22,808 research outputs found
Aspects of Quantum Gravity in Cosmology
We review some aspects of quantum gravity in the context of cosmology. In
particular, we focus on models with a phenomenology accessible to current and
near-future observations, as the early Universe might be our only chance to
peep through the quantum gravity realm.Comment: 15 pages, 1 figure. Invited review for Modern Physics Letter A.
Version 2: minor typos corrected, few references adde
Particle production and transplanckian problem on the non-commutative plane
We consider the coherent state approach to non-commutativity, and we derive
from it an effective quantum scalar field theory. We show how the
non-commutativity can be taken in account by a suitable modification of the
Klein-Gordon product, and of the equal-time commutation relations. We prove
that, in curved space, the Bogolubov coefficients are unchanged, hence the
number density of the produced particle is the same as for the commutative
case. What changes though is the associated energy density, and this offers a
simple solution to the transplanckian problem.Comment: Minor typos corrected, references added. Accepted for publication by
Modern Physics Letter
Perpendicular magnetic anisotropy in bulk and thin-film CuMnAs for antiferromagnetic memory applications
CuMnAs with perpendicular magnetic anisotropy is proposed as an active
material for antiferromagnetic memory. Information can be stored in the
antiferromagnetic domain state, while writing and readout can rely on the
existence of the surface magnetization. It is predicted, based on
first-principles calculations, that easy-axis anisotropy can be achieved in
bulk CuMnAs by substituting a few percent of As atoms by Ge, Si, Al, or B. This
effect is attributed to the changing occupation of certain electronic bands
near the Fermi level induced by the hole doping. The calculated temperature
dependence of the magnetic anisotropy does not exhibit any anomalies. Thin
CuMnAs(001) films are also predicted to have perpendicular magnetic anisotropy.Comment: 5 pages, 8 figure
A review of assessment methods for river hydromorphology
The work leading to this paper has received funding for the EU’s FP7 under Grant Agreement No. 282656 (REFORM
Spiral attractors as the root of a new type of "bursting activity" in the Rosenzweig-MacArthur model
We study the peculiarities of spiral attractors in the Rosenzweig-MacArthur
model, that describes dynamics in a food chain "prey-predator-superpredator".
It is well-known that spiral attractors having a "teacup" geometry are typical
for this model at certain values of parameters for which the system can be
considered as slow-fast system. We show that these attractors appear due to the
Shilnikov scenario, the first step in which is associated with a supercritical
Andronov-Hopf bifurcation and the last step leads to the appearance of a
homoclinic attractor containing a homoclinic loop to a saddle-focus equilibrium
with two-dimension unstable manifold. It is shown that the homoclinic spiral
attractors together with the slow-fast behavior give rise to a new type of
bursting activity in this system. Intervals of fast oscillations for such type
of bursting alternate with slow motions of two types: small amplitude
oscillations near a saddle-focus equilibrium and motions near a stable slow
manifold of a fast subsystem. We demonstrate that such type of bursting
activity can be either chaotic or regular
Immune cells and preterm labour:do invariant NKT cells hold the key?
We have developed our original made-to-measure (M2M) algorithm, PRIMAL, with the aim of modelling the Galactic disc from upcoming Gaia data. From a Milky Way like N-body disc galaxy simulation, we have created mock Gaia data using M0III stars as tracers, taking into account extinction and the expected Gaia errors. In PRIMAL, observables calculated from the N-body model are compared with the target stars, at the position of the target stars. Using PRIMAL, the masses of the N-body model particles are changed to reproduce the target mock data, and the gravitational potential is automatically adjusted by the changing mass of the model particles. We have also adopted a new resampling scheme for the model particles to keep the mass resolution of the N-body model relatively constant. We have applied PRIMAL to this mock Gaia data and we show that PRIMAL can recover the structure and kinematics of a Milky Way like barred spiral disc, along with the apparent bar structure and pattern speed of the bar despite the galactic extinction and the observational errors
Data and performance of an active-set truncated Newton method with non-monotone line search for bound-constrained optimization
In this data article, we report data and experiments related to the research article entitled “A Two-Stage Active-Set Algorithm for Bound-Constrained Optimization”, by Cristofari et al. (2017). The method proposed in Cristofari et al. (2017), tackles optimization problems with bound constraints by properly combining an active-set estimate with a truncated Newton strategy. Here, we report the detailed numerical experience performed over a commonly used test set, namely CUTEst (Gould et al., 2015). First, the algorithm ASA-BCP proposed in Cristofari et al. (2017) is compared with the related method NMBC (De Santis et al., 2012). Then, a comparison with the renowned methods ALGENCAN (Birgin and Martínez et al., 2002) and LANCELOT B (Gould et al., 2003) is reported
Nootropics use in the workplace. Psychiatric and ethical aftermath towards the new frontier of bioengineering
OBJECTIVE:
The authors have sought to expound upon and shed a light on the rise of nootropics, which have gradually taken on a more and more relevant role in workplaces and academic settings.
MATERIALS AND METHODS:
Multidisciplinary databases have been delved into by entering the following keys: "nootropics", "cognitive enhancement", "workplace", "productivity", "ethics", "bioengineering". In addition, a broad-ranging search has been undertaken on institutional websites in order to identify relevant analysis and recommendations issued by international institutions and agencies. Papers and reports have been independently pored over by each author. This search strategy has led to the identification of 988 sources but only 64 were considered appropriate for the purposes of the paper after being selected by at least 3 of the authors, independently.
RESULTS:
The notion of an artificially enhanced work performance - carried out by the 'superworker' - is particularly noteworthy and resonates with the conception of contemporary work on so many different levels: the rising need and demands for higher degrees of flexibility and productivity on the job, the implications of a '24/7' society, where more and more services are available at any time, the ever greater emphasis on entrepreneurial spirit, individual self-reliance and self-improvement, and last but not least, the impact of an ageing society on economic standards and performance.
CONCLUSIONS:
Moreover, it is worth mentioning that human enhancement technologies will predictably and increasingly go hand in hand with gene editing, bioengineering, cybernetics and nanotechnology. Applications are virtually boundless, and may ultimately affect all human traits (physical strength, endurance, vision, intelligence and even personality and mood)
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