53 research outputs found
Synchronization of multi-phase oscillators: An Axelrod-inspired model
Inspired by Axelrod's model of culture dissemination, we introduce and
analyze a model for a population of coupled oscillators where different levels
of synchronization can be assimilated to different degrees of cultural
organization. The state of each oscillator is represented by a set of phases,
and the interaction --which occurs between homologous phases-- is weighted by a
decreasing function of the distance between individual states. Both ordered
arrays and random networks are considered. We find that the transition between
synchronization and incoherent behaviour is mediated by a clustering regime
with rich organizational structure, where some of the phases of a given
oscillator can be synchronized to a certain cluster, while its other phases are
synchronized to different clusters.Comment: 6 pages, 5 figure
On the possibility of a terahertz light emitting diode based on a dressed quantum well
We consider theoretically the realization of a tunable terahertz light
emitting diode from a quantum well with dressed electrons placed in a highly
doped p-n junction. In the considered system the strong resonant dressing field
forms dynamic Stark gaps in the valence and conduction bands and the electric
field inside the p-n junction makes the QW asymmetric. It is shown that the
electrons transiting through the light induced Stark gaps in the conduction
band emit photons with energy directly proportional to the dressing field. This
scheme is tunable, compact, and shows a fair efficiency.Comment: 6 pages, 5 figure
Quantum Rings in Electromagnetic Fields
This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThis chapter is devoted to optical properties of so-called Aharonov-Bohm
quantum rings (quantum rings pierced by a magnetic flux resulting in AharonovBohm
oscillations of their electronic spectra) in external electromagnetic fields.
It studies two problems. The first problem deals with a single-electron AharonovBohm
quantum ring pierced by a magnetic flux and subjected to an in-plane (lateral)
electric field. We predict magneto-oscillations of the ring electric dipole moment.
These oscillations are accompanied by periodic changes in the selection rules for
inter-level optical transitions in the ring allowing control of polarization properties
of the associated terahertz radiation. The second problem treats a single-mode microcavity
with an embedded Aharonov-Bohm quantum ring which is pierced by a
magnetic flux and subjected to a lateral electric field. We show that external electric
and magnetic fields provide additional means of control of the emission spectrum
of the system. In particular, when the magnetic flux through the quantum ring is
equal to a half-integer number of the magnetic flux quanta, a small change in the
lateral electric field allows for tuning of the energy levels of the quantum ring into
resonance with the microcavity mode, thus providing an efficient way to control
the quantum ring-microcavity coupling strength. Emission spectra of the system are
discussed for several combinations of the applied magnetic and electric fields
Compulsory admissions of patients with mental disorders : State of the art on ethical and legislative aspects in 40 European countries
Background. Compulsory admission procedures of patients with mental disorders vary between countries in Europe. The Ethics Committee of the European Psychiatric Association (EPA) launched a survey on involuntary admission procedures of patients with mental disorders in 40 countries to gather information from all National Psychiatric Associations that are members of the EPA to develop recommendations for improving involuntary admission processes and promote voluntary care. Methods. The survey focused on legislation of involuntary admissions and key actors involved in the admission procedure as well as most common reasons for involuntary admissions. Results. We analyzed the survey categorical data in themes, which highlight that both medical and legal actors are involved in involuntary admission procedures. Conclusions. We conclude that legal reasons for compulsory admission should be reworded in order to remove stigmatization of the patient, that raising awareness about involuntary admission procedures and patient rights with both patients and family advocacy groups is paramount, that communication about procedures should be widely available in lay-language for the general population, and that training sessions and guidance should be available for legal and medical practitioners. Finally, people working in the field need to be constantly aware about the ethical challenges surrounding compulsory admissions.Peer reviewe
Polariton laser diodes
Exciton-polariton lasers are operated in the strong light matter coupling regime. They promise low threshold operation since population inversion is not inherently necessary. Hence they are of great interest for next generation coherent light sources.Published versio
An electrically driven polariton laser
Polariton lasing under electrical pumping is observed in a GaAs multi-quantum-well microcavity diode. Lasing in the strong-coupling regime is unambiguously evidenced by detection of Zeeman-split emission in an external magnetic field as a result of the polaritons' excitonic content
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