14233055
Towards a perfect QCD gravity dual
Many examples of gravitational duals exist of theories that are highly supersymmetric and conformal in the UV yet have the same massless states as QCD. We discuss such theories with an explicit UV cutoff and propose that, by tuning higher dimension operators at the cutoff by hand, the effects of the extra matter states in the UV may be removed from the IR physics. We explicitly work in the AdS–Schwarzschild description of QCD4 and tune the operator TrF4 by relaxing the near horizon limit to reproduce the lattice 0++ glueball mass results. We find that to reproduce the lattice data, the IR and UV cutoffs lie close to each other and there is essentially no AdS-like period between them. The improved geometry gives a better match to the lattice data for 0?+ glueball masses.
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.
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.
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.
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.
119405423
The spitzer c2d survey of large, nearby, interstellar clouds. I. Chamaeleon II observed with MIPS
We present maps of over 1.5 deg2 in Chamaeleon (Cha) II at 24, 70, and 160 μm observed with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) and a 1.2 deg2 millimeter map from SIMBA on the Swedish-ESO Submillimetre Telescope (SEST). The c2d Spitzer Legacy Team's data reduction pipeline is described in detail. Over 1500 24 μm sources and 41 70 μm sources were detected by MIPS with fluxes greater than 10 σ. More than 40 potential YSOs are identified with a MIPS and 2MASS color-color diagram and by their spectral indices, including two previously unknown sources with 24 μm excesses. Our new SIMBA millimeter map of Cha II shows that only a small fraction of the gas is in compact structures with high column densities. The extended emission seen by MIPS is compared with previous CO observations. Some selected interesting sources, including two detected at 1 mm, associated with Cha II are discussed in detail, and their SEDs are presented. The classification of these sources using MIPS data is found to be consistent with that of previous studies.
119319202
THE SPITZER c2d SURVEY OF LARGE, NEARBY, INTERSTELLAR CLOUDS. IX. THE SERPENS YSO POPULATION AS OBSERVED WITH IRAC AND MIPS
We discuss the combined IRAC/MIPS c2d Spitzer Legacy observations of the Serpens star-forming region. We describe criteria for isolating bona fide YSOs from the extensive background of extragalactic objects. We then discuss the properties of the resulting high-confidence set of 235 YSOs. An additional 51 lower confidence YSOs outside this area are identified from the MIPS data and 2MASS photometry. We present color-color diagrams to compare our observed source properties with those of theoretical models for star/disk/envelope systems and our own modeling of the objects that are well represented by a stellar photosphere plus circumstellar disk. These objects exhibit a wide range of disk properties, from many with actively accreting disks to some with both passive disks and even possibly debris disks. The YSO luminosity function extends down to at least a few times 10^(-3) L_☉ or lower. The lower limit may be set more by our inability to distinguish YSOs from extragalactic sources than by the lack of YSOs at very low luminosities. We find no evidence for variability in the shorter IRAC bands between the two epochs of our data set, Δt ~ 6 hr. A spatial clustering analysis shows that the nominally less evolved YSOs are more highly clustered than the later stages. The background extragalactic population can be fitted by the same two-point correlation function as seen in other extragalactic studies. We present a table of matches between several previous infrared and X-ray studies of the Serpens YSO population and our Spitzer data set. The clusters in Serpens have a very high surface density of YSOs, primarily with SEDs suggesting extreme youth. The total number of YSOs, mostly Class II, is greater outside the clusters.
53331129
Low abundance, strong features: window-dressing crystalline forsterite in the disk wall of HD 100546
Context. Forsterite is one of the crystalline dust species that is often observed in protoplanetary disks and solar system comets. Being absent in the interstellar medium, it must be produced during the disk lifetime. It can therefore serve as a tracer of dust processing and disk evolution, which can lead to a better understanding of the physical processes occurring in the disk, and possibly planet formation. However, the connection of these processes with the overall disk crystallinity remains unclear. Aims. We aim to characterize the forsterite abundance and spatial distribution in the disk of the Herbig Be star HD 100546, to investigate if a connection exists with the large disk gap. Methods. We use a 2D radiative transfer code, MCMax, to model the circumstellar dust around HD 100546. We use VISIR Q-band imaging to probe the outer disk geometry and mid-infrared features to model the spatial distribution of forsterite. The temperaturedependent shape of the 69 μm feature observed with Herschel ��� /PACS is used as a critical tool to constrain this distribution. Results. We find a crystalline mass fraction of 40–60%, located close to the disk wall between 13 and 20 AU, and possibly farther out at the disk surface. The forsterite is in thermal contact with the other dust species. We put an upper limit on the iron content of forsterite of 0.3%. Conclusions. Optical depth effects play a key role in explaining the observed forsterite features, hiding warm forsterite from view at short wavelengths. The disk wall acts as a showcase: it displays a localized high abundance of forsterite, which gives rise to a high observed crystallinity, while the overall mass fraction of forsterite is a factor of ten lower.
818125
Looking for Distributed Star Formation in L1630: A Near-Infrared (J, H, K) Survey
We have carried out a simultaneous, multiband (J, H, K) survey over an area of 1320 arcmin2 in the L1630 region, concentrating on the region away from the dense molecular cores with modest visual extinctions (≤10 mag). Previous studies by Lada and coworkers showed that star formation in L1630 occurs mainly in four localized clusters, which in turn are associated with the four most massive molecular cores. The goal of this study is to look for a distributed population of pre-main-sequence stars in the outlying areas outside the known star-forming cores. More than 60% of the pre-main-sequence stars in the active star-forming regions of NGC 2024 and NGC 2023 show a near-infrared excess in the color-color diagram. In the outlying areas of L1630, excluding the known star-forming regions, we found that among 510 infrared sources with the near-infrared colors (J-H and H-K) determined and photometric uncertainty at K better than 0.10 mag, the fraction of the sources with a near-infrared excess is 3%-8%; the surface density of the sources with a near-infrared excess is less than one-seventh of that found in the distributed population in L1641, and 1/20 of that in the young cluster NGC 2023. This extremely low fraction and low surface density of sources with a near-infrared excess strongly indicates that recent star formation activity has been very low in the outlying region of L1630. The sources without a near-infrared excess could be either background/foreground field stars or associated with the cloud, but formed a long time ago (more than 2 Myr). Our results are consistent with McKee's model of photoionization-regulated star formation.