198 research outputs found
An sl(2, R) current algebra from AdS_3 gravity
We provide a set of chiral boundary conditions for three-dimensional gravity
that allow for asymptotic symmetries identical to those of two-dimensional
induced gravity in light-cone gauge considered by Polyakov. These are the most
general boundary conditions consistent with the boundary terms introduced by
Compere, Song and Strominger recently. We show that the asymptotic symmetry
algebra of our boundary conditions is an sl(2,R) current algebra with level
given by c/6. The fully non-linear solution in Fefferman--Graham coordinates is
also provided along with its charges.Comment: 8 page
Benzyl N-{2-[5-(4-chlorophenyl)-1,2,4-oxadiazol-3-yl]propan-2-yl}carbamate
In the title 1,2,4-oxadiazole derivative, C19H18ClN3O3, the 1,2,4-oxadiazole ring makes dihedral angles of 12.83 (8) and 4.89 (8)°, respectively, with the benzyl and 4-chlorophenyl rings, while the dihedral angle between the benzyl and 4-chlorophenyl rings is 11.53 (7)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds into helical chains along the b axis. A weak C—H⋯π interaction is also present
1-{4-Chloro-2-[2-(2-fluorophenyl)-1,3-dithiolan-2-yl]phenyl}-2-methyl-1H-imidazole-5-carbaldehyde
There are two molecules in the asymmetric unit of the title imidazole derivative, C20H16ClFN2OS2. In one molecule, the dithiolane ring is disordered over two positions in a 0.849 (9):0.151 (10) ratio. The imidazole ring makes dihedral angles of 79.56 (9) and 18.45 (9)° with the 4-chlorophenyl and 2-fluorophenyl rings, respectively, in one molecule; in the other molecule, the corresponding angles are 82.72 (9) and 17.39 (10)°. In the crystal, molecules are linked by weak C—H⋯O interactions and these linked molecules are stacked along the b axis by π–π interactions with a centroid–centroid distance of 3.4922 (11) Å. In addition, π–π interactions between the imidazole and 2-fluorophenyl rings are also observed, with centroid–centroid distances of 3.4867 (11) and 3.4326 (10) Å. The crystal is further consolidated by weak C—H⋯π interactions. Cl⋯S [3.5185 (8) Å], C⋯O [3.192 (3) Å] and C⋯C [3.326 (2)–3.393 (3) Å] short contacts are also observed
A recent survey of permutation trinomials over finite fields
Constructing permutation polynomials is a hot topic in the area of finite fields, and permutation polynomials have many applications in different areas. Recently, several classes of permutation trinomials were constructed. In 2015, Hou surveyed the achievements of permutation polynomials and novel methods. But, very few were known at that time. Recently, many permutation binomials and trinomials have been constructed. Here we survey the significant contribution made to the construction of permutation trinomials over finite fields in recent years. Emphasis is placed on significant results and novel methods. The covered material is split into three aspects: the existence of permutation trinomials of the respective forms , and , with Niho-type exponents
TIRSPEC : TIFR Near Infrared Spectrometer and Imager
We describe the TIFR Near Infrared Spectrometer and Imager (TIRSPEC) designed
and built in collaboration with M/s. Mauna Kea Infrared LLC, Hawaii, USA, now
in operation on the side port of the 2-m Himalayan Chandra Telescope (HCT),
Hanle (Ladakh), India at an altitude of 4500 meters above mean sea level. The
TIRSPEC provides for various modes of operation which include photometry with
broad and narrow band filters, spectrometry in single order mode with long
slits of 300" length and different widths, with order sorter filters in the Y,
J, H and K bands and a grism as the dispersing element as well as a cross
dispersed mode to give a coverage of 1.0 to 2.5 microns at a resolving power R
of ~1200. The TIRSPEC uses a Teledyne 1024 x 1024 pixel Hawaii-1 PACE array
detector with a cutoff wavelength of 2.5 microns and on HCT, provides a field
of view of 307" x 307" with a plate scale of 0.3"/pixel. The TIRSPEC was
successfully commissioned in June 2013 and the subsequent characterization and
astronomical observations are presented here. The TIRSPEC has been made
available to the worldwide astronomical community for science observations from
May 2014.Comment: 20 pages, 21 figures, 2 tables. Accepted for publication in Journal
of Astronomical Instrumentatio
N′-(4-Fluorobenzylidene)-2-(4-fluorophenyl)acetohydrazide
In the title compound, C15H12F2N2O, the dihedral angle between the two benzene rings is 48.73 (8)°. The hydrazine group is twisted slightly, with a C—N—N—C torsion angle of 172.48 (12)°. In the crystal, molecules are connected by strong N—H⋯O and weak C—H⋯O hydrogen bonds, forming supramolecular chains along the c axis. The structure is consolidated by π–π [centroid–centroid separation = 3.6579 (10) Å] and C—H⋯π interactions
SYNTHESIS, AB INITIO STRUCTURE DETERMINATION, AND CHARACTERIZATION OF MANGANESE(III) PHENYL PHOSPHONATES
ABSTRACT , space group P1, and Z ϭ 2. The final agreement factors were R WP ϭ 12.8%, R P ϭ 9.1%, and R F ϭ 3.2%. There are 22 non-hydrogen atoms in the asymmetric part of the unit cell, and the positional parameters were refined with the help of soft constraints. The octahedral manganese coordination spheres are distorted due to the Jahn-Teller effect. The structure of this organic-inorganic compound is layered. The thermal behavior of Mn(HO 3 PC 6 H 5 )(O 3 PC 6 H 5 )⅐H 2 O was studied and its thermal decomposition product was identified. © 1998 Elsevier Science Lt
- …