119157863
A study of the parity-odd nucleon-nucleon potential
We investigate the parity-violating nucleon-nucleon potential as obtained in chiral effective field theory. By using resonance saturation we compare the chiral potential to the more traditional one-meson-exchange potential. In particular, we show how parameters appearing in the different approaches can be compared with each other and demonstrate that analyses of parity violation in proton-proton scattering within the different approaches are in good agreement. In the second part of this work, we extend the parity-violating potential to next-to-next-to-leading order. We show that generally it includes both one-pion- and two-pion-exchange corrections, but the former play no significant role. The two-pion-exchange corrections depend on five new low-energy constants which only become important if the leading-order weak pion-nucleon constant hπ turns out to be very small.
119203346
Radiative transitions in charmonium from N f = 2 twisted mass lattice QCD ⁄
We present an exploratory study for charmonium radiative transitions: J/psi -> eta(c)gamma, chi(c0) -> J/Psi gamma, and h(c) -> eta(c)gamma using Nf = 2 twisted-mass lattice QCD gauge configurations. The single-quark vector form factors for eta(c) and chi(c0) are also determined. The simulation is performed at a lattice spacing of a = 0.067(2) fm and the lattice size is 32(3) x 64 with a pion mass of about 485 MeV. After extrapolation of lattice data at nonzero Q(2) to 0, we compare our results with previous quenched lattice results and the available experimental values.
123103309
Molecular states with two heavy quarks
Within the one-boson-exchange (OBE) potential model, we perform a coupled-channel study of the possible deuteron-like molecular states with two heavy flavor quarks. In our study, we take into account the S-D mixing and the coupled-channel effect in the flavor space. Interestingly, we predict some molecular states which are suggested to be searched for in the further experiments.
119397554
Lifetime of Antibaryon Bound in Finite Nuclei
The study of finite nuclei containing antibaryon(s) in addition to nucleons is an interesting topic in nuclear physics. The calculation of the lifetime of an antibaryon embedded in a nucleus was performed in the framework of the standard quantum field theory. It was shown that the annihilation probability of the antibaryon in nuclei is strongly dependent on the effective masses of mesons involved in the annihilation channels. The contribution of the Dirac sea to the annihilation probability makes the lifetime of the antibaryon short. If the Dirac sea effect is neglected, the lifetime of the bound antibaryon tends to be longer with the nuclear density increasing. Particularly, when the nuclear density is larger than a critical value, the antibaryon may exist stably in a nucleus.
119180642
More on volume dependence of spectral weight function
Spectral weight functions are easily obtained from two-point correlation functions and they might be used to distinguish single-particle from multi-particle states in a finite-volume lattice calculation, a problem crucial for many lattice QCD simulations. In previous studies, it is shown that the spectral weight function for a broad resonance shares the typical volume dependence of a two-particle scattering state i.e. proportional to $1/L^3$ in a large cubic box of size $L$ while the narrow resonance case requires further investigation. In this paper, a generalized formula is found for the spectral weight function which incorporates both narrow and broad resonance cases. Within L\"uscher's formalism, it is shown that the volume dependence of the spectral weight function exhibits a single-particle behavior for a extremely narrow resonance and a two-particle behavior for a broad resonance. The corresponding formulas for both $A^+_1$ and $T^-_1$ channels are derived. The potential application of these formulas in the extraction of resonance parameters are also discussed.
118586717
Generalized Lüscher formula in multichannel baryon-meson scattering
L\"uscher's formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center of mass frame. In this paper, we consider the case for the scattering of a spin 1/2 particle with a spinless particle in multi-channel scattering. A generalized relation between the energy of two particle system and the scattering matrix elements is established. We first obtain this relation using quantum-mechanics in both center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory using methods outlined in Ref. \cite{Hansen:2012tf}. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size.
17605820
Is dark energy an effect of averaging
Fakulta¨t fu¨r Physik, Universita¨t Bielefeld, Postfach 100131, D-33501 BielefeldKey words cosmology, dark energy, Hubble expansionThe present standard model of cosmology states that the known particles carry only a tiny fraction of totalmass and energy of the Universe. Rather, unknown dark matter and dark energy are the dominant contribu-tions to the cosmic energy budget. We review the logic that leads to the postulated dark energy and presentan alternative point of view, in which the puzzle may be solved by properly taking into account the inﬂuenceof cosmic structures on global observables. We illustrate the effect of averaging on the measurement of theHubble constant.
121054260
RELATIVE INFORMATION ENTROPY AND WEYL TENSOR
Due to cosmic structures in the Universe, the inhomogeneities influence the evolution of the background Universe. To characterize this influence, we extend the Kullback-Leibler relative entropy in information theory to cosmology. We study the relation between the relative entropy and the averaging problem in the perturbed Universe, and explore the temporal evolution in linear cosmological perturbation theory and beyond. The possible relationship of the relative entropy and the Weyl tensor is also discussed briefly.
118421293
Scale dependence of cosmological backreaction
Because of the noncommutation of spatial averaging and temporal evolution, inhomogeneities and anisotropies (cosmic structures) influence the evolution of the averaged Universe via the cosmological backreaction mechanism. We study the backreaction effect as a function of averaging scale in a perturbative approach up to higher orders. We calculate the hierarchy of the critical scales, at which 10% effects show up from averaging at different orders. The dominant contribution comes from the averaged spatial curvature, observable up to scales of similar to 200 Mpc. The cosmic variance of the local Hubble rate is 10% (5%) for spherical regions of radius 40 (60) Mpc. We compare our result to the one from Newtonian cosmology and Hubble Space Telescope Key Project data.
11338423
Cusp-core problem and strong gravitational lensing ∗
Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation curves of cold dark matter-dominated dwarf and low surface brightness disk galaxies, with the latter tending to favor mass profiles with a flat central core. Many efforts have been devoted to resolving this cusp-core problem in recent years, among them, baryon-cold dark matter interactions are considered to be the main physical mechanisms erasing the cold dark matter (CDM) cusp into a flat core in the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are not customized only for CDM-dominated disk galaxies, but for all types, including giant ellipticals. We first fit the most recent high resolution observations of rotation curves with the Burkert profile, then use the constrained core size-halo mass relation to calculate the lensing frequency, and compare the predicted results with strong lensing observations. Unfortunately, it turns out that the core size constrained from rotation curves of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that, in the standard cosmological paradigm, baryon-cold dark matter interactions are not universal mechanisms for galaxy formation, and therefore, they cannot be true solutions to the cusp-core problem.