103 research outputs found
Supersymmetric Fluid Dynamics
Recently Navier-Stokes (NS) equations have been derived from the duality
between the black branes and a conformal fluid on the boundary of AdS_5.
Nevertheless, the full correspondence has to be established between solutions
of supergravity in AdS_5 and supersymmetric field theories on the boundary.
That prompts the construction of NS equations for a supersymmetric fluid. In
the framework of rigid susy, there are several possibilities and we propose one
candidate. We deduce the equations of motion in two ways: both from the
divergenless condition on the energy-momentum tensor and by a suitable
parametrization of the auxiliary fields. We give the complete component
expansion and a very preliminary analysis of the physics of this supersymmetric
fluid.Comment: 24 pages, Latex2
Torsion formulation of gravity
We make it precise what it means to have a connection with torsion as
solution of the Einstein equations. While locally the theory remains the same,
the new formulation allows for topologies that would have been excluded in the
standard formulation of gravity. In this formulation it is possible to couple
arbitrary torsion to gauge fields without breaking the gauge invariance.Comment: AMS-LaTeX, 25 pages. Appendices have been eliminated and the
necessary concepts have been inroduced in the text. We have added some
reference
Warm dust in high-z galaxies: origin and implications
ALMA observations have revealed the presence of dust in galaxies in the Epoch
of Reionization (redshift ). However, the dust temperature, , remains
unconstrained, and this introduces large uncertainties, particularly in the
dust mass determinations. Using an analytical and physically-motivated model,
we show that dust in high-, star-forming giant molecular clouds (GMC),
largely dominating the observed far-infrared luminosity, is warmer ($T_d > 60\
\mathrm{K}\sim 40\%T_dz\beta$ relation, (b) alleviates the
problem of the uncomfortably large dust masses deduced from observations of
some EoR galaxies.Comment: 14 pages, 6 figures, accepted for publication in MNRA
Dust temperature in {ALMA} [C~ii]-detected high-z galaxies
At redshift z > 5, the far-infrared (FIR) continuum spectra of main-sequence galaxies are sparsely sampled, often with a single data point. The dust temperature T-d(,SED), thus has to be assumed in the FIR continuum fitting. This introduces large uncertainties regarding the derived dust mass (M-d), FIR luminosity, and obscured fraction of the star formation rate. These are crucial quantities to quantify the effect of dust obscuration in high-z galaxies. To overcome observation limitations, we introduce a new method that combines dust continuum information with the overlying [C II] 158 mu m line emission. By breaking the M-d T-d(,SED) degeneracy, with our method, we can reliably constrain the dust temperature with a single observation at 158 mu m. This method can be applied to all Atacama Large Millimeter Array (ALMA) and NOEMA [C II] observations, and exploited in ALMA Large Programs such as ALPINE and REBELS targeting [C II] emitters at high-z. We also provide a physical interpretation of the empirical relation recently found between molecular gas mass and [C II] luminosity. We derive an analogous relation linking the total gas surface density and [C II] surface brightness. By combining the two, we predict the cosmic evolution of the surface density ratio Sigma(H2) / Sigma(gas). We find that Sigma(H2)/ Sigma(gas) slowly increases with redshift, which is compatible with current observations at 0 < z < 4
Dust attenuation law in JWST galaxies at z = 7-8
Attenuation curves in galaxies depend on dust chemical composition, content,
and grain size distribution. Such parameters are related to intrinsic galaxy
properties such as metallicity, star formation rate, and stellar age. Due to
the lack of observational constraints at high redshift, dust empirical curves
measured in the local Universe (e.g. Calzetti and SMC curves) have been
employed to describe the dust attenuation at early epochs. We exploit the high
sensitivity and spectral resolution of the JWST to constrain the dust
attenuation curves in high-z galaxies. Our goals are to check whether dust
attenuation curves evolve with redshift and quantify the dependence of the
inferred galaxy properties on the assumed dust attenuation law. We develop a
modified version of the SED fitting code BAGPIPES by including a detailed dust
attenuation curve parametrization. Dust parameters are derived, along with
galaxy properties, from the fit to the data from FUV to mm bands. Once applied
to three star-forming galaxies at z = 7-8, we find that their attenuation
curves differ from local templates. One out of three galaxies shows a
characteristic MW bump, typically associated to the presence of small
carbonaceous dust grains such as PAHs. This is one of the first evidences
suggesting the presence of PAHs in early galaxies. Galaxy properties such as
stellar mass and SFR inferred from SED fitting are strongly affected by the
assumed attenuation curve, though the adopted star formation history also plays
a major role. Our results highlight the importance of accounting for the
potential diversity of dust attenuation laws when analyzing the properties of
galaxies at the EoR, whose dust properties are still poorly understood. The
application of our method to a larger sample of galaxies observed with JWST can
provide us important insights into the properties of dust and galaxies in the
early universe.Comment: 19 pages, 10 figure
Effective Actions for Massive Kaluza-Klein States on AdS_3 x S^3 x S^3
We construct the effective supergravity actions for the lowest massive
Kaluza-Klein states on the supersymmetric background AdS_3 x S^3 x S^3. In
particular, we describe the coupling of the supergravity multiplet to the
lowest massive spin-3/2 multiplet which contains 256 physical degrees of
freedom and includes the moduli of the theory. The effective theory is realized
as the broken phase of a particular gauging of the maximal three-dimensional
supergravity with gauge group SO(4) x SO(4). Its ground state breaks half of
the supersymmetries leading to 8 massive gravitinos acquiring mass in a super
Higgs effect. The holographic boundary theory realizes the large N=(4,4)
superconformal symmetry.Comment: 31 pages, v2: minor change
Scherk-Schwarz Reduction of D=5 Special and Quaternionic Geometry
We give the N=2 gauged supergravity interpretation of a generic D=4, N=2
theory as it comes from generalized Scherk-Schwarz reduction of D=5, N=2
(ungauged) supergravity. We focus on the geometric aspects of the D=4 data such
as the general form of the scalar potential and masses in terms of the gauging
of a ``flat group''. Higgs and super-Higgs mechanism are discussed in some
detail.Comment: final version to be published on Class.Quant.Gra
A survey of high-z galaxies: serra simulations
We introduce SERRA, a suite of zoom-in high-resolution (1.2 ×104 M⊙, ≃ 25 pc at z = 7.7) cosmological simulations including non-equilibrium chemistry and on-the-fly radiative transfer. The outputs are post-processed to derive galaxy ultraviolet (UV) + far-infrared (FIR) continuum and emission line properties. Results are compared with available multiwavelength data to constrain the physical properties [e.g. star formation rates (SFRs), stellar/gas/dust mass, metallicity] of high-redshift 6 ≲ z ≲ 15 galaxies. This flagship paper focuses on the z = 7.7 sub-sample, including 202 galaxies with stellar mass 107 M⊙ ≲ M⊙ ≲ 5 ×1010 M⊙, and specific star formation rate ranging from sSFR ∼100 Gyr-1 in young, low-mass galaxies to ∼10 Gyr-1 for older, massive ones. At this redshift, SERRA galaxies are typically bursty, i.e. they are located abo v e the Schmidt-Kennicutt relation by a factor κs = 3.03+4.9-1.8, consistent with recent findings for [O III ] and [C II ] emitters at high z. They also show relatively large InfraRed eXcess (IRX = LFIR/LUV) values as a result of their compact/clumpy morphology effectively blocking the stellar UV luminosity. Note that this conclusion might be affected by insufficient spatial resolution at the molecular cloud level. We confirm that early galaxies lie on the standard [C II ] -SFR relation; their observed L[OIII]/L [CII] ≃ 1-10 ratios can be reproduced by a part of the SERRA galaxies without the need of a top-heavy initial mass function and/or anomalous C/O abundances. [O I] line intensities are similar to local ones, making ALMA high-z detections challenging but feasible ( ∼6 h for an SFR of 50 M⊙yr-1)
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