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  • Journal article
    Dolan D, Jensen H, Martinez Mediano P, Molina-Solana MJ, Rajpal H, Rosas De Andraca F, Sloboda JAet al., 2018,

    The improvisational state of mind: a multidisciplinary study of an improvisatory approach to classical music repertoire performance

    , Frontiers in Psychology, Vol: 9, ISSN: 1664-1078

    The recent re-introduction of improvisation as a professional practice within classical music, however cautious and still rare, allows direct and detailed contemporary comparison between improvised and “standard” approaches to performances of the same composition, comparisons which hitherto could only be inferred from impressionistic historical accounts. This study takes an interdisciplinary multi-method approach to discovering the contrasting nature and effects of prepared and improvised approaches during live chamber-music concert performances of a movement from Franz Schubert’s “Shepherd on the Rock”, given by a professional trio consisting of voice, flute, and piano, in the presence of an invited audience of 22 adults with varying levels of musical experience and training. The improvised performances were found to be differ systematically from prepared performances in their timing, dynamic, and timbral features as well as in the degree of risk-taking and “mind reading” between performers including during moments of added extemporised notes. Post-performance critical reflection by the performers characterised distinct mental states underlying the two modes of performance. The amount of overall body movements was reduced in the improvised performances, which showed less unco-ordinated movements between performers when compared to the prepared performance. Audience members, who were told only that the two performances would be different, but not how, rated the improvised version as more emotionally compelling and musically convincing than the prepared version. The size of this effect was not affected by whether or not the audience could see the performers, or by levels of musical training. EEG measurements from 19 scalp locations showed higher levels of Lempel-Ziv complexity (associated with awareness and alertness) in the improvised version in both performers and audience. Results are discussed in terms of their potential

  • Journal article
    Jensen HJ, Pazuki RH, Pruessner G, Tempesta Pet al., 2018,

    Statistical mechanics of exploding phase spaces: ontic open systems

    , Journal of Physics A: Mathematical and Theoretical, Vol: 51, ISSN: 1751-8113

    The volume of phase space may grow super-exponentially ('explosively') with the number of degrees of freedom for certain types of complex systems such as those encountered in biology and neuroscience, where components interact and create new emergent states. Standard ensemble theory can break down as we demonstrate in a simple model reminiscent of complex systems where new collective states emerge. We present an axiomatically defined entropy and argue that it is extensive in the micro-canonical, equal probability, and canonical (max-entropy) ensemble for super-exponentially growing phase spaces. This entropy may be useful in determining probability measures in analogy with how statistical mechanics establishes statistical ensembles by maximising entropy.

  • Journal article
    Palmieri L, Jensen HJ, 2018,

    The emergence of weak criticality in SOC systems

    , EPL, Vol: 123, ISSN: 0295-5075

    Since Self-Organised Criticality (SOC) was introduced in 1987, both the nature of the self-organisation and the criticality have remained controversial. Besides, SOC-like dynamics has recently been observed in many natural processes like brain activity and rain precipitations, making a better understanding of such systems more urgent. Here we focus on the Drossel-Schwabl forest-fire model (FFM) of SOC and show that despite the model is not critical, it nevertheless exhibits a behaviour that justifies the introduction of a new kind of weak criticality. We present a method that allows to quantify the degree of criticality of a system and to introduce a new class of critical systems. This method can be easily adapted to experimental settings and contribute to a better understanding of real systems.

  • Journal article
    Cofré R, Maldonado C, Rosas De Andraca F, 2018,

    Large deviations properties of maximum entropy Markov chains from spike trains

    , Entropy, Vol: 20, ISSN: 1099-4300

    We consider the maximum entropy Markov chain inference approach to characterize the collective statistics of neuronal spike trains, focusing on the statistical properties of the inferred model. To find the maximum entropy Markov chain, we use the thermodynamic formalism, which provides insightful connections with statistical physics and thermodynamics from which large deviations properties arise naturally. We provide an accessible introduction to the maximum entropy Markov chain inference problem and large deviations theory to the community of computational neuroscience, avoiding some technicalities while preserving the core ideas and intuitions. We review large deviations techniques useful in spike train statistics to describe properties of accuracy and convergence in terms of sampling size. We use these results to study the statistical fluctuation of correlations, distinguishability, and irreversibility of maximum entropy Markov chains. We illustrate these applications using simple examples where the large deviation rate function is explicitly obtained for maximum entropy models of relevance in this field.

  • Journal article
    Cofré R, Maldonado C, Rosas F, 2018,

    Large Deviations Properties of Maximum Entropy Markov Chains from Spike Trains

    , Entropy, Vol: 20, Pages: 573-573

    <jats:p>We consider the maximum entropy Markov chain inference approach to characterize the collective statistics of neuronal spike trains, focusing on the statistical properties of the inferred model. To find the maximum entropy Markov chain, we use the thermodynamic formalism, which provides insightful connections with statistical physics and thermodynamics from which large deviations properties arise naturally. We provide an accessible introduction to the maximum entropy Markov chain inference problem and large deviations theory to the community of computational neuroscience, avoiding some technicalities while preserving the core ideas and intuitions. We review large deviations techniques useful in spike train statistics to describe properties of accuracy and convergence in terms of sampling size. We use these results to study the statistical fluctuation of correlations, distinguishability, and irreversibility of maximum entropy Markov chains. We illustrate these applications using simple examples where the large deviation rate function is explicitly obtained for maximum entropy models of relevance in this field.</jats:p>

  • Journal article
    Goto H, Viegas E, Jensen HJ, Takayasu H, Takayasu Met al., 2018,

    Smoluchowski equation for networks: merger induced intermittent giant node formation and degree gap

    , Journal of Statistical Physics, Vol: 172, Pages: 1086-1100, ISSN: 1572-9613

    The dynamical phase diagram of a network undergoing annihilation, creation, and coagulation of nodes is found to exhibit two regimes controlled by the combined effect of preferential attachment for initiator and target nodes during coagulation and for link assignment to new nodes. The first regime exhibits smooth dynamics and power law degree distributions. In the second regime, giant degree nodes and gaps in the degree distribution are formed intermittently. Data for the Japanese firm network in 1994 and 2014 suggests that this network is moving towards the intermittent switching region.

  • Conference paper
    Azari MM, Rosas De Andraca FE, Pollin S, 2018,

    Reshaping cellular networks for the sky: major factors and feasibility

    , 2018 IEEE International Conference on Communications (ICC), Publisher: IEEE, ISSN: 1938-1883

    This paper studies the feasibility of supporting drone operations using existent cellular infrastructure. We propose an analytical framework that includes the effects of base station (BS) height and antenna radiation pattern, drone antenna directivity and various propagation environments. With this framework, we derive an exact expression for the coverage probability of ground and drone users through a practical cell association strategy. Our results show that a carefully designed network can control the radiated interference that is received by the drones, and therefore guarantees a satisfactory quality of service. Moreover, as the network density grows the increasing level of interference can be partially managed by lowering the drone flying altitude. However, even at optimal conditions the drone coverage performance converges to zero considerably fast, suggesting that ultra-dense networks might be poor candidates for serving aerial users.

  • Journal article
    Garcia Millan R, Pruessner G, Pickering L, Christensen Ket al., 2018,

    Correlations and hyperuniformity in the avalanche size of the Oslo Model

    , Europhysics Letters: a letters journal exploring the frontiers of physics, Vol: 122, ISSN: 1286-4854

    Certain random processes display anticorrelations resulting in local Poisson-like disorder and global order, where correlations suppress fluctuations. Such processes are called hyperuniform. Using a map to an interface picture we show via analytic calculations that a sequence of avalanche sizes of the Oslo model is hyperuniform in the temporal domain with the minimal exponent $\lambda=0$ . We identify the conserved quantity in the interface picture that gives rise to the hyperuniformity in the avalanche size. We further discuss the fluctuations of the avalanche size in two variants of the Oslo model. We support our findings with numerical results.

  • Conference paper
    Azari MM, Rosas F, Chiumento A, Ligata A, Pollin Set al., 2018,

    Uplink performance analysis of a drone cell in a random field of ground interferers

    , 2018 IEEE Wireless Communications and Networking Conference (WCNC), Publisher: Institute of Electrical and Electronics Engineers, ISSN: 1558-2612

    Aerial base stations are a promising technology to increase the capabilities of existing communication networks. However, existing analytical frameworks do not sufficiently characterize the impact of ground interferers on aerial base stations. In order to address this issue, we model the effect of interference coming from coexisting ground networks on the aerial link, which could be the uplink of an aerial cell served by a drone base station. By considering a Poisson field of ground interferers, we characterize aggregate interference experienced by the drone. This result includes the effect of drone antenna pattern, the height-dependent shadowing, and various types of environment. We show that benefits a drone obtains from a better line-of-sight (LoS) at high altitudes is counteracted by a high vulnerability to the interference coming from ground. However, by deriving link coverage probability and transmission rate we show that a drone base station is still a promising technology if the overall system is properly dimensioned according to given density and transmission power of interferers. Particularly, our results illustrate how benefits of such network is maximized by defining the optimal drone altitude and signal-to-interference (SIR) requirement.

  • Conference paper
    Rosas F, Chen K-C, Gunduz D, 2018,

    Social diversity for reducing the impact of information cascades on social learning

    Collective behavior in online social media and networks is known to becapable of generating non-intuitive dynamics associated with crowd wisdom andherd behaviour. Even though these topics have been well-studied in socialscience, the explosive growth of Internet computing and e-commerce makes urgentto understand their effects within the digital society. In this work we explorehow the stochasticity introduced by social diversity can help agents involvedin a inference process to improve their collective performance. Our resultsshow how social diversity can reduce the undesirable effects of informationcascades, in which rational agents choose to ignore personal knowledge in orderto follow a predominant social behaviour. Situations where social diversity isnever desirable are also distinguished, and consequences of these findings forengineering and social scenarios are discussed.

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