12,884 research outputs found
On the Regularized Fermionic Projector of the Vacuum
We construct families of fermionic projectors with spherically symmetric
regularization, which satisfy the condition of a distributional -product. The method is to analyze regularization tails with a power-law or
logarithmic scaling in composite expressions in the fermionic projector. The
resulting regularizations break the Lorentz symmetry and give rise to a
multi-layer structure of the fermionic projector near the light cone. The
remaining freedom for the regularization parameters and the consequences for
the normalization of the fermionic states are discussed.Comment: 66 pages, LaTeX, 8 figures, minor improvements (published version
Lost and found dark matter in elliptical galaxies
The kinematical properties of elliptical galaxies formed during the mergers
of equal mass, stars+gas+dark matter spiral galaxies are compared to the
observed low velocity dispersions found for planetary nebulae on the outskirts
of ellipticals, which have been interpreted as pointing to a lack of dark
matter in ellipticals (which poses a problem for the standard model of galaxy
formation). We find that the velocity dispersion profiles of the stars in the
simulated ellipticals match well the observed ones. The low outer stellar
velocity dispersions are mainly caused by the radial orbits of the outermost
stars, which, for a given binding energy must have low angular momentum to
reach their large radial distances, usually driven out along tidal tails.Comment: Talk presented at 21st IAP meeting, Mass Profiles andShapes of
Cosmological Structures. Ed. G. A. Mamon, F. Combes, C. Deffayet & B. Fort
(Paris: EDP), 4 pages, 3 figures (4 plots
The decays h+- -> W-+ h0(a0) within an extension of the MSSM with one complex Higgs triplet
The vertex H+-W-+h0, involving the gauge bosons W-+, the charged (H+-) and
the lightest neutral (h0) Higgs bosons, arises within the context of many
extensions of the SM, and it can be used to probe the Higgs sector of such
extensions via the decay H+- -> W+- h0. We discuss the strength of this vertex
for an extension of the MSSM with an additional complex Higgs triplet. By using
this model, we find regions of the parameter space where the decay H+- -> W+-
h0 is not only kinematically allowed, but it also becomes an important decay
mode and in some cases the dominant one.Comment: 10 figure
Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects
Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code
Flavor Changing Neutral Current Effects and CP Violation in the Minimal 3-3-1 Model
We investigate in detail the flavor structure of the minimal 331 model and
its implications for several flavor changing neutral current (FCNC) processes.
In this model, where the weak SU(2)_L gauge group of the Standard Model is
extended to a SU(3)_L, the by far dominant new contributions come from an
additional neutral Z' gauge boson, that can transmit FCNCs at tree-level. At
the same time, electroweak precision observables receive new contributions only
at the loop level and do not constrain the model very strongly. In our
analysis, we take into account new CP violating effects that have been
neglected in earlier analyses, and account for a general flavor structure
without reference to a certain parameterization of the new mixing matrix. We
begin by studying the bounds obtained from quantities such as Delta M_K,
epsilon_K, Delta M_{d/s} as well as sin 2 beta|_{J/psi K_S}, and go on to
explore the implications for several clean rare decay channels, namely the
decays K+->pi+ nu nu, K_L -> pi0 nu nu, B_{d/s} -> mu+ mu- and K_L -> pi0 l+l-.
We find sizeable effects in all these decays, but the most interesting quantity
turns out to be the B_s - bar B_s mixing phase beta_s, as measured in the
mixing induced CP asymmetry of B_s -> J/psi phi, which can be large. In
general, we find effects in purely hadronic channels to be larger than in
(semi-)leptonic ones, due to a suppression of the Z'-lepton couplings.Comment: 29 pages, 11 figures, Some Comments and References added, version to
appear in Phys Rev
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