8365482
Non-equilibrium physics at a holographic chiral phase transition
The D3/D7 system holographically describes an $ \mathcal{N} = 2 $ gauge theory which spontaneously breaks a chiral symmetry by the formation of a quark condensate in the presence of a magnetic field. At finite temperature it displays a first order phase transition. We study out of equilibrium dynamics associated with this transition by placing probe D7 branes in a geometry describing a boost-invariant expanding or contracting plasma. We use an adiabatic approximation to track the evolution of the quark condensate in a heated system and reproduce the phase structure expected from equilibrium dynamics. We then study solutions of the full partial differential equation that describes the evolution of out of equilibrium configurations to provide a complete description of the phase transition including describing aspects of bubble formation.
13898734
Confinement, glueballs and strings from deformed AdS
We study aspects of confinement in two deformed versions of the AdS/CFT correspondence — the GPPZ dual of Script N = 1* Yang Mills, and the Yang Mills* Script N = 0 dual. Both geometries describe discrete glueball spectra which we calculate numerically. The results agree at the 10% level with previous AdS/CFT computations in the Klebanov Strassler background and AdS Schwarzchild respectively. We also calculate the spectra of bound states of the massive fermions in these geometries and show that they are light, so not decoupled from the dynamics. We then study the behaviour of Wilson loops in the 10d lifts of these geometries. We find a transition from AdS-like strings in the UV to strings that interact with the unknown physics of the central singularity of the space in the IR.
120735486
Exact results in softly broken SUSY theories
Soft SUSY breaking parameters may be introduced into SUSY theories through non-zero F-components of spurion fields. We discuss the resulting solutions of softly broken N =2 SQCD close in parameter space to the SUSY limit.
119206061
Hadronization at the AdS wall
We describe hadronization events, using the AdS/CFT Correspondence, which display many of the qualitative features expected in QCD. In particular we study the motion of strings with separating end points in a back-reacted hard wall geometry. The solutions show the development of a linear QCD-like string. The end points oscillate in the absence of string breaking. We introduce string breaking by hand and evolve the new state forward in time to observe the separation of two string segments. A kink associated with this breaking evolves to the end points of the string inducing rho meson production. We explicitly compute the rho meson production at the end point.
7462815
Softly broken SQCD: in the continuum, on the lattice, on the brane
Abstract We review progress in studying the solutions of SQCD in the presence of explicit, soft SUSY breaking terms. Massive N = 1 SQCD in the presece of a small gaugino mass leads to a controlled solution which has interesting phase structure with changing θ angle reminiscent of the QCD chiral Lagrangian. Current attempts to test the solutions of pure glue SQCD on the lattice require a theoretical understandinf of the theory with small gaugino mass in order to understand the approach to the SUSY point. We provide such a description making predictions for the gaugino condensate and lightest bound state masses. Finally we briefly review recent D-brane constructions of 4D gauge theories in string theory including a non-supersymmetric configuration. We identify this configuration with softly broken N = 2 SQCD.
18555159
Additional fermion families and precision electroweak data
Abstract The S , T , and U formalism for studying electroweak precision data has recently been updated to include the effects of new light physics and within this analysis the latest LEP and SLC data tightly constrain models of physics beyond the Standard Model. We re-examine the constraints on additional strong and weakly interacting fermion families in the light of these developments. We conclude that the precision data favour models with at least one fermion with a mass below 150 GeV.
29208353
The Spitzer c2d Survey of Nearby Dense Cores. I. First Direct Detection of the Embedded Source in IRAM 04191+1522
We report the first detections of the Class 0 protostellar source IRAM 04191+1522 at wavelengths shortward of 60 μm with the Spitzer Space Telescope. We see extended emission in the Spitzer images that suggests the presence of an outflow cavity in the circumstellar envelope. We combine the Spitzer observations with existing data to form a complete data set ranging from 3.6 to 1300 μm and use these data to construct radiative transfer models of the source. We conclude that the internal luminosity of IRAM 04191+1522, defined to be the sum of the luminosity from the internal sources (a star and a disk), is L_(int) = 0.08 ± 0.04 L_⊙, placing it among the lowest luminosity protostars known. Although it was discovered before the launch of the Spitzer Space Telescope, IRAM 04191+1522 falls within a new class of very low luminosity objects being discovered by Spitzer. Unlike the two other well-studied objects in this class, which are associated either with weak, compact outflows or no outflows at all, IRAM 04191+1522 has a well-defined molecular outflow with properties consistent with those expected based on relations derived from higher luminosity (L_(int) ≥ 1 L_⊙) protostars. We discuss the difficulties in understanding IRAM 04191+1522 in the context of the standard model of star formation and suggest a possible explanation for the very low luminosity of this source.
14925292
A PARAMETER STUDY OF THE DUST AND GAS TEMPERATURE IN A FIELD OF YOUNG STARS
We model the thermal effect of young stars on their surrounding environment in order to understand clustered star formation. We take radiative heating of dust, dust-gas collisional heating, cosmic-ray heating, and molecular cooling into account. Using DUSTY, a spherical continuum radiative transfer code, we model the dust temperature distribution around young stellar objects with various luminosities and surrounding gas and dust density distributions. We have created a grid of dust temperature models, based on our modeling with DUSTY, which we can use to calculate the dust temperature in a field of stars with various parameters. We then determine the gas temperature assuming energy balance. Our models can be used to make large-scale simulations of clustered star formation more realistic.
38395512
Atomic Carbon Is a Temperature Probe in Dark Clouds
We have mapped the C I 3P1 ? 3P0 line at 492 GHz in three molecular clouds immersed in weak ultraviolet radiation fields, TMC-1, L134N, and IC 5146. In all three clouds, the C I peak T ~ 1 K, with very small dispersion. The spatial C I distribution is extended and rather smooth. The J = 2 ? 1 transitions of CO isotopomers were observed at the same angular resolution as C I. The C I peak T is typically one-third of the peak T of 13CO J = 2 ? 1, and the C I emission is usually more extended than emission in 13CO or C18O J = 2 ? 1. The C I line width is close to the 13CO J = 2 ? 1 line width, larger than the C18O J = 2 ? 1 line width and smaller than the 12CO J = 2 ? 1 line width. The shapes of these lines occasionally differ significantly, probably because of the combined effects of differing opacities and the physical separation of the line-forming regions. The uniformity of the C I peak T is remarkable for a line in the Wien portion of the Planck function and indicates a very uniform excitation temperature. This uniformity is best explained if the line is opaque and thermalized. If so, the C I line probes kinetic temperature in clouds exposed to low-ultraviolet fluxes. This conclusion has significant implications for the thermal balance in such clouds. At AV 2, these clouds have a remarkably constant temperature from place to place and from cloud to cloud (7.9 ? 0.8 K). Photodissociation region models of clouds immersed in the mean interstellar radiation field tend to predict stronger lines than we see, but this may be an artifact of assumptions about the temperature.
120641577
Spitzer discovery of very low luminosity objects
The Spitzer Space Telescope allows for the .rst time to search systematically for very low luminosity (≲0.1 L⊙) objects (VeLLOs) associated with dense molecular cores. They may be the .rst candidate Class 0 sources with sub-stellar masses. We describe such a source in the dense molecular core L1148. VeLLO natal cores show properties that are unusual for star-forming cores. The low luminosity and in some cases the lack of prominent out.ow could be the result of the small gas supply near the VeLLO. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
54618971
The Spitzer c2d Survey of Nearby Dense Cores. IV. Revealing the Embedded Cluster in B59
Infrared images of the dark cloud core B59 were obtained with the Spitzer Space Telescope as part of the "Cores to Disks" Legacy Science project. Photometry from 3.6-70 μm indicates at least 20 candidate low-mass young stars near the core, more than doubling the previously known population. Out of this group, 13 are located within ~0.1 pc in projection of the molecular gas peak, where a new embedded source is detected. Spectral energy distributions span the range from small excesses above photospheric levels to rising in the mid-infrared. One other embedded object, probably associated with the millimeter source B59-MMS1, with a bolometric luminosity L_(bol) ~ 2 L_⊙, has extended structure at 3.6 and 4.5 μm, possibly tracing the edges of an outflow cavity. The measured extinction through the central part of the core is A_V ≳ 45 mag. The B59 core is producing young stars with a high efficiency.