33 research outputs found
Ultra-high neutrino fluxes as a probe for non-standard physics
We examine how light neutrinos coming from distant active galactic nuclei
(AGN) and similar high energy sources may be used as tools to probe
non-standard physics. In particular we discuss how studying the energy spectra
of each neutrino flavour coming from such distant sources and their distortion
relative to each other may serve as pointers to exotic physics such as neutrino
decay, Lorentz symmetry violation, pseudo-Dirac effects, CP and CPT violation
and quantum decoherence. This allows us to probe hitherto unexplored ranges of
parameters for the above cases, for example lifetimes in the range s/eV for the case of neutrino decay. We show that standard
neutrino oscillations ensure that the different flavours arrive at the earth
with similar shapes even if their flavour spectra at source may differ strongly
in both shape and magnitude. As a result, observed differences between the
spectra of various flavours at the detector would be signatures of non-standard
physics altering neutrino fluxes during propagation rather than those arising
during their production at source. Since detection of ultra-high energy (UHE)
neutrinos is perhaps imminent, it is possible that such differences in spectral
shapes will be tested in neutrino detectors in the near future. To that end,
using the IceCube detector as an example, we show how our results translate to
observable shower and muon-track event rates.Comment: 16 pages, 10 figure
Black holes and Hawking radiation in spacetime and its analogues
These notes introduce the fundamentals of black hole geometry, the thermality
of the vacuum, and the Hawking effect, in spacetime and its analogues.
Stimulated emission of Hawking radiation, the trans-Planckian question, short
wavelength dispersion, and white hole radiation in the setting of analogue
models are also discussed. No prior knowledge of differential geometry, general
relativity, or quantum field theory in curved spacetime is assumed.Comment: 31 pages, 9 figures; to appear in the proceedings of the IX SIGRAV
School on 'Analogue Gravity', Como (Italy), May 2011, eds. D. Faccio et. al.
(Springer
On the Behavior of the Effective QCD Coupling alpha_tau(s) at Low Scales
The hadronic decays of the tau lepton can be used to determine the effective
charge alpha_tau(m^2_tau') for a hypothetical tau-lepton with mass in the range
0 < m_tau' < m_tau. This definition provides a fundamental definition of the
QCD coupling at low mass scales. We study the behavior of alpha_tau at low mass
scales directly from first principles and without any renormalization-scheme
dependence by looking at the experimental data from the OPAL Collaboration. The
results are consistent with the freezing of the physical coupling at mass
scales s = m^2_tau' of order 1 GeV^2 with a magnitude alpha_tau ~ 0.9 +/- 0.1.Comment: 15 pages, 4 figures, submitted to Physical Review D, added
references, some text added, no results nor figures change
Lorentz breaking Effective Field Theory and observational tests
Analogue models of gravity have provided an experimentally realizable test
field for our ideas on quantum field theory in curved spacetimes but they have
also inspired the investigation of possible departures from exact Lorentz
invariance at microscopic scales. In this role they have joined, and sometime
anticipated, several quantum gravity models characterized by Lorentz breaking
phenomenology. A crucial difference between these speculations and other ones
associated to quantum gravity scenarios, is the possibility to carry out
observational and experimental tests which have nowadays led to a broad range
of constraints on departures from Lorentz invariance. We shall review here the
effective field theory approach to Lorentz breaking in the matter sector,
present the constraints provided by the available observations and finally
discuss the implications of the persisting uncertainty on the composition of
the ultra high energy cosmic rays for the constraints on the higher order,
analogue gravity inspired, Lorentz violations.Comment: 47 pages, 4 figures. Lecture Notes for the IX SIGRAV School on
"Analogue Gravity", Como (Italy), May 2011. V.3. Typo corrected, references
adde
Postnatal Zika virus infection is associated with persistent abnormalities in brain structure, function, and behavior in infant macaques
The Zika virus (ZIKV) epidemic is associated with fetal brain lesions and other serious birth defects classified as congenital ZIKV syndrome. Postnatal ZIKV infection in infants and children has been reported; however, data on brain anatomy, function, and behavioral outcomes following infection are absent. We show that postnatal ZIKV infection of infant rhesus macaques (RMs) results in persistent structural and functional alterations of the central nervous system compared to age-matched controls. We demonstrate ZIKV lymphoid tropism and neurotropism in infant RMs and histopathologic abnormalities in the peripheral and central nervous systems including inflammatory infiltrates, astrogliosis, and Wallerian degeneration. Structural and resting-state functional magnetic resonance imaging (MRI/rs-fMRI) show persistent enlargement of lateral ventricles, maturational changes in specific brain regions, and altered functional connectivity (FC) between brain areas involved in emotional behavior and arousal functions, including weakened amygdala-hippocampal connectivity in two of two ZIKV-infected infant RMs several months after clearance of ZIKV RNA from peripheral blood. ZIKV infection also results in distinct alterations in the species-typical emotional reactivity to acute stress, which were predicted by the weak amygdala-hippocampal FC. We demonstrate that postnatal ZIKV infection of infants in this model affects neurodevelopment, suggesting that long-term clinical monitoring of pediatric cases is warranted
Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.publishedVersio
A RAPD-PCR genotyping assay which correlates with serotypes of group B streptococci
Aims: The purpose of this study was to determine if DNA polymorphisms generated by RAPD-PCR could be used to characterize Group B streptococci (GBS) for epidemiological purposes.
Methods and Results: 30 unrelated, previously serotyped strains were analysed by RAPD-PCR using two 10-mer primers (5' TGCGAGAGTC 3' and 5' AGAGGGCACA 3'). Both primers generated DNA electropherotype patterns which, on analysis, clustered the isolates within their respective serotypes. A blind test of a further 3 field isolates also defined these strains within their subsequently determined serotypes. The detection of DNA polymorphisms between isolates within a serotype confirmed previous reports of the heterogenous nature of individual GBS serotypes.
Conclusions: The RAPD-PCR is a potentially useful assay for the rapid characterization of neonatal infections associated with group B streptococci. The method appears to be more discriminatory than conventional serological assays.
Significance and Impact of the Study: The RAPD-PCR assay is faster, more convenient and easier to perform than alternative DNA analytical procedures such as Pulsfield Gel Electrophoresis. We were able to reproduce the same results following re-testing of all isolates some 12 months later which suggests that the assay may be robust enough for use in routine epidemiological investigations
All-orders infrared freezing of Re+e− in perturbative QCD.
We consider the behaviour of the perturbative QCD corrections to the Re+e− ratio, in the limit that the c.m. energy vanishes. Writing , with Qf denoting the electric charge of quark flavour f, we find that for Nf<9 flavours of massless quarks, the perturbative correction to the parton model result smoothly approaches from below the infrared limit , as s→0. Here b=(33−2Nf)/6 is the first QCD beta-function coefficient. This freezing holds to all-orders in perturbation theory. The s-dependence can be written analytically in closed form in terms of the Lambert W function