Thursday. Hoping my luggage and computer will arrive today, but no guarantee...
RPM@LBL, 6/16
Beyond Standard SUSY searches at the LHC
Andy Haas (SLAC)
Standard searches for SUSY at LCH look for high energy (prompt) jets and/or leptons and large missing transverse energy from escaping dark matter, well motivated by minimal models of SUSY-breaking (i.e., MSSM). No evidence of this in early LHC data. Maybe SUSY produce long-lived particles, no missing energy, leptonic jets, or other more exotic signatures.
1106.2165
Resolved optical-infrared SEDs of galaxies: universal relations and their breakdown on local scales
Zibetti, Groves
* Oooh, I was in the middle of reading this one.
The spectra are resolved, so one can see the scatter in the optical-IR correlation in a given galaxy. IR dominated component is associated with sSFR, while optical-dominated is associated with stellar mass density. When all pixels are combined, then the usual optical-IR correlations return, demonstrating that the variance within a galaxy is around a mean that is a common trend. Also see dust in IRAC bands; dust correction needed.
1106.0745
Limits on the GeV Emission from GRB
Beniamini, Guetta, Nakar, Piran
Only a small fraction long GRB's show above-30MeV emission, which were the brightest among the GBM (GRB detected by GBM monitor of 8keV-10MeV) bursts. Find an upper limit average of fluence ratio of 0.13 at GeV during T_90, and 0.45 for the first 10 minutes after trigger. Measurement rule out SSC models of prompt emission. Possible evidence for the pair creation limit in the excess of GeV fluence.
* what is a fluence? Fluence is the flux (particle or radiative) integrated over time. For particles, it's defined as the total number of particles thati ntersect a unit area in a specific time interval of interest, and has units of m^{-2}. Fluence can also be used to describe the energy delivered per unit area, in which case it has units of J m^{-2}. It is one of the fundamental units in dosimetry.
* what is fluence ratio in this context? ... donno.
* what is the SSC models of prompt emission? SSC = synchrotron self Compton = inverse Compton scattering of syncrotron radiation by the same relativistic electrons that produce the synchrotron radiation.
* Inverse Compton radiation: upscattering radio photons to become optical or x-ray photons.
* what is the "long sought after pair creation limit"? ... donno.
1105.6101
Stochastic star formaiton and a (nearly) uniform stellar initial mass function
Fumagalli, da Silva, Krumholz
* IMF paper
Halpha and FUV originate in different stars, so their luminosity ratio is a sensitive probe to IMF. Observation of dwarf galaxies suggest a truncated and/or steeper IMF in small galaxies [what does that mean? more low mass stars?] But FUV and Halpha ratio can scatter even for a fixed IMF, so use simulation to test this scatter. Looks like observed luminosity is a function of SFR, cluster mass function and a universal IMF.
1105.6097
The global evolution of giant molecular clouds II: the role of accretion
Goldbaum, Krumhholz, Matzner, McKee
Virial models of evolution of giant molecular clouds [must cool the gas, I guess]. Accretion and star formation contribute roughtly equal amounts of turbulent kinetic energy over the lifetime of the cloud. Clouds grow over time to maintain roughly constant surface densities: 50-100 M_sun pc^{-2}.
* I couldn't skim the big, basic picture of molecular cloud growth from this abstract. Or maybe I'm confused, because no cooling is mentioned. Shouldn't there be cooling, not just accretion?
1105.6096
Nuclear-dominated accretion and subluminous supernovae from the merger of a white dwarf with a neutron star or black hole
Metzger
* That's interesting and obscure.
1D steady state model of accretion disks produced by the tidal disruption of a WD by a NS or BH. At some radius (1e9cm) and smaller, density and temperature sufficiently high to progressivly burn heavier elements, such as Mg, Si, S, Ca, Fe and Ni. When nuclear reaction-released energy is the same as gravitationally released energy. Fe photo-disinterates into He and then free nuclei [? do they mean nucleus?]; cooling by neutrinos may be efficient. Study EM counterpart; maybe the subluminous Type I SNe are a result from WD-NS/BH mergers.
1105.3069
A quasi-radial stability criterion for rotating relativistic stars
Takami, Rezzolla, Yoshida
* stability properties of relativistic stars against gravitational collapse!
A sequence of uniformaly rotating barotropic stars is secularly unstable on one side of a turning point [one side of what? turning point?] They show that the opposite side is not stable either. Assess dynamical stability of relativistic rotating stars.
* bah, I don't know enough for this abstract to be interesting to me.
1105.6339
Limits on the local dark matter density
Garbari, Read, Lake
* determine local dark matter density from the vertical motion of stars in the solar neighbourhood!
Revisit sytematics in doing so. [How is it done in the first place anyways?] Simulation of MW show that their method works well, apply it to Hipparcos data. Assume A and F stars are isothermal tracers. Local density is 0.003+0.009-0.007 M_sun pc^{-3} with 90% confidence; this is consistent with previous measurements. Need vertical measurements, still lacking.
1106.0065
Tests of modified gravity with dwarf galaxies
Jain, Vanderplas
* what is a scalar-tensor theory? A theory that includes both a scalar field and a tensor field to represent a certain interaction. Examples: Brans-Dicke theory of gravitation, f(R) gravity.
* what is scalar field theory? A field which is invariant under any Lorentz transformation is called a "scalar", in contrast to a vector or tensor field. The quanta of the quantized scalar field are spin-zero particles (i.e., bosons). No fundamental scalar fields have been observed in nature, but the Higgs boson may prove to be the first example.
Scalar-tensor theories, objects in low-density environment, such as dwarf galaxies, can be subject to enhanced forces. Study observable deviations from GR in the disks of late-type dwarf galaxies moving under gravity. The 5th force acts on the DM and HI gas disk, but not on stellar disk (main sequence stars have self-screening and evades it). HI displacement from stellar disk (~1kpc), warping of stellar disk, enhancement of rotation curve of HI compared to stellar (~10km/s), or asymmetry in the rotation curve of the stellar disk are observational signatures.
1106.0106
Beyond the standard cosmological model with CMB
Souradeep
* what can we do extra with the CMB? It has been very good at constraining the cosmology.
Important basic tenets established with CMB: 'acausally' correlated, adiabatic, primordial perturbations in a flat, statistically isotropic universe---consistent with inflation. Gravitational instability is the established mechanism for structure formation from these initial perturbations. Primordial perturbations observed as the CMB anisostropy and polarizaton is the most compelling evidence for new, possibly fundamental, physics in the early universe.
* didn't say anything that we didn't know already. It was a 4-page paper.
1106.0126
Horava-Lifshitz quantum cosmology
Bertolami, Zarro
* okay, what's "Horava-Lifshitz"?
* Horava-Lifshitz gravity: thoery of quantum gravity proposed by Horava in 2009; solves the different concepts of time in quantum field theory and general relativity by treating the quantum concept as the more fundamental, so that space and time are not equivalent (anisotropic). Causal structure relies on the theory of foliations (bundles). Solution for spherical sun "different." Inconsistencies remain.
* Wheeler-DeWitt equation?
* A functional differential equation. Important in quantum gravity, ill defined in the general case. Has the form of an operator acting on a functional. Well defined in mini-superspaces (e.g., configuration space of cosmological theories). It's a hamiltonian constraint in quantized general relativity. Appearance may be familiar, but their interpretation in the Wheeler-DeWitt equation is substantially different from non-relativistic quantum mechanics. Wave function(al) contains all of the information about the geometry and matter content of the universe. H does not determine evolution of the system (timelessness). Reemergence of time requires the tools of decoherence and clock operators. In minisuperspace, only one Hamiltonian constraint.
* minisuperspace?
* In quantum gravity, the phase space is infinite dimensional (it's a field theory). Approximation: only consider the largest wavelength modes of the order of the size of the universe (when considering cosmological models). This is the minisuperspace approximation. Holds as long as the adiabatic approximation holds. E.g., consider only scale factor and Hubble constant for a FRW model.
* Hamilton-Jacobi equation?
* necessary condition describing extremal geometry in generalization of calculus of variations problems. Particularly useful in identifying conserved quantities for mechanical systems, even if the mechanical problem itself cannot be solved completely.
Investigate HL gravity w/o detailed balance condition (minisuperspace model). Study Wheeler-deWitt equation & solutions; for some cases, there is a potential barrier near a=0. Find normalizable wave function of the universe. Use Hamilton-Jacobi equation discuss how the transition from quantum to classical regime occurs. For a positive cosmological constant, the scale factor grows exponentially, hence recovering the GR behaviour for the late universe.
* oh well.
1011.2239
Characterizing and propagating modeling uncertainties in photometrically-derived redshift distributions
Abrahamse, Knox, Schmidt, Thorman, Tyson, Zhan
* this is actually relevant to my current paper.
Focus on the effects of SED fitting methods of photoz estimation (two types): uncertainties in the SED template set, and uncertainties in the magnitude and type priors used in Bayesian photoz estimation. Find SED template selection effects dominated over magnitude prior errors. Introduce a method for parameterizing the resulting ignorance of z distributions [?], and for propagating these uncertainties to cosmological parameters.
* they study template uncertainty (S3) and magnitude and type error distribution (S4).
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