Information-theoretic sensitivity analysis: a general method for credit assignment in complex networks

Most systems can be represented as networks that couple a series of nodes to each other via one or more edges, with typically unknown equations governing their quantitative behaviour. A major question then pertains to the importance of each of the elements that act as system inputs in determining the output(s). We show that any such system can be treated as a ‘communication channel’ for which the associations between inputs and outputs can be quantified via a decomposition of their mutual information into different components characterizing the main effect of individual inputs and their interactions. Unlike variance-based approaches, our novel methodology can easily accommodate correlated inputs

Model for the hydration of non-polar compounds and polymers

We introduce an exactly solvable statistical-mechanical model of the hydration of non-polar compounds, based on grouping water molecules in clusters where hydrogen bonds and isotropic interactions occur; interactions between clusters are neglected. Analytical results show that an effective strengthening of hydrogen bonds in the presence of the solute, together with a geometric reorganization of water molecules, are enough to yield hydrophobic behavior. We extend our model to describe a non-polar homopolymer in aqueous solution, obtaining a clear evidence of both ``cold'' and ``warm'' swelling transitions. This suggests that our model could be relevant to describe some features of protein folding.Comment: REVTeX, 6 pages, 3 figure

Noncommutative Self-dual Gravity

Starting from a self-dual formulation of gravity, we obtain a noncommutative theory of pure Einstein theory in four dimensions. In order to do that, we use Seiberg-Witten map. It is shown that the noncommutative torsion constraint is solved by the vanishing of commutative torsion. Finally, the noncommutative corrections to the action are computed up to second order.Comment: 15+1 pages, LaTeX, no figure

Landau Analog Levels for Dipoles in the Noncommutative Space and Phase Space

In the present contribution we investigate the Landau analog energy quantization for neutral particles, that possesses a nonzero permanent magnetic and electric dipole moments, in the presence of an homogeneous electric and magnetic external fields in the context of the noncommutative quantum mechanics. Also, we analyze the Landau--Aharonov--Casher and Landau--He--McKellar--Wilkens quantization due to noncommutative quantum dynamics of magnetic and electric dipoles in the presence of an external electric and magnetic fields and the energy spectrum and the eigenfunctions are obtained. Furthermore, we have analyzed Landau quantization analogs in the noncommutative phase space, and we obtain also the energy spectrum and the eigenfunctions in this context.Comment: 20 pages, references adde

Noncommutative Topological Theories of Gravity

The possibility of noncommutative topological gravity arising in the same manner as Yang-Mills theory is explored. We use the Seiberg-Witten map to construct such a theory based on a SL(2,C) complex connection, from which the Euler characteristic and the signature invariant are obtained. This gives us a way towards the description of noncommutative gravitational instantons as well as noncommutative local gravitational anomalies.Comment: 17+1 pages, LaTeX, no figures, some clarifications, comments and references added, style improve

Effects of a nanoscopic filler on the structure and dynamics of a simulated polymer melt and the relationship to ultra-thin films

We perform molecular dynamics simulations of an idealized polymer melt surrounding a nanoscopic filler particle to probe the effects of a filler on the local melt structure and dynamics. We show that the glass transition temperature $T_g$ of the melt can be shifted to either higher or lower temperatures by appropriately tuning the interactions between polymer and filler. A gradual change of the polymer dynamics approaching the filler surface causes the change in the glass transition. We also find that while the bulk structure of the polymers changes little, the polymers close to the surface tend to be elongated and flattened, independent of the type of interaction we study. Consequently, the dynamics appear strongly influenced by the interactions, while the melt structure is only altered by the geometric constraints imposed by the presence of the filler. Our findings show a strong similarity to those obtained for ultra-thin polymer films (thickness $\lesssim 100$ nm) suggesting that both ultra-thin films and filled-polymer systems might be understood in the same context

Physical and emotional nourishment: Food as the embodied component of loving care of elderly family relatives

Purpose This purpose of this study is to examine the fluidity of family life which continues to attract attention. This is increasingly significant for the intergenerational relationship between adult children and their elderly parents. Using practice theory, the aims are to understand the role of food in elderly families and explore how family practices are maintained when elderly transition into care. Design/methodology/approach A phenomenological research approach was used as the authors sought to build an understanding of the social interactions between family and their lifeworld. Findings This study extends theory on the relationship between the elderly parent and their family and explores through practice theory how families performed their love, how altered routines and long standing rituals provided structure to the elderly relatives and how care practices were negotiated as the elderly relatives transitioned from independence to dependence and towards care. A theoretical framework is introduced that provides guidance for the transition stages and the areas for negotiation. Research limitations/implications This research has implications for food manufacturers and marketers, as the demand for healthy food for the elderly is made more widely available, healthy and easy to prepare. The limitations of the research are due to the sample located in East Yorkshire only. Practical implications This research has implications for brand managers of food manufacturers and supermarkets that need to create product lines that target this segment by producing healthy, convenience food. Social implications It is also important for health and social care policy as the authors seek to understand the role of food, family and community and how policy can be devised to provide stability in this transitional and uncertain lifestage. Originality/value This research extends the body of literature on food and the family by focussing on the elderly cared for and their family. The authors show how food can be construed as loving care, and using practice theory, a theoretical framework is developed that can explain the transitions and how the family negotiates the stages from independence to dependence

Physical and emotional nourishment: Food as the embodied component of loving care of elderly family relatives

Purpose This purpose of this study is to examine the fluidity of family life which continues to attract attention. This is increasingly significant for the intergenerational relationship between adult children and their elderly parents. Using practice theory, the aims are to understand the role of food in elderly families and explore how family practices are maintained when elderly transition into care. Design/methodology/approach A phenomenological research approach was used as the authors sought to build an understanding of the social interactions between family and their lifeworld. Findings This study extends theory on the relationship between the elderly parent and their family and explores through practice theory how families performed their love, how altered routines and long standing rituals provided structure to the elderly relatives and how care practices were negotiated as the elderly relatives transitioned from independence to dependence and towards care. A theoretical framework is introduced that provides guidance for the transition stages and the areas for negotiation. Research limitations/implications This research has implications for food manufacturers and marketers, as the demand for healthy food for the elderly is made more widely available, healthy and easy to prepare. The limitations of the research are due to the sample located in East Yorkshire only. Practical implications This research has implications for brand managers of food manufacturers and supermarkets that need to create product lines that target this segment by producing healthy, convenience food. Social implications It is also important for health and social care policy as the authors seek to understand the role of food, family and community and how policy can be devised to provide stability in this transitional and uncertain lifestage. Originality/value This research extends the body of literature on food and the family by focussing on the elderly cared for and their family. The authors show how food can be construed as loving care, and using practice theory, a theoretical framework is developed that can explain the transitions and how the family negotiates the stages from independence to dependence

Black hole thermodynamical entropy

As early as 1902, Gibbs pointed out that systems whose partition function diverges, e.g. gravitation, lie outside the validity of the Boltzmann-Gibbs (BG) theory. Consistently, since the pioneering Bekenstein-Hawking results, physically meaningful evidence (e.g., the holographic principle) has accumulated that the BG entropy $S_{BG}$ of a $(3+1)$ black hole is proportional to its area $L^2$ ($L$ being a characteristic linear length), and not to its volume $L^3$. Similarly it exists the \emph{area law}, so named because, for a wide class of strongly quantum-entangled $d$-dimensional systems, $S_{BG}$ is proportional to $\ln L$ if $d=1$, and to $L^{d-1}$ if $d>1$, instead of being proportional to $L^d$ ($d \ge 1$). These results violate the extensivity of the thermodynamical entropy of a $d$-dimensional system. This thermodynamical inconsistency disappears if we realize that the thermodynamical entropy of such nonstandard systems is \emph{not} to be identified with the BG {\it additive} entropy but with appropriately generalized {\it nonadditive} entropies. Indeed, the celebrated usefulness of the BG entropy is founded on hypothesis such as relatively weak probabilistic correlations (and their connections to ergodicity, which by no means can be assumed as a general rule of nature). Here we introduce a generalized entropy which, for the Schwarzschild black hole and the area law, can solve the thermodynamic puzzle.Comment: 7 pages, 2 figures. Accepted for publication in EPJ

Categorizing Different Approaches to the Cosmological Constant Problem

We have found that proposals addressing the old cosmological constant problem come in various categories. The aim of this paper is to identify as many different, credible mechanisms as possible and to provide them with a code for future reference. We find that they all can be classified into five different schemes of which we indicate the advantages and drawbacks. Besides, we add a new approach based on a symmetry principle mapping real to imaginary spacetime.Comment: updated version, accepted for publicatio