On the impact of large amplitude pairing fluctuations on nuclear spectra

The influence of large amplitude pairing fluctuations is investigated in the framework of beyond mean field symmetry conserving configuration mixing calculations. In the numerical application the finite range density dependent Gogny force is used. We investigate the nucleus ⁵⁴Cr with particle number and angular momentum projected wave functions considering the axial quadrupole deformation and the pairing gap degree of freedom as generator coordinates. We find that the effects of the pairing fluctuations increase with the excitation energy and the angular momentum. The self-consistency in the determination of the basis states plays an important role.     

Angular momentum mixing in single flavor color superconductivity with transverse pairing

Because of the equal strength of the pairing potential mediated by one-gluon exchange for all partial waves to the leading order QCD running coupling constant and the nonlinearity of the gap equation, the non-spherical pairing in single flavor color superconductivity (CSC) cannot be restricted in a single non-s-wave channel and the mixing among different angular momenta will occur. In this paper, we examine the angular momentum mixing in single flavor CSC of massless quarks with transverse pairing, in which the pairing quarks have opposite helicity. We find that the free energy of all non-spherical pairing states are lowered by angular momentum mixing compared with that contain p-wave only, though the amount of the free energy drop is numerically small. Consequently the most stable pairing state in the ultra-relativistic limit remains the spherical color-spin-locked state (CSL).     

Angular momentum mixing in a non-spherical color superconductor

We study the angular momentum mixing effects in the color superconductor with non-spherical pairing. We first clarify the concept of the angular momentum mixing with a toy model for non-relativistic and spinless fermions. Then we derive the gap equation for the polar phase of dense QCD by minimizing the CJT free energy. The solution of the gap equation consists of all angular momentum partial waves of odd parity. The corresponding free energy is found to be lower than that reported in the literature with p-wave only.     

Theory of angular momentum waves in solid ortho-hydrogen

The Theory of angular momentum waves in pure ortho-hydrogen is presented in the Bloch spin wave approximation. Since there is a large energy gap between the ground state and the excitation this approximation can be justified. Quadrupole-quadrupole interaction of nearest neighbours is used. We have derived some dispersion curves and the spectrum.     

Study ofpf-shell nuclei with a symmetry conserving generator coordinate method

Bands based on the 0⁺ ground state and the first excited 0⁺ pairing vibrational state of⁴⁸Ti,⁵²Cr and⁵⁶Fe are studied with the generator coordinate method. The generating wave functions for each value of the angular momentumJ are angular momentum and particle number projected selfconsistent Hartree-Fock-Bogoliubov states where the constrained amount of pairing correlations serves as the generator coordinate. The interaction is given by reaction matrix elements derived from the Hamada-Johnston force. The basis includes the four lowest oscillator shells. The excitation energies of the pairing vibrational states can be reproduced fairly well by the present choice of the generating wave functions, whereas the ground band is not much improved compared to projected Hartree-Bogoliubov calculations. We find that the strength of the pairing correlations in the 0⁺ and 2⁺ states of the ground state and the pairing vibrational bands can be related to data of two-particle transfer reactions. The angular momentum dependence of the pairing correlations and of the moments of inertia are studied. The results show that for a strongly paired ground state the ground state band and the pairing vibrational band intersect. This may produce in the yrast band the anomaly of the moment of inertia known from rare earth nuclei.     

Nuclear Level Density with Non-zero Angular Momentum

The statistical properties of interacting fermions have been studied for various angular momentum with the inclusion of pairing interaction. The dependence of the critical temperature on angular momentum for several nuclei,have been studied. The yrast energy as a function of angular momentum for 28 Si and 24Mg nuclei have been calculated up to 60.0 MeV of excitation energy. The computed limiting angular momenta are compared with the experimental results for 26Al produced by 12C 14N reaction. The relevant nuclear level densities for non-zero angular momentum have been computed for 44Ti and l36Ba nuclei. The results are compared with their corresponding values obtained from the approximateformulas.     

State-specified protonium formation in low-energy antiproton-hydrogen-atom collisions

We calculate state-specified protonium-formation cross sections in low-energy antiproton-hydrogen-atom collisions by solving the Chew-Goldberger-type integral equation directly instead of integrating the traditional differential scattering equation. Separating the incident wave from the total wave function, we calculate only the scattered outgoing wave propagated by the Green function. The scattering boundary condition is hence automatically satisfied without the tedious procedure of adjusting the wave function at the asymptotic region. The formed protonium atoms tend to be distributed in higher angular momentum l and higher principle quantum number n states as the collision energy increases. The present method has the advantage over the traditional ones in the sense that the required memory size and the computational time are much smaller, and accordingly the problem can be solved with higher accuracy.     

Nodal d + id pairing and topological phases on the triangular lattice of Na(x)CoO(2).yH(2)O: evidence for an unconventional superconducting state

We show that finite angular momentum pairing chiral superconductors on the triangular lattice have point zeroes in the complex gap function. A topological quantum phase transition takes place through a nodal superconducting state at a specific carrier density x(c) where the normal state Fermi surface crosses the isolated zeros. For spin-singlet pairing, we show that the second-nearest-neighbor (d+id)-wave pairing can be the dominant pairing channel. The gapless critical state at x (c) approximately 0.25 has six Dirac points and is topologically nontrivial with a T3 spin relaxation rate below T(c). This picture provides a possible explanation for the unconventional superconducting state of Na(x)Co O(2). yH(2)O. Analyzing a pairing model with strong correlation using the Gutzwiller projection and symmetry arguments, we study these topological phases and phase transitions as a function of Na doping.     

On the QCD pomeron at large momentum transfer

We investigate the asymptotics of the QCD scattering amplitude with vacuum quantum number exchange in the region where the energy is large and the momentum transfer is much smaller than the energy but large compared to the hadronic scale. The appropriate modification of the QCD pomeron partial wave equation is derived. The singularities in the angular momentum which arise at relatively large momentum transfer are studied in double logarithmic approximation.     

Small-q phonon-mediated superconductivity in organic kappa-BEDT-TTF compounds

We propose a new picture for superconductivity in kappa-(BEDT-TTF)2X salts arguing that small- q electron-phonon scattering dominates the pairing. We reproduce the distinct X-shaped d-wave gap reported recently by magneto-optic measurements and we argue that the softness of the momentum structure of the gap and the near degeneracy of s- and d-wave gap states may be at the origin of the experimental controversy about the gap symmetry. We show that a magnetic field applied parallel to the planes may induce extended gapless regions on the Fermi surface accounting for the experimental signatures of a Fulde-Ferrel-Larkin-Ovchinikov state and it may induce gap symmetry transitions as well.     

Angular momentum analysis of a composite particle scattering problem and its cross channel analog

We investigate the solutions, by a determinental method, for a partial wave Bethe-Salpeter equation describing composite particle scattering and for its cross channel analog. We compare the behavior at s = ?∞ of the leading angular momentum singularity from the Bethe-Salpeter equation with that of the leading Regge singularity of the cross channel equation. We mention the effect of the general properties of the kernel of the Bethe-Salpeter equation on the angular momentum structure of the solution.     

低能π介子—核子散射

本文应用向前方向附近的定角色散关系推出了π介子-核子散射的s波和p波振幅的积分方程。方程中包含湮没过程的贡献,其中主要贡献来自二π介子中间态,为了检验ππ作用在π介子-核子散射过程中的效应,将散射相移观察值代入方程中作了数值计算。利用了核子电磁结构形式因子的实验知識,取共振能量平方t_r=20,得到了I=J=1ππ散射共振宽度参数r≌0.1。此结果可同时符合三个低角动量分波振幅的实验材料,但共振宽度要比观察值小。     

Superfluid pairing gap in strong coupling

The zero-temperature pairing gap is a fundamental property of interacting Fermions, providing a crucial test of many-body theories in strong coupling. We analyze recent cold-atom experiments on imbalanced Fermi systems using Quantum Monte Carlo results for the superfluid and normal phases. Through this analysis we extract, for the first time, the experimental zero-temperature pairing gap in the fully paired superfluid state at unitarity where the two-body scattering length is infinite. We find that the zero-temperature pairing gap is greater than 0.4 times the Fermi energy E(F), with a preferred value of (0.45+/-0.05) E(F). The ratio of the pairing gap to the Fermi Energy is larger here than in any other Fermi system measured to date.     

Probing superconducting phase fluctuations from the current noise spectrum of pseudogapped metal-superconductor tunnel junctions

We study the current noise spectra of a tunnel junction of a metal with strong pairing phase fluctuation and a superconductor. It is shown that there is a characteristic peak in the noise spectrum at the intrinsic Josephson frequency omega(J) = 2eV when omega(J) is smaller than the pairing gap but larger than the pairing scattering rate. In the presence of an ac voltage, the tunneling current noise shows a series of characteristic peaks with increasing dc voltage. Experimental observation of these peaks will give direct evidence of the pair fluctuation in the normal state of high- T(c) superconductors and the pair decay rate can be estimated from the half width of the peaks.     

Investigation on phase and shape transitions in the hot rotating nucleus <Superscript>154</Superscript>Dy

A statistical theory for hot rotating nuclei incorporating deformation, collective and non-collective rotational degrees of freedom, shell effects and pairing correlations is used to investigate the occurrence of phase and shape transitions in the hot rotating deformed nucleus ¹⁵⁴Dy . The interplay of various degrees of freedom and their influence on the behavior of nuclei formed as fused compounds in heavy-ion reactions are studied. A phase transition from the superfluid to normal state in the nucleus with increasing temperature and angular momentum is observed. The effect of pairing on the level density parameter and nucleon separation energy has been analyzed and is found to be substantial. The neutron and proton separation energies extracted as a function of the angular momentum and temperature is found to decrease sharply for particular angular momentum states of the nucleus due to shape transitions from prolate collective to oblate non-collective at higher temperatures.     

Absorption of a massless scalar wave from a Schwarzschild black hole surrounded by quintessence

By using the partial wave method,we investigate the absorption of a massless scalar wave from a Schwarzschild black hole surrounded by quintessence.We obtained the expression of absorption cross section σabs(ω)=π/ω2sum from l=0 to ∞(2l+1)|Tωl(ω)|2=π/ω2sum from l=0 to ∞(2l+1)Γωl(ω).Then we numerically carry out the absorption cross section and we find that the larger the angular momentum quantum number l is,the smaller the corresponding maximum value of the partial absorption cross section is,and that the total absorption cross section tends to the geometric-optical limit σ hf abs ≈πb 2 c.We also find that higher value of ω q(state parameter of quintessence) corresponds to the higher value of absorption cross section σ abs.     

平均场加邻近轨道对力模型描述N=94同中异质素性质

利用严格可解的Nilsson平均场加邻近轨道对力模型,在区分质子和中子情况下,研究了大形变核的性质,主要计算了中子数为N=94的同中异质素的结合能、奇偶能差和转动惯量,并与相应的实验值进行了系统比较,结果表明此模型可以合理描述这些性质,正确反映原子核奇偶性质的变化规律。然后以偶偶核160Dy为例,研究了基态中各角动量J=0,1,...,12价核子对的占有率。结果表明,偶角动量占有率远高于奇角动量占有率,其中S,D,G价核子对各组份在基态波函数中是主要的。The Nilsson mean-field plus the nearest orbit pairing model for deformed nuclei is applied to investigate systematically the properties of the N=94 nuclei,employing both proton-proton and neutron-neutron pairing interactions.The binding energies,even-odd mass differences,moments of inertia are calculated and compared with the corresponding experimental data.The results show that this model can reasonably describe these properties.Further,the ground-state occupation probabilities of valence nucleon pairs with angular momentum J=0,1,...,12 for even-even 160Dy are calculated,and the results show that it is much higher for the even angular momenta than the odd angular momenta,and the S,D,G components in the ground-state wave function are dominant.     

Generalized counting rule for hard exclusive processes

We derive a generalized counting rule for hard exclusive processes involving parton orbital angular momentum and hadron helicity flip. We start with a systematic way to enumerate the Fock components of a hadronic light-cone wave function with n partons and orbital angular momentum projection l(z). We show that the wave-function amplitude psi(n)(x(i),k(i perpendicular ),l(zi)) has a leading behavior 1/(k(2)( perpendicular ))[n(+|l(z)|+min(n(')+|l(')(z)|)]/2-1) when all parton transverse momenta are uniformly large, where n(') and l(')(z) are the number of partons and orbital angular momentum projection, respectively, of an amplitude that mixes under renormalization. Besides the generalized counting rule, the result can be used as a constraint in modeling the hadronic light-cone wave functions.