6,373 research outputs found
Aspects of Warped AdS/CFT Correspondence
In this paper we apply the thermodynamics method to investigate the
holographic pictures for the BTZ black hole, the spacelike and the null warped
black holes in three-dimensional topologically massive gravity (TMG) and new
massive gravity (NMG). Even though there are higher derivative terms in these
theories, the thermodynamics method is still effective. It gives consistent
results with the ones obtained by using asymptotical symmetry group (ASG)
analysis. In doing the ASG analysis we develop a brute-force realization of the
Barnich-Brandt-Compere formalism with Mathematica code, which also allows us to
calculate the masses and the angular momenta of the black holes. In particular,
we propose the warped AdS/CFT correspondence in the new massive
gravity, which states that quantum gravity in the warped spacetime could
holographically dual to a two-dimensional CFT with
c_R=c_L=\f{24}{Gm\b^2\sr{2(21-4\b^2)}}.Comment: 22 pages, references added, published version, link of Mathematica
code changed to https://s.yunio.com/Mtus0z or http://pan.baidu.com/s/1mToF
Yangian Symmetry for Bi-Scalar Loop Amplitudes
We establish an all-loop conformal Yangian symmetry for the full set of
planar amplitudes in the recently proposed integrable bi-scalar field theory in
four dimensions. This chiral theory is a particular double scaling limit of
gamma-twisted weakly coupled N=4 SYM theory. Each amplitude with a certain
order of scalar particles is given by a single fishnet Feynman graph of disc
topology cut out of a regular square lattice. The Yangian can be realized by
the action of a product of Lax operators with a specific sequence of
inhomogeneity parameters on the boundary of the disc. Based on this
observation, the Yangian generators of level one for generic bi-scalar
amplitudes are explicitly constructed. Finally, we comment on the relation to
the dual conformal symmetry of these scattering amplitudes.Comment: 40 pages, 20 figure
Line operators in Chern-Simons-Matter theories and Bosonization in Three Dimensions II -Perturbative Analysis and All-loop Resummation
We study mesonic line operators in Chern-Simons theories with bosonic or
fermionic matter in the fundamental representation. In this paper, we elaborate
on the classification and properties of these operators using all loop
resummation of large perturbation theory. We show that these theories
possess two conformal line operators in the fundamental representation. One is
a stable renormalization group fixed point, while the other is unstable. They
satisfy first-order chiral evolution equations, in which a smooth variation of
the path is given by a factorized product of two mesonic line operators. The
boundary operators on which the lines can end are classified by their conformal
dimension and transverse spin, which we compute explicitly at finite 't Hooft
coupling. We match the operators in the bosonic and fermionic theories.Comment: 105 pages, 17 figures. v2: extended to mass deformed CS-matter
theories, (section 8). Some details about anomalous spin moved to appendix.
Typos corrected. JHEP versio
The AdS Veneziano amplitude at small curvature
We compute the AdS Veneziano amplitude for type IIB gluon scattering in AdS5 × S3 to all orders in α′ in a small curvature expansion. This is achieved by combining a dispersion relation in the dual 4dN = 2 SCFT with an ansatz for the amplitude as a worldsheet integral in terms of multiple polylogarithms. The first curvature correction is fully fixed in this way and satisfies consistency checks in the high energy limit, the low energy expansion as previously fixed using supersymmetric localisation, and for the energy of massive string operators, which we independently compute using a semiclassical expansion. We also combine localisation with this first curvature correction to fix the unprotected D4F4 correction to the amplitude at finite curvature
A large sample of low surface brightness disc galaxies from the SDSS- II. Metallicities in surface brightness bins
We study the spectroscopic properties of a large sample of Low Surface
Brightness galaxies (LSBGs) (with B-band central surface brightness mu0(B)>22
mag arcsec^(-2)) selected from the Sloan Digital Sky Survey Data Release 4
(SDSS-DR4) main galaxy sample. A large sample of disk-dominated High Surface
Brightness galaxies (HSBGs, with mu0(B)<22 mag arcsec^(-2)) are also selected
for comparison simultaneously. To study them in more details, these sample
galaxies are further divided into four subgroups according to mu0(B) (in units
of mag arcsec^(-2)): vLSBGs (24.5-22.75),iLSBGs (22.75-22.0), iHSBGs
(22.0-21.25), and vHSBGs (<21.25). The diagnostic diagram from spectral
emission-line ratios shows that the AGN fractions of all the four subgroups are
small (<9%). The 21,032 star-forming galaxies with good quality spectroscopic
observations are further selected for studying their dust extinction,
strong-line ratios, metallicities and stellar mass-metallicities relations. The
vLSBGs have lower extinction values and have less metal-rich and massive
galaxies than the other subgroups. The oxygen abundances of our LSBGs are not
as low as those of the HII regions in LSBGs studied in literature, which could
be because our samples are more luminous, and because of the different
metallicity calibrations used. We find a correlation between 12+log(O/H) and
mu0(B) for vLSBGs, iLSBGs and iHSBGs but show that this could be a result of
correlation between mu0(B) and stellar mass and the well-known mass-metallicity
relation. This large sample shows that LSBGs span a wide range in metallicity
and stellar mass, and they lie nearly on the stellar mass vs. metallicity and
N/O vs. O/H relations of normal galaxies. This suggests that LSBGs and HSBGs
have not had dramatically different star formation and chemical enrichment
histories.Comment: 14 pages, 11 figures, accepted for publication in MNRA
The star formation histories of red and blue low surface brightness disk galaxies
We study the star formation histories (SFH) and stellar populations of 213
red and 226 blue nearly face-on low surface brightness disk galaxies (LSBGs),
which are selected from the main galaxy sample of Sloan Digital Sky Survey
(SDSS) Data Release Seven (DR7). We also want to compare the stellar
populations and SFH between the two groups. The sample of both red and blue
LSBGs have sufficient signal-to-noise ratio in the spectral continua. We obtain
their absorption-line indices (e.g. Mg_2, H\delta_A), D_n(4000) and stellar
masses from the MPA/JHU catalogs to study their stellar populations and SFH.
Moreover we fit their optical spectra (stellar absorption lines and continua)
by using the spectral synthesis code STARLIGHT on the basis of the templates of
Simple Stellar Populations (SSPs). We find that red LSBGs tend to be relatively
older, higher metallicity, more massive and have higher surface mass density
than blue LSBGs. The D_n(4000)-H\delta_A plane shows that perhaps red and blue
LSBGs have different SFH: blue LSBGs are more likely to be experiencing a
sporadic star formation events at the present day, whereas red LSBGs are more
likely to form stars continuously over the past 1-2 Gyr. Moreover, the fraction
of galaxies that experienced recent sporadic formation events decreases with
increasing stellar mass. Furthermore, two sub-samples are defined for both red
and blue LSBGs: the sub-sample within the same stellar mass range of 9.5 <=
log(M_\star/M_\odot) <= 10.3, and the surface brightness limiting sub-sample
with \mu_0(R) <= 20.7 mag arcsec^{-2}. They show consistent results with the
total sample in the corresponding relationships, which confirm that our results
to compare the blue and red LSBGs are robust.Comment: 9 pages, 7 figures, 2 tables, Accepted for publication in A&
Chitosan in non-viral gene delivery: Role of structure, characterization methods, and insights in cancer and rare diseases therapy
Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver pDNA, chitosan has been regarded as a highly attractive biopolymer to deliver nucleic acids intracellularly and induce a transgenic response resulting in either upregulation of protein expression (for pDNA, mRNA) or its downregulation (for siRNA or microRNA). This is explained as the consequence of a multi-step process involving condensation of nucleic acids, protection against degradation, stabilization in physiological conditions, cellular internalization, release from the endolysosome (“proton sponge” effect), unpacking and enabling the trafficking of pDNA to the nucleus or the siRNA to the RNA interference silencing complex (RISC). Given the multiple steps and complexity involved in the gene transfection process, there is a dearth of understanding of the role of chitosan’s structural features (Mw and degree of acetylation, DA%) on each step that dictates the net transfection efficiency and its kinetics. The use of fully characterized chitosan samples along with the utilization of complementary biophysical and biological techniques is key to bridging this gap of knowledge and identifying the optimal chitosans for delivering a specific gene. Other aspects such as cell type and administration route are also at play. At the same time, the role of chitosan structural features on the morphology, size and surface composition of synthetic virus-like particles has barely been addressed. The ongoing revolution brought about by the recent discovery of CRISPR-Cas9 technology will undoubtedly be a game changer in this field in the short term. In the field of rare diseases, gene therapy is perhaps where the greatest potential lies and we anticipate that chitosans will be key players in the translation of research to the clinic
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