444 research outputs found
Aerodynamic analysis of several high throat Mach number inlets for the quiet clean short-haul experimental engine
The results of an analytical study to investigate internal and external surface Mach numbers on several inlet geometries for possible application to the nacelle of the Quiet Clean Short-Haul Experimental Engine (QCSEE) are presented. The effects of external forebody geometry and internal lip geometry were illustrated at both low-speed and cruise conditions. Boundary-layer analyses were performed on several geometries to determine if lip flow separation might exist. The results indicated that inner-surface Mach number level and gradient could be reduced with inlets at a 50 deg incidence angle by blunting the external forebody geometry. The external Mach numbers at cruise conditions indicated that a compromise in the external forebody bluntness might be required to satisfy both low-speed and cruise conditions. For a fixed value of bluntness parameter, no lip flow separation was indicated for the 1.46- and 1.57-area-contraction-ratio inlets at low-speed conditions. However, a lip separation condition was obtained with the 1.37-contraction-ratio inlet. The QCSEE nacelle design takeoff operating condition (incidence angle of 50 deg and free-stream Mach number of 0.12) resulted in higher peak surface Mach numbers than the design crosswind (incidence angle of 90 deg and free-stream Mach number of 0.05) or static condition
On the Evaluation of Gluon Condensate Effects in the Holographic Approach to QCD
In holographic QCD the effects of gluonic condensate can be encoded in a
suitable deformation of the 5D metric. We develop two different methods for the
evaluation of first order perturbative corrections to masses and decay
constants of vector resonances in 5D Hard-Wall models of QCD due to small
deformations of the metric. They are extracted either from a novel compact form
for the first order correction to the vector two-point function, or from
perturbation theory for vector bound-state eigenfunctions: the equivalence of
the two methods is shown. Our procedures are then applied to flat and to AdS 5D
Hard-Wall models; we complement results of existing literature evaluating the
corrections to vector decay constant and to two-pion-one-vector couplings: this
is particularly relevant to satisfy the sum rules. We concentrate our attention
on the effects for the Gasser-Leutwyler coefficients; we show that, as in the
Chiral Quark model, the addition of the gluonic condensate improves the
consistency, the understanding and the agreement with phenomenology of the
holographic model.Comment: 23 pages, three figures, sign error in pion wave function fixed,
numerical analysis extended, general conclusions unchange
Distinguishing among Technicolor/Warped Scenarios in Dileptons
Models of dynamical electroweak symmetry breaking usually include new spin-1
resonances, whose couplings and masses have to satisfy electroweak precision
tests. We propose to use dilepton searches to probe the underlying structure
responsible for satisfying these. Using the invariant mass spectrum and charge
asymmetry, we can determine the number, parity, and isospin of these
resonances. We pick three models of strong/warped symmetry breaking, and show
that each model produces specific features that reflect this underlying
structure of electroweak symmetry breaking and cancellations.Comment: Added missing referenc
Mass-Matching in Higgsless
Modern extra-dimensional Higgsless scenarios rely on a mass-matching between
fermionic and bosonic KK resonances to evade constraints from precision
electroweak measurements. After analyzing all of the Tevatron and LEP bounds on
these so-called Cured Higgsless scenarios, we study their LHC signatures and
explore how to identify the mass-matching mechanism, the key to their
viability. We find singly and pair produced fermionic resonances show up as
clean signals with 2 or 4 leptons and 2 hard jets, while neutral and charged
bosonic resonances are visible in the dilepton and leptonic WZ channels,
respectively. A measurement of the resonance masses from these channels shows
the matching necessary to achieve . Moreover, a large single
production of KK-fermion resonances is a clear indication of compositeness of
SM quarks. Discovery reach is below 10 fb of luminosity for resonances
in the 700 GeV range.Comment: 28 pages, 18 figure
Effective Action and Holography in 5D Gauge Theories
We apply the holographic method to 5D gauge theories on the warped interval.
Our treatment includes the scalars associated with the fifth gauge field
component, which appear as 4D Goldstone bosons in the holographic effective
action. Applications are considered to two classes of models in which these
scalars play an important role. In the Composite-Higgs (and/or Gauge-Higgs
Unification) scenario, the scalars are interpreted as the Higgs field and we
use the holographic recipe to compute its one-loop potential. In AdS/QCD
models, the scalars are identified with the mesons and we compute
holographically the Chiral Perturbation Theory Lagrangian up to p^4 order. We
also discuss, using the holographic perspective, the effect of including a
Chern-Simons term in the 5D gauge Lagrangian. We show that it makes a
Wess-Zumino-Witten term to appear in the holographic effective action. This is
immediately applied to AdS/QCD, where a Chern-Simons term is needed in order to
mimic the Adler-Bardeen chiral anomaly.Comment: 37 pages; v2, minor changes, one reference added; v3, minor
corrections, version published in JHE
Hellenic subduction earthquake locations including OBS, ocean bottom seismometers and hints at shallow slab structure from teleseismic conversions : a pilot experiment
Holographic Technidilaton and LHC searches
We analyze in detail the phenomenology of a model of dynamical electroweak
symmetry breaking inspired by walking technicolor, by using the techniques of
the bottom-up approach to holography. The model admits a light composite scalar
state, the dilaton, in the spectrum. We focus on regions of parameter space for
which the mass of such dilaton is 125 GeV, and for which the bounds on the
precision electroweak parameter S are satisfied. This requires that the
next-to-lightest composite state is the techni-rho meson, with a mass larger
than 2.3 TeV. We compute the couplings controlling the decay rates of the
dilaton to two photons and to two (real or virtual) Z and W bosons. For generic
choices of the parameters, we find a suppression of the decay into heavy gauge
bosons, in respect to the analog decay of the standard-model Higgs. We find a
dramatic effect on the decay into photons, which can be both strongly
suppressed or strongly enhanced, the latter case corresponding to the large-N
regime of the dual theory. There is a correlation between this decay rate of
the dilaton into photons and the mass splitting between the techni-rho meson
and its axial-vector partner: if the decay is enhanced in respect to the
standard-model case, then the heavy spin-1 resonances are nearly degenerate in
mass, otherwise their separation in mass is comparable to the mass scale
itself.Comment: Very minor typos corrected. References adde
Crustal thickening and variations in architecture from the Qaidam basin to the Qang Tang (North–Central Tibetan Plateau) from wide-angle reflection seismology
Interpolating between low and high energy QCD via a 5D Yang-Mills model
We describe the Goldstone bosons of massless QCD together with an infinite
number of spin-1 mesons. The field content of the model is SU(Nf)xSU(Nf)
Yang-Mills in a compact extra-dimension. Electroweak interactions reside on one
brane. Breaking of chiral symmetry occurs due to the boundary conditions on the
other brane, away from our world, and is therefore spontaneous. Our
implementation of the holographic recipe maintains chiral symmetry explicit
throughout. For intermediate energies, we extract resonance couplings. These
satisfy sum rules due to the 5D nature of the model. These sum rules imply,
when taking the high energy limit, that perturbative QCD constraints are
satisfied. We also illustrate how the 5D model implies a definite prescription
for handling infinite sums over 4D resonances. Taking the low energy limit, we
recover the chiral expansion and the corresponding non-local order parameters.
All local order parameters are introduced separately.Comment: Corresponds to published version, with some typos correcte
Chiral Extrapolation of the Strangeness Changing K pi Form Factor
We perform a chiral extrapolation of lattice data on the scalar K pi form
factor and the ratio of the kaon and pion decay constants within Chiral
Perturbation Theory to two loops. We determine the value of the scalar form
factor at zero momentum transfer, at the Callan-Treiman point and at its soft
kaon analog as well as its slope. Results are in good agreement with their
determination from experiment using the standard couplings of quarks to the W
boson. The slope is however rather large. A study of the convergence of the
chiral expansion is also performed.Comment: few minor change
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