7,321 research outputs found
Conformal Invariance in Percolation, Self-Avoiding Walks and Related Problems
Over the years, problems like percolation and self-avoiding walks have
provided important testing grounds for our understanding of the nature of the
critical state. I describe some very recent ideas, as well as some older ones,
which cast light both on these problems themselves and on the quantum field
theories to which they correspond. These ideas come from conformal field
theory, Coulomb gas mappings, and stochastic Loewner evolution.Comment: Plenary talk given at TH-2002, Paris. 21 pages, 9 figure
Refining the scalar and tensor contributions in decays
In this article we analyze the contribution from intermediate spin-0 and
spin-2 resonances to the decay by means of a chiral
invariant Lagrangian incorporating these mesons. In particular, we study the
corresponding axial-vector form-factors. The advantage of this procedure with
respect to previous analyses is that it incorporates chiral (and isospin)
invariance and, hence, the partial conservation of the axial-vector current.
This ensures the recovery of the right low-energy limit, described by chiral
perturbation theory, and the transversality of the current in the chiral limit
at all energies. Furthermore, the meson form-factors are further improved by
requiring appropriate QCD high-energy conditions. We end up with a brief
discussion on its implementation in the Tauola Monte Carlo and the prospects
for future analyses of Belle's data.Comment: 32 pages, 13 figures. Extended discussion on the numerical importance
of the tensor and scalar resonances and the parametrization of the scalar
propagator. Version published in JHE
Direct CP violation in charm and flavor mixing beyond the SM
We analyze possible interpretations of the recent LHCb evidence for CP
violation in D meson decays in terms of physics beyond the Standard Model. On
general grounds, models in which the primary source of flavor violation is
linked to the breaking of chiral symmetry (left-right flavor mixing) are
natural candidates to explain this effect, via enhanced chromomagnetic
operators. In the case of supersymmetric models, we identify two motivated
scenarios: disoriented A-terms and split families. These structures predict
other non-standard signals, such as nuclear EDMs close to their present bounds
and, possibly, tiny but visible deviations in K and B physics, or even sizable
flavor-violating processes involving the top quark or the stops. Some of these
connections, especially the one with nuclear EDMs, hold beyond supersymmetry,
as illustrated with the help of prototype non-supersymmetric models.Comment: 30 pages, 6 figure
Mathematical Evaluation of Community Level Impact of Combining Bed Nets and Indoor Residual Spraying upon Malaria Transmission in Areas where the main Vectors are Anopheles Arabiensis Mosquitoes.
Indoor residual insecticide spraying (IRS) and long-lasting insecticide treated nets (LLINs) are commonly used together even though evidence that such combinations confer greater protection against malaria than either method alone is inconsistent. A deterministic model of mosquito life cycle processes was adapted to allow parameterization with results from experimental hut trials of various combinations of untreated nets or LLINs (Olyset, PermaNet 2.0, Icon Life nets) with IRS (pirimiphos methyl, lambda cyhalothrin, DDT), in a setting where vector populations are dominated by Anopheles arabiensis, so that community level impact upon malaria transmission at high coverage could be predicted. Intact untreated nets alone provide equivalent personal protection to all three LLINs. Relative to IRS plus untreated nets, community level protection is slightly higher when Olyset or PermaNet 2.0 nets are added onto IRS with pirimiphos methyl or lambda cyhalothrin but not DDT, and when Icon Life nets supplement any of the IRS insecticides. Adding IRS onto any net modestly enhances communal protection when pirimiphos methyl is sprayed, while spraying lambda cyhalothrin enhances protection for untreated nets but not LLINs. Addition of DDT reduces communal protection when added to LLINs. Where transmission is mediated primarily by An. arabiensis, adding IRS to high LLIN coverage provides only modest incremental benefit (e.g. when an organophosphate like pirimiphos methyl is used), but can be redundant (e.g. when a pyrethroid like lambda cyhalothin is used) or even regressive (e.g. when DDT is used for the IRS). Relative to IRS plus untreated nets, supplementing IRS with LLINs will only modestly improve community protection. Beyond the physical protection that intact nets provide, additional protection against transmission by An. arabiensis conferred by insecticides will be remarkably small, regardless of whether they are delivered as LLINs or IRS. The insecticidal action of LLINs and IRS probably already approaches their absolute limit of potential impact upon this persistent vector so personal protection of nets should be enhanced by improving the physical integrity and durability. Combining LLINs and non-pyrethroid IRS in residual transmission systems may nevertheless be justified as a means to manage insecticide resistance and prevent potential rebound of not only An. arabiensis, but also more potent, vulnerable and historically important species such as Anopheles gambiae and Anopheles funestus
Inflation and dark matter in two Higgs doublet models
We consider the Higgs inflation in the extension of the Standard Model with
two Higgs doublets coupled to gravity non-minimally. In the presence of an
approximate global U(1) symmetry in the Higgs sector, both radial and angular
modes of neutral Higgs bosons drive inflation where large non-Gaussianity is
possible from appropriate initial conditions on the angular mode. We also
discuss the case with single-field inflation for which the U(1) symmetry is
broken to a Z_2 subgroup. We show that inflationary constraints, perturbativity
and stability conditions restrict the parameter space of the Higgs quartic
couplings at low energy in both multi- and single-field cases. Focusing on the
inert doublet models where Z_2 symmetry remains unbroken at low energy, we show
that the extra neutral Higgs boson can be a dark matter candidate consistent
with the inflationary constraints. The doublet dark matter is always heavy in
multi-field inflation while it can be light due to the suppression of the
co-annihilation in single-field inflation. The implication of the extra quartic
couplings on the vacuum stability bound is also discussed in the light of the
recent LHC limits on the Higgs mass.Comment: (v1) 28 pages, 8 figures; (v2) 29 pages, a new subsection 3.3 added,
references added and typos corrected, to appear in Journal of High Energy
Physic
Marginalization of end-use technologies in energy innovation for climate protection
Mitigating climate change requires directed innovation efforts to develop and deploy energy technologies. Innovation activities are directed towards the outcome of climate protection by public institutions, policies and resources that in turn shape market behaviour. We analyse diverse indicators of activity throughout the innovation system to assess these efforts. We find efficient end-use technologies contribute large potential emission reductions and provide higher social returns on investment than energy-supply technologies. Yet public institutions, policies and financial resources pervasively privilege energy-supply technologies. Directed innovation efforts are strikingly misaligned with the needs of an emissions-constrained world. Significantly greater effort is needed to develop the full potential of efficient end-use technologies
AdS/QCD: The Relevance of the Geometry
We investigate the relevance of the metric and of the geometry in
five-dimensional models of hadrons. Generically, the metric does not affect
strongly the results and even flat space agrees reasonably well with the data.
Nevertheless, we observe a preference for a decreasing warp factor, for example
AdS space. The Sakai-Sugimoto model reduces to one of these models and the
level of agreement is similar to the one of flat space. We also consider the
discrete version of the five-dimensional models, obtained by dimensional
deconstruction. We find that essentially all the relevant features of
"holographic" models of QCD can be reproduced with a simple 3-site model
describing only the states below the cut-off of the theory.Comment: 25 pages + appendix. v2 minor changes and Refs. adde
SUSY Splits, But Then Returns
We study the phenomenon of accidental or "emergent" supersymmetry within
gauge theory and connect it to the scenarios of Split Supersymmetry and Higgs
compositeness. Combining these elements leads to a significant refinement and
extension of the proposal of Partial Supersymmetry, in which supersymmetry is
broken at very high energies but with a remnant surviving to the weak scale.
The Hierarchy Problem is then solved by a non-trivial partnership between
supersymmetry and compositeness, giving a promising approach for reconciling
Higgs naturalness with the wealth of precision experimental data. We discuss
aspects of this scenario from the AdS/CFT dual viewpoint of higher-dimensional
warped compactification. It is argued that string theory constructions with
high scale supersymmetry breaking which realize warped/composite solutions to
the Hierarchy Problem may well be accompanied by some or all of the features
described. The central phenomenological considerations and expectations are
discussed, with more detailed modelling within warped effective field theory
reserved for future work.Comment: 29 pages. Flavor and CP constraints on left-right symmetric structure
briefly discussed. References adde
Charming CP Violation and Dipole Operators from RS Flavor Anarchy
Recently the LHCb collaboration reported evidence for direct CP violation in
charm decays. The value is sufficiently large that either substantially
enhanced Standard Model contributions or non-Standard Model physics is required
to explain it. In the latter case only a limited number of possibilities would
be consistent with other existing flavor-changing constraints. We show that
warped extra dimensional models that explain the quark spectrum through flavor
anarchy can naturally give rise to contributions of the size required to
explain the the LHCb result. The D meson asymmetry arises through a sizable
CP-violating contribution to a chromomagnetic dipole operator. This happens
naturally without introducing inconsistencies with existing constraints in the
up quark sector. We discuss some subtleties in the loop calculation that are
similar to those in Higgs to \gamma\gamma. Loop-induced dipole operators in
warped scenarios and their composite analogs exhibit non-trivial dependence on
the Higgs profile, with the contributions monotonically decreasing when the
Higgs is pushed away from the IR brane. We show that the size of the dipole
operator quickly saturates as the Higgs profile approaches the IR brane,
implying small dependence on the precise details of the Higgs profile when it
is quasi IR localized. We also explain why the calculation of the coefficient
of the lowest dimension 5D operator is guaranteed to be finite. This is true
not only in the charm sector but also with other radiative processes such as
electric dipole moments, b to s\gamma, \epsilon'/\epsilon_K and \mu\ to
e\gamma. We furthermore discuss the interpretation of this contribution within
the framework of partial compositeness in four dimensions and highlight some
qualitative differences between the generic result of composite models and that
obtained for dynamics that reproduces the warped scenario.Comment: 14 page
Magnetic graphene oxide nanocarrier for targeted delivery of cisplatin: A perspective for glioblastoma treatment
Selective vectorization of Cisplatin (CisPt) to Glioblastoma U87 cells was exploited by the fabrication of a hybrid nanocarrier composed of magnetic γ-Fe2 O3 nanoparticles and nanographene oxide (NGO). The magnetic component, obtained by annealing magnetite Fe3 O4 and characterized by XRD measurements, was combined with NGO sheets prepared via a modified Hummer’s method. The morphological and thermogravimetric analysis proved the effective binding of γ-Fe2 O3 nanoparticles onto NGO layers. The magnetization measured under magnetic fields up to 7 Tesla at room temperature revealed superparamagnetic-like behavior with a maximum value of MS = 15 emu/g and coercivity HC ≈ 0 Oe within experimental error. The nanohybrid was found to possess high affinity towards CisPt, and a rather slow fractional release profile of 80% after 250 h. Negligible toxicity was observed for empty nanoparticles, while the retainment of CisPt anticancer activity upon loading into the carrier was observed, together with the possibility to spatially control the drug delivery at a target site
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