Divergence of the quark self-energy in the second quantized chiral bag model

When summing over the intermediate quark states of a spherical cavity, the quark self-energy of the chiral bag model, in lowest order of the pion coupling, is shown to generate a series of terms, each one growing linearly with the angular variable κ. However, there is a cancellation between terms for different κ, which finally leads to an overall linearly divergent series.     

Quantum entanglement in second quantized fermion systems

In this communication we consider the zero temperature properties of entanglement in free and interacting fermion systems following Bogoliubov’s excitation approach. We investigate spin biparticle entanglement in BCS superconductor ground state of electron gas and in EPS state of ³He atoms. The relation between pair-distribution functions and biparticle quantum entanglement is discussed.     

From the first to the second quantized string theory

Starting from the hamiltonian formulation of the bosonic string we calculate the Feynman transition amplitude D. Inverting D we get the kinetic operator and thus the free field action.     

Electrical engineering implications of the quantized sine-Gordon model

Using the Coleman mapping, for a particular value of the coupling constant, the forced sine-Gordon theory is transformed into massive 1+1 dimensional quantum electrodynamics. For the latter, Schwinger's paper time method is employed to calculate the exact transition rate and the resulting V-I characteristic for a model Josephson junction.     

A model for charged second class currents

Choosing a model for the second class axial current composed of an s-wave vector current pseudoscalar meson pair to fix commutation relations, and using vector dominance (B-meson) techniques to calculate, we use recent experimental results to estimate the coupling strength of the second class current. Remarkably, within experimental errors we find that this coupling strength is the same as for the first class current, with the most natural normalization of the second class current. We comment on B-production and Δ production by neutrinos.     

Dynamical charges in the quantized renormalized massive Thirring model

Within Luther's approach to the quantization of the massive Thirring model we construct infinitely many commuting local, conserved charges for the lattice theory. The values of these charges on soliton, antisoliton and breather states are calculated exactly. Scattering processes for these particles are discussed and it is shown that there is no particle production in the lattice nor in the renormalized continuum massive Thirring model.     

A mechanism for the low temperature anharmonicity in CuCl

It is suggested that the ground state of Cu¹⁺ in CuCl contains an appreciable amount of dsp hybridization that depends sensitively on the CuCu distance. Zero point vibrations impose fluctuations in this distance and therefore cause low temperature anharmonicity in CuCl. Diluting CuCl with F may enhance the anomalies in CuCl.     

Delocalization-localization transition due to anharmonicity

Analytical and numerical calculations for a reduced Fermi-Pasta-Ulam chain demonstrate that energy localization does not require more than one conserved quantity. Clear evidence for the existence of a sharp delocalization-localization transition at a critical amplitude A_c is given. Approaching A_c from above and below, diverging time scales occur. Above A_c, the energy packet converges towards a discrete breather. Nevertheless, ballistic energy transportation is present, demonstrating that its existence does not necessarily imply delocalization.     

Onsets of anharmonicity in protein dynamics

Two onsets of anharmonicity are observed in the dynamics of the protein lysozyme. One at T approximately 100 K appears in all samples regardless of hydration level and is consistent with methyl group rotation. The second, the well-known dynamical transition at T approximately 200-230 K, is only observed at a hydration level h greater than approximately 0.2 and is ascribed to the activation of an additional relaxation process. Its variation with hydration correlates well with variations of catalytic activity suggesting that the relaxation process is directly related to the activation of modes required for protein function.     

Scattering theory for a model of an atom in a quantized field

We compute the scattering operator for a simplified model of an atom interacting a with a quantized field. The field is restricted to the vacuum and one-particle sectors, and the atom has only two states. We also solve the inverse scattering problem for the same model. The methods used rely on the particular form of the interaction, which is chosen to mimic the interaction between radiation and matter.This work was partially supported by NSF Grant DMS-8922941.     

Quantum phase transition of entanglement in Heisenberg spin model with quantized field

In this paper, we investigate the entanglement of a two-spin system with Heisenberg exchange interaction in a quantized field. The pairwise entanglement between bipartite subsystems is obtained. It is shown that the entanglement exhibits a quantum phase transition due to the variation of exchang coupling. Phase diagrams are obtained explicitly. The analogy of the quantum phase transition compared to the case under a classical field are addressed.     

Path integral computation of phonon anharmonicity

The partition function of an oscillator disturbed by a set of electron particle paths has been computed by a path integral formalism which permits to evaluate at any temperature the relevant cumulant terms in the series expansion. The low temperature cutoffs in the anharmonic cumulant series are determined fulfilling the constraint of the third law of thermodynamics. The general method here proposed has been applied to the semiclassical Su-Schrieffer-Heeger model whose time dependent source current is linear in the oscillator displacement field. We find that this peculiar current induces large electron-phonon anharmonicities on the phonon subsystem. As a signature of anharmonicity the phonon heat capacity shows a peak whose temperature location strongly varies with the strength of the e-ph coupling. Since the electron hopping potential provides a sizeable background in the low and intermediate temperature range, such a peak is partly smeared in the total heat capacity. Low energy oscillators are more sensitive to anharmonic perturbations.Received: 7 January 2004, Published online: 3 August 2004PACS: 71.20.Rv Polymers and organic compounds - 31.15.Kb Path-integral methods - 63.20.Kr Phonon-electron and phonon-phonon interactions     

A model ferromagnet with first and second order phase transitions

A model ferromagnet with pair and four spin interaction strengths in the ratio x is shown to have classical behaviour for x > 3, and discontinuous magnetization for x ? 3, the point x = 3 corresponding to a tricritical point.     

A new approach to the quantized electrical conductance

The quanta of electrical conductance is derived for a one-dimensional electron gas both by making use of the quasi-classical motion of a quantum fluid and by using arguments related to the uncertainty principle. The result is extended to a nanowire of finite cross section area and to electrons in magnetic field, and the quantization of the electrical conductance is shown. An additional application is made to the two-dimensional electron gas.     

Simple model calculations of spin and quantized aligment for the A ∼ 60–90 superdeformed mass region

We have used a simple model based on the rotational energy formula E(I, K) to study the structure of the superdeformed (SD) mass region 60–90. The higher order inertial parameters A and B of such model were determined by using the Marquardt method of nonlinear least-squares routines to fit the proposed transition energies with their observed values. A good agreement between the calculated and corresponding experimental transition energies of the SD bands is obtained which supports our proposed model. In addition, the frequency dependence of the dynamic, θ⁽²⁾, and static, θ⁽¹⁾, moments of inertia is used to determine the lowest spin (I_f) and the K-value of the considered SD bands; namely, ⁵⁸Ni(b1), ⁵⁸Cu, ⁵⁹Cu(b1), ⁶¹Zn, ⁶²Zn, ⁶⁵Zn, ⁶⁸Zn, ⁸⁴Zr, ⁸⁶Zr(b1), ⁸⁸Mo(b1, b2, b3) and ⁸⁹Tc. As a result of the identity exist among some of the considered SD bands, we have studied the incremental alignment and also the angular momentum alignment.