54611279
Number-conserving theory of nuclear pairing gaps: A global assessment
We study odd-even mass staggering of nuclei, also called pairing gaps, using a Skyrme self-consistent mean-field theory and a numerically exact treatment of the pairing Hamiltonian. We find that the configuration-space Monte Carlo method proposed by Cerf and Martin [Phys. Rev. C 47, 2610 (1993)] offers a practical computational procedure to carry out the numerical solutions in large-dimensional model spaces. Refitting the global strength of the pairing interaction for 443 neutron pairing gaps in our number-conserving treatment, we find the correction to the pairing correlation energies and pairing gaps to have rms values of 0.6 and 0.12 MeV, respectively. The exact treatment provides a significant improvement in the fit to experimental gaps, although it is partially masked by a larger rms error due to deficiencies in other aspects of the theory, such as the mean-field energy functional.
124451495
Lefschetz thimble Monte Carlo for many-body theories: A Hubbard model study
118570813
Configuration-interaction Monte Carlo method and its application to the trapped unitary Fermi gas
We develop a quantum Monte Carlo method to estimate the ground-state energy of a fermionic many-particle system in the configuration-interaction shell model approach. The fermionic sign problem is circumvented by using a guiding wave function in Fock space. The method provides an upper bound on the ground-state energy whose tightness depends on the choice of the guiding wave function. We argue that the antisymmetric geminal product class of wave functions is a good choice for guiding wave functions. We demonstrate our method for the trapped two-species fermionic cold atom system in the unitary regime of infinite scattering length using the particle-number projected Hartree-Fock-Bogoliubov wave function as the guiding wave function. We estimate the ground-state energy and energy-staggering pairing gap as a function of the number of particles. Our results compare favorably with exact numerical diagonalization results and with previous coordinate-space Monte Carlo calculations.
119254846
Variational theory of hot nucleon matter. II. Spin-isospin correlations and equation of state of nuclear and neutron matter
We apply the variational theory for fermions at finite temperature and high density, developed in an earlier paper, to symmetric nuclear matter and pure neutron matter. This extension generalizes to finite temperatures, the many body technique used in the construction of the zero temperature Akmal-Pandharipande-Ravenhall equation of state. We discuss how the formalism can be used for practical calculations of hot dense matter. Neutral pion condensation along with the associated isovector spin longitudinal sum rule is analyzed. The equation of state is calculated for temperatures less than 30 MeV and densities less than three times the saturation density of nuclear matter. The behavior of the nucleon effective mass in medium is also discussed.
119532334
Variational theory of hot nucleon matter
We develop a variational theory of hot nuclear matter in neutron stars and supernovae. It can also be used to study charged, hot nuclear matter which may be produced in heavy-ion collisions. This theory is a generalization of the variational theory of cold nuclear and neutron star matter based on realistic models of nuclear forces and pair correlation operators. The present approach uses microcanonical ensembles and the variational principle obeyed by the free energy. In this paper we show that the correlated states of the microcanonical ensemble at a given temperature T and density {rho} can be orthonormalized preserving their diagonal matrix elements of the Hamiltonian. This allows for the minimization of the free energy without corrections from the nonorthogonality of the correlated basis states, similar to that of the ground state energy. Samples of the microcanonical ensemble can be used to study the response, and the neutrino luminosities and opacities of hot matter. We present methods to orthonormalize the correlated states that contribute to the response of hot matter.
117551201
Quantum field theories on the Lefschetz thimble
In these proceedings, we summarize the Lefschetz thimble approach to the sign problem of Quantum Field Theories. In particular, we review its motivations, and we summarize the results of the application of two different algorithms to two test models.
119238580
Asymmetries involving dihadron fragmentation functions: from DIS to e+e- annihilation
Using a model calculation of dihadron fragmentation functions, we fit the spin asymmetry recently extracted by HERMES for the semi-inclusive pion pair production in deep-inelastic scattering on a transversely polarized proton target. By evolving the obtained dihadron fragmentation functions, we make predictions for the correlation of the angular distributions of two pion pairs produced in electron-positron annihilations at BELLE kinematics. Our study shows that the combination of two-hadron inclusive deep-inelastic scattering and electron-positron annihilation measurements can provide a valid alternative to Collins effect for the extraction of the quark transversity distribution in the nucleon.
15766151
Twist Four Longitudinal Structure Function for a Positronium-like Bound State in Weak Coupling Light-Front QED
To have an analytic understanding of the higher-twist structure functions, we calculate twist four longitudinal structure function for a positronium-like bound state in weak coupling light-front QED. We verify a previously proposed sum rule for twist four FL in the weak coupling theory. We find that in the weakly coupled system, the fermionic part of FL, which is actually measured in DIS experiments, is related to the kinetic energy of the fermions and not to the interaction. The sum rule in this case reduces to a relation connecting the kinetic and the potential energies to the binding energy of positronium in the non-relativistic limit. Using the analytic form of the wave function of positronium in this limit, we find that FL is sharply peaked at x = 12 at fixed value of Q 2.
15898613
Diffraction patterns in deeply virtual compton scattering
We report on a calculation to show that the Fourier transform of the Deeply Virtual Compton Scattering (DVCS) amplitude with respect to the skewness variable ζ at fixed invariant momentum transfer squared t gives results that are analogous to the diffractive scattering of a wave in optics. As a specific example, we utilize the quantum fluctuations of a fermion state at one loop in QED to obtain the behavior of the DVCS amplitude for electron‐photon scattering. We then simulate the wavefunctions for a hadron by differentiating the above LFWFs with respect to M2 and study the corresponding DVCS amplitudes in light‐front longitudinal space.
55544629
Universality of TMD correlators
In a high-energy scattering process with hadrons in the initial state, color is involved. Transverse momentum dependent distribution functions (TMDs) describe the quark and gluon distributions in these hadrons in momentum space with the inclusion of transverse directions. Apart from the (anti)-quarks and gluons that are involved in the hard scattering process, additional gluon emissions by the hadrons have to be taken into account as well, giving rise to Wilson lines or gauge links. The TMDs involved are sensitive to the process under consideration and hence potentially nonuniversal due to these Wilson line interactions with the hard process; different hard processes give rise to different Wilson line structures. We will show that in practice only a finite number of universal TMDs have to be considered, which come in different linear combinations depending on the hard process under consideration, ensuring a generalized universality. For quarks this gives rise to three Pretzelocity functions, whereas for gluons a richer structure of functions arises.
118529485
Off-axis excitation of hydrogenlike atoms by twisted photons
We show that the twisted photon states, or photon states with large ($> \hbar$) angular momentum projection ($m_\gamma$) in the direction of motion, can photoexcite atomic levels for a hydrogen-like atom that are novel and distinct and are not restricted by $m_\gamma$, when the symmetry axis of the twisted-photon beam does not coincide with the center of the atomic target. Selection rules are given and interesting implications and observables for the above process are pointed out.