Uniformly Accelerated Mirrors. Part 1: Mean Fluxes

The Davies-Fulling model describes the scattering of a massless field by a moving mirror in 1+1 dimensions. When the mirror travels under uniform acceleration, one encounters severe problems which are due to the infinite blue shift effects associated with the horizons. On one hand, the Bogoliubov coefficients are ill-defined and the total energy emitted diverges. On the other hand, the instantaneous mean flux vanishes. To obtained well-defined expressions we introduce an alternative model based on an action principle. The usefulness of this model is to allow to switch on and off the interaction at asymptotically large times. By an appropriate choice of the switching function, we obtain analytical expressions for the scattering amplitudes and the fluxes emitted by the mirror. When the coupling is constant, we recover the vanishing flux. However it is now followed by transients which inevitably become singular when the switching off is performed at late time. Our analysis reveals that the scattering amplitudes (and the Bogoliubov coefficients) should be seen as distributions and not as mere functions. Moreover, our regularized amplitudes can be put in a one to one correspondence with the transition amplitudes of an accelerated detector, thereby unifying the physics of uniformly accelerated systems. In a forthcoming article, we shall use our scattering amplitudes to analyze the quantum correlations amongst emitted particles which are also ill-defined in the Davies-Fulling model in the presence of horizons.Comment: 23 pages, 7 postscript figure

Multidisciplinary team meetings in community mental health: a systematic review of their functions

Purpose – Previous research has identified a need for greater clarity regarding the functions of multidisciplinary team (MDT) meetings in UK community mental health services. The purpose of this paper is to identify the functions of these meetings by systematically reviewing both primary research and academic discussion papers. Design/methodology/approach – Papers relating to adult community mental health teams (CMHTs) in the UK and published between September 1999 and February 2014 were reviewed and appraised using NICE quality checklists. The search was broad in scope to include both general CMHTs and specialist CMHTs such as early intervention psychosis services and forensic mental health teams. A thematic synthesis of the findings was performed to develop an overarching thematic framework of the reported functions of MDT meetings. Findings – None of the 4,046 studies identified directly investigated the functions of MDT meetings. However, 49 mentioned functions in passing. These functions were categorised into four thematic domains: discussing the care of individual patients, teamwork, team management and learning and development. Several papers reported a lack of clarity about the purpose of MDT meetings and the roles of different team members which hindered effective collaboration. Practical implications – Without clearly agreed objectives for MDT meetings, monitoring their effectiveness is problematic. Unwarranted variation in their functioning may undermine the quality of care. Originality/value – This is the first systematic review to investigate the functions of CMHT MDT meetings in the UK. The findings highlight a need for empirical research to establish how MDT meetings are being used so that their effectiveness can be understood, monitored and evaluated

From Vacuum Fluctuations to Radiation: Accelerated Detectors and Black Holes

The vacuum fluctuations that induce the transitions and the thermalisation of a uniformly accelerated two level atom are studied in detail. Their energy content is revealed through the weak measurement formalism of Aharonov et al. It is shown that each time the detector makes a transition it radiates a Minkowski photon. The same analysis is then applied to the conversion of vacuum fluctuations into real quanta in the context of black hole radiation. Initially these fluctuations are located around the light like geodesic that shall generate the horizon and carry zero total energy. However upon exiting from the star they break up into two pieces one of which gradually acquires positive energy and becomes a Hawking quantum, the other, its ''partner", ends up in the singularity. As time goes by the vacuum fluctuations generating Hawking quanta have exponentially large energy densities. This implies that back reaction effects are large.Comment: definitive version, 39 pages and 5 figures available upon request from S.M., ULB-TH 94/0

Comparative Effects of Haemodialysis and Haemofiltration on Plasma Atrial Natriuretic Peptide

The effects of 4 h haemodialysis (15 patients) or 4 h haemofiltration (five patients) on plasma concentrations of atrial natriuretic peptide (ANP) were compared by means of a sensitive radioreceptor binding assay, and related to accompanying changes in body weight, blood pressure and plasma renin activity. Before dialysis, plasma ANP concentrations were considerably elevated: haemodialysis group 10-484 pmol/l (mean 156 pmol/l); haemofiltration group 72-320 pmol/l (mean 170 pmol/l). Although plasma concentrations of ANP fell markedly with treatment in both groups: post-haemodialysis 2-187 pmol/l (mean 67 pmol/l); post-haemofiltration 47-135 pmol/l (mean 79 pmol/l), after treatment it remained above the normal range in 14 of the 20 patients. Pretreatment plasma ANP was related to systolic blood pressure (r=0.459; P<0.05) but bore no relationship to mean or diastolic blood pressure, or plasma renin activity. The fall in plasma ANP concentration during treatment correlated with the postural blood pressure drop after dialysis (r=0.505; P<0.05), but was unrelated to changes in weight or plasma renin activity with haemodialysis or haemofiltration. Plasma ANP concentrations rose rapidly again in the 60 min after dialysis treatment, without change in body weight. These results show that high levels of biologically active ANP circulate in end-stage renal disease. The fact that these are not reduced to normal by haemodialysis or haemofiltration, despite restoration to normovolaemic or hypovolaemic state, suggests that the increased levels of ANP in end-stage renal failure are due to both hypervolaemia and other factors, which may include occult cardiac dysfunction and loss of renal clearanc

The Energy-Momentum Tensor in Fulling-Rindler Vacuum

The energy density in Fulling-Rindler vacuum, which is known to be negative "everywhere" is shown to be positive and singular on the horizons in such a fashion as to guarantee the positivity of the total energy. The mechanism of compensation is displayed in detail.Comment: 9 pages, ULB-TH-15/9

Quantum field and uniformly accelerated oscillator

We present an exact treatment of the influences on a quantum scalar field in its Minkowski vacuum state induced by coupling of the field to a uniformly accelerated harmonic oscillator. We show that there are no radiation from the oscillator in the point of view of a uniformly accelerating observer. On the other hand, there are radiations in the point of view of an inertial observer. It is shown that Einstein-Podolsky-Rosen (EPR) like correlations of Rindler particles in Minkowski vacuum states are modified by a phase factor in front of the momentum-symmetric Rindler operators. The exact quantization of a time-dependent oscillator coupled to a massless scalar field was given.Comment: 28 pages, LaTe

Radiation from a uniformly accelerating harmonic oscillator

We consider a radiation from a uniformly accelerating harmonic oscillator whose minimal coupling to the scalar field changes suddenly. The exact time evolutions of the quantum operators are given in terms of a classical solution of a forced harmonic oscillator. After the jumping of the coupling constant there occurs a fast absorption of energy into the oscillator, and then a slow emission follows. Here the absorbed energy is independent of the acceleration and proportional to the log of a high momentum cutoff of the field. The emitted energy depends on the acceleration and also proportional to the log of the cutoff. Especially, if the coupling is comparable to the natural frequency of the detector ($e^2/(4m) \sim \omega_0$) enormous energies are radiated away from the oscillator.Comment: 26 pages, 1 eps figure, RevTeX, minor correction in grammar, add a discussio

Black Stork Down: Military Discourses in Bird Conservation in Malta

Tensions between Maltese hunters and bird conservation NGOs have intensified over the past decade. Conservation NGOs have become frustrated with the Maltese State for conceding to the hunter lobby and negotiating derogations from the European Union’s Bird Directive. Some NGOs have recently started to organize complex field-operations where volunteers are trained to patrol the landscape, operate drones and other surveillance technologies, detect illegalities, and lead police teams to arrest poachers. We describe the sophisticated military metaphors which conservation NGOs have developed to describe, guide and legitimize their efforts to the Maltese public and their fee-paying members. We also discuss why such groups might be inclined to adopt these metaphors. Finally, we suggest that anthropological studies of discourse could help understand delicate contexts such as this where conservation NGOs, hunting associations and the State have ended in political deadlock

A toy model of the five-dimensional universe with the cosmological constant

A value of the cosmological constant in a toy model of the five-dimensional universe is calculated in such a manner that it remains in agreement with both astronomical observations and the quantum field theory concerning the zero-point fluctuations of the vacuum. The (negative) cosmological constant is equal to the inverse of the Planck length squared, which means that in the toy model the vanishing of the observed value of the cosmological constant is a consequence of the existence of an energy cutoff exactly at the level of the Planck scale. In turn, a model for both a virtual and a real particle-antiparticle pair is proposed which describes properly some energetic properties of both the vacuum fluctuations and created particles, as well as it allows one to calculate the discrete "bare" values of an elementary-particle mass, electric charge and intrinsic angular momentum (spin) at the energy cutoff. The relationships between the discussed model and some phenomena such as the Zitterbewegung and the Unruh-Davies effect are briefly analyzed, too. The proposed model also allows one to derive the Lorentz transformation and the Maxwell equations while considering the properties of the vacuum filled with the sea of virtual particles and their antiparticles. Finally, the existence of a finite value of the vacuum-energy density resulting from the toy model leads us to the formulation of dimensionless Einstein field equations which can be derived from the Lagrangian with a dimensionless (naively renormalized) coupling constant.Comment: 52 pages, 1 figure; a post-final, rewritten version with a number of new remarks and conclusion

Accelerated Detector - Quantum Field Correlations: From Vacuum Fluctuations to Radiation Flux

In this paper we analyze the interaction of a uniformly accelerated detector with a quantum field in (3+1)D spacetime, aiming at the issue of how kinematics can render vacuum fluctuations the appearance of thermal radiance in the detector (Unruh effect) and how they engender flux of radiation for observers afar. Two basic questions are addressed in this study: a) How are vacuum fluctuations related to the emitted radiation? b) Is there emitted radiation with energy flux in the Unruh effect? We adopt a method which places the detector and the field on an equal footing and derive the two-point correlation functions of the detector and of the field separately with full account of their interplay. From the exact solutions, we are able to study the complete process from the initial transient to the final steady state, keeping track of all activities they engage in and the physical effects manifested. We derive a quantum radiation formula for a Minkowski observer. We find that there does exist a positive radiated power of quantum nature emitted by the detector, with a hint of certain features of the Unruh effect. We further verify that the total energy of the dressed detector and a part of the radiated energy from the detector is conserved. However, this part of the radiation ceases in steady state. So the hint of the Unruh effect in radiated power is actually not directly from the energy flux that the detector experiences in Unruh effect. Since all the relevant quantum and statistical information about the detector (atom) and the field can be obtained from the results presented here, they are expected to be useful, when appropriately generalized, for addressing issues of quantum information processing in atomic and optical systems, such as quantum decoherence, entanglement and teleportation.Comment: 24 pages, 11 figures, new results and comments added in Secs.VI and VII, with other corresponding change