2,299 research outputs found
The shear viscosity of the non-commutative plasma
We compute the shear viscosity of the non-commutative N=4 super Yang-Mills
quantum field theory at strong coupling using the dual supergravity background.
Special interest derives from the fact that the background presents an
intrinsic anisotropy in space through the distinction of commutative and
non-commutative directions. Despite this anisotropy the analysis exhibits the
ubiquitous result \eta/s = 1/4\pi for two different shear channels. In order to
derive this result, we show that the boundary energy momentum tensor must
couple to the open string metric. As a byproduct we compute the renormalised
holographic energy momentum tensor and show that it coincides with one in the
commutative theory.Comment: 17 pages. v2: reference adde
Mapping Luminous Blue Compact Galaxies with VIRUS-P: morphology, line ratios and kinematics
[abridged] We carry out an integral field spectroscopy (IFS) study of a
sample of luminous BCGs, with the aim to probe the morphology, kinematics, dust
extinction and excitation mechanisms of their warm interstellar medium (ISM).
IFS data for five luminous BCGs were obtained using VIRUS-P, the prototype
instrument for the Visible Integral Field Replicable Unit Spectrograph,
attached to the 2.7m Harlan J. Smith Telescope at the McDonald Observatory.
VIRUS-P consists of a square array of 247 optical fibers, which covers a
109"x109" field of view, with a spatial sampling of 4.2" and a 0.3 filling
factor. We observed in the 3550-5850 Angstrom spectral range, with a resolution
of 5 A FWHM. From these data we built two-dimensional maps of the continuum and
the most prominent emission-lines ([OII]3727, Hgamma, Hbeta and [OIII]5007),
and investigate the morphology of diagnostic emission-line ratios and the
extinction patterns in the ISM as well as stellar and gas kinematics.
Additionally, from integrated spectra we infer total line fluxes and
luminosity-weighted extinction coefficients and gas-phase metallicities. All
galaxies exhibit an overall regular morphology in the stellar continuum, while
their warm ISM morphology is more complex: in II Zw 33 and Mrk 314, the
star-forming regions are aligned along a chain-structure; Haro 1, NGC 4670 and
III Zw 102 display several salient features, such as extended gaseous filaments
and bubbles. A significant intrinsic absorption by dust is present in all
galaxies, the most extreme case being III Zw 102. Our data reveal a manifold of
kinematical patterns, from overall regular gas and stellar rotation to complex
velocity fields produced by structurally and kinematically distinct components.Comment: Accepted for publication in A&A. 16 pages, 10 figure
Evolution of innovation policy in Emilia-Romagna and Valencia: Similar reality, similar results?
This is an author's accepted manuscript of an article published in:
“European Planning Studies"; Volume 22, Issue 11, 2014; copyright Taylor & Francis; available online at: http://dx.doi.org/10.1080/09654313.2013.831398[EN] This paper examines the evolution of regional innovation policy in Emilia-Romagna and
Valencia, two regions with similar economic features that implemented close innovation policies in
the 1970s and 1980s. We investigate whether their similarities have led to parallel targets, policy
tools and governance developments. We show that innovation policy in both regions suffered
from the effects of privatization, budget constraints and changes to manufacturing during the
1990s and we highlight the consequences. Although Emilia-Romagna experienced deeper changes
to its innovation policy, privatizations and/or the replacement of public funds promoted
commercial approaches and induced market failures in both regions. The worst effects of these
policies were the implementation of less-risky innovation projects, the shift towards extraregional
projects and markets, and the favouring of large firms.López Estornell, M.; Barberá Tomás, JD.; Garcia Reche, A.; Mas Verdú, F. (2013). Evolution of innovation policy in Emilia-Romagna and Valencia: Similar reality, similar results?. European Planning Studies. 22(11):2287-2304. doi:10.1080/09654313.2013.831398S22872304221
The temporal and spatial evolution of the starburst in ESO 338-IG04 as probed by its star clusters
In this paper we use ultra-violet (UV) and optical HST photometry in five
bands, and an extensive set of spectral evolutionary synthesis scenarios to
investigate the age and masses of 124 star clusters in the luminous blue
compact galaxy ESO338-IG04 (Tololo 1924-416). The very small internal reddening
makes ESO 338-IG04 an excellent laboratory for studying the formation of
massive star clusters. We have used the star clusters to trace the temporal and
spatial evolution of the starburst, and to put constraints on the star
formation activity over a cosmological time-scale. The present starburst has
been active for about 40 Myr. A standard Salpeter initial mass function (IMF)
extending up to 120 solar masses provides the best fit to the data, although a
flatter IMF cannot be excluded. The compact star clusters provide 30-40 percent
of the UV luminosity and star formation activity. We find no evidence for dust
obscuration even among the youngest (< 1 Myr) clusters. The fraction of stellar
mass contained in compact star clusters is found to be several percent, which
is an unusually high value. The intermediate age clusters show a flattened
space distribution which agrees with the isophotal shape of the galaxy, whereas
the oldest clusters seem to have a spherical distribution.(abridged)Comment: Accepted for publication in A&
Mapping the properties of blue compact dwarf galaxies: integral field spectroscopy with PMAS
(Abridged) We perform integral field spectroscopy of a sample of Blue compact
dwarf (BCD) galaxies with the aim of analyzing their morphology, the spatial
distribution of some of their physical properties (excitation, extinction, and
electron density) and their relationship with the distribution and evolutionary
state of the stellar populations. Integral field spectroscopy observations of
the sample galaxies were carried out with the Potsdam Multi-Aperture
Spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. An
area 16 arcsec x 16 arcsec in size was mapped with a spatial sampling of 1
arcsec x 1 arcsec. We obtained data in the 3590-6996 Angstroms spectral range,
with a linear dispersion of 3.2 Angstroms per pixel. From these data we built
two-dimensional maps of the flux of the most prominent emission lines, of two
continuum bands, of the most relevant line ratios, and of the gas velocity
field. Integrated spectra of the most prominent star-forming regions and of
whole objects within the FOV were used to derive their physical parameters and
the gas metal abundances. Six galaxies display the same morphology both in
emission line and in continuum maps; only in two objects, Mrk 32 and Tololo
1434+032, the distributions of the ionized gas and of the stars differ
considerably. In general the different excitation maps for a same object
display the same pattern and trace the star-forming regions, as expected for
objects ionized by hot stars; only the outer regions of Mrk 32, I Zw 123 and I
Zw 159 display higher [SII]/Halpha values, suggestive of shocks. Six galaxies
display an inhomogeneous dust distribution. Regarding the kinematics, Mrk 750,
Mrk 206 and I Zw 159 display a clear rotation pattern, while in Mrk 32, Mrk 475
and I Zw 123 the velocity fields are flat.Comment: 27 pages, 11 figures; Accepted for publication in A&
An fMRI study of cognitive reappraisal in major depressive disorder and borderline personality disorder
Background: One common denominator to the clinical phenotypes of borderline personality disorder (BPD) and major depressive disorder (MDD) is emotion regulation impairment. Although these two conditions have been extensively studied separately, it remains unclear whether their emotion regulation impairments are underpinned by shared or distinct neurobiological alterations.
Methods: We contrasted the neural correlates of negative emotion regulation across an adult sample of BPD patients (n = 19), MDD patients (n = 20), and healthy controls (HCs; n = 19). Emotion regulation was assessed using an established functional magnetic resonance imaging cognitive reappraisal paradigm. We assessed both task-related activations and modulations of interregional connectivity.
Results: When compared to HCs, patients with BPD and MDD displayed homologous decreased activation in the right ventrolateral prefrontal cortex (vlPFC) during cognitive reappraisal. In addition, the MDD group presented decreased activations in other prefrontal areas (i.e., left dorsolateral and bilateral orbitofrontal cortices), while the BPD group was characterized by a more extended pattern of alteration in the connectivity between the vlPFC and cortices of the visual ventral stream during reappraisal.
Conclusions: This study identified, for the first time, a shared neurobiological contributor to emotion regulation deficits in MDD and BPD characterized by decreased vlPFC activity, although we also observed disorder-specific alterations. In MDD, results suggest a primary deficit in the strength of prefrontal activations, while BPD is better defined by connectivity disruptions between the vlPFC and temporal emotion processing regions. These findings substantiate, in neurobiological terms, the different profiles of emotion regulation alterations observed in these disorders
Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at z>1
We identify an abundant population of extreme emission line galaxies (EELGs)
at redshift z~1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy
Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3
(HST/WFC3). 69 EELG candidates are selected by the large contribution of
exceptionally bright emission lines to their near-infrared broad-band
magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission
lines -- with rest-frame equivalent widths ~1000\AA -- in the four candidates
that have HST/WFC3 grism observations, we conclude that these objects are
galaxies with 10^8 Msol in stellar mass, undergoing an enormous starburst phase
with M_*/(dM_*/dt) of only ~15 Myr. These bursts may cause outflows that are
strong enough to produce cored dark matter profiles in low-mass galaxies. The
individual star formation rates and the co-moving number density (3.7x10^-4
Mpc^-3) can produce in ~4 Gyr much of the stellar mass density that is
presently contained in 10^8-10^9 Msol dwarf galaxies. Therefore, our
observations provide a strong indication that many or even most of the stars in
present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z>1.Comment: accepted for publication in ApJ; 10 pages; 6 figures; 1 tabl
Collective Excitations of Holographic Quantum Liquids in a Magnetic Field
We use holography to study N=4 supersymmetric SU(Nc) Yang-Mills theory in the
large-Nc and large-coupling limits coupled to a number Nf << Nc of
(n+1)-dimensional massless supersymmetric hypermultiplets in the Nc
representation of SU(Nc), with n=2,3. We introduce a temperature T, a baryon
number chemical potential mu, and a baryon number magnetic field B, and work in
a regime with mu >> T,\sqrt{B}. We study the collective excitations of these
holographic quantum liquids by computing the poles in the retarded Green's
function of the baryon number charge density operator and the associated peaks
in the spectral function. We focus on the evolution of the collective
excitations as we increase the frequency relative to T, i.e. the
hydrodynamic/collisionless crossover. We find that for all B, at low
frequencies the tallest peak in the spectral function is associated with
hydrodynamic charge diffusion. At high frequencies the tallest peak is
associated with a sound mode similar to the zero sound mode in the
collisionless regime of a Landau Fermi liquid. The sound mode has a gap
proportional to B, and as a result for intermediate frequencies and for B
sufficiently large compared to T the spectral function is strongly suppressed.
We find that the hydrodynamic/collisionless crossover occurs at a frequency
that is approximately B-independent.Comment: 45 pages, 8 png and 47 pdf images in 22 figure
Localized Intersections of Non-Extremal p-branes and S-branes
A class of solutions to Supergravity in 10 or 11 dimensions is presented
which extends the non-standard or semi-local intersections of Dp-branes to the
case of non-extremal p-branes. The type of non-extremal solutions involved in
the intersection is free and we provide two examples involving black-branes
and/or D-\bar{D} systems. After a rotation among the time coordinate and a
relatively transverse radial direction the solutions admit the interpretation
of an intersection among D-branes and S-branes. We speculate on the relevance
of these configurations both to study time dependent phenomena in the AdS/CFT
correspondence as well as to construct cosmological brane-world scenarios
within String Theory admitting accelerating expansion of the Universe.Comment: 31 pages, latex file; v2: typos corrected and references adde
INTEGRAL observations of the field of the BL Lacertae object S5~0716+714
We have performed observations of the blazar S5 0716+714 with INTEGRAL on 2-6
April 2004. In the first months of 2004, the source had increased steadily in
optical brightness and had undergone two outbursts. During the latter, occurred
in March, it reached the extreme level of R = 12.1 mag, which triggered our
INTEGRAL program. The target has been detected with IBIS/ISGRI up to 60 keV,
with a flux of ~3 x 10e-11 erg/s/cm2 in the 30-60 keV interval, a factor of ~2
higher than observed by the BeppoSAX PDS in October 2000. In the field of S5
0716+714 we have also detected the Flat Spectrum Radio Quasar S5 0836+710 and
the two Seyfert galaxies Mkn 3 and Mkn 6. Their IBIS/ISGRI spectra are rather
flat, albeit consistent with those measured by BeppoSAX. In the spectrum of Mkn
3 we find some evidence of a break between ~60 and ~100 keV, reminiscent of the
high energy cut-offs observed in other Seyfert galaxies. This is the first
report of INTEGRAL spectra of weak Active Galactic Nuclei.Comment: 5 pages, 5 figures, in press in A&
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