22188300
Differences between mean-field dynamics and N-particle quantum dynamics as a signature of entanglement.
A Bose-Einstein condensate in a tilted double-well potential under the influence of time-periodic potential differences is investigated in the regime where the mean-field (Gross-Pitaevskii) dynamics become chaotic. For some parameters near stable regions, even averaging over several condensate oscillations does not remove the differences between mean-field and N-particle results. While introducing decoherence via piecewise deterministic processes reduces those differences, they are due to the emergence of mesoscopic entangled states in the chaotic regime.
27937897
Creation and detection of a mesoscopic gas in a nonlocal quantum superposition.
We investigate the scattering of a quantum matter wave soliton on a barrier in a one-dimensional geometry, and we show that it can lead to mesoscopic quantum superposition states, where the atomic gas is in a coherent superposition of being in the half-space to the left of the barrier and being in the half-space to the right of the barrier. We propose an interferometric method to reveal the coherent nature of this superposition, and we discuss in detail the experimental feasibility.
2549351
Two-pion light-cone distribution amplitudes from the instanton vacuum
We calculate the two-pion light-cone distribution amplitudes in the effective low-energy theory based on the instanton vacuum. These generalized distribution amplitudes describe the soft (non-perturbative) part of the process ${\ensuremath{\gamma}}^{*}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}\ensuremath{\pi}\ensuremath{\pi}$ in the region where the c.m. energy is much smaller than the photon virtuality. They can also be used in the analysis of exclusive processes such as ${\ensuremath{\gamma}}^{*}\stackrel{\ensuremath{\rightarrow}}{p}p+2\ensuremath{\pi},3\ensuremath{\pi},$ etc.
16720591
Flavor asymmetry of polarized and unpolarized sea quark distributions in the large-N_c limit
We summarize recent attempts to calculate the flavor asymmetry of the nucleon's sea quark distributions in the large-$N_c$ limit, where the nucleon can be described as a soliton of an effective chiral theory. We discuss the leading-twist longitudinally polarized and transversity antiquark distributions, $\Delta\bar u (x) - \Delta\bar d (x)$ and $\delta\bar u (x) - \delta\bar d (x)$, as well as the unpolarized one, $\bar u (x) - \bar d (x)$, which appears only in the next-to-leading order of the $1/N_c$-expansion. Results for $\bar u (x) - \bar d (x)$ are in good agreement with the recent Drell-Yan data from the FNAL E866 experiment. The longitudinally polarized antiquark asymmetry, $\Delta\bar u (x) - \Delta\bar d (x)$, is found to be larger than the unpolarized one.