Bag-model quantum chromodynamics at low energy

Gluon-exchange mediating quark-exchange scattering is the mechanism of lowest order in perturbative QCD that contributes to the strong interactions at low energy. When it is dressed with long-range quark-gluon correlations by means of bag-model wavefunctions, this quark interchange force becomes bilocal in the quark-gluon sector involving the whole bag and non-perturbative. When it is Fierz-rearranged, the quark-interchange amplitude takes on the usual local form for each hadron that is expected from the wealth of empirical knowledge at low energy. This quark interchange is calculated here in the MIT bag model, which is supplemented by tunneling rules, and then applied to elastic NN scattering, and subsequently toπN andππ scattering. For each reaction the OBE interaction is obtained in agreement with meson theoretic models. Repulsive axial-vector meson exchanges are predicted for NN scattering at short range. The chiral structure of the quark interchange force in conjunction with its tunneling aspects suggest an interpretation of the strong interactions at low energy as Josephson currents of non-Abelian superconductivity.     

Bag-model quantum chromodynamics for hyperons at low energy

In a non-perturbative bag model framework, gluon exchange which mediates quark exchange scattering in conjunction with quark interchange is shown to be the basis of the OBE interactions of hyperons at low energy.     

Planck scale effects on some low energy quantum phenomena

Almost all theories of Quantum Gravity predict modifications of the Heisenberg Uncertainty Principle near the Planck scale to a so-called Generalized Uncertainty Principle (GUP). Recently it was shown that the GUP gives rise to corrections to the Schrödinger and Dirac equations, which in turn affect all non-relativistic and relativistic quantum Hamiltonians. In this Letter, we apply it to superconductivity and the quantum Hall effect and compute Planck scale corrections. We also show that Planck scale effects may account for a (small) part of the anomalous magnetic moment of the muon. We obtain (weak) empirical bounds on the undetermined GUP parameter from present-day experiments.     

Photoproduction of pions at low energy

Presented in this paper is a field theory model for photoproduction of pions at low energy. In particular, it is shown that certain interaction terms, which were previously considered to be essential in order to explain the experimental situation corresponding to the spin-3/2 resonances, are really unnecessary and that the presence of these terms are not justifiable from the theoretical point of view. Further, the free parameters in the theory representing the off-mass-shell effects of the spin-3/2 particles are fixed on the basis of theoretical considerations.     

Effective charge-spin models for the low energy excitations in quantum dots

It is shown that the few, strongly correlated electrons in quantum dots can be described by a lattice model at low energies which for many dot-geometries reduces to a spin model. This can be achieved since the low electron density localizes the electrons near their classical ground-state position. Some cases require a generalization of the Ileisenberg model to include “ring” processes, which involve cyclic rotations of more than two electrons. The energy spectra from these effective models are compared with exact and other approximative results.     

Photoluminescence quantum yield and excitation energy migration in low viscosity solutions

An expression for the relative quantum yield is derived for the general case of energy transfer accompanied by diffusion. The migration of excitation energy among donors has been taken into account. Detailed discussion of the case of moderate diffusion is given.     

Braneworld cosmological perturbation theory at low energy

Homogeneous cosmology in the braneworld can be studied without solving bulk equations of motion explicitly. The reason is simply because the symmetry of the spacetime restricts possible corrections in the 4-dimensional effective equations of motion. It would be great if we could analyze cosmological perturbations without solving the bulk. For this purpose, we combine the geometrical approach and the low energy gradient expansion method to derive the 4-dimensional effective action. Given our effective action, the standard procedure to obtain the cosmological perturbation theory can be utilized and the temperature anisotropy of the cosmic background radiation can be computed without solving the bulk equations of motion explicitly.     

Fractional quantum Hall effect at a suppressed energy gap

In the fractional quantum Hall effect regime, the diagonal (ρ_xx) and Hall (ρ_xy) magnetoresistivity tensor components of the two-dimensional electron system (2DES) in gated GaAs/Al_xGa_1−x As heterojunctions are measured together with the capacitance between 2DES and the gate. The 1/3-and 2/3-fractional quantum Hall effects are observed at rather low magnetic fields where the corresponding fractional minima in the thermodynamic density of the states have already disappeared, thus, implying the suppression of the quasiparticle energy gaps. The text was submitted by the authors in English.     

Lattice controlled transport in quantum wires at low temperatures

Theory of acoustic scattering rate of the carriers in a quantum wire has been developed under the condition of low temperature when the approximations of the traditional theory are hardly valid. The scattering rates thus obtained are then used to estimate the zero-field mobility characteristics in a narrow channel GaAs–GaAlAs quantum wire. On comparison with other available results it is revealed that the finite energy of the acoustic phonons and the complete phonon distribution without any truncation lead to significantly different transport characteristics at low temperatures.     

Boundary entropy of one-dimensional quantum systems at low temperature

The boundary beta function generates the renormalization group acting on the universality classes of one-dimensional quantum systems with boundary which are critical in the bulk but not critical at the boundary. We prove a gradient formula for the boundary beta function, expressing it as the gradient of the boundary entropy s at fixed nonzero temperature. The gradient formula implies that s decreases under renormalization, except at critical points (where it stays constant). At a critical point, the number exp((s) is the "ground-state degeneracy," g, of Affleck and Ludwig, so we have proved their long-standing conjecture that g decreases under renormalization, from critical point to critical point. The gradient formula also implies that s decreases with temperature, except at critical points, where it is independent of temperature. It remains open whether the boundary entropy is always bounded below.     

Chiral dynamics in bag-model QCD at low energy

The Goldberger-Treiman relation is studied in bagged QCD and related to the lowest order of chiral expansions of hadronic wave functions involving quark-antiquark admixtures. The latter contribute to meson-nuclear dynamics, e.g. the pion-nucleon absorption vertex and the neutron charge from factor.     

Perspectives for low energy antiproton physics at FAIR

The CRYRING accelerator, previously located at the Manne Siegbahn Laboratory of Stockholm University, has been chosen by the FLAIR collaboration as the central accelerator for the planned facility. It has been modified to allow for high-energy injection and extraction and is capable of providing fast and slow extracted beams of antiprotons and highly charged ions. It is currently being installed at the ESR of GSI Darmstadt where it can be used with highly charged ions. The future possibilities for its use with slow antiprotons will be discussed.     

Transmission phase lapses at zero energy in graphene quantum dots

We address theoretically the electronic transport through graphene quantum dots with the emphasis on the transmission phase. Analytical and numerical results are presented regarding the existence – or not – of a π lapse of the transmittance phase (and, consequentially, a Fano zero in the transmittance) at the charge neutrality point. A simple universal criterium is found, the phase lapses being always present if the contact sites belong to the same sub‐lattice. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Anisotropy-induced quantum critical behavior of magnetite nanoparticles at low temperatures

The classical, thermally driven transition from ferrimagnets to superparamagnets in Fe₃O₄ nanoparticles can be converted into another quantum phase by a transverse microwave magnetic field or by a strong internal anisotropic field. These fields, perpendicular to the Ising axis, can destroy the magnetic long-range order to quantum paramagnets as the fields exceed some critical values. We have exploited the spin resonance spectrometer to determine the dynamic spin susceptibility and the critical exponent γ, which is a power-law dependent spanning of the quantum critical point. Quantum phase transition observed at low temperatures for small magnetite nanoparticles induced by strong surface anisotropic field illustrates the fascinating interplay between thermal and quantum fluctuations in the vicinity of a quantum critical point.