6,055 research outputs found
A Continuum,O(N) Monte-Carlo algorithm for charged particles
We introduce a Monte-Carlo algorithm for the simulation of charged particles
moving in the continuum. Electrostatic interactions are not instantaneous as in
conventional approaches, but are mediated by a constrained, diffusing electric
field on an interpolating lattice. We discuss the theoretical justifications of
the algorithm and show that it efficiently equilibrates model polyelectrolytes
and polar fluids. In order to reduce lattice artifacts that arise from the
interpolation of charges to the grid we implement a local, dynamic subtraction
algorithm. This dynamic scheme is completely general and can also be used with
other Coulomb codes, such as multigrid based methods
Phase fluctuations and first-order correlation functions of dissipative Bose-Einstein condensates
We investigate the finite lifetime effects on first-order correlation
functions of dissipative Bose-Einstein condensates. By taking into account the
phase fluctuations up to all orders, we show that the finite lifetime effects
are neglible for the spatial first-order correlation functions, but have an
important effect on the temporal correlations. As an application, we calculate
the one-particle density matrix of a quasi-condensate of photons. Finally, we
also consider the photons in the normal state and we demonstrate that the
finite lifetime effects decrease both the spatial and temporal first-order
correlation functions.Comment: 8 pages, 5 figure
Schwinger-Keldysh theory for Bose-Einstein condensation of photons in a dye-filled optical microcavity
We consider Bose-Einstein condensation of photons in an optical cavity filled
with dye molecules that are excited by laser light. By using the
Schwinger-Keldysh formalism we derive a Langevin field equation that describes
the dynamics of the photon gas, and in particular its equilibrium properties
and relaxation towards equilibrium. Furthermore we show that the finite
lifetime effects of the photons are captured in a single dimensionless damping
parameter, that depends on the power of the external laser pumping the dye.
Finally, as applications of our theory we determine spectral functions and
collective modes of the photon gas in both the normal and the Bose-Einstein
condensed phase
Multidisciplinary integrated parent and child centres in Amsterdam: a qualitative study
Background: In several countries centres for the integrated delivery of services to the parent and child have been established. In the Netherlands family health care service centres, called Parent and Child Centres (PCCs) involve multidisciplinary teams. Here doctors, nurses, midwives, maternity help professionals and educationists are integrated into multidisciplinary teams in neighbourhood-based centres. To date there has been little research on the implementation of service delivery in these centres.
Study Design: A SWOT analysis was performed by use of triangulation data; this took place by integrating all relevant published documents on the origin and organization of the PCCs and the results from interviews with PCC experts and with PCC professionals (N=91). Structured interviews were performed with PCC-professionals (health care professionals (N=67) and PCC managers N=12)) and PCC-experts (N=12) in Amsterdam and qualitatively analysed thematically. The interview themes were based on a pre-set list of codes, derived from a prior documentation study and a focus group with PCC experts.
Results: Perceived advantages of PCCs were more continuity of care, shorter communication lines, low-threshold contact between professionals and promising future perspectives. Perceived challenges included the absence of uniform multidisciplinary guidelines, delays in communication with hospitals and midwives, inappropriate accommodation for effective professional integration, differing expectations regarding the PCC-manager role among PCC-partners and the danger of professionals' needs dominating clients' needs.
Conclusions: Professionals perceive PCCs as a promising development in the integration of services. Remaining challenges involved improvements at the managerial and organizational level. Quantitative research into the improvements in quality of care and child health is recommended
Asymptotic one-point functions in AdS/dCFT
We take the first step in extending the integrability approach to one-point
functions in AdS/dCFT to higher loop orders. More precisely, we argue that the
formula encoding all tree-level one-point functions of SU(2) operators in the
defect version of N=4 SYM theory, dual to the D5-D3 probe-brane system with
flux, has a natural asymptotic generalization to higher loop orders. The
asymptotic formula correctly encodes the information about the one-loop
correction to the one-point functions of non-protected operators once dressed
by a simple flux-dependent factor, as we demonstrate by an explicit computation
involving a novel object denoted as an amputated matrix product state.
Furthermore, when applied to the BMN vacuum state, the asymptotic formula gives
a result for the one-point function which in a certain double-scaling limit
agrees with that obtained in the dual string theory up to wrapping order.Comment: 6 pages; v2: statement about match up to wrapping order clarified,
version accepted for publicatio
Two-point functions in AdS/dCFT and the boundary conformal bootstrap equations
We calculate the leading contributions to the connected two-point functions
of protected scalar operators in the defect version of N=4 SYM theory which is
dual to the D5-D3 probe-brane system with k units of background gauge field
flux. This involves several types of two-point functions which are vanishing in
the theory without the defect, such as two-point functions of operators of
unequal conformal dimension. We furthermore exploit the operator product
expansion (OPE) and the boundary operator expansion (BOE), which form the basis
of the boundary conformal bootstrap equations, to extract conformal data both
about the defect CFT and about N=4 SYM theory without the defect. From the
knowledge of the one- and two-point functions of the defect theory, we extract
certain structure constants of N=4 SYM theory using the (bulk) OPE and
constrain certain bulk-bulk-to-boundary couplings using the BOE. The extraction
of the former relies on a non-trivial, polynomial k dependence of the one-point
functions, which we explicitly demonstrate. In addition, it requires the
knowledge of the one-point functions of SU descendant operators, which we
likewise explicitly determine.Comment: 34 pages, 2 figure
Phase diffusion in a Bose-Einstein condensate of light
We study phase diffusion in a Bose-Einstein condensate of light in a
dye-filled optical microcavity, i.e., the spreading of the probability
distribution for the condensate phase. To observe this phenomenon, we propose
an interference experiment between the condensed photons and an external laser.
We determine the average interference patterns, considering quantum and thermal
fluctuations as well as dissipative effects due to the dye. Moreover, we show
that a representative outcome of individual measurements can be obtained from a
stochastic equation for the global phase of the condensate
Interaction Effects on Number Fluctuations in a Bose-Einstein Condensate of Light
We investigate the effect of interactions on condensate-number fluctuations
in Bose-Einstein condensates. For a contact interaction we variationally obtain
the equilibrium probability distribution for the number of particles in the
condensate. To facilitate comparison with experiment, we also calculate the
zero-time delay autocorrelation function for different strengths
of the interaction. Finally, we focus on the case of a condensate of photons
and discuss possible mechanisms for the interaction.Comment: 13 pages, version 3, 4 figure
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