114 research outputs found
Liouville Field Theory on an Unoriented Surface
Liouville field theory on an unoriented surface is investigated, in
particular, the one point function on a RP^2 is calculated. The constraint of
the one point function is obtained by using the crossing symmetry of the two
point function. There are many solutions of the constraint and we can choose
one of them by considering the modular bootstrap.Comment: 13 pages, no figures, LaTeX, minor changes, equations in section 4
are correcte
New Branes and Boundary States
We examine D-branes on , and find a three-brane wrapping the entire
, in addition to 1-branes and instantonic 2-branes previously discussed
in the literature. The three-brane is found using a construction of Maldacena,
Moore, and Seiberg. We show that all these branes satisfy Cardy's condition and
extract the open string spectrum on them.Comment: 18 pages, late
Magnetic Glass Ceramics by Sintering of Borosilicate Glass and Inorganic Waste
Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based on two iron-rich slags, coming from non-ferrous metallurgy and recycled borosilicate glass. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1000 °C), whereas glass/slag interactions resulted in the formation of magnetite crystals, providing ferrimagnetism. Such behavior could be exploited for applying the obtained glass ceramics as induction heating plates, according to preliminary tests (showing the rapid heating of selected samples, even above 200 °C). The chemical durability and safety of the obtained glass ceramics were assessed by both leaching tests and cytotoxicity tests
Braiding and fusion properties of the Neveu-Schwarz super-conformal blocks
We construct, generalizing appropriately the method applied by J. Teschner in
the case of the Virasoro conformal blocks, the braiding and fusion matrices of
the Neveu-Schwarz super-conformal blocks. Their properties allow for an
explicit verification of the bootstrap equation in the NS sector of the N=1
supersymmetric Liouville field theory.Comment: 41 pages, 3 eps figure
Boundary states in the Nappi-Witten model
We investigate D-branes in the Nappi-Witten model. Classically symmetric
D-branes are classified by the (twisted) conjugacy classes of the Nappi-Witten
group, which specify the geometry of the corresponding D-branes. Quantum
description of the D-branes is given by boundary states, and we need one point
functions of closed strings to construct the boundary states. We compute the
one point functions solving conformal bootstrap constraints, and check that the
classical limit of the boundary states reproduces the geometry of D-branes.Comment: 19 pages, no figure; minor changes, references adde
D1-brane with Overcritical Electric Field in AdS3 and S-brane
We study aspects of Dirichlet S-branes, which are defined as Dirichlet
boundary condition on a time like embedding of open strings, in general
backgrounds. By applying T-duality along an isometry of the unphysical
dS2-branes in NS-NS supported AdS3-background, we find S0-brane. We also study
the time dependent tachyon condensation on the unstable Dp-brane and interpret
the singular solutions as lower dimensional S(p-1)-brane that couples to real
Ramond-Ramond fields while to imaginary NS-NS modes.Comment: 23 pages, JHEP style, V2: minor changes, typos fixe
A large-scale optical-near infrared survey for brown dwarfs and very low-mass stars in the Orion OB1 association
We report the initial results of a large-scale optical-near infrared survey
to extend the known young population of the entire Orion star-forming region
down to the substellar domain. Using deep optical I-band photometry and data
from the 2MASS survey, we selected candidates across ~14.8 deg^2 in the ~8 Myr
old Ori OB1a subassociation and over ~6.7 deg^2 in the Ori OB1b subassociation
(age ~3), with completeness down to 0.05Mo and 0.072Mo respectively. We
obtained low resolution optical spectra for a subsample of 4 candidates in Ori
OB1a and 26 in Ori OB1b; as a result we confirmed 3 new members in Ori OB1a,
one of which is substellar, and 19 new members in Ori OB1b, out of which 7 are
at the substellar limit and 5 are substellar. We looked into the presence of
accretion signatures by measuring the strength of the Ha line in emission.
Accordingly, we classified the new members as having Classical T-Tauri star
(CTTS) or Weak Lined T Tauri star-like (WTTS) nature. We found that all the new
members confirmed in Ori OB1a are WTTSs, while 39 +25/-22 % of the new members
in Ori OB1b exhibit CTTS-like behavior, suggestive of ongoing accretion from a
circum(sub)stellar disk. Additionally we found that none of the members
confirmed in OB1a show near-IR color excess while 38 +26/-21 % of OB1b members
show H-K color excess. These results are consistent with recent findings for
low mass young stars in Orion OB1. The similarity in CTTS-like properties and
near-IR excess across the substellar boundary gives support to the idea of a
common formation mechanism for low mass stars and at least the most massive
brown dwarfs. Finally, we remark the discovery of two new members classified as
CTTSs, both exhibiting W(Ha) < -140 A, suggesting significant ongoing
accretion.Comment: Accepted for publication in Astronomical Journa
D-branes in the Euclidean and T-duality
We show that D-branes in the Euclidean can be naturally associated to
the maximally isotropic subgroups of the Lu-Weinstein double of SU(2). This
picture makes very transparent the residual loop group symmetry of the D-brane
configurations and gives also immediately the D-branes shapes and the
-model boundary conditions in the de Sitter T-dual of the
WZW model.Comment: 29 pages, LaTeX, references adde
Crosscap States for Orientifolds of Euclidean AdS_3
Crosscap states for orientifolds of Euclidean AdS_3 are constructed. We show
that our crosscap states describe the same orientifolds which were obtained by
the classical analysis. The spectral density of open strings in the system with
orientifold can be read from the M"obius strip amplitudes and it is compared to
that of the open strings stretched between branes and their mirrors. We also
compute the Klein bottle amplitudes.Comment: 17 pages, LaTeX2e, v2: clarification and discussion added, v3: minor
changes, to appear in JHE
Boundary Liouville theory at c=1
The c=1 Liouville theory has received some attention recently as the
Euclidean version of an exact rolling tachyon background. In an earlier paper
it was shown that the bulk theory can be identified with the interacting c=1
limit of unitary minimal models. Here we extend the analysis of the c=1-limit
to the boundary problem. Most importantly, we show that the FZZT branes of
Liouville theory give rise to a new 1-parameter family of boundary theories at
c=1. These models share many features with the boundary Sine-Gordon theory, in
particular they possess an open string spectrum with band-gaps of finite width.
We propose explicit formulas for the boundary 2-point function and for the
bulk-boundary operator product expansion in the c=1 boundary Liouville model.
As a by-product of our analysis we also provide a nice geometric interpretation
for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result
(1.6
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