Irfan U. Chaudhary

Electron mass shift in nonthermal systems

The electron mass is known to be sensitive to local fluctuations in the electromagnetic field, and undergoes a small shift in a thermal field. It was claimed recently that a very large electron mass shift should be expected near the surface of a metal hydride (Widom and Larsen 2006 Eur. Phys. J. C 46 107). We examine the shift using a formulation based on the Coulomb gauge, which leads to a much smaller shift. The maximization of the electron mass shift under nonequilibrium conditions seems nonetheless to be an interesting problem. We consider a scheme in which a current in a hollow wire produces a large vector potential in the wire centre. Fluctuations in an LC circuit with nearly matched loss and gain can produce large current fluctuations; and these can increase the electron mass shift by orders of magnitude over its room temperature value.

Level splitting in association with the multiphoton Bloch–Siegert shift

We present a unitary equivalent spin-boson Hamiltonian in which terms can be identified which contribute to the Bloch–Siegert shift, and to the level splittings at the anticrossings associated with the Bloch–Siegert resonances. First-order degenerate perturbation theory is used to develop approximate results in the case of moderate coupling for the level splitting.

Excitation transfer in two two-level systems coupled to an oscillator

We consider a generalization of the spin-boson model in which two different two-level systems are coupled to an oscillator, under conditions where the oscillator energy is much less than the two-level system energies, and where the oscillator is highly excited. We find that the two-level system transition energy is shifted, producing a Bloch–Siegert shift in each two-level system similar to what would be obtained if the other were absent. At resonances associated with energy exchange between a two-level system and the oscillator, the level splitting is about the same as would be obtained in the spin-boson model at a Bloch–Siegert resonance. However, there occur resonances associated with the transfer of excitation between one two-level system and the other, an effect not present in the spin-boson model. We use a unitary transformation leading to a rotated system in which terms responsible for the shift and splittings can be identified. The level splittings at the anticrossings associated with both energy exchange and excitation transfer resonances are accounted for with simple two-state models and degenerate perturbation theory using operators that appear in the rotated Hamiltonian.

PROGRESS TOWARD A THEORY FOR EXCESS HEAT IN METAL DEUTERIDES

The strength of the experimental evidence for an excess heat effect in metal deuterides has motivated us to consider theoretical models. The observation of 4He correlated with energy with an associated reaction Q‐value determined experimentally to be near 24 MeV implicates reaction mechanisms consistent with d+d⇥4He+heat. Most significant is that the reaction energy is not expressed through the emission of energetic reaction products. Hence, whatever process is involved constitutes a fundamentally new kind of physical mechanism unlike anything seen previously in nuclear physics.Here we discuss a theoretical model that consists of sets of two‐level systems coupled indirectly through a low‐energy oscillator that is off‐resonant. The two‐level systems represent nuclear states, and the oscillator stands in for a highly excited phonon mode. This kind of model exhibits an excitation transfer effect, in which the excitation at one site is transferred to another site. This is interesting since it corresponds to a...

FEW-BODY NUCLEAR WAVE FUNCTIONS

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A New Approach to Theory for the Rhodes Group Experiments with Channeled Pulse Excitation in Xe and Kr Clusters

Rhodes and coworkers have reported a great many results over the last decade showing directional keV x-ray emission in laser pulse channeling experiments in Xe and in Kr clusters. Selective inner-shell ionization has been proposed as a mechanism to produce gain. We propose that directional emission might be due instead to a phased array emission effect, following up-conversion through a new quantum effect.

Multiphoton Bloch–Siegert shifts and level-splittings in spin-one systems

We consider a spin-boson model in which a spin-1 system is coupled to an oscillator. A unitary transformation is applied which allows a separation of terms responsible for the Bloch–Siegert shift, and terms responsible for the level splittings at anticrossings associated with Bloch–Siegert resonances. When the oscillator is highly excited, the system can maintain resonance for sequential multiphoton transitions. At lower levels of excitation, resonance cannot be maintained because energy exchange with the oscillator changes the level shift. An estimate for the critical excitation level of the oscillator is developed.

Multiphoton Bloch–Siegert shifts and level splittings in a three-level system

We consider a generalization of the spin-boson model consisting of a three-level system in a ladder configuration coupled to an oscillator. We find that this model is much more complicated than the spin-boson model, due in part to the presence of more levels and resonances, and because the middle level can be pushed into the upper or lower levels. We make use of a unitary transformation that results in a rotated version of the problem, in which terms primarily responsible for the Bloch–Siegert shift can be isolated from other terms responsible for producing level splittings at anticrossings associated with the Bloch–Siegert resonances. We present a useful approximation to the energy levels in the multiphoton region of the new problem. Good approximate results are obtained for the level splittings at the anticrossings for resonances involving the lower two levels in regions away from accidental or low-order resonances of the upper two levels.

FOUR-BODY RST GENERAL NUCLEAR WAVEFUNCTIONS AND MATRIX ELEMENTS

Physicists have long assumed that the dynamics of nuclear reactions in condensed matter proceeds fast enough that successful approximations can be obtained using a vacuum approximation. Such an approach has been widely successful for many decades in the case of nuclei that have been accelerated. The many experimental claims for anomalous effects in metal deuterides, such as excess heat, helium, low-level fusion, and fast alpha emission, suggest that the use of the vacuum approximation may not be universally applicable. We have been interested in the development of models in which the vacuum approximation is not made, and in which the nuclear system interacts with the local condensed matter environment. Our focus in recent years has been on models in which we propose that phonon exchange takes place during a nuclear reaction that occurs in a lattice. If exchange happens in the case of a highly-excited phonon mode, quantum coupling may occur with other processes that exchange phonons with the same phonon mode. In the case of deuteron-deuteron fusion reactions, the resonating group approximation was used for many years as the primary theoretical tool with which to understand reactions, and to predict reaction cross sections. We have been interested in the generalization of the resonating group method to include lattice effects. A possible generalization is one in which the channel separation factors of the resonating group method, which describe the center-of-mass dynamics, is replaced by a more general channel separation factor which describes the center-of-mass dynamics of the reacting nuclei on the same footing with other nuclei in the lattice. We have termed this a ”lattice resonating group method.” To make detailed calculations with this approach, we need to be able to compute matrix elements and interaction potentials in the presence of phonon exchange. To