1N expansion and renormalization in quantum gravity

Gravity coupled to N massless fermions is expanded in powers of $\text{1}\text{N}$, keeping κ²N fixed. The resulting lowest order graviton propagator has (k⁴log k²)^?1 asymptotic behavior, and no tachyon or unphysical real bound state poles. There are, however, complex conjugate poles on the physical sheet. This leads to a unitary, and renormalizable, though “non-analytical” S-matrix.     

Gauge sets and the 1N expansion

All the linearly independent gauge-invariant relations, up to order ten in the coupling constant, are obtained as coefficients of the $\text{1}\text{N}$ expansion in a generic non-abelian gauge theory. The large-order expansion of the group SO(N) × U(1) is the most effective tool.     

Quantum collective field and 1N correction

The collective field method and the large-N limit are applied to go beyond the Hartree-Fock approximation. The correction to the ground-state energy is presented and explicit results are calculated for interacting oscillators and the Bose gas with the δ interaction.     

Spontaneous supersymmetry breaking in 1N leading order

We present a supersymmetric model, with only chiral superfields, invariant under an internal O(N) global symmetry. We show that, to leading order in $\text{1}\text{N}$, an auxiliary scalar field acquires a non-vanishing vacuum expectation value, that is, supersymmetry is spontaneously broken to this order of the approximation.     

On the validity of the 1N expansion

We consider possible effects that may invalidate the $\text{1}\text{N}$ method in some statistical and field models. Discussion is in the framework of the model of charged, non-relativistic fermions with N-component spin. The static dielectric function ?(q, 0) is predicted to have a pole in N. The real parameter of the $\text{1}\text{N}$ expansion is shown to be an increasing function of the coupling constant.     

Consistency requirements for 1N expandable field theories

It is demonstrated that $\text{1}\text{N}$ expansion in a class of field theories with an internal O(N) symmetry leads to pathologies. Therefore, these models are either not internally consistent, or their perturbation expansions (ordinary as well as $\text{1}\text{N}$ are unreliable.     

Interacting instantons, 1N expansion and the gluon condensate

Based on the dilute gas approximation (DGA) with repulsive and dipole interactions we discuss the N dependence of the vacuum energy density, 〈α_SF_μν^aF_μν^a〉 and of the topological charge correlation function at the crossover point of the instanton driven β function with the strong coupling one.     

Q gravity

The geometrical structure of an extended theory of gravitation incorporating the quaternion field is investigated. A lagrangian is constructed and shown to be pure real as a consequence of the geometrical structure. The structure of spacetime becomes nonabelian; however, the base manifold in which physics takes place, remains real and n-dimensional.     

Electronic structure of the GeGaAs (111) and (111) heterojunctions

The electronic density of states for GeGaAs (111) and ($\text{1}$$\text{1}$$\text{1}$) heterojunctions has been calculated. No interface states in the fundamental gap are found. A sizeable density of interface states below the top of the valence band is found for GeGa bonds-(111) junctions-interface states in the ionic gap are reported. The effect of varying the amount of the valence band discontinuity across the interface is discussed.     

A study of ππ → NN partial-wave amplitudes using hyperbolic dispersion relations

We investigate $\text{ππ →}\text{N}\text{N}$ partial-wave amplitudes, using a spin separation method based on hyperbolic dispersion relations. Partial-wave amplitudes with J ? 3 are dominant in the pseudophysical region between the ππ and $\text{N}\text{N}$ thresholds, but we find clear evidence for J = 4 and J = 5 contributions from regions near and above the $\text{N}\text{N}$ threshold. We isolate J = 2 and J = 3 partial waves and determine the couplings of f₀(1270) and g (1680). Knowing the high-spin contributions, we are able to eliminate thse and to study s- and p-waves. We find evidence for small p-wave contributions above the ?, having the same sign as the ? contributions. We develop methods for determining the I = J = 0 ππ scattering length a₀⁰ and find a₀⁰ = 0.30 ± 0.15.     

Origin of 1ƒ noise

$\text{1}\text{?}$ noise dependence on temperature for both n- and p-type silicon has been measured. The formula for calculation of $\text{1}\text{?}$ noise is presented. The formula has been derived by presumption that only lattice scattering gives $\text{1}\text{?}$ noise. A good agreement between calculations and experimental results is found.     

Phonon observations from 1ƒ noise measurements

From mobility fluctuation $\text{1}\text{?}$ noise parameter measurements five phononic energies corresponding to LO, TO vibrational modes as well as TA + S₂ or O, TO + TA, TO + O combined modes were identified. They stand for phonon replicas of non-radiative recombination processes. It is thus demonstrated that the carrier-phonon interaction is the source of $\text{1}\text{?}$ noise in semiconductors.     

KN data and Λ (1405)

A re-analysis of low-energy $\text{K}\text{N}$ data has been made to investigate the effects of imposing constraints below the elastic threshold. Our results show that without below-threshold constraints little information about the parameters of the Λ(1405) can be determined.     

Analysis of topological cross sections in pp interactions at 22.4 GeVc

The multiplicity distribution for 11558 events in $\text{p}\text{p}$ interactions at 22.4 $\text{GeV}\text{c}$ was analyzed. The average charged multiplicity 〈n_ch〉 for inelastic events was found to be 4.69 ±0.05 and $\text{〈n}{}_{\mathrm{ch}}\text{〉}\text{D=2.04 ± 0.05}$. The early KNO scaling of normalized topological cross sections has been tested.     

The spin 12 gravitational anomalous magnetic moment

The gravitational anomalous magnetic moment of a spin $\text{1}\text{2}$ particle is calculated and compared with an earlier dimensional regularization result. The answers disagree although both agree the answer is finite. It is argued that this quantity is not uniquely determined by physical requirements. The methods used are shown to respect the gravitational and electromagnetic gauge invariances. In addition, a physical interpretation of the regularization method employed is offered.     

Relativistic transport equation for spin 12 particles

For the model of positive energy Dirac particles with short range interaction a transport equation for the one- particle Wigner function is obtained. This transport equation is a generalization of the non-relativistic Walsmann- Snider equation for spin particles.     

On the low-frequency current 1f noise in metals

The spectral density of the resistivity noise caused by those relaxation mechanisms of the defects which are responsible for the low-frequency internal friction is calculated. The $\text{1}\text{f}$ noise is related to the magnitude of the background in the internal friction spectrum of the metal. The current noise arising from two-level tunneling systems is also evaluated.     

Electrical conduction and 1ƒ noise in Li-DOPED MnO

Electrical resistivity, thermoelectric power and current noise were measured on Li-doped MnO single crystals in the temperature range from 300 to 1000 K. Below 700 K the crystals are p-type and the activation energy of the resistivity is 0.75 eV. Around 700 K the activation energy changes from 0.75 to 1.25 eV owing to a change from p- to n-type conduction. The depth of the Li acceptor is found to be 0.65 eV. From resistivity and thermoelectric power data it is concluded that the bandgap in first approximation can be written as E_s(T) = E_o ? γT between 750 and 1000 K, with E_o = 1.9 eV and γ = 6 × 10^?4 eV/K. The current noise spectra show $\text{1}\text{?}$ noise. The magnitude of the $\text{1}\text{?}$ noise is strongly temperature dependent. From the noise data it is deduced that E_o = 2.2 eV and γ = 10^?3 eV/K in the temperature range 430–700 K.     

Possible mechanism contributing to 1f noise in SQUIDs

It is shown that $\text{1}\text{f}$ noise, which is observed in SQUIDs, could arise from thermal noise in any superconducting or normal metal loop (e.g. a shield) surrounding the SQUID. Numerical results agree well with existing experimental data.