Symmetry Origin of Nonlinear Monopole

We revisit the non-linear BPS equation: the Dirac monopole of the Born-Infeld theory in the B-field background. The rotation used in our previous papers to discuss the scalar field by transforming the BPS equation into a linear one is extended to the case of gauge field. We also find that this transformation is a symmetry of the action. Moreover using the Legendre-dual formalism we present a simple expression of the BPS equation.Comment: 29 pages, 1 fugur

Time-dependent Solutions with Null Killing Spinor in M-theory and Superstrings

Imposing the condition that there should be a null Killing spinor with all the metrics and background field strengths being functions of the light-cone coordinates, we find general 1/2 BPS solutions in D=11 supergravity, and discuss several examples. In particular we show that the linear dilaton background is the most general supersymmetric solution without background under the additional requirement of flatness in the string frame. We also give the most general solutions for flat spacetime in the string frame with RR or NS-NS backgrounds, and they are characterized by a single function.Comment: 12 pages; v2: typos corrected, refs. added; v3: typos corrected, to appear in PL

Holographic QCD and Pion Mass

To realize massive pions, we study variations of the holographic model of massless QCD using the D4/D8/anti-D8 brane configuration proposed by Sakai and Sugimoto. We propose deformations which break the chiral symmetry explicitly and compute the mass of the pions and vector mesons. The observed value of the pion mass can be obtained. We also argue a chiral perturbation corresponding to our deformation.Comment: 23pages, minor changes, references adde

Matrix String Description of Cosmic Singularities in a Class of Time-dependent Solutions

A large class of time-dependent solutions with 1/2 supersymmetry were found previously. These solutions involve cosmic singularities at early time. In this paper, we study if matrix string description of the singularities in these solutions with backgrounds is possible and present several examples where the solutions can be described well in the perturbative picture.Comment: 12 pages, v2: typos corrected, a ref. adde

The Structure of a Self-Gravitating Protoplanetary Disk and its Implications to Direct Imaging Observations

We consider the effects of self-gravity on the hydrostatic balance in the vertical direction of a gaseous disk and discuss the possible signature of the self-gravity that may be captured by the direct imaging observations of protoplanetary disks in future. In this paper, we consider a vertically isothermal disk in order to isolate the effects of self-gravity. The specific disk model we consider in this paper is the one with a radial surface density gap, at which the Toomre's $Q$-parameter of the disk varies rapidly in the radial direction. We calculate the vertical structure of the disk including the effects of self-gravity. We then calculate the scattered light and the dust thermal emission. We find that if the disk is massive enough and the effects of self-gravity come into play, a weak bump-like structure at the gap edge appears in the near-infrared (NIR) scattered light, while no such bump-like structure is seen in the sub-mm dust continuum image. The appearance of the bump is caused by the variation of the height of the surface in the NIR wavelength. If such bump-like feature is detected in future direct imaging observations, with the combination of sub-mm observations, it will bring us useful information about the physical states of the disk.Comment: 12 pages, 9 figures, ApJ accepte

The Eccentric Cavity, Triple Rings, Two-armed Spirals, and Double Clumps of the MWC 758 Disk

Spatially resolved structures in protoplanetary disks hint at unseen planets. Previous imaging observations of the transitional disk around MWC 758 revealed an inner cavity, a ring-like outer disk, emission clumps, and spiral arms, all possibly generated by companions. We present ALMA dust continuum observations of MWC 758 at 0.87 mm wavelength with 43 × 39 mas angular resolution (6.9 × 6.2 au) and 20 μJy beam−1 rms. The central submillimeter emission cavity is revealed to be eccentric; once deprojected, its outer edge can be well fitted by an ellipse with an eccentricity of 0.1 and one focus on the star. The broad ring-like outer disk is resolved into three narrow rings with two gaps in between. The outer two rings tentatively show the same eccentricity and orientation as the innermost ring bounding the inner cavity. The two previously known dust emission clumps are resolved in both the radial and azimuthal directions, with radial widths equal to ~4× the local scale height. Only one of the two spiral arms previously imaged in near-infrared (NIR) scattered light is revealed in ALMA dust emission, at a slightly larger stellocentric distance owing to projection effects. We also submit evidence of disk truncation at ~100 au based on comparing NIR imaging observations with models. The spirals, the north clump, and the truncated disk edge are all broadly consistent with the presence of one companion exterior to the spirals at roughly 100 au