19,616 research outputs found
Inverse Beta Decay in a Nonequilibrium Antineutrino Flux from a Nuclear Reactor
The evolution of the reactor antineutrino spectrum toward equilibrium above
the inverse beta-decay threshold during the reactor operating period and the
decay of residual antineutrino radiation after reactor shutdown are considered.
It is found that, under certain conditions, these processes can play a
significant role in experiments seeking neutrino oscillations.Comment: 8 pages including 5 ps figure
Non-exponential relaxation and hierarchically constrained dynamics in a protein
A scaling analysis within a model of hierarchically constrained dynamics is
shown to reproduce the main features of non-exponential relaxation observed in
kinetic studies of carbonmonoxymyoglobin.Comment: 4 pages, 3 figures in text. Reference errors have been correcte
Uncertainty in the 0νββ decay nuclear matrix elements
The nuclear matrix elements M0nu of the neutrinoless double-beta decay (0nubetabeta) are evaluated for 76Ge,100Mo,130Te, and 136Xe within the renormalized quasiparticle random phase approximation (RQRPA) and the simple QRPA. Three sets of single particle level schemes are used, ranging in size from 9 to 23 orbits. When the strength of the particle-particle interaction is adjusted so that the 2nubetabeta decay rate is correctly reproduced, the resulting M0nu values become essentially independent of the size of the basis, and of the form of different realistic nucleon-nucleon potentials. Thus, one of the main reasons for variability of the calculated M0nu within these methods is eliminated
Probing Grand Unification Through Neutrino Oscillations, Leptogenesis, and Proton Decay
Evidence in favor of supersymmetric grand unification including that based on
the observed family multiplet-structure, gauge coupling unification, neutrino
oscillations, baryogenesis, and certain intriguing features of quark-lepton
masses and mixings is noted. It is argued that attempts to understand (a) the
tiny neutrino masses (especially Delta m^2 (nu_2 -nu_3)), (b) the baryon
asymmetry of the universe (which seems to need leptogenesis), and (c) the
observed features of fermion masses such as the ratio m_b/m_tau, the smallness
of V_cb and the maximality of theta_{nu_mu-nu_tau}, seem to select out the
route to higher unification based on an effective string-unified G(224) =
SU(2)_L x SU(2)_R x SU(4)^c or SO(10)-symmetry, operative in 4D, as opposed to
other alternatives.
A predictive framework based on an effective SO(10) or G(224) symmetry
possessing supersymmetry is presented that successfully describes the masses
and mixings of all fermions including neutrinos. It also accounts for the
observed baryon asymmetry of the universe by utilizing the process of
leptogenesis, which is natural to this framework. It is argued that a
conservative upper limit on the proton lifetime within this
SO(10)/G(224)-framework, which is so far most successful, is given by (1/3-2) x
10^34 years. This in turn strongly suggests that an improvement in the current
sensitivity by a factor of five to ten (compared to SuperK) ought to reveal
proton decay. Implications of this prediction for the next-generation nucleon
decay and neutrino-detector are noted.Comment: 40 page, 3 figures. Conference proceedings from Erice School (Sept
2002), Neutrino Conference (Stony Brook, 2002), PASCOS Conference (Mumbai,
2003) Version 2: New references and some clarifications adde
Evaluation of the InDUCKtion project at UCL
Executive summary: There is evidence that a good induction to university life can help with student retention; however, there is also a danger of overwhelming students during the intense period of fresher’s week. Under the auspices of a small grant from the Higher Education Academy’s ‘Changing the Learning Landscape’ funding stream, staff at two universities (University College London and Southampton Solent University) collaborated to produce an innovative and engaging induction project entitled ‘InDUCKtion’, based on the idea of an induction duck being a fun character for students to interact with. At UCL, the InDUCKtion duck existed in the form of a physical plastic duck included in international postgraduate student induction packs, and they were encouraged to take photos of themselves in and around UCL and London as part of a photo challenge using social media. It was anticipated that this would enable students to familiarise themselves with the locale, make friends and have fun at the same time. The InDUCKtion duck was also evident on flyers and posters with QR codes advertising an online tour to enable students to gain an accelerated familiarisation with the campus and its facilities. Within UCL, the project was a collaborative, cross-departmental venture instigated by members of UCL’s E-Learning Environments (ELE) working in partnership with the Centre for the Advancement of Learning and Teaching (CALT) and Student Support and Wellbeing (SSW). The logistics of the project meant that the team members also had to liaise with a number of other individuals and departments around UCL, to help promote and implement the project. Despite a rapid following on Twitter in a relatively short period, a reasonable hit rate on the QR code for the main page of the online tour resource, and some engagement with the photo challenges using social media, participation in the project was lower than anticipated. Lessons learned from an evaluation perspective revealed that adding another activity to an already overwhelming fresher’s week was problematic, despite its innovative and interactive nature. The use of QR codes was problematic for a number of reasons, and the project needed more buy-in from student representatives and academics to provide institutional endorsement. Recommendations for future instances of the project include securing student representation and academic endorsement, integrating the activity with parallel induction activities – particularly with academic departments, replacing QR codes with an alternative technology-enhanced learning approach and optimising the learning design to better motivate students and promote groupwork
Experimental determination of a nonclassical Glauber-Sudarshan P function
A quantum state is nonclassical if its Glauber-Sudarshan P function fails to
be interpreted as a probability density. This quantity is often highly
singular, so that its reconstruction is a demanding task. Here we present the
experimental determination of a well-behaved P function showing negativities
for a single-photon-added thermal state. This is a direct visualization of the
original definition of nonclassicality. The method can be useful under
conditions for which many other signatures of nonclassicality would not
persist.Comment: 4 pages, 4 figure
Nonclassical Moments and their Measurement
Practically applicable criteria for the nonclassicality of quantum states are
formulated in terms of different types of moments. For this purpose the moments
of the creation and annihilation operators, of two quadratures, and of a
quadrature and the photon number operator turn out to be useful. It is shown
that all the required moments can be determined by homodyne correlation
measurements. An example of a nonclassical effect that is easily characterized
by our methods is amplitude-squared squeezing.Comment: 12 pages, 6 figure
Third type of domain wall in soft magnetic nanostrips
Magnetic domain walls (DWs) in nanostructures are low-dimensional objects
that separate regions with uniform magnetisation. Since they can have different
shapes and widths, DWs are an exciting playground for fundamental research, and
became in the past years the subject of intense works, mainly focused on
controlling, manipulating, and moving their internal magnetic configuration. In
nanostrips with in-plane magnetisation, two DWs have been identified: in thin
and narrow strips, transverse walls are energetically favored, while in thicker
and wider strips vortex walls have lower energy. The associated phase diagram
is now well established and often used to predict the low-energy magnetic
configuration in a given magnetic nanostructure. However, besides the
transverse and vortex walls, we find numerically that another type of wall
exists in permalloy nanostrips. This third type of DW is characterised by a
three-dimensional, flux closure micromagnetic structure with an unusual length
and three internal degrees of freedom. Magnetic imaging on
lithographically-patterned permalloy nanostrips confirms these predictions and
shows that these DWs can be moved with an external magnetic field of about 1mT.
An extended phase diagram describing the regions of stability of all known
types of DWs in permalloy nanostrips is provided.Comment: 19 pages, 7 figure
Adiabatic Control of Spin-Wave Propagation using Magnetisation Gradients
Spin waves are of large interest as data carriers for future logic devices.
However, due to the strong anisotropic dispersion relation of dipolar
spin-waves in in-plane magnetised films the realisation of two-dimensional
information transport remains a challenge. Bending of the energy flow is
prohibited since energy and momentum of spin waves cannot be conserved while
changing the direction of wave propagation. Thus, non-linear or non-stationary
mechanisms are usually employed. Here, we propose to use reconfigurable
laser-induced magnetisation gradients to break the system's translational
symmetry. The resulting changes in the magnetisation shift the dispersion
relations locally and allow for operating with different spin-wave modes at the
same frequency. Spin-wave momentum is first transformed via refraction at the
edge of the magnetisation gradient region and then adiabatically modified
inside it. Along these lines the spin-wave propagation direction can be
controlled in a broad frequency range with high efficiency
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