Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu2_2(BO3_3)2_2

The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu$_2$(BO$_3$)$_2$ is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature while the integrated spectral weight can be explained by an isolated dimer model up to 10~K. Analyzing this anomalous spectral line-shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long-lived if no thermally populated triplons are near-by but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry--Sutherland lattice.Comment: 5 pages, 4 figure

Particle and Antiparticle sectors in DSR1 and kappa-Minkowski space-time

In this paper we explore the problem of antiparticles in DSR1 and $\kappa$-Minkowski space-time following three different approaches inspired by the Lorentz invariant case: a) the dispersion relation, b) the Dirac equation in space-time and c) the Dirac equation in momentum space. We find that it is possible to define a map $S_{dsr}$ which gives the antiparticle sector from the negative frequency solutions of the wave equation. In $\kappa$-Poincar\'e, the corresponding map $S_{kp}$ is the antipodal mapping, which is different from $S_{dsr}$. The difference is related to the composition law, which is crucial to define the multiparticle sector of the theory. This discussion permits to show that the energy of the antiparticle in DSR is the positive root of the dispersion relation, which is consistent with phenomenological approaches.Comment: 15 pages, no figures, some references added, typos correcte

Limited domestic introgression in a final refuge of the wild pigeon

Domesticated animals have been culturally and economically important throughout history. Many of their ancestral lineages are extinct or genetically en dangered following hybridization with domesticated relatives. Consequently, they have been understudied compared to the ancestral lineages of domestic plants. The domestic pigeon Columba livia, which was pivotal in Darwin’s studies, has maintained outsized cultural significance. Its role as a model organism spans the fields of behavior, genetics, and evolution. Domestic pigeons have hybridized with their progenitor, the Rock Dove, rendering the latter of dubious genetic sta tus. Here, we use genomic and morphological data from the putative Rock Doves of the British Isles to identify relictual undomesticated populations. We reveal that Outer Hebridean Rock Doves have experienced minimal levels of introgres sion. Our results outline the contemporary status of these wild pigeons, high lighting the role of hybridization in the homogenization of genetic lineages.publishedVersio

‘Paying Attention’ in a Digital Economy: Reflections on the Role of Analysis and Judgement Within Contemporary Discourses of Mindfulness and Comparisons with Classical Buddhist Accounts of Sati

This chapter examines the question of the role of intellectual analysis and ethical judgement in ancient Indian Buddhist accounts of sati and contemporary discourses about ‘mindfulness’. Attention is paid to the role of paññ? (Sanskrit: prajñ?: ‘wisdom’ or ‘analytical insight’) and ethical reflection in the cultivation of sati in mainstream Abhidharma and early Mah?y?na philosophical discussions in India, noting the existence of a subordinate strand of Buddhist thought which focuses upon the non-conceptuality of final awakening (bodhi) and the quiescence of mind. Modern discourses of mindfulness are examined in relation to detraditionalization, the global spread of capitalism and widespread adoption of new information technologies. It is argued that analysis of the exponential growth in popularity of ‘mindfulness’ techniques must be linked to an exploration of the modern history of attention, more specifically, the possibility that the use of fast-paced, digital, multimedia technologies is facilitating a demand for fragmented or dispersed attention. It is argued that the fault line between divergent contemporary accounts of mindfulness can be seen most clearly over the issue of the role of ethical judgements and mental ratiocination within mindfulness practice. The two most extreme versions on this spectrum see mindfulness on the one hand as a secular mental technology for calming the mind and reducing stress and discomfort, and on the other as a deeply ethical and experiential realization of the geopolitics of human experience. These, it is suggested, constitute an emerging discursive split in accounts of mindfulness reflective of divergent responses to the social, economic, political and technological changes occurring in relation to the global spread of neoliberal forms of capitalism

Effect of Long-Term Climbing Training on Cerebellar Ataxia: A Case Series

Background. Efficient therapy for both limb and gait ataxia is required. Climbing, a complex task for the whole motor system involving balance, body stabilization, and the simultaneous coordination of all 4 limbs, may have therapeutic potential. Objective. To investigate whether long-term climbing training improves motor function in patients with cerebellar ataxia. Methods. Four patients suffering from limb and gait ataxia underwent a 6-week climbing training. Its effect on ataxia was evaluated with validated clinical balance and manual dexterity tests and with a kinematic analysis of multijoint arm and leg pointing movements. Results. The patients increased their movement velocity and achieved a more symmetric movement speed profile in both arm and leg pointing movements. Furthermore, the 2 patients who suffered the most from gait ataxia improved their balance and 2 of the 4 patients improved manual dexterity. Conclusion. Climbing training has the potential to serve as a new rehabilitation method for patients with upper and lower limb ataxia

Could dark energy be vector-like?

In this paper I explore whether a vector field can be the origin of the present stage of cosmic acceleration. In order to avoid violations of isotropy, the vector has be part of a ``cosmic triad'', that is, a set of three identical vectors pointing in mutually orthogonal spatial directions. A triad is indeed able to drive a stage of late accelerated expansion in the universe, and there exist tracking attractors that render cosmic evolution insensitive to initial conditions. However, as in most other models, the onset of cosmic acceleration is determined by a parameter that has to be tuned to reproduce current observations. The triad equation of state can be sufficiently close to minus one today, and for tachyonic models it might be even less than that. I briefly analyze linear cosmological perturbation theory in the presence of a triad. It turns out that the existence of non-vanishing spatial vectors invalidates the decomposition theorem, i.e. scalar, vector and tensor perturbations do not decouple from each other. In a simplified case it is possible to analytically study the stability of the triad along the different cosmological attractors. The triad is classically stable during inflation, radiation and matter domination, but it is unstable during (late-time) cosmic acceleration. I argue that this instability is not likely to have a significant impact at present.Comment: 28 pages, 6 figures. Uses RevTeX4. v2: Discussion about relation to phantoms added and additional references cite

GPS network monitor the Western Alps deformation over a five year period: 1993-1998

GPS surveys in the Western Alps, performed in the time span 1993-2003, estimated the current crustal deformation of this area.Published63-763.2. Tettonica attivaJCR Journalreserve

Quantum gauge models without classical Higgs mechanism

We examine the status of massive gauge theories, such as those usually obtained by spontaneous symmetry breakdown, from the viewpoint of causal (Epstein-Glaser) renormalization. The BRS formulation of gauge invariance in this framework, starting from canonical quantization of massive (as well as massless) vector bosons as fundamental entities, and proceeding perturbatively, allows one to rederive the reductive group symmetry of interactions, the need for scalar fields in gauge theory, and the covariant derivative. Thus the presence of higgs particles is explained without recourse to a Higgs(-Englert-Brout-Guralnik-Hagen-Kibble) mechanism. Along the way, we dispel doubts about the compatibility of causal gauge invariance with grand unified theories.Comment: 20 pages in two-column EPJC format, shortened version accepted for publication. For more details, consult version

Solubilization of Proteins in 2DE: An Outline

Protein solubilization for two-dimensional electrophoresis (2DE) has to break molecular interactions to separate the biological contents of the material of interest into isolated and intact polypeptides. This must be carried out in conditions compatible with the first dimension of 2DE, namely isoelectric focusing. In addition, the extraction process must enable easy removal of any nonprotein component interfering with the isoelectric focusing. The constraints brought in this process by the peculiar features of isoelectric focusing are discussed, as well as their consequences in terms of possible solutions and limits for the solubilization process

The Algebra of Physical Observables in Nonlinearly Realized Gauge Theories

We classify the physical observables in spontaneously broken nonlinearly realized gauge theories in the recently proposed loopwise expansion governed by the Weak Power-Counting (WPC) and the Local Functional Equation. The latter controls the non-trivial quantum deformation of the classical nonlinearly realized gauge symmetry, to all orders in the loop expansion. The Batalin-Vilkovisky (BV) formalism is used. We show that the dependence of the vertex functional on the Goldstone fields is obtained via a canonical transformation w.r.t. the BV bracket associated with the BRST symmetry of the model. We also compare the WPC with strict power-counting renormalizability in linearly realized gauge theories. In the case of the electroweak group we find that the tree-level Weinberg relation still holds if power-counting renormalizability is weakened to the WPC condition.Comment: 20 pages, 1 figur