117963955
Electroweak Symmetry Breaking from the Top
The last decade of high energy collider experiments has verified the high accuracy of the Standard Model (SM) at describing physics below ~ 90GeV and thus placed strong constraints on extensions to the SM. The mechanism by which electroweak symmetry (EWS) is broken, however, has not been experimentally investigated and remains an open question. In the minimal SM of Glashow, Weinberg and Salam the fermion, W ± and Z 0 mass terms that break the SU(2)L ⊗ U(1) Y symmetry are replaced by gauge invariant interactions with a fundamental scalar Higgs field that acquires a non zero vacuum expectation value (vev) and breaks EWS. However, the fermion masses are replaced by Yukawa couplings to the Higgs field giving no understanding of the mass structure of the SM. Similarly the vev of the Higgs field that minimizes its potential is an arbitrary parameter of the theory. This lack of predictive power suggests that the Higgs model is at best a low energy effective theory of physics at the EW scale.
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.
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.
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.
119498034
Submillimeter Dust Continuum Studies of Low and High Mass Star Formation
Studying the physical environments of low mass and high mass cores using dust continuum emission provides important observational constraints on theoretical models of star formation. The motivation and procedure for modeling dust continuum emission is reviewed and the results of recent surveys towards low mass and high mass star forming regions are compared.
117869925
Dust Continuum Observations of Massive Star Forming Regions
We have observed 51 high mass star forming cores associated with water masers at 350 micron. The spectral energy distributions (SEDs) and dust continuum normalized radial intensity profiles were modeled for 28 sources using a one-dimensional dust radiative transfer code assuming a power law density distribution in the envelope n = n_0 (r/r_0)^{-p}. The best fit density power law exponent, p, ranged from 1.0 to 2.5 with a mean value of p = 1.72. We determined the dust masses for the modeled cores and found a mean mass of 209 M_{sun}.
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.
17826176
The Mass Distribution And Lifetime Of Prestellar Cores In Perseus, Serpens, And Ophiuchus
We present an unbiased census of starless cores in Perseus, Serpens, and Ophiuchus, assembled by comparing large-scale Bolocam 1.1 mm continuum emission maps with Spitzer c2d surveys. We use the c2d catalogs to separate 108 starless from 92 protostellar cores in the 1.1 mm core samples from Enoch and Young and their coworkers. A comparison of these populations reveals the initial conditions of the starless cores. Starless cores in Perseus have similar masses but larger sizes and lower densities on average than protostellar cores, with sizes that suggest density profiles substantially flatter than ρ∝r^-2. By contrast, starless cores in Serpens are compact and have lower masses than protostellar cores; future star formation will likely result in lower mass objects than the currently forming protostars. Comparison to dynamical masses estimated from the NH3 survey of Perseus cores by Rosolowsky and coworkers suggests that most of the starless cores are likely to be gravitationally bound, and thus prestellar. The combined prestellar core mass distribution includes 108 cores and has a slope of α = -2.3 ± 0.4 for M > 0.8 M☉. This slope is consistent with recent measurements of the stellar initial mass function, providing further evidence that stellar masses are directly linked to the core formation process. We place a lower limit on the core-to-star efficiency of 25%. There are approximately equal numbers of prestellar and protostellar cores in each cloud; thus the dense prestellar core lifetime must be similar to the lifetime of embedded protostars, or 4.5 x 10^5 yr, with a total uncertainty of a factor of 2. Such a short lifetime suggests a dynamic, rather than quasi-static, core evolution scenario, at least at the relatively high mean densities (n > 2 x 10^4 cm^-3) to which we are sensitive.
14721548
Discovery Of A Low-Mass Bipolar Molecular Outflow From L1014-Irs With The Submillimeter Array
Using the Submillimeter Array, we report the discovery of a compact low-mass bipolar molecular outflow from L1014-IRS and confirm its association with the L1014 dense core at 200 pc. Consequently, L1014-IRS is the lowest luminosity (L ~ 0.09 L☉), and perhaps the lowest mass, source known to be driving a bipolar molecular outflow, which is one of the smallest known in size (~500 AU), mass (<10-4 M☉), and energetics (e.g., with a force <10-7 M☉ km s-1 yr-1).