Precision Measurement of the Position-space Wave Functions of Gravitationally Bound Ultracold Neutrons

Gravity is the most familiar force at our natural length scale. However, it is still exotic from the view point of particle physics. The first experimental study of quantum effects under gravity was performed using a cold neutron beam in 1975. Following this, an investigation of gravitationally bound quantum states using ultracold neutrons was started in 2002. This quantum bound system is now well understood, and one can use it as a tunable tool to probe gravity. In this paper, we review a recent measurement of position-space wave functions of such gravitationally bound states, and discuss issues related to this analysis, such as neutron loss models in a thin neutron guide, the formulation of phase space quantum mechanics, and UCN position sensitive detectors. The quantum modulation of neutron bound states measured in this experiment shows good agreement with the prediction from quantum mechanics.Comment: 13 pages, 5 figure

Effectively Closed Infinite-Genus Surfaces and the String Coupling

The class of effectively closed infinite-genus surfaces, defining the completion of the domain of string perturbation theory, can be included in the category $O_G$, which is characterized by the vanishing capacity of the ideal boundary. The cardinality of the maximal set of endpoints is shown to be 2^{\mit N}. The product of the coefficient of the genus-g superstring amplitude in four dimensions by $2^g$ in the $g\to \infty$ limit is an exponential function of the genus with a base comparable in magnitude to the unified gauge coupling. The value of the string coupling is consistent with the characteristics of configurations which provide a dominant contribution to a finite vacuum amplitude.Comment: TeX, 33 page

The contrasting fission potential-energy structure of actinides and mercury isotopes

Fission-fragment mass distributions are asymmetric in fission of typical actinide nuclei for nucleon number $A$ in the range $228 \lnsim A \lnsim 258$ and proton number $Z$ in the range $90\lnsim Z \lnsim 100$. For somewhat lighter systems it has been observed that fission mass distributions are usually symmetric. However, a recent experiment showed that fission of $^{180}$Hg following electron capture on $^{180}$Tl is asymmetric. We calculate potential-energy surfaces for a typical actinide nucleus and for 12 even isotopes in the range $^{178}$Hg--$^{200}$Hg, to investigate the similarities and differences of actinide compared to mercury potential surfaces and to what extent fission-fragment properties, in particular shell structure, relate to the structure of the static potential-energy surfaces. Potential-energy surfaces are calculated in the macroscopic-microscopic approach as functions of fiveshape coordinates for more than five million shapes. The structure of the surfaces are investigated by use of an immersion technique. We determine properties of minima, saddle points, valleys, and ridges between valleys in the 5D shape-coordinate space. Along the mercury isotope chain the barrier heights and the ridge heights and persistence with elongation vary significantly and show no obvious connection to possible fragment shell structure, in contrast to the actinide region, where there is a deep asymmetric valley extending from the saddle point to scission. The mechanism of asymmetric fission must be very different in the lighter proton-rich mercury isotopes compared to the actinide region and is apparently unrelated to fragment shell structure. Isotopes lighter than $^{192}$Hg have the saddle point blocked from a deep symmetric valley by a significant ridge. The ridge vanishes for the heavier Hg isotopes, for which we would expect a qualitatively different asymmetry of the fragments.Comment: 8 pages, 9 figure

The Cosmic Neutrino Background and the Age of the Universe

We discuss the cosmological degeneracy between the age of the Universe, the Hubble parameter and the effective number of relativistic particles N_eff. We show that independent determinations of the Hubble parameter H(z) as those recently provided by Simon,Verde, Jimenez (2006), combined with other cosmological data sets can provide the most stringent constraint on N_eff, yielding N_eff=3.7 (-1.2) (+1.1) at 95% confidence level. A neutrino background is detected with high significance: N_eff >1.8 at better than 99% confidence level. Constraints on the age of the universe in the framework of an extra background of relativistic particles are improved by a factor 3.Comment: JCAP, in pres

Thermoelectric properties of the layered Pd oxide R_2PdO_4 (R = La, Nd, Sm and Gd)

We prepared polycrystalline samples of R$_2$PdO$_4$ (R = La, Nd, Sm and Gd) using a NaCl-flux technique. The measured resistivity is of the order of 10$^3-10^4$ $\Omega$cm at room temperature, which is two orders of magnitude smaller than the values reported so far. We further studied the substitution effects of Ce for Nd in Nd$_{1.9}$Ce$_{0.1}$PdO$_4$, where the substituted Ce decreases the resistivity and the magnitude of the thermopower. The activation energy gap of 70-80 meV and the effective mass of 15 evaluated from the measured data are suitable for thermoelectric materials, but the mobility of 10$^{-6}$ cm$^2$/Vs is much lower than a typical value of 1-10 cm$^2$/Vs for other thermoelectric oxides.Comment: 5 pages, 5 figures, to appear in J. Phys. Soc. Jp

Ca2+-induced fusion of Golgi-derived secretory vesicles isolated from rat liver

During the transport of plasma proteins from the cytoplasma of hepatocytes to the extracellular fluid srnall vesicles may act as shuttles between the Golgi complex and the plasma membrane. This type of intracellular transfer is weil established for various secretory cells and may be adopted also for the hepatocyte. Recent investigations have shown that secretory vesicles fuse with each other during secretion in mast cells [4] exocrine [5,6] and endocrine pancreatic tissue [7]. The intervesicular fusion provides a tool for studies on membrane fusion, since Golgi-derived vesicles can be isolated from the hepatocyte and their interaction with various agents, suggested to trigger membrane fusion, can be monitored by freeze-cleaving

Entanglement Measures for Intermediate Separability of Quantum States

We present a family of entanglement measures R_m which act as indicators for separability of n-qubit quantum states into m subsystems for arbitrary 2 \leq m \leq n. The measure R_m vanishes if the state is separable into m subsystems, and for m = n it gives the Meyer-Wallach measure while for m = 2 it reduces, in effect, to the one introduced recently by Love et al. The measures R_m are evaluated explicitly for the GHZ state and the W state (and its modifications, the W_k states) to show that these globally entangled states exhibit rather distinct behaviors under the measures, indicating the utility of the measures R_m for characterizing globally entangled states as well.Comment: 8 pages, 8 figure