Competing valence bond and symmetry breaking Mott states of spin-3/2 fermions on a honeycomb lattice

We investigate magnetic properties of strongly interacting four component spin-3/2 ultracold fermionic atoms in the Mott insulator limit with one particle per site in an optical lattice with honeycomb symmetry. In this limit, atomic tunneling is virtual, and only the atomic spins can exchange. We find a competition between symmetry breaking and liquid like disordered phases. Particularly interesting are valence bond states with bond centered magnetizations, situated between the ferromagnetic and conventional valence bond phases. In the framework of a mean-field theory, we calculate the phase diagram and identify an experimentally relevant parameter region where a homogeneous SU(4) symmetric Affleck-Kennedy-Lieb-Tasaki-like valence bond state is present

Optimally Dense Packings for Fully Asymptotic Coxeter Tilings by Horoballs of Different Types

The goal of this paper to determine the optimal horoball packing arrangements and their densities for all four fully asymptotic Coxeter tilings (Coxeter honeycombs) in hyperbolic 3-space $\mathbb{H}^3$. Centers of horoballs are required to lie at vertices of the regular polyhedral cells constituting the tiling. We allow horoballs of different types at the various vertices. Our results are derived through a generalization of the projective methodology for hyperbolic spaces. The main result states that the known B\"or\"oczky--Florian density upper bound for "congruent horoball" packings of $\mathbb{H}^3$ remains valid for the class of fully asymptotic Coxeter tilings, even if packing conditions are relaxed by allowing for horoballs of different types under prescribed symmetry groups. The consequences of this remarkable result are discussed for various Coxeter tilings.Comment: 26 pages, 10 figure

Phase Separation of Superfluids in the Chain of Four-Component Ultracold Atoms

We investigate the competition of various exotic superfluid states in a chain of spin-polarized ultracold fermionic atoms with hyperfine spin $F = 3/2$ and s-wave contact interactions. We show that the ground state is an exotic inhomogeneous mixture in which two distinct superfluid phases --- spin-carrying pairs and singlet quartets --- form alternating domains in an extended region of the parameter space

SU(N) quantum spin models: A variational wavefunction study

The study of SU(N) quantum spin models is relevant to a variety of physical systems including ultracold atoms in optical lattices, and also leads to insights into novel quantum phases and phase transitions of SU(2) spin models. We use Gutzwiller projected fermionic variational wavefunctions to explore the phase diagram and correlation functions of SU(N) spin models in the self-conjugate representation, with Heisenberg bilinear and biquadratic interactions. In 1D, the variational phase diagram of the SU(4) spin chain is constructed by examining instabilities of the Gutzwiller projected free fermion ground state to various broken symmetries, and it agrees well with exact results.The spin and dimer correlations of the Gutzwiller projected free fermion state with N flavors of fermions are also in good agreement with exact and 1/N calculations for the critical points of SU(N) spin chains. In 2D, the variational phase diagram on the square lattice is obtained by studying instabilities of the Gutzwiller projected pi-flux state. The variational ground state of the pure Heisenberg model is found to exhibit long range Neel order for N=2,4 and spin Peierls order for N > 4. For N=4 and 6, biquadratic interactions lead to a complex phase diagram which includes an extended valence bond crystal in both cases, as well as a stable pi-flux phase for N=6. The spin correlations of the projected pi-flux state at N=4 are in good agreement with 1/N calculations. We find that this state also shows strongly enhanced dimer correlations, in qualitative accord with the large-N results. We compare our results with a recent QMC study of the SU(4) Heisenberg model.Comment: 22 pages, 7 figs, added references to arxiv versio

The betatron and its medical application

It is well known, that high-energy electrons can be used for tumor therapy. The so-called conventionel therapy with 100 through 250keV x· rays causes a great part of the x.rays to be scattered and absorbed in the sane tissue. In spite of the medicamental radiation prophylaxis additional radiation diseaes result by those compton scattered rays. By application of fast electrons and hard x.rays (so called gamma. rays) one tries to diminish those undesired side-effects and at the same time to increase the therapeutical effect of the ray treatment. As radiation source for fast electrons and hard gamma.rays one uses the Betatron, which was developed by NBRST in 1941 after preliminary operation of SLEPIAN, WALTON, WIDEROE and STEENDECK. The following statements are based on the references (1) through (6).</p

Possible phases of two coupled n-component fermionic chains

A two-leg ladder with $n$-component fermionic fields in the chains has been considered using an analytic renormalization group method. The fixed points and possible phases have been determined for generic filling as well as for a half-filled system and for the case when one of the subbands is half filled. A weak-coupling Luttinger-liquid phase and several strong-coupling gapped phases have been found. In the Luttinger liquid phase, for the most general spin dependence of the couplings, all $2n$ modes have different velocities if the interband scattering processes are scaled out, while $n$ doubly degenerate modes appear if the interband scattering processes remain finite. The role of backward-scattering, charge-transfer and umklapp processes has been analysed using their bosonic form and the possible phases are characterized by the number of gapless modes. As a special case the SU($n$) symmetric Hubbard ladder has been investigated numerically. It was found that this model does not scale to the Luttinger liquid fixed point. Even for generic filling gaps open up in the spectrum of the spin or charge modes, and the system is always insulator in the presence of umklapp processes

Die wahl der richti-gen therapie bei verschidenen Krankheitbildern durch Registrierung mittels des Szirmaischen Myographen und durch die Berechnung des Reaktions-indexes (R. I.)

Die Autoren haben mit Hilfe des Szirmaischen Myographen auf Grund der Messung vor und nach der Behandlung den Reaktions-Index aus den Myogrammen erhalten. Mit dieser Methode la&#946;t sich in einer sehr kurzen Zeit bei verschiedenen Krankheiten die gunstigste Therapie auswahlen und deren Wirksamkeit in Prozenten auswerten.</p

Neues stomatologisches verfahren : Myologische bestimmung der funktion der kaumuskulatur bzw. des M. masseters mit dem Szirmaischen myotonometer

Die Autoren haben festgestellt, da&#946; man mit Hilfe des Myotonometers auf Grund von Kau- bzw. Masseterfunktionsmessung auf verschiedene stomatologische Krankheiten, bzw. auf verschiedene Veranderungen schliessen kann. Man kann feststellen, ob die Muskeln atrophisch sind oder nicht, was fur eine Prothese bei einzelnen Individuen der Funktion der Muskeln entspricht, ob eine Prothese schlecht ist, welche Verfahren fur die Orthodontie bzw. Prognathie notwendig sind und welche Medikamente eine gute stomatologische Wirkung haben. Auch die verschiedenen orthopadischen Fragen sind erleichtert.</p