Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass

Metastable pionic helium ($\pi{\rm He}^+$) is a three-body atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\pi^-$ in a Rydberg state with principal- and orbital angular momentum quantum numbers of $n\sim \ell+1\sim 16$. We calculate the spin-independent energies of the $\pi{\rm ^3He}^+$ and $\pi{\rm ^4He}^+$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders $R_{\infty}\alpha^2$ and $R_{\infty}\alpha^3$ in atomic units, where $R_{\infty}$ and $\alpha$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\pi^-$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\ell)=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against $\pi^-$ absorption into the helium nucleus. We propose to use laser pulses to induce $\pi^-$ transitions from these metastable states, to states with large ($\sim 10^{11}$ s$^{-1}$) Auger rates. The $\pi{\rm He}^{2+}$ ion that remains after Auger emission of the $1s$ electron undergoes Stark mixing with the $s$, $p$, and $d$ states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the $\pi^-$. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge....(continued)Comment: 25 pages, 3 tables, 11 figure

Density-Matrix Renormalization Group Study of Trapped Imbalanced Fermi Condensates

The density-matrix renormalization group is employed to investigate a harmonically-trapped imbalanced Fermi condensate based on a one-dimensional attractive Hubbard model. The obtained density profile shows a flattened population difference of spin-up and spin-down components at the center of the trap, and exhibits phase separation between the condensate and unpaired majority atoms for a certain range of the interaction and population imabalance $P$. The two-particle density matrix reveals that the sign of the order parameter changes periodically, demonstrating the realization of the Fulde-Ferrell-Larkin-Ovchinnikov phase. The minority spin atoms contribute to the quasi-condensate up to at least $P \simeq 0.8$. Possible experimental situations to test our predictions are discussed.Comment: 4 pages, 3 figures; added references; accepted for publication in Phys. Rev. Let

Exotic branes and non-geometric backgrounds

When string/M-theory is compactified to lower dimensions, the U-duality symmetry predicts so-called exotic branes whose higher dimensional origin cannot be explained by the standard string/M-theory branes. We argue that exotic branes can be understood in higher dimensions as non-geometric backgrounds or U-folds, and that they are important for the physics of systems which originally contain no exotic charges, since the supertube effect generically produces such exotic charges. We discuss the implications of exotic backgrounds for black hole microstate (non-)geometries.Comment: 4 pages. v2: journal version. The discussion on "double puff-up" revise

Dynamics of one-dimensional Bose liquids: Andreev-like reflection at Y-junctions and absence of the Aharonov-Bohm effect

We study one dimensional Bose liquids of interacting ultracold atoms in the Y-shaped potential when each branch is filled with atoms. We find that the excitation packet incident on a single Y-junction should experience a negative density reflection analogous to the Andreev reflection at normal-superconductor interfaces, although the present system does not contain fermions. In a ring interferometer type configuration, we find that the transport is completely insensitive to the (effective) flux contained in the ring, in contrast to the Aharonov-Bohm effect of a single particle in the same geometry.Comment: 4 pages, 2 figures, final versio

Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium

Numerical ab initio variational calculations of the transition probabilities and ac Stark shifts in two-photon transitions of antiprotonic helium atoms driven by two counter-propagating laser beams are presented. We found that sub-Doppler spectroscopy is in principle possible by exciting transitions of the type (n,L)->(n-2,L-2) between antiprotonic states of principal and angular momentum quantum numbers n~L-1~35, first by using highly monochromatic, nanosecond laser beams of intensities 10^4-10^5 W/cm^2, and then by tuning the virtual intermediate state close (e.g., within 10-20 GHz) to the real state (n-1,L-1) to enhance the nonlinear transition probability. We expect that ac Stark shifts of a few MHz or more will become an important source of systematic error at fractional precisions of better than a few parts in 10^9. These shifts can in principle be minimized and even canceled by selecting an optimum combination of laser intensities and frequencies. We simulated the resonance profiles of some two-photon transitions in the regions n=30-40 of the \bar{p}^4He^+ and \bar{p} ^3He^+ isotopes to find the best conditions that would allow this.Comment: 18 pages 2 tables 12 figures, submitted to Phys. Rev.

Boundary Critical Phenomena in SU(3) "Spin" Chains

SU(3)-invariant "spin" chains with a single impurity, such as a modified exchange coupling on one link, are analyzed using boundary conformal field theory techniques. These chains are equivalent to a special case of the "tJV" model, i.e. the t-J model with a nearest neighbour repulsion added. In the continuum limit they are equivalent to two free bosons at a special value of the compactification radii. The SU(3) symmetry, which is made explicit in this formulation, provides insight into the exact solution of a non-trivial boundary critical point found earlier in another formulation of this model as a theory of quantum Brownian motion.Comment: 19 pages, Rev Te

Mesospheric anomalous diffusion during noctilucent clouds

The Andenes specular meteor radar shows meteor-trail diffusion rates increasing on average by ~ 20% at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC but this study shows that such behaviors result predominantly from thermal tides. To make this claim, the current study evaluates data from three stations, at high-, mid-, and low-latitudes, for the years 2012 to 2016, comparing diffusion to show that thermal tides correlate strongly with the presence of NLCs. This data also shows that the connection between meteor-trail diffusion and thermal tide occurs at all altitudes in the mesosphere, while the NLC influence exists only at high-latitudes and at around peak of NLC layer. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars.Public versio