Ab initio theory of complex electronic ground state of superconductors: I. Nonadiabatic modification of the Born-Oppenheimer approximation

The ARPES of high-T_c cuprates and theoretical results of low-Fermi energy band structure fluctuation for different groups of superconductors indicate that electron coupling to pertinent phonon modes drive system from adiabatic into anti-adiabatic state (ω>E_F). At these circumstances, not only Migdal-Eliashberg approximation is not valid, but basic adiabatic Born-Oppenheimer approximation (BOA) does not hold. At these circumstances, electronic structure has to be studied as explicitly dependent on instantaneous nuclear coordinates Q as well as on instantaneous nuclear momenta P.In the present paper—part I, it has been shown that Q, P-dependent modification of the BOA for ground electronic state can be derived by sequence of canonical transformations of the basis functions. The effect of nuclear coordinates and momenta on electronic structure is presented in the form of corrections to zero-, one- and two-particle terms of clamped nuclear Hamiltonian. In the anti-adiabatic state, correction to electronic ground state energy (zero-particle term correction) is negative and system can be stabilized in the anti-adiabatic state at distorted geometry with respect to adiabatic equilibrium structure and gap in one-particle spectrum of quasi-continuum states at Fermi level can be opened. Stabilization effect is solely the consequence of nuclear dynamics (P) that is crucial in anti-adiabatic state. It has been shown that nuclear dynamics also increases electron correlation until system at nuclear motion remains in a bound state. Corresponding corrections to electronic wave function are also specified.On the other hand, when system remains at vibration motion of nuclei in adiabatic state, the influence of nuclear dynamics (P-dependence) is negligible. In this case, all basic effects are covered through nuclear coordinates (Q-dependence) within the adiabatic BOA and standard results of solid-state (or molecular) physics are recovered.     

A Conversation with William A. Fowler – Part II

Physicist William A.Fowler initiated an experimental program in nuclear astrophysics after World War II. He recalls here the Steady State versus Big Bang controversy and his celebrated collaboration with Fred Hoyle and Geoffrey and Margaret Burbidge on nucleosynthesis in stars. He also comments on the shift away from nuclear physics in universities to large accelerators and national laboratories.John Greenberg received his Ph.D. degree from the University of Wisconsin and was Caltech research fellow in history from 1980–1984. The Editors were saddened to learn that he died while this interview was in press. Requests for reprints may be directed to Judith R. Goodstein, Institute Archives 015A-74, Caltech, Pasadena, CA 91125 USA; e-mail: jrg@caltech.edu.     

Hyperfine switching triggered by resonant tunneling for the detection of a single nuclear spin qubit

A novel detection mechanism and a robust control of a single nuclear spin-flip by hyperfine interactions between the nuclear spin and tunneling electron spin are proposed on the basis of ab initio non-equilibrium Green's function calculations. The calculated relaxation times of the nuclear spin of proton in a nano-contact system, Pd(electrode)-H₂-Pd(electrode), show that ON/OFF switching of hyperfine interactions is effectively triggered by resonant tunneling mediated through the d-orbitals of Pd. The relaxation times at ON-resonance are ∼¹⁰³ times faster than those at OFF-resonance, indicating that ON-resonance is suitable for the detection (read-out) of nuclear spin states. In addition, the effectiveness of bias voltage applications at OFF-resonance for selective operations on the proton qubit is demonstrated in the calculations of the resonant frequencies of proton using the gauge-invariant atomic orbital method.     

Surface Emission of Quark Gluon Plasma at RHIC and LHC

Within the framework of a factorization model, we study the behaviour of nuclear modification factor in Au Au collisions at RHIC and Pb-Pb collisions at LHC. We find that the nuclear modification factor is inversely proportional to the radius of the quark-gluon plasma and is dominated by the surface emission of hard jets. We predict the nuclear modification factor R^LHC AA - 0.15 in central Pb-Pb collisions at LHC. The study shows that the factorization model can be used to describe the centrality dependence of nuclear modification factor of the high transverse momentum particles produced in heavy ion collisions at both RHIC and LHC.     

Ordered phase of nuclear spins in uniaxial ferromagnets at ultralow temperatures

Paper investigates the onset of nuclear magnetic ordering caused by the indirect Suhl-Nakamura interaction in ferromagnets. The necessary condition for nuclear spin ordering with definite ordering vector is obtained. Particularly, it is shown that ferromagnetically ordered phase of nuclear spins could be observed only in case of disk shaped samples. The spectrum of the nuclear spin excitations is also found. Received 25 January 1999 and Received in final form 5 May 1999     

γ-radiation of excited nuclear discrete levels in peripheral heavy ion collisions

A new process of a nuclear excitation to discrete states in peripheral heavy ion collisions is studied. High-energy photons are emitted by the exited nuclei with energies up to a few tens of GeV at angles of a few hundred microradians with respect to the beam direction. We show that a two-stage process, where an electron-positron pair is produced by virtual photons emitted by nuclei and then the electron or positron excites the nucleus, has a large cross-section. It is equal to about 5 b for CaCa collisions. On the one hand, it produces a significant γ-rays background in the nuclear fragmentation region but, on the other hand, it could be used for monitoring the nuclear beam intensity at the LHC. These secondary nuclear photons could be a good signal for triggering peripheral nuclear collisions. Received: 14 December 2001 / Accepted: 22 January 2002     

Nuclear Effects in Structure Functions xFa（x, Q^2） from Charge Current Neutrino Deep Inelastic Scattering

By taking advantage of the model-independent nuclear parton distributions, the structure functions xF3（x, Q^2） are calculated, in comparison with the experimental data from CCFR neutrino-nuclei charge current deep inelastic scattering. It is shown that shadowing and anti-shadowing effects occur in valence quark distributions for small and medium x regions, respectively. It is suggested that the neutrino experimental data should be employed in the future for pinning down the nuclear patton distributions.     

Nuclear excitation by electron capture followed by fast x-ray emission

The resonance strength of the two-step process of nuclear excitation by electron capture followed by γ decay of the nucleus can be significantly increased in highly charged ions if the resonant capture proceeds via an excited electronic state with subsequent fast x-ray emission. For fully ionized ²³⁸₉₂U and ²³²₉₀Th, the x-ray decay stabilizes the system against internal conversion of the captured electron, with an increase of both nuclear lifetimes and resonance strengths of up to two orders of magnitude compared with the case when occupied atomic orbitals prevent the x-ray de-excitation. Applications of this effect to the measurement of the not yet experimentally observed nuclear excitation by electron capture and to dense astrophysical plasmas are discussed.     

Towards a new Gogny force parameterization: Impact of the neutron matter equation of state

A new parameterization of the effective nucleon–nucleon Gogny interaction is proposed. It reproduces the neutron matter equation of state much better than the commonly used D1S Gogny interaction and furthermore reduces the binding energies' drift for the major part of the isotopic chains. Other important nuclear properties related both to nuclear matter and finite nuclei are studied and shown to be of similar quality as with D1S.     

Nuclear Hexadecapole Deformation Effects on the Production of Super-Heavy Elements

We investigate the effects of the nuclear hexadecapole deformations on the interaction potentials between nuclei, the driving potentials and the fusion probabilities for some cold fusion reactions leading to super-heavy elements. It is found that nuclear hexadecapole deformations change significantly the structure of the driving potentials and the fusion probabilities for some reaction channels.     

A Conversation with William A. Fowler – Part I

Nobel laureate William A. Fowler recalls his early education in physics; his part in the history of nuclear physics at the California Institute of Technology in the 1930s; parallel efforts elsewhere, particularly at Berkeley and the Department of Terrestrial Magnetism in Washington,D.C.; his contacts with J. Robert Oppenheimer; and his work with Charles C. Lauritsen and Tommy Lauritsen before and after World War II.John Greenberg received his Ph.D. degree from the University of Wisconsin and was Caltech research fellow in history from 1980–1984. The Editors were saddened to learn that he died while this interview was in press. Requests for reprints may be directed to Judith R. Goodstein, Institute Archives 015A-74, Caltech, Pasadena, CA 91125 USA; e-mail: jrg@caltech.edu.     

Systematic Study on System Size Dependence of Global Stopping: Role of Momentum-Dependent Interactions and Symmetry Energy

Using the isospin-dependent quantum molecular dynamical model, we systematically study the role of symme- try energy with and without momentum-dependent interactions on the global nuclear stopping. We simulate the reactions by varying the total mass of the system from 80 to 394 at different beam energies from 30 to 1000 Me V/nucleon over central and semi-central geometries. The nuclear stopping is found to be sensitive towards the momentum-dependent interactions and symmetry energy at low incident energies. The momentum-dependent interactions are found to weaken the finite size effects in nuclear stopping.     

Fragmentation Cross Sections of 158 AGeV Pb Projectiles

We investigate the fragmentation cross sections of 158 AGeV ^207Pb projectile interacting with different targets using CR39 nuclear track detectors. The exposure is made at SPS beam facility of CERN. The detectors are chemically etched to obtain data in the form of etched cone length. The nuclear and electromagnetic contributions to the measured total charge-changing cross sections are investigated. The estimated results are compared with those found in the literature for similar research work.     

Kohn–Sham density functional inspired approach to nuclear binding

A non-relativistic nuclear density functional theory is constructed, not as done most of the time, from an effective density dependent nucleon–nucleon force but directly introducing in the functional results from microscopic nuclear and neutron matter Bruckner G-matrix calculations at various densities. A purely phenomenological finite range part to account for surface properties is added. The striking result is that only four to five adjustable parameters, spin–orbit included, suffice to reproduce nuclear binding energies and radii with the same quality as obtained with the most performant effective forces. In this pilot work, for the pairing correlations, simply a density dependent zero range force is adopted from the literature. Possible future extensions of this approach are pointed out.     

Liquid Nuclear Magnetic Resonance Implementation of Quantum Computation in Subspace

Based on the logical labelling method, we prepare an effective pure state in a subsystem of a three spin system via liquid nuclear magnetic resonance technique. Then with this subspace effective pure state we implement the Deutsch-Jozsa algorithm. The tomography for the subspace effective pure state and the corresponding spectrum of the output for the Deutsch-Jozsa algorithm agree with theoretical predictions, which shows that we have successfully implemented the Deutsch-Jozsa algorithm in a subsystem of a nuclear spin system and demonstrated a subspace quantum computation.     

Moment analysis and Zipf law

The moment analysis method and nuclear Zipf's law of fragment size distributions are reviewed to study nuclear disassembly. In this report, we present a compilation of both theoretical and experimental studies on moment analysis and Zipf law performed so far. The relationship of both methods to a possible critical behavior or phase transition of nuclear disassembly is discussed. In addition, scaled factorial moments and intermittency are reviewed.     

EMC and polarized EMC effects in nuclei

We determine nuclear structure functions and quark distributions for ⁷Li, ¹¹B, ¹⁵N and ²⁷Al. For the nucleon bound state we solve the covariant quark–diquark equations in a confining Nambu–Jona-Lasinio model, which yields excellent results for the free nucleon structure functions. The nucleus is described using a relativistic shell model, including mean scalar and vector fields that couple to the quarks in the nucleon. The nuclear structure functions are then obtained as a convolution of the structure function of the bound nucleon with the light-cone nucleon distributions. We find that we are readily able to reproduce the EMC effect in finite nuclei and confirm earlier nuclear matter studies that found a large polarized EMC effect.