133 research outputs found
Momentum-resolved tunneling between Luttinger liquids
We study tunneling between two nearby cleaved edge quantum wires in a
perpendicular magnetic field. Due to Coulomb forces between electrons, the
wires form a strongly-interacting pair of Luttinger liquids. We calculate the
low-temperature differential tunneling conductance, in which singular features
map out the dispersion relations of the fractionalized quasiparticles of the
system. The velocities of several such spin-charge separated excitations can be
explicitly observed. Moreover, the proposed measurement directly demonstrates
the splintering of the tunneling electrons into a multi-particle continuum of
these quasiparticles, carrying separately charge from spin. A variety of
corrections to the simple Luttinger model are also discussed.Comment: 4 pages, 5 figures (1 in color
Thermodynamics of d-dimensional charged rotating black brane and AdS/CFT correspondence
We compute the Euclidean actions of a -dimensional charged rotating black
brane both in the canonical and the grand-canonical ensemble through the use of
the counterterms renormalization method, and show that the logarithmic
divergencies associated with the Weyl anomalies and matter field vanish. We
obtain a Smarr-type formula for the mass as a function of the entropy, the
angular momenta, and the electric charge, and show that these quantities
satisfy the first law of thermodynamics. Using the conserved quantities and the
Euclidean actions, we calculate the thermodynamics potentials of the system in
terms of the temperature, angular velocities, and electric potential both in
the canonical and grand-canonical ensembles. We also perform a stability
analysis in these two ensembles, and show that the system is thermally stable.
This is commensurate with the fact that there is no Hawking-Page phase
transition for a black object with zero curvature horizon. Finally, we obtain
the logarithmic correction of the entropy due to the thermal fluctuation around
the equilibrium.Comment: REVTEX4, 15 pages, 1 figur
Global embeddings of scalar-tensor theories in (2+1)-dimensions
We obtain (3+3)- or (3+2)-dimensional global flat embeddings of four
uncharged and charged scalar-tensor theories with the parameters B or L in the
(2+1)-dimensions, which are the non-trivially modified versions of the
Banados-Teitelboim-Zanelli (BTZ) black holes. The limiting cases B=0 or L=0
exactly are reduced to the Global Embedding Minkowski Space (GEMS) solution of
the BTZ black holes.Comment: 19 pages, 2 figure
Thermodynamic analysis of black hole solutions in gravitating nonlinear electrodynamics
We perform a general study of the thermodynamic properties of static
electrically charged black hole solutions of nonlinear electrodynamics
minimally coupled to gravitation in three space dimensions. The Lagrangian
densities governing the dynamics of these models in flat space are defined as
arbitrary functions of the gauge field invariants, constrained by some
requirements for physical admissibility. The exhaustive classification of these
theories in flat space, in terms of the behaviour of the Lagrangian densities
in vacuum and on the boundary of their domain of definition, defines twelve
families of admissible models. When these models are coupled to gravity, the
flat space classification leads to a complete characterization of the
associated sets of gravitating electrostatic spherically symmetric solutions by
their central and asymptotic behaviours. We focus on nine of these families,
which support asymptotically Schwarzschild-like black hole configurations, for
which the thermodynamic analysis is possible and pertinent. In this way, the
thermodynamic laws are extended to the sets of black hole solutions of these
families, for which the generic behaviours of the relevant state variables are
classified and thoroughly analyzed in terms of the aforementioned boundary
properties of the Lagrangians. Moreover, we find universal scaling laws (which
hold and are the same for all the black hole solutions of models belonging to
any of the nine families) running the thermodynamic variables with the electric
charge and the horizon radius. These scale transformations form a one-parameter
multiplicative group, leading to universal "renormalization group"-like
first-order differential equations. The beams of characteristics of these
equations generate the full set of black hole states associated to any of these
gravitating nonlinear electrodynamics...Comment: 51 single column pages, 19 postscript figures, 2 tables, GRG tex
style; minor corrections added; final version appearing in General Relativity
and Gravitatio
Higher dimensional flat embeddings of (2+1) dimensional black holes
We obtain the higher dimensional global flat embeddings of static, rotating,
and charged BTZ black holes. On the other hand, we also study the similar
higher dimensional flat embeddings of the (2+1) de Sitter black holes which are
the counterparts of the anti-de Sitter BTZ black holes. As a result, the
charged dS black hole is shown to be embedded in (3+2) GEMS, contrast to the
charged BTZ one having (3+3) GEMS structure.Comment: 16pages, revtex, no figures, to appear in Phys. Rev.
Higher dimensional flat embeddings of black strings in (2+1) dimensions
We obtain (3+1) and (3+2) dimensional global flat embeddings of (2+1)
uncharged and charged black strings, respectively. In particular, the charged
black string, which is the dual solution of the Banados-Teitelboim-Zanelli
black holes, is shown to be embedded in the same global embedding Minkowski
space structure as that of the (2+1) charged de Sitter black hole solution.Comment: 11 pages, REVTEX, no figur
Age-related changes in global motion coherence: conflicting haemodynamic and perceptual responses
Our aim was to use both behavioural and neuroimaging data to identify indicators of perceptual decline in motion processing. We employed a global motion coherence task and functional Near Infrared Spectroscopy (fNIRS). Healthy adults (nâ=â72, 18-85) were recruited into the following groups: young (nâ=â28, mean ageâ=â28), middle-aged (nâ=â22, mean ageâ=â50), and older adults (nâ=â23, mean ageâ=â70). Participants were assessed on their motion coherence thresholds at 3 different speeds using a psychophysical design. As expected, we report age group differences in motion processing as demonstrated by higher motion coherence thresholds in older adults. Crucially, we add correlational data showing that global motion perception declines linearly as a function of age. The associated fNIRS recordings provide a clear physiological correlate of global motion perception. The crux of this study lies in the robust linear correlation between age and haemodynamic response for both measures of oxygenation. We hypothesise that there is an increase in neural recruitment, necessitating an increase in metabolic need and blood flow, which presents as a higher oxygenated haemoglobin response. We report age-related changes in motion perception with poorer behavioural performance (high motion coherence thresholds) associated with an increased haemodynamic response
Holographic phase diagram of quark-gluon plasma formed in heavy-ions collisions
The phase diagram of quark gluon plasma (QGP) formed at a very early stage
just after the heavy ion collision is obtained by using a holographic dual
model for the heavy ion collision. In this dual model colliding ions are
described by the charged shock gravitational waves. Points on the phase diagram
correspond to the QGP or hadronic matter with given temperatures and chemical
potentials. The phase of QGP in dual terms is related to the case when the
collision of shock waves leads to formation of trapped surface. Hadronic matter
and other confined states correspond to the absence of trapped surface after
collision.
Multiplicity of the ion collision process is estimated in the dual language
as area of the trapped surface. We show that a non-zero chemical potential
reduces the multiplicity. To plot the phase diagram we use two different dual
models of colliding ions, the point and the wall shock waves, and find
qualitative agreement of the results.Comment: 33 pages, 14 figures, typos correcte
Redshift identification of X-ray-selected active galactic nuclei in the J1030 field: searching for large-scale structures and high-redshift sources
We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the z = 6.3 quasar SDSS J1030+0525. This is currently the fifth-deepest extragalactic X-ray field, and reaches a 0.5 2 keV flux limit of f0:5-2 = 6 à 10-17 erg s-1 cm-2. Using two independent methods, we measure a photometric redshift for 243 objects, while 123 (51%) sources also have a spectroscopic redshift, 110 of which come from an INAF-Large Binocular Telescope (LBT) Strategic Program.We use the spectroscopic redshifts to determine the quality of the photometric ones, and find it to be in agreement with that of other X-ray surveys which used a similar number of photometric data points. In particular, we measure a sample normalized median absolute deviation of NMAD = 1.48 à median(||zphot - zspec||/(1 + zspec)) = 0.065. We use these new spectroscopic and photometric redshifts to study the properties of the Chandra J1030 field.We observe several peaks in our spectroscopic redshift distribution between z = 0.15 and z = 1.5, and find that the sources in each peak are often distributed across the whole Chandra field of view. This confirms that X-ray-selected AGNs can efficiently track large-scale structures over physical scales of several megaparsecs. Finally, we computed the Chandra J1030 z > 3 number counts: while the spectroscopic completeness of our sample is limited at high redshift, our results point towards a potential source excess at z ⼠4, which we plan to either confirm or reject in the near future with dedicated spectroscopic campaigns
Ethylene Synthesis and Regulated Expression of Recombinant Protein in Synechocystis sp PCC 6803
The ethylene-forming enzyme (EFE) from Pseudomonas syringae catalyzes the synthesis of ethylene which can be easily detected in the headspace of closed cultures. A synthetic codon-optimized gene encoding N-terminal His-tagged EFE (EFEh) was expressed in Synechocystis sp. PCC 6803 (Synechocystis) and Escherichia coli (E. coli) under the control of diverse promoters in a self-replicating broad host-range plasmid. Ethylene synthesis was stably maintained in both organisms in contrast to earlier work in Synechococcus elongatus PCC 7942. The rate of ethylene accumulation was used as a reporter for protein expression in order to assess promoter strength and inducibility with the different expression systems. Several metal-inducible cyanobacterial promoters did not function in E. coli but were well-regulated in cyanobacteria, albeit at a low level of expression. The E. coli promoter P(trc) resulted in constitutive expression in cyanobacteria regardless of whether IPTG was added or not. In contrast, a Lac promoter variant, P(A1lacO-1), induced EFE-expression in Synechocystis at a level of expression as high as the Trc promoter and allowed a fine level of IPTG-dependent regulation of protein-expression. The regulation was tight at low cell density and became more relaxed in more dense cultures. A synthetic quorum-sensing promoter system was also constructed and shown to function well in E. coli, however, only a very low level of EFE-activity was observed in Synechocystis, independent of cell density
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