the SU(\nu)-symmetric and asymmetric models.Comment: 19 pages, RevTe

Rußlands Perspektiven: kritische Faktoren und mögliche Entwicklungen bis 2010

'Rußland hat erhebliche Probleme, den Erwartungen seiner Partner als berechenbarer Akteur in den internationalen Beziehungen zu entsprechen. Die Transformation ist auf halbem Wege steckengeblieben, die finanzielle Basis für eine strukturelle Erneuerung ist drastisch geschrumpft. Der inzwischen eingetretene Kontrollverlust der Verantwortlichen ist besorgniserregend. Nationalistische Kräfte in Rußland denunzieren den Verfall der russischen Wirtschaft als Ergebnis einer Diskriminierungs-, ja Zersetzungspolitik des Westens. Auf der anderen Seite haben Geldgeber und Öffentlichkeit im Westen kein Verständnis mehr für Forderungen der Regierung in Moskau, ihr immer aufs neue durch finanzielle Stützungsaktionen entgegenzukommen. Die russische Politik hat sich in eine prekäre wirtschaftliche Abhängigkeit von westlicher Kooperation manövriert, die auch dem Westen wenig politischen Spielraum läßt. Die Erfahrung der letzten Jahre zeigt indes, daß Appelle von außen zur Behebung dieser Probleme solange ins Leere gehen, wie es den in demokratischen Wahlen legitimierten Eliten an Verantwortungsbewußtsein und Konsensfähigkeit fehlt.' (Textauszug)'Russia is having major problems fulfilling the expectations of its partners with regard to becoming a predictable actor in international relations. The transformation process has come to a standstill and the financial basis for structural renewal has shrunk drastically. The loss, of control of those in positions of responsibility is worrying. Nationalist forces in Russia are blaming the collapse of the Russian economy on a discriminatory or even subversive policy on the part of the West. At the same time, financiers and the Western public have run out of patience with the Russian government's continual demands for the West to keep propping it up with new financial aid packages. Russian politicians have manoeuvred themselves into a position of precarious economic dependence on Western co-operation, which has the effect of limiting the West's political options as well. The experience of the past few years has shown, moreover, that appeals from outside to resolve these problems will go on falling on deaf ears as long as the democratically elected, and therefore legitimate, elite falls to show a sense of responsibility and consensus-achieving ability.' (extract

Two-color rubidium fiber frequency standard

We demonstrate an optical frequency standard based on rubidium vapor loaded within a hollow-core photonic crystal fiber. We use the 5S(1/2)→5D(5/2) two-photon transition, excited with two lasers at 780 and 776 nm. The sum-frequency of these lasers is stabilized to this transition using modulation transfer spectroscopy, demonstrating a fractional frequency stability of 9.8×10(-12) at 1 s. The current performance limitations are presented, along with a path to improving the performance by an order of magnitude. This technique will deliver a compact, robust standard with potential applications in commercial and industrial environments.C. Perrella, P. S. Light, J. D. Anstie, F. N. Baynes, F. Benabid, and A. N. Luite