A proposal for a new type of thin-film field-emission display by edge breakdown of MIS structure

A new type of field emission display(FED) based on an edge-enhance electron emission from metal-insulator-semiconductor (MIS) thin film structure is proposed. The electrons produced by an avalanche breakdown in the semiconductor near the edge of a top metal electrode are initially injected to the thin film of an insulator with a negative electron affinity (NEA), and then are injected into vacuum in proximity to the top electrode edge. The condition for the deep-depletition breakdown near the edge of the top metal electrode is analytically found in terms of ratio of the insulator thickness to the maximum (breakdown) width of the semiconductor depletition region: this ratio should be less than 2/(3 \pi - 2) = 0.27. The influence of a neighboring metal electrode and an electrode thickness on this condition are analyzed. Different practical schemes of the proposed display with a special reference to M/CaF_2/Si structure are considered.Comment: 11 pages, 5 figure

The Megasecond Chandra X-Ray Visionary Project Observation of NGC 3115 (III): luminosity functions of LMXBs and dependence on stellar environments

We have studied the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXBs) in the nearby lenticular galaxy NGC 3115, using the Megasecond Chandra X-Ray Visionary Project Observation. With a total exposure time of ~1.1 Ms, we constructed the XLF down to a limiting luminosity of ~10^36 erg/s, much deeper than typically reached for other early-type galaxies. We found significant flattening of the overall LMXB XLF from dN/dL \propto L^{-2.2\pm0.4} above 5.5x10^37 erg/s to dN/dL \propto L^{-1.0\pm0.1} below it, though we could not rule out a fit with a higher break at ~1.6x10^38 erg/s. We also found evidence that the XLF of LMXBs in globular clusters (GCs) is overall flatter than that of field LMXBs. Thus our results for this galaxy do not support the idea that all LMXBs are formed in GCs. The XLF of field LMXBs seems to show spatial variation, with the XLF in the inner region of the galaxy being flatter than that in the outer region, probably due to contamination of LMXBs from undetected and/or disrupted GCs in the inner region. The XLF in the outer region is probably the XLF of primordial field LMXBs, exhibiting dN/dL \propto L^{-1.2\pm0.1} up to a break close to the Eddington limit of neutron star LMXBs (~1.7x10^38 erg/s). The break of the GC LMXB XLF is lower, at ~1.1x10^37 erg/s. We also confirm previous findings that the metal-rich/red GCs are more likely to host LMXBs than the metal-poor/blue GCs, which is more significant for more luminous LMXBs, and that more massive GCs are more likely to host LMXBs.Comment: 12 pages, 8 figures, accepted for publication in Ap

The Megasecond Chandra X-Ray Visionary Project Observation of NGC 3115 (II): properties of point sources

We have carried out an in-depth study of low-mass X-ray binaries (LMXBs) detected in the nearby lenticular galaxy NGC 3115, using the Megasecond Chandra X-Ray Visionary Project observation (total exposure time 1.1 Ms). In total we found 136 candidate LMXBs in the field and 49 in globular clusters (GCs) above 2\sigma\ detection, with 0.3--8 keV luminosity L_X ~10^36-10^39 erg/s. Other than 13 transient candidates, the sources overall have less long-term variability at higher luminosity, at least at L_X > 2x10^37 erg/s. In order to identify the nature and spectral state of our sources, we compared their collective spectral properties based on single-component models (a simple power law or a multicolor disk) with the spectral evolution seen in representative Galactic LMXBs. We found that in the L_X versus photon index \Gamma_PL and L_X versus disk temperature kT_MCD plots, most of our sources fall on a narrow track in which the spectral shape hardens with increasing luminosity below L_X~7x10^37 erg/s but is relatively constant (\Gamma_PL~1.5 or kT_MCD~1.5 keV) above this luminosity, similar to the spectral evolution of Galactic neutron star (NS) LMXBs in the soft state in the Chandra bandpass. Therefore we identified the track as the NS LMXB soft-state track and suggested sources with L_X7x10^37 erg/s as Z sources. Ten other sources (five are transients) displayed significantly softer spectra and are probably black hole X-ray binaries in the thermal state. One of them (persistent) is in a metal-poor GC.Comment: 26 pages, 9 figures, four online tables, accepted for publication in Ap

Revisiting the Globular Cluster System of the Merger Remnant Elliptical NGC 3610

We have obtained Keck spectra of six candidate globular clusters (GCs) in the dynamically young elliptical galaxy NGC 3610, supplementing our previous Keck spectra of eight confirmed GCs (Strader et al. 2003). Five of our new candidates are confirmed to be GCs. Of the thirteen GCs, eleven are located within the K band effective radius of 7 kpc. Two of these thirteen clusters are found to be young (~ 2 Gyr) and very metal-rich ([Z/H] ~ +0.5), three are old and metal-poor, and the remaining eight clusters are old and metal-rich. The ages of the young clusters are consistent with a recent spectroscopic age estimate of 1.6+/-0.5 Gyr for the galaxy itself (Denicolo et al. 2003) and suggest that these clusters formed in the disk-disk merger which likely created NGC 3610. Intriguingly, both young GCs have [alpha/Fe] ~ +0.3, while the majority of the old clusters are not alpha-enhanced, in contrast to Galactic and M31 GCs, and contrary to predictions of nucleosynthetic calculations. The two old subpopulations of GCs can be attributed to the merger progenitors. The relative numbers of old and new metal-rich GCs are poorly constrained because of the expected differences in radial distributions of the two subpopulations. However, based on our spectroscopic results and a comparison of the Hubble Space Telescope color magnitude diagram (Whitmore et al. 2002) with stellar population models, we argue that more than half of the metal-rich GCs are likely to be old.Comment: 21 pages, 6 figures, accepted for Jan 2004 A

Dissipative quantum mechanics and Kondo-like impurities on noncommutative two-tori

In a recent paper, by exploiting the notion of Morita equivalence for field theories on noncommutative tori and choosing rational values of the noncommutativity parameter $\theta$ (in appropriate units), a general one-to-one correspondence between the $m$-reduced conformal field theory (CFT) describing a quantum Hall fluid (QHF) at paired states fillings $\nu =\frac{m}{pm+2}$ and an Abelian noncommutative field theory (NCFT) has been established . That allowed us to add new evidence to the relationship between noncommutativity and quantum Hall fluids\cite% {ncmanybody}. On the other hand, the $m$-reduced CFT is equivalent to a system of two massless scalar bosons with a magnetic boundary interaction as introduced by Callan et al., at the so called ``magic''\ points. We are then able to describe, within such a framework, the dissipative quantum mechanics of a particle confined to a plane and subject to an external magnetic field normal to it. Here we develop such a point of view by focusing on the case $m=2$ which corresponds to a quantum Hall bilayer. The key role of a localized impurity which couples the two layers is emphasized and the effect of noncommutativity in terms of generalized magnetic translations (GMT) is fully exploited. As a result, general GMT operators are introduced, in the form of a tensor product, which act on the QHF and defect space respectively, and a comprehensive study of their rich structure is performed.Comment: 18 pages, 1 figure, accepted for publication in International Journal of Modern Physics

Three-point Green function of the stress-energy tensor in the AdS/CFT correspondence

We compute the 3-point function of the stress-energy tensor in the d-dimensional CFT from the AdS_{d+1} gravity. For d=4 the coefficients of the three linearly independent conformally covariant forms entering the 3-point function are exactly the same as given by the free field computations in the ${\cal N}=4$ SYM just as expected from the known renormalization theorems. For d=3 and d=6 our results give the value of the corresponding 3-point function in the theories of strongly coupled ${\cal N}=8$ superconformal scalar and (2,0) tensor multiplets respectively.Comment: Latex, 13 pages, eq. (2.10) is correcte

Some Cubic Couplings in Type IIB Supergravity on AdS5×S5AdS_5\times S^5 and Three-point Functions in SYM_4 at Large N

All cubic couplings in type IIB supergravity on $AdS_5\times S^5$ that involve two scalar fields $s^I$ that are mixtures of the five form field strength on $S^5$ and the trace of the graviton on $S^5$ are derived by using the covariant equations of motion and the quadratic action for type IIB supergravity on $AdS_5\times S^5$. All corresponding three-point functions in SYM$_4$ are calculated in the supergravity approximation. It is pointed out that the scalars $s^I$ correspond not to the chiral primary operators in the ${\cal N}=4$ SYM but rather to a proper extension of the operators.Comment: Latex, 24p, misprints are correcte