Results for "Diederik S. Wiersma"

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Multiple scattering of light in superdiffusive mediaMar 10 2010Oct 25 2010Light transport in superdiffusive media of finite size is studied theoretically. The intensity Green's function for a slab geometry is found by discretizing the fractional diffusion equation and employing the eigenfunction expansion method. Truncated ... More
Weak* tensor products for von Neumann algebrasJun 04 2015The category of $C^*$-algebras is blessed with many different tensor products. In contrast, virtually the only tensor product ever used in the category of von Neumann algebras is the normal spatial tensor product. We propose a definition of what a generic ... More
Statistical regimes of random laser fluctuationsNov 06 2006Feb 07 2007Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on ... More
Spatio-temporal visualization of light transport in complex photonic structuresSep 18 2015Jun 16 2016Spatio-temporal imaging of light propagation is very important in photonics because it provides the most direct tool available to study the interaction between light and its host environment. Sub-ps time resolution is needed to investigate the fine and ... More
Photon Management in Two-Dimensional Disordered MediaFeb 21 2012Apr 09 2013Elaborating reliable and versatile strategies for efficient light coupling between free space and thin films is of crucial importance for new technologies in energy efficiency. Nanostructured materials have opened unprecedented opportunities for light ... More
Localization in one-dimensional chains with Lévy-type disorderDec 05 2014We study Anderson localization of the classical lattice waves in a chain with mass impurities distributed randomly through a power-law relation $s^{-(1+\alpha)}$ with $ s $ as the distance between two successive impurities and $\alpha>0$. This model of ... More
Optimized White Reflectance in Photonic Network StructuresMay 28 2019Three-dimensional disordered networks are receiving increasing attention as versatile architectures for highly scattering materials. However, due to their complex morphology, little is still known about the interplay between their structural and optical ... More
Photonic Crystals with Controlled DisorderNov 05 2010Photonic crystals are extremely sensitive to structural disorder even to the point of completely losing their functionalities. While on one side this can be detrimental for applications in traditional optical devices, on the other side, it gives also ... More
Magnetic field generation in relativistic shocks - An early end of the exponential Weibel instability in electron-proton plasmasAug 30 2004We discuss magnetic field generation by the proton Weibel instability in relativistic shocks, a situation that applies to the external shocks in the fireball model for Gamma-ray Bursts, and possibly also to internal shocks. Our analytical estimates show ... More
Activated Transport in the individual Layers that form the $ν_T$=1 Exciton CondensateJul 22 2004We observe the total filling factor $\nu_{T}$=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunnelling. We find thermally activated transport in the balanced system with a monotonic increase of the activation energy ... More
Multichannel remote polarization control enabled by nanostructured Liquid Crystalline NetworksJun 08 2019In this article we demonstrate that a grating fabricated through nanoscale volumetric crosslinking of a liquid crystalline polymer enables remote polarization control over the diffracted channels. This functionality is a consequence of the responsivity ... More
Structured Optical Materials Controlled by LightOct 08 2018Materials of which the optical response is determined by their structure are of much interest both for their fundamental properties and applications. Examples range from simple gratings to photonic crystals. Obtaining control over the optical properties ... More
Weak localization of light in superdiffusive random systemsOct 07 2011L\'evy flights constitute a broad class of random walks that occur in many fields of research, from animal foraging in biology, to economy to geophysics. The recent advent of L\'evy glasses allows to study L\'evy flights in controlled way using light ... More
CELES: CUDA-accelerated simulation of electromagnetic scattering by large ensembles of spheresJun 06 2017CELES is a freely available MATLAB toolbox to simulate light scattering by many spherical particles. Aiming at high computational performance, CELES leverages block-diagonal preconditioning, a lookup-table approach to evaluate costly functions and massively ... More
Two-dimensional disorder for broadband, omnidirectional and polarization-insensitive absorptionNov 27 2012The surface of thin-film solar cells can be tailored with photonic nanostructures to allow light trapping in the absorbing medium. This in turn increases the optical thickness of the film and thus enhances their absorption. Such a coherent light trapping ... More
Light transport and localization in two-dimensional correlated disorderJul 07 2013Feb 03 2014Structural correlations in disordered media are known to affect significantly the propagation of waves. In this article, we theoretically investigate the transport and localization of light in 2D photonic structures with short-range correlated disorder. ... More
Holey Random Walks: Optics of Heterogeneous Turbid CompositesNov 08 2012We present a probabilistic theory of random walks in turbid media with non-scattering regions. It is shown that important characteristics such as diffusion constants, average step lengths, crossing statistics and void spacings can be analytically predicted. ... More
Exploiting breakdown of the similarity relation for diffuse light transport: simultaneous retrieval of scattering anisotropy and diffusion constantNov 28 2012As manifested in the similarity relation of diffuse light transport, it is difficult to assess single scattering characteristics from multiply scattered light. We take advantage of the limited validity of the diffusion approximation of light transport ... More
Walk dimension for light in complex disordered mediaDec 20 2013Aug 21 2014Transport in complex systems is characterized by a fractal dimension -- the walk dimension -- that indicates the diffusive or anomalous nature of the underlying random walk process. Here we report on the experimental retrieval of this key quantity, using ... More
Transport in quenched disorder: light diffusion in strongly heterogeneous turbid mediaOct 23 2013We present a theoretical and experimental study of light transport in disordered media with strongly heterogeneous distribution of scatterers formed via non-scattering regions. Step correlations induced by quenched disorder are found to prevent diffusivity ... More
Path length enhancement in disordered media for increased absorptionJul 13 2015Sep 04 2015We theoretically and numerically investigate the capability of disordered media to enhance the optical path length in dielectric slabs and augment their light absorption efficiency due to scattering. We first perform a series of Monte Carlo simulations ... More
Biomimetic Polymer Film with Brilliant Brightness Using a One-Step Water Vapor-Induced Phase Separation MethodJun 11 2019The scales of the white Cyphochilus beetles are endowed with unusual whiteness arising from the exceptional scattering efficiency of their disordered ultrastructure optimized through millions of years of evolution. Here, a simple, one-step method based ... More
Deducing effective light transport parameters in optically thin systemsSep 14 2015Sep 21 2015We present an extensive Monte Carlo study on light transport in optically thin slabs, addressing both axial and transverse propagation. We completely characterize the so-called ballistic-to-diffusive transition, notably in terms of the spatial variance ... More
Diffusion of light in semitransparent mediaSep 14 2015Sep 21 2015Light diffusion is usually associated with thick, opaque media. Indeed, multiple scattering is necessary for the onset of the diffusive regime and such condition is generally not met in almost transparent media. Nonetheless, at long enough times, transport ... More
A Cross-disciplinary Framework for the Description of Contextually Mediated ChangeJun 01 2007We present a mathematical framework (referred to as Context-driven Actualization of Potential, or CAP) for describing how entities change over time under the influence of a context. The approach facilitates comparison of change of state of entities studied ... More
General sGoldstino InflationAug 12 2016We prove that all inflationary models, including those with dark energy after the end of inflation, can be embedded in minimal supergravity with a single chiral superfield. Moreover, the amount of supersymmetry breaking is independently tunable due to ... More
Are globular clusters the natural outcome of regular high-redshift star formation?Sep 09 2015We summarise some of the recent progress in understanding the formation and evolution of globular clusters (GCs) in the context of galaxy formation and evolution. It is discussed that an end-to-end model for GC formation and evolution should capture four ... More
The dynamics of star-forming regions - which mechanisms set the cluster formation efficiency?Jul 11 2011The fraction of star formation that results in bound stellar clusters (cluster formation efficiency or CFE) is a central quantity in many studies of star formation, star clusters and galaxies. Recent results suggest that contrary to popular assumption, ... More
Spin and Wind Directions: Identifying Entanglement in Nature and CognitionJul 31 2015Aug 20 2015We performed a cognitive experiment in which we asked the participants to pick a pair of directions they considered as the 'preferred good example of two different wind directions'. The results of the experiment reveal that the 'Clauser Horne Shimony ... More
On the fraction of star formation occurring in bound stellar clustersAug 14 2012We present a theoretical framework in which bound stellar clusters arise naturally at the high-density end of the hierarchy of the interstellar medium (ISM). Due to short free-fall times, these high-density regions achieve high local star formation efficiencies, ... More
Collateral Damage: the Implications of Utrecht Star Cluster Astrophysics for Galaxy EvolutionJun 06 2012Until the early 2000s, the research portfolio of the Astronomical Institute in Utrecht (SIU) did not include galaxy evolution. Somewhat serendipitously, this changed with the advent of the star cluster group. In only a few years, a simple framework was ... More
A galactic-scale origin for stellar clusteringAug 31 2012We recently presented a model for the cluster formation efficiency (CFE), i.e. the fraction of star formation occurring in bound stellar clusters. It utilizes the idea that the formation of stars and stellar clusters occurs across a continuous spectrum ... More
Towards a multi-scale understanding of the gas-star formation cycle in the Central Molecular ZoneSep 26 2016The Central Molecular Zone (CMZ, the central 500 pc of the Milky Way) contains the largest reservoir of high-density molecular gas in the Galaxy, but forms stars at a rate 10-100 times below commonly-used star formation relations. We discuss recent efforts ... More
Experimental and theoretical investigation of statistical regimes in random laser emissionSep 10 2013We present a theoretical and experimental study aimed at characterizing statistical regimes in a random laser. Both the theoretical simulations and the experimental results show the possibility of three region of fluctuations increasing the pumping energy. ... More
The Effect of Pre-Main Sequence Stars on Star Cluster DynamicsOct 07 2005We investigate the effects of the addition of pre-main sequence evolution to star cluster simulations. We allowed stars to follow pre-main sequence tracks that begin at the deuterium burning birthline and end at the zero age main sequence. We compared ... More
The Optical Colors of Giant Elliptical Galaxies and their Metal-Rich Globular Clusters Indicate a Bottom-Heavy Initial Mass FunctionNov 21 2012Jan 02 2013We report a systematic and statistically significant offset between the optical (g-z or B-I) colors of seven massive elliptical galaxies and the mean colors of their associated massive metal-rich globular clusters (GCs) in the sense that the parent galaxies ... More
Color-Magnitude Relations within Globular Cluster Systems of Giant Elliptical Galaxies: The Effects of Globular Cluster Mass Loss and the Stellar Initial Mass FunctionOct 21 2013Oct 28 2013Several recent studies have provided evidence for a `bottom-heavy' stellar initial mass function (IMF) in massive elliptical galaxies. Here we investigate the influence of the IMF shape on the recently discovered color-magnitude relation (CMR) among globular ... More
The Liar-paradox in a Quantum Mechanical PerspectiveJul 16 2000In this paper we concentrate on the nature of the liar paradox as a cognitive entity; a consistently testable configuration of properties. We elaborate further on a quantum mechanical model [Aerts, Broekaert, Smets 1999] that has been proposed to analyze ... More
Metal-line emission from the warm-hot intergalactic medium: II. UltravioletFeb 18 2010Jun 14 2010Approximately half the baryons in the local Universe are thought to reside in the warm-hot intergalactic medium (WHIM). Emission lines from metals in the UV band are excellent tracers of the cooler fraction of this gas. We present predictions for the ... More
A Geometric Formulation of SupersymmetrySep 23 2016The scalar fields of supersymmetric models are coordinates of a geometric space. We propose a formulation of supersymmetry that is covariant with respect to reparametrizations of this target space. Employing chiral multiplets as an example, we introduce ... More
Multiple Membranes from Gauged SupergravityJun 16 2008Aug 26 2008Starting from gauged N=8 supergravity in three dimensions we construct actions for multiple membranes by taking the limit to global supersymmetry for different choices of the embedding tensor. This provides a general framework that reproduces many recent ... More
Off-shell Poincare SupergravityJan 18 2017Feb 21 2017We present the action and transformation rules of Poincare supergravity coupled to chiral multiplets $(z^\alpha, \chi^\alpha, h^\alpha)$ with off-shell auxiliary fields. Starting from the geometric formulation of the superconformal theory with auxiliary ... More
Do Spectroscopic Dense Gas Fractions Track Molecular Cloud Surface Densities?Nov 19 2018We use ALMA and IRAM 30-m telescope data to investigate the relationship between the spectroscopically-traced dense gas fraction and the cloud-scale (120 pc) molecular gas surface density in five nearby, star-forming galaxies. We estimate the dense gas ... More
Cloud-Scale Molecular Gas Properties in 15 Nearby GalaxiesMay 02 2018We measure the velocity dispersion, $\sigma$, and surface density, $\Sigma$, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution $45$-$120$ pc, matched to the size of individual giant molecular clouds. Combining ... More
Effect of optical disorder and single defects on the expansion of a Bose-Einstein condensate in a one-dimensional waveguideJul 06 2005We investigate the one-dimensional expansion of a Bose-Einstein condensate in an optical guide in the presence of a random potential created with optical speckles. With the speckle the expansion of the condensate is strongly inhibited. A detailed investigation ... More
Magnetic field generation in relativistic shocksDec 08 2003We present an analytical estimate for the magnetic field strength generated by the Weibel instability in ultra-relativistic shocks in a hydrogen plasma. We find that the Weibel instability is, by itself, not capable of converting the kinetic energy of ... More
Optimal error estimates for corrected trapezoidal rulesMay 16 2012Corrected trapezoidal rules are proved for $\int_a^b f(x)\,dx$ under the assumption that $f"\in L^p([a,b])$ for some $1\leq p\leq\infty$. Such quadrature rules involve the trapezoidal rule modified by the addition of a term $k[f'(a)-f'(b)]$. The coefficient ... More
A new chiral electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric fieldJun 24 2003We report the observation of sum-frequency signals that depend linearly on an applied electrostatic field and that change sign with the handedness of an optically active solution. This recently predicted chiral electro-optic effect exists in the electric-dipole ... More
Effect of interactions on the localization of a Bose-Einstein condensate in a quasi-periodic latticeNov 06 2006The transport properties of a Bose-Einstein condensate in a 1D incommensurate bichromatic lattice are investigated both theoretically and experimentally. We observe a blockage of the center of mass motion with low atom number, and a return of motion when ... More
Observations of metals in the intra-cluster mediumJan 07 2008Because of their deep gravitational potential wells, clusters of galaxies retain all the metals produced by the stellar populations of the member galaxies. Most of these metals reside in the hot plasma which dominates the baryon content of clusters. This ... More
Observation of coherent backscattering of light by cold atomsApr 20 2000Coherent backscattering (CBS) of light waves by a random medium is a signature of interference effects in multiple scattering. This effect has been studied in many systems ranging from white paint to biological tissues. Recently, we have observed CBS ... More
Directed Policy Gradient for Safe Reinforcement Learning with Human AdviceAug 13 2018Many currently deployed Reinforcement Learning agents work in an environment shared with humans, be them co-workers, users or clients. It is desirable that these agents adjust to people's preferences, learn faster thanks to their help, and act safely ... More
Young star cluster populations in the E-MOSAICS simulationsJul 23 2019We present an analysis of young star clusters (YSCs) that form in the E-MOSAICS cosmological, hydrodynamical simulations of galaxies and their star cluster populations. Through comparisons with observed YSC populations, this work aims to test models for ... More
Prevalent externally-driven protoplanetary disc dispersal as a function of the galactic environmentJul 10 2019The stellar birth environment can significantly shorten protoplanetary disc (PPD) lifetimes due to the influence of stellar feedback mechanisms. The degree to which these mechanisms suppress the time and mass available for planet formation is dependent ... More
A fundamental test for stellar feedback recipes in galaxy simulationsMay 23 2019Direct comparisons between galaxy simulations and observations that both reach scales < 100 pc are strong tools to investigate the cloud-scale physics of star formation and feedback in nearby galaxies. Here we carry out such a comparison for hydrodynamical ... More
Exotic C*-algebras of geometric groupsSep 19 2018We consider a new class of potentially exotic group C*-algebras $C^*_{PF_p^*}(G)$ for a locally compact group $G$, and its connection with the class of potentially exotic group C*-algebras $C^*_{L^p}(G)$ introduced by Brown and Guentner. Surprisingly, ... More
How sustainable are different levels of consciousness?May 12 2017The human brain processes a wide variety of inputs and does so either consciously or subconsciously. According to the Global Workspace theory, conscious processing involves broadcasting of information to several regions of the brain and subconscious processing ... More
Simple derivation of basic quadrature formulasFeb 01 2012Simple proofs of the midpoint, trapezoidal and Simpson's rules are proved for numerical integration on a compact interval. The integrand is assumed to be twice continuously differentiable for the midpoint and trapezoidal rules, and to be four times continuously ... More
Cosmological simulations of the formation of the stellar haloes around disc galaxiesFeb 12 2011Jul 18 2011We use the Galaxies-Intergalactic Medium Interaction Calculation (GIMIC) suite of cosmological hydrodynamical simulations to study the formation of stellar spheroids of Milky Way-mass disc galaxies. The simulations contain accurate treatments of metal-dependent ... More
The dynamical evolution of molecular clouds near the Galactic Centre -- III. Tidally--induced star formation in protocluster cloudsMar 25 2019As part of a series of papers aimed at understanding the evolution of the Milky Way's Central Molecular Zone (CMZ), we present hydrodynamical simulations of turbulent molecular clouds orbiting in an accurate model of the gravitational potential extant ... More
On exotic group C*-algebrasMay 04 2015Mar 09 2016Let $\Gamma$ be a discrete group. A $C^*$-algebra $A$ is an exotic $C^*$-algebra (associated to $\Gamma$) if there exist proper surjective $C^*$-quotients $C^*(\Gamma)\to A\to C^*_r(\Gamma)$. In this paper, we show that a large class of exotic $C^*$-algebras ... More
Measuring Meaning on the World-Wide WebJun 09 2010We introduce the notion of the 'meaning bound' of a word with respect to another word by making use of the World-Wide Web as a conceptual environment for meaning. The meaning of a word with respect to another word is established by multiplying the product ... More
Quantum Interference and Superposition in Cognition: Development of a Theory for the Disjunction of ConceptsMay 07 2007May 01 2010We elaborate a theory for the modeling of concepts using the mathematical structure of quantum mechanics. Concepts are represented by vectors in the complex Hilbert space of quantum mechanics and membership weights of items are modeled by quantum weights ... More
Reality and Probability: Introducing a New Type of Probability CalculusMay 26 2002We consider a conception of reality that is the following: An object is 'real' if we know that if we would try to test whether this object is present, this test would give us the answer 'yes' with certainty. If we consider a conception of reality where ... More
A conceptual study on real-time adaptive radiation therapy optimization through ultra-fast beamlet controlNov 08 2018Mar 04 2019A central problem in the field of radiation therapy (RT) is how to optimally deliver dose to a patient in a way that fully accounts for anatomical position changes over time. As current RT is a static process, where beam intensities are calculated before ... More
Universality classes of inflationSep 05 2013Dec 23 2013We investigate all single-field, slow-roll inflationary models whose slow-roll parameters scale as 1/N in the limit of a large number of e-folds N. We proof that all such models belong to two universality classes, characterised by a single parameter. ... More
Interpreting Quantum Particles as Conceptual EntitiesApr 15 2010We elaborate an interpretation of quantum physics founded on the hypothesis that quantum particles are conceptual entities playing the role of communication vehicles between material entities composed of ordinary matter which function as memory structures ... More
Foundations of quantum physics: a general realistic and operational approachMay 23 2001We present a general formalism with the aim of describing the situation of an entity, how it is, how it reacts to experiments, how we can make statistics with it, and how it changes under the influence of the rest of the universe. Therefore we base our ... More
The Description of Joint Quantum Entities and the Formulation of a ParadoxMay 22 2001We formulate a paradox in relation to the description of a joint entity consisting of two subentities by standard quantum mechanics. We put forward a proposal for a possible solution, entailing the interpretation of density states as pure states. We explain ... More
Relativity Theory RefoundedNov 27 2015We put forward a new view of relativity theory that makes the existence of a flow of time compatible with the four-dimensional block universe. To this end, we apply the creation-discovery view elaborated for quantum mechanics to relativity theory and ... More
Quantum and Concept Combination, Entangled Measurements and Prototype TheoryMar 11 2013May 19 2013We analyze the meaning of the violation of the marginal probability law for situations of correlation measurements where entanglement is identified. We show that for quantum theory applied to the cognitive realm such a violation does not lead to the type ... More
Quantum Theory and Human Perception of the Macro-WorldMar 17 2014May 29 2014We investigate the question of 'why customary macroscopic entities appear to us humans as they do, i.e. as bounded entities occupying space and persisting through time', starting from our knowledge of quantum theory, how it affects the behavior of such ... More
Operational Quantum Mechanics, Quantum Axiomatics and Quantum StructuresNov 15 2008The role of operational quantum mechanics, quantum axiomatics and quantum structures in general is presented as a contribution to a compendium on quantum physics, its history and philosophy.
Towards a New Democracy: Consensus Through Quantum ParliamentMar 09 2005We compare different actual forms of democracy and analyse in which way they are variations of a 'natural consensus decision process'. We analyse how 'consensus decision followed by majority voting' is open to 'false play' by the majority, and investigate ... More
A Potentiality and Conceptuality Interpretation of Quantum PhysicsMay 20 2010We elaborate on a new interpretation of quantum mechanics which we introduced recently. The main hypothesis of this new interpretation is that quantum particles are entities interacting with matter conceptually, which means that pieces of matter function ... More
M-theory and Gauged SupergravitiesAug 23 2004Aug 31 2004We present a pedagogical discussion of the emergence of gauged supergravities from M-theory. First, a review of maximal supergravity and its global symmetries and supersymmetric solutions is given. Next, different procedures of dimensional reduction are ... More
Gaugings at angles from orientifold reductionsFeb 03 2009Jun 10 2009We consider orientifold reductions to N=4 gauged supergravity in four dimensions. A special feature of this theory is that different factors of the gauge group can have relative angles with respect to the electro-magnetic SL(2) symmetry. These are crucial ... More
Quantum Structure in CognitionMay 25 2008Mar 12 2009The broader scope of our investigations is the search for the way in which concepts and their combinations carry and influence meaning and what this implies for human thought. More specifically, we examine the use of the mathematical formalism of quantum ... More
General Quantum Modeling of Combining Concepts: A Quantum Field Model in Fock SpaceMay 11 2007We extend a quantum model in Hilbert space developed in Aerts (2007a) into a quantum field theoric model in Fock space for the modeling of the combination of concepts. Items and concepts are represented by vectors in Fock space and membership weights ... More
Being and Change: Foundations of a Realistic Operational FormalismMay 26 2002The aim of this article is to represent the general description of an entity by means of its states, contexts and properties. The entity that we want to describe does not necessarily have to be a physical entity, but can also be an entity of a more abstract ... More
Quantum Structures: An Attempt to Explain the Origin of their Appearance in NatureNov 13 2001We explain the quantum structure as due to the presence of two effects, (a) a real change of state of the entity under influence of the measurement and, (b) a lack of knowledge about a deeper deterministic reality of the measurement process. We present ... More
The stuff the world is made of: physics and realityJul 07 2001Taking into account the results that we have been obtained during the last decade in the foundations of quantum mechanic we put forward a view on reality that we call the 'creation discovery view'. In this view it is made explicit that a measurement is ... More
Quantum Mechanics: Structures, Axioms and ParadoxesJun 24 2001We present an analysis of quantum mechanics and its problems and paradoxes taking into account the results that have been obtained during the last two decades by investigations in the field of `quantum structures research'. We concentrate mostly on the ... More
Quantum Theory and Conceptuality: Matter, Stories, Semantics and Space-TimeOct 21 2011We elaborate the new interpretation of quantum theory that we recently proposed, according to which quantum particles are considered conceptual entities mediating between pieces of ordinary matter which are considered to act as memory structures for them. ... More
The hidden measurement formalism: what can be explained and where quantum paradoxes remainMay 24 2001In the hidden measurement formalism that we develop in Brussels we explain the quantum structure as due to the presence of two effects, (a) a real change of state of the system under influence of the measurement and, (b) a lack of knowledge about a deeper ... More
Quantum Particles as Conceptual Entities: A Possible Explanatory Framework for Quantum TheoryApr 15 2010We put forward a possible new interpretation and explanatory framework for quantum theory. The basic hypothesis underlying this new framework is that quantum particles are conceptual entities. More concretely, we propose that quantum particles interact ... More
Using young massive star clusters to understand star formation and feedback in high-redshift-like environmentsJan 11 2016The formation environment of stars in massive stellar clusters is similar to the environment of stars forming in galaxies at a redshift of 1 - 3, at the peak star formation rate density of the Universe. As massive clusters are still forming at the present ... More
De Sitter in Extended SupergravityDec 22 2009We show that known de Sitter solutions in extended gauged supergravity theories are interrelated via a web of supersymmetry-breaking truncations. In particular, all N=8 models reduce to a subset of the N=4 possibilities. Furthermore, a different subset ... More
Globular clusters as the relics of regular star formation in 'normal' high-redshift galaxiesSep 07 2015We present an end-to-end, two-phase model for the origin of globular clusters (GCs). In the model, populations of stellar clusters form in the high-pressure discs of high-redshift ($z>2$) galaxies (a rapid-disruption phase due to tidal perturbations from ... More
The evolution of the stellar mass function in star clustersOct 24 2009(Abridged) The dynamical ejection of stars from star clusters affects the shape of the stellar mass function (MF) in these clusters, because the escape probability of a star depends on its mass. The objective of this paper is to provide and to apply a ... More
Distilling the Essence of an Evolutionary Process and Implications for a Formal Description of CultureSep 18 2013It has been proposed that, since the origin of life and the ensuing evolution of biological species, a second evolutionary process has appeared on our planet. It is the evolution of culture-e.g., ideas, beliefs, and artifacts. Does culture evolve in the ... More
Quantum Structure in Cognition: Why and How Concepts are EntangledApr 07 2011Sep 08 2013One of us has recently elaborated a theory for modelling concepts that uses the state context property (SCoP) formalism, i.e. a generalization of the quantum formalism. This formalism incorporates context into the mathematical structure used to represent ... More
Tensor-product vs. geometric-product codingSep 10 2007Quantum computation is based on tensor products and entangled states. We discuss an alternative to the quantum framework where tensor products are replaced by geometric products and entangled states by multivectors. The resulting theory is analogous to ... More
Modeling Concept Combinations in a Quantum-theoretic FrameworkJan 15 2014We present modeling for conceptual combinations which uses the mathematical formalism of quantum theory. Our model faithfully describes a large amount of experimental data collected by different scholars on concept conjunctions and disjunctions. Furthermore, ... More
Distilling the Essence of an Evolutionary Process and Implications for a Formal Description of CultureSep 18 2013Jul 05 2019It has been proposed that, since the origin of life and the ensuing evolution of biological species, a second evolutionary process has appeared on our planet. It is the evolution of culture-e.g., ideas, beliefs, and artifacts. Does culture evolve in the ... More
Quantum Entanglement in Concept CombinationsFeb 15 2013Aug 15 2013Research in the application of quantum structures to cognitive science confirms that these structures quite systematically appear in the dynamics of concepts and their combinations and quantum-based models faithfully represent experimental data of situations ... More
A model of the emergence and evolution of integrated worldviewsJan 09 2010It is proposed that the ability of humans to flourish in diverse environments and evolve complex cultures reflects the following two underlying cognitive transitions. The transition from the coarse-grained associative memory of Homo habilis to the fine-grained ... More
A Cross-disciplinary Framework for the Description of Contextually Mediated ChangeJun 01 2007Jul 05 2019We present a mathematical framework (referred to as Context-driven Actualization of Potential, or CAP) for describing how entities change over time under the influence of a context. The approach facilitates comparison of change of state of entities studied ... More
Cartoon Computation: Quantum-like computing without quantum mechanicsNov 28 2006Feb 18 2007We present a computational framework based on geometric structures. No quantum mechanics is involved, and yet the algorithms perform tasks analogous to quantum computation. Tensor products and entangled states are not needed -- they are replaced by sets ... More
State Property Systems and Closure Spaces: Extracting the Classical and Nonclassical PartsApr 12 2004We introduce classical properties using the concept of super selection rule, i.e. two properties are separated by a superselection rule iff there do not exist 'superposition states' related to these two properties. Then we show that the classical properties ... More