119208225
The baryonic phase in holographic descriptions of the QCD phase diagram
A bstractWe study holographic models of the QCD temperature-chemical potential phase diagram based on the D3/D7 system with chiral symmetry breaking. The baryonic phase may be included through linked D5-D7 systems. In a previous analysis of a model with a running gauge coupling a baryonic phase was shown to exist to arbitrarily large chemical potential. Here we explore this phase in a more generic phenomenological setting with a step function dilaton profile. The change in dilaton generates a linear confining qq potential and opposes the screening effect of temperature. We show that the persistence of the baryonic phase depends on the step size and that QCD-like phase diagrams can be described. The baryonic phase’s existence is qualitatively linked to the existence of confinement in Wilson loop computations in the background.
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.
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.
118470786
Chemical potential in the gravity dual of a 2 + 1 dimensional system
We study probe D5 branes in D3 brane AdS5 and AdS5-Schwarzschild backgrounds as a prototype dual description of strongly coupled 2+1 dimensional quasiparticles. We introduce a chemical potential through the U(1)R symmetry group, U(1) baryon number, and a U(1) of isospin in the multiflavor case. We find the appropriate D5 embeddings in each case—the embeddings do not exhibit the spontaneous symmetry breaking that would be needed for a superconductor. The isospin chemical potential does induce the condensation of charged meson states.
14538317
Field theory operator encoding in N = 2 geometries
We investigate supergravity solutions describing D5-branes wrapped on a two cycle which are dual to = 2 super Yang Mills theory. Brane probing these solutions allows the moduli space of the field theory to be identified. There are a unique set of coordinates in which the field theory on the probe takes an = 2 form and in these coordinates the running coupling of the gauge theory may be identified. We show that the geometry, when restricted to the moduli space, takes a very simple form involving only two functions. One is the running gauge coupling whilst the other parametrizes the scalar operators of the field theory. The D5-brane distributions, for the full set of solutions in the literature, can be determined by assuming the field theory's form for the running coupling as a function of scalar vevs. We show that the resulting distributions also correctly reproduce the scalar operators parametrized elsewhere providing the first non-trivial consistency check on the duality.
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.
15940232
Comparisons of an evolutionary chemical model with other models
We compare an evolutionary chemical model with simple empirical models of the abundance and with static chemical models. We focus on the prediction of molecular line profiles that are commonly observed in low-mass star forming cores. We show that empirical models can be used to constrain evaporation radii and infall radii using lines of some species. Species with more complex abundance profiles are not well represented by the empirical models. Static chemical models produce abundance profiles different from those obtained from an evolutionary calculation, because static models do not account for the flow of matter inward from the outer regions. The resulting profiles of lines used to probe infall may differ substantially.
119478666
A CS J = 5 ->4 Mapping Survey Towards High Mass Star Forming Cores Associated with H2O Masers
Sixty-three high mass star forming cores selected from the study of Plume et al. (1997; T ∗ R > 1K) were mapped in CS J= 5 → 4 at the CSO between September 1996 and July 1999. Nearly all of the cores observed lie in the first and second galactic quadrants. The cores were mapped using the on-the-fly technique with a square grid in RA-DEC coordinates oversampled at 10 resolution. The maps were extended until the CS emission was negligible (±50 for the average map).
1577928
Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. I. Perseus
We present a large-scale millimeter continuum map of the Ophiuchus molecular cloud. Nearly 11 deg2, including all of the area in the cloud with AV ≥ 3 mag, was mapped at 1.1 mm with Bolocam on the Caltech Submillimeter Observatory (CSO). By design, the map also covers the region mapped in the infrared with the Spitzer Space Telescope. We detect 44 definite sources, and a few likely sources are also seen along a filament in the eastern streamer. The map indicates that dense cores in Ophiuchus are very clustered and often found in filaments within the cloud. Most sources are round, as measured at the half-power point, but elongated when measured at lower contour levels, suggesting spherical sources lying within filaments. The masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 M☉, with a mean value of 0.96 M☉. The total mass in distinct cores is 42 M☉, 0.5%-2% of the total cloud mass, and the total mass above 4 σ is about 80 M☉. The mean densities in the cores are quite high, with an average of 1.6 × 106 cm-3, suggesting short free-fall times. The core mass distribution can be fitted with a power law with slope α = 2.1 ± 0.3 for M > 0.5 M☉, similar to that found in other regions, but slightly shallower than that of some determinations of the local IMF. In agreement with previous studies, our survey shows that dense cores account for a very small fraction of the cloud volume and total mass. They are nearly all confined to regions with AV ≥ 9 mag, a lower threshold than found previously.
119282091
The Spitzer c2d Survey Of Nearby Dense Cores. XI. Infrared And Submillimeter Observations Of CB130
We present new observations of the CB130 region composed of three separate cores. Using the Spitzer Space Telescope, we detected a Class 0 and a Class II object in one of these, CB130-1. The observed photometric data from Spitzer and ground-based telescopes are used to establish the physical parameters of the Class 0 object. Spectral energy distribution fitting with a radiative transfer model shows that the luminosity of the Class 0 object is 0.14-0.16 L ⊙ , which is low for a protostellar object. In order to constrain the chemical characteristics of the core having the low-luminosity object, we compare our molecular line observations to models of lines including abundance variations. We tested both ad hoc step function abundance models and a series of self-consistent chemical evolution models. In the chemical evolution models, we consider a continuous accretion model and an episodic accretion model to explore how variable luminosity affects the chemistry. The step function abundance models can match observed lines reasonably well. The best-fitting chemical evolution model requires episodic accretion and the formation of CO 2 ice from CO ice during the low-luminosity periods. This process removes C from the gas phase, providing a much improved fit to the observed gas-phase molecular lines and the CO 2 ice absorption feature. Based on the chemical model result, the low luminosity of CB 130-1 is explained better as a quiescent stage between episodic accretion bursts rather than being at the first hydrostatic core stage.
53582826
The spitzer c2d survey of nearby dense cores. II. Discovery of a low-luminosity object in the "evolved starless core" L1521F
We present Spitzer Space Telescope observations of the "evolved starless core" L1521F that reveal the presence of a very low luminosity object (L 5μm), but only in scattered light at shorter infrared wavelengths, showing a bipolar nebula oriented east-west that is probably tracing an outflow cavity. The nebula strongly suggests that L1521F-IRS is embedded in the L1521F core. Thus, L1521F-IRS is similar to the recently discovered L1014-IRS and the previously known IRAM 04191 in its substellar luminosity and dense core environment. However, these objects differ significantly in their core density, core chemistry, and outflow properties, and some may be destined to be brown dwarfs rather than stars.