123269953
QCD‐like gauge dynamics from gravity duals
We describe attempts to study QCD-like gauge dynamics using a deformed version of the AdS/CFT Correspondence. The Yang Mills* geometry is dual to a gauge theory that is non-supersymmetric Yang Mills in the infra-red but reverts to N = 4 super Yang Mills in the ultra-violet. The geometry describes a discrete, calculable glueball spectrum with a mass gap. Wilson loops in the geometry display QCD string breaking.
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.
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.
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.
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.
15916297
Constraining the structure of the non-spherical pre-protostellar core L1544
We present a study of the pre-protostellar core L1544. A series of self-consistent, three-dimensional continuum radiative transfer models is constructed. The outputs of these models are convolved with appropriate telescope beam responses, and compared with existing SCUBA data. The resulting comparison allows us to constrain the structure of L1544. We find that the source is well-fitted by a prolate spheroid, having an ellipsoidal power-law density distribution of index m ∼ 2(1.75 < m < 2.25) in to at least r ∼ 1600 au. For r < 1600 au, the data are consistent with either an extension of the power law to smaller radii, or a flattened (Bonner-Ebert-like) density distribution. Furthermore, we find an optical depth along the short axis at 1300 μm of τ 1300,short = 5 x 10 -3 (2 x 10 -3 < τ 1300,short < 8 x 10 -3 ), a central luminosity L* =0(<10 -3 L ○. ), a long-axis diameter D = 0.1 pc [0.08 < D(pc) < 0.16; 16000 < D(au) < 32 000], an axis ratio q = 2 (1.7 < q < 2.5), and an external interstellar radiation field (ISRF) defined by Mathis et al. to within 50 per cent. The outer diameter and axis ratio may each be somewhat larger due to potential on-source chopping in the observations, and the projection of the long axis on to the plane of the sky. While these results are similar to those inferred directly from observations or spherical modelling due to the source transparency at submillimetre wavelengths, we infer a smaller size, lower mass, and higher optical depth/column density, exposed to a stronger external radiation field than previously assumed. Finally, we find that both the spectral energy distribution (SED) and surface brightness distribution are necessary to constrain the source properties in this way, and even a modest variation in X 2 can significantly alter the fit quality.
118394652
Dust, Ice, and Gas In Time (DIGIT) Herschel program first results A full PACS-SED scan of the gas line emission in protostar DK Chamaeleontis
Aims. We aim to study the composition and energetics of the circumstellar material of DK Cha, an intermediate-mass star in transition from an 
embedded configuration to a star plus disk stage, during this pivotal stage of its evolution. 
Methods. Using the range scan mode of PACS on the Herschel Space Observatory, we obtained a spectrum of DK Cha from 55 to 210 μm as part 
of the DIGIT key program. 
Results. Almost 50 molecular and atomic lines were detected, many more than the 7 lines detected in ISO-LWS. Nearly the entire ladder of CO 
from J = 14–13 to 38–37 (E_u/k = 4080 K), water from levels as excited as J_(K−1 K+1) = 7_(07) (E_u/k = 843 K), and OH lines up to E_u/k = 290 K were 
detected. 
Conclusions. The continuum emission in our PACS SED scan matches the flux expected by a model consisting of a star, a surrounding disk of 
0.03 M_⊙, and an envelope of a similar mass, supporting the suggestion that the object is emerging from its main accretion stage. Molecular, atomic, 
and ionic emission lines in the far-infrared reveal the outflow’s influence on the envelope. The inferred hot gas may be photon-heated, but some 
emission may be caused by C-shocks in the walls of the outflow cavity.
119355247
Studying Infall
The study of protostellar collapse or infall has proven unusually difficult and controversial. Some historical context will be provided, against which recent advances can be measured. We now have a substantial number of objects with signatures that can be interpreted in terms of collapse, but a number of issues remain. One issue is the effect of chemical variations, especially depletion in the dense, cold interiors of cores that are likely to form low mass stars. Strategies for dealing with this issue depend on using dust emission to constrain the density and temperature distribution, leaving molecular line observations to constrain dynamics and abundance distributions. Recent progress in this area will be described and we will consider the next challenges to be overcome. Interferometeric observations, especially with future instruments, will provide a powerful tool. In combination with chemical studies coupled with dynamical models, the observations made possible by interferometers should finally put this subject on a firm foundation.
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).
7260455
HIGH-RESOLUTION MID-INFRARED SPECTROSCOPY OF NGC 7538 IRS 1: PROBING CHEMISTRY IN A MASSIVE YOUNG STELLAR OBJECT
We present high-resolution (R = 75,000-100,000) mid-infrared spectra of the high-mass embedded young star IRS 1 in the NGC 7538 star-forming region. Absorption lines from many rotational states of C{sub 2}H{sub 2}, {sup 13}C{sup 12}CH{sub 2}, CH{sub 3}, CH{sub 4}, NH{sub 3}, HCN, HNCO, and CS are seen. The gas temperature, column density, covering factor, line width, and Doppler shift for each molecule are derived. All molecules were fit with two velocity components between -54 and -63 km s{sup -1}. We find high column densities ({approx}10{sup 16} cm{sup -2}) for all the observed molecules compared to values previously reported and present new results for CH{sub 3} and HNCO. Several physical and chemical models are considered. The favored model involves a nearly edge-on disk around a massive star. Radiation from dust in the inner disk passes through the disk atmosphere, where large molecular column densities can produce the observed absorption line spectrum.