1,887 research outputs found
Antibranes don't go black
When D-branes are inserted in flux backgrounds of opposite charge, the
resulting solution has a certain singularity in the fluxes. Recently it has
been argued, using numerical solutions, that for anti-D3 branes in the
Klebanov-Strassler background these singularities cannot be cloaked by a
horizon, which strongly suggests they are not physical. In this note we provide
an analytic proof that the singularity of all codimension-three antibrane
solutions (such as anti-D6 branes in massive type IIA supergravity or anti-D3
branes smeared on the T^3 of R^3xT^3 with fluxes) cannot be hidden behind a
horizon, and that the charge of black branes with smooth event horizons must
have the same sign as the charge of the flux background. Our result indicates
that infinitesimally blackening the antibranes immediately triggers brane-flux
annihilation, and strengthens the intuition that antibranes placed in flux with
positive charge immediately annihilate against it.Comment: 9 pages, 1 figur
Systematic reviews of complementary therapies - an annotated bibliography. Part 1: Acupuncture
Background Complementary therapies are widespread but controversial. We aim to provide a comprehensive collection and a summary of systematic reviews of clinical trials in three major complementary therapies (acupuncture, herbal medicine, homeopathy). This article is dealing with acupuncture. Potentially relevant reviews were searched through the register of the Cochrane Complementary Medicine Field, the Cochrane Library, Medline, and bibliographies of articles and books. To be included articles had to review prospective clinical trials of acupuncture; had to describe review methods explicitly; had to be published; and had to focus on treatment effects. Information on conditions, interventions, methods, results and conclusions was extracted using a pretested form and summarized descriptively. Results From a total of 48 potentially relevant reviews preselected in a screeening process 39 met the inclusion criteria. 22 were on various pain syndromes or rheumatic diseases. Other topics addressed by more than one review were addiction, nausea, asthma and tinnitus. Almost unanimously the reviews state that acupuncture trials include too few patients. Often included trials are heterogeneous regarding patients, interventions and outcome measures, are considered to have insufficient quality and contradictory results. Convincing evidence is available only for postoperative nausea, for which acupuncture appears to be of benefit, and smoking cessation, where acupuncture is no more effective than sham acupuncture. Conclusions A large number of systematic reviews on acupuncture exists. What is most obvious from these reviews is the need for (the funding of) well-designed, larger clinical trials
Localised anti-branes in non-compact throats at zero and finite T
We investigate the 3-form singularities that are typical to anti-brane
solutions in supergravity and check whether they can be cloaked by a finite
temperature horizon. For anti-D3-branes in the Klebanov-Strassler background,
this was already shown numerically to be impossible when the branes are
partially smeared. In this paper, we present analytic arguments that also
localised branes remain with singular 3-form fluxes at both zero and finite
temperature. These results may have important, possibly fatal, consequences for
constructions of meta-stable de Sitter vacua through uplifting.Comment: 18 + 9 page
Characterization and Modeling of DHBT in InP/GaAsSb Technology for the Design and Fabrication of a Ka Band MMIC Oscillator
This paper presents the design of an MMIC oscillator operating at a 38âGHz frequency. This circuit was fabricated by the IIIâV Lab with the new InP/GaAsSb Double Heterojunction Bipolar Transistor (DHBT) submicronic technology (We=700ânm). The transistor used in the circuit has a 15 ÎŒm long two-finger emitter. This paper describes the complete nonlinear modeling of this DHBT, including the cyclostationary modeling of its low frequency (LF) noise sources. The specific interest of the methodology used to design this oscillator resides in being able to choose a nonlinear operating condition of the transistor from an analysis in amplifier mode. The oscillator simulation and measurement results are compared. A 38âGHz oscillation frequency with 8.6âdBm output power and a phase noise of â80âdBc/Hz at 100âKHz offset from carrier have been measured
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