13148151
Modular invariant critical superstrings on four-dimensional Minkowski space times two-dimensional black hole
Extending the seminal work of Bilal and Gervais, we construct a tachyon-free, modular invariant partition function for critical superstrings on four-dimensional Minkowski × two-dimensional black hole. This model may be thought of as an SL(2,)/U(1) version of Gepner models and corresponds to a conifold point on the moduli space of Calabi-Yau compactifications. We directly deal with N = 2, c = 9 unitary superconformal characters. Modular invariance is achieved by requiring the string to have a momentum along an extra noncompact direction, in agreement with the picture of singular CFTs advocated by Witten. The four-dimensional massless spectrum coincides with that of the tensionless strings, supporting the proposal made by Bershadsky et al. concerning a dual description of type-II strings on a conifold in terms of two intersecting NS5-branes. An interesting relation to D = 6, N = 4 gauged supergravity is also discussed.
18770957
Progress toward the determination of complete vertex operators for the IIB matrix model
We report on progress in determining the complete form of vertex operators for the IIB matrix model. The exact expressions are obtained for those emitting massless IIB supergravity fields up to sixth order in the light-cone superfield, in which the conjugate gravitino and conjugate two-form vertex operators are newly determined. We also provide a consistency check by computing the kinematical factor of a four-point graviton amplitude in a D-instanton background. We conjecture that the low-energy effective action of the IIB matrix model at large N is given by tree-level supergravity coupled to the vertex operators.
119274935
General Kaluza-Klein black holes with all six independent charges in five-dimensional minimal supergravity
Using the SL(2,R)-duality in a dimensionally reduced spacetime in (the bosonic sector of) five-dimensional minimal supergravity, we construct general Kaluza-Klein black hole solutions which carry six independent charges, its mass, angular momentum along four dimensions, electric and magnetic charges of the Maxwell fields in addition to Kaluza-Klein electric and magnetic monopole charges.
8428441
Wound D-branes in Gepner models
We propose a new prescription of how to represent D-branes in Gepner models in more general homology classes than those in the previous constructions. The central role is played by a certain projection acting on the Recknagel–Schomerus boundary states. Consequently, the boundary states are in most cases no longer a sum of products of N=2 Ishibashi states, but nevertheless preserve spacetime supersymmetry and satisfy the Cardy condition. We demonstrate these in the (k=1)3 Gepner model in detail, and construct boundary states for D-branes wound around arbitrary rigid 1-cycles on the corresponding 2-torus. We also emphasize the necessity of some angle-dependent transformations in identifying a proper free-field realization for each brane tilted at an angle. In particular, this is essential for the Witten index to give the correct intersection numbers between the different D-branes.
119112005
TAUB-NUT CRYSTAL
We consider the Gibbons–Hawking metric for a three-dimensional periodic array of multi-Taub-NUT centers, containing not only centers with a positive NUT charge but also ones with a negative NUT charge. The latter are regarded as representing the asymptotic form of the Atiyah–Hitchin metric. The periodic arrays of Taub-NUT centers have close parallels with ionic crystals, where the Gibbons–Hawking potential plays the role of the Coulomb static potential of the ions, and are similarly classified according to their space groups. After a periodic identification and a Z2 projection, the array is transformed by T-duality to a system of NS5-branes with the SU(2) structure, and a further standard embedding yields, though singular, a half-BPS heterotic 5-brane background with warped compact transverse dimensions. A discussion is given on the possibility of probing the singular geometry by two-dimensional gauge theories.
33408165
BPS saturation from null reduction
We show that any d-dimensional strictly stationary, asymptotically Minkowskian solution of a null reduction of (d + 1)-dimensional pure gravity must saturate the BPS bound if the spacetime admits another commuting Killing vector field so that the Kaluza-Klein vector field can be identified appropriately. We also argue that it is consistent with the field equations.
118546306
Discovery of Multiple High-Velocity Narrow Circumstellar NaI D Lines in Nova V1280 Sco
We discovered multiple high-velocity (ranging from � 900 to � 650 km s � 1 ) and narrow (FWHM � 15 km s � 1 ) absorption components corresponding to both the D2 and the D1 lines of Na I on a high-dispersion spectrum of V1280 Sco, observed on 2009 May 9 (UT), 814 d after the V band maximum. Subsequent observations carried out on 2009 June and July confirmed at least 11 distinct absorption components in both systems. Some components had deepened during the two-month period while their HWHMs and wavelengths remained nearly constant. We suggest that these high-velocity components originated in cool clumpy gas clouds moving on the line-of-sight, produced during interactions between pre-existing cool circumstellar gas and high-velocity gas ejected in the nova explosion. The optical region spectrum of V1280 Sco in 2009 is dominated by the continuum radiation, and exhibits no forbidden line characterizing the nebular phase of typical novae. Permitted Fe II lines show doubly peaked emission profiles, and some strong Fe II lines are accompanied by a blue-shifted ( �� 255 km s � 1 ) absorption component. However, no high-velocity and narrow components corresponding to those of Na I could be detected in Fe II lines nor in the Balmer lines. The 255 km s � 1 low-velocity absorption component most probably originates in the wind from the nova.
119197153
Optical light curves of RS Oph (2006) and hydrogen burning turnoff
We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady hydrogen shell-burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the hydrogen burning turnoff. Observational data of y magnitudes are provided here together with other multi-wavelength light curve data.
119301785
Five-year optical and near-infrared observations of the extremely slow nova V1280 Scorpii ,
We present optical (B, V, R c , I c and y) and near-infrared (J, H, and K s ) photometric and spectroscopic observations of a classical nova V 1280 Scorpii for five years from 2007 to 2011. Our photometric observations show a declining event in optical bands shortly after the maximum light, which took about 250 days to recover. This event was most probably caused by dust formation. The event was accompanied by a short (∼30 days) re-brightening episode (∼2.5 mag in V), which suggests that there had been some re-ignition of the surface nuclear burning. After 2008, the y band observations show a very long plateau at around y = 10.5 for more than 1000 days until April 2011 (∼1500 days after the maximum light). The nova had taken a very long time (∼50 months) to enter the nebular phase, according to a clear detection of both [O III] 4959 and 5007 and is still continuing to generate the wind caused by H-burning. This finding suggests that historically V1280 Sco is evolving at its slowest ever measured rate. The interval from the maximum light (2007 February 16) to the beginning of the nebular phase is longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10 months), or HR Del (8 months). It suggests that the mass of a white dwarf in the V1280 Sco system might be 0.6 M ⊙ or lower. The distance, based on our measurements of the expansion velocity combined with the directly measured size of the dust shell, is estimated to be 1.1 ± 0.5 kpc.