Broken detailed balance and entropy production in the human brain

Living systems break detailed balance at small scales, consuming energy and producing entropy in the environment to perform molecular and cellular functions. However, it remains unclear how broken detailed balance manifests at macroscopic scales and how such dynamics support higher-order biological functions. Here we present a framework to quantify broken detailed balance by measuring entropy production in macroscopic systems. We apply our method to the human brain, an organ whose immense metabolic consumption drives a diverse range of cognitive functions. Using whole-brain imaging data, we demonstrate that the brain nearly obeys detailed balance when at rest, but strongly breaks detailed balance when performing physically and cognitively demanding tasks. Using a dynamic Ising model, we show that these large-scale violations of detailed balance can emerge from fine-scale asymmetries in the interactions between elements, a known feature of neural systems. Together, these results suggest that violations of detailed balance are vital for cognition and provide a general tool for quantifying entropy production in macroscopic systems.

Evaluating Belief System Networks as a Theory of Political Belief System Dynamics

A theory of political belief system dynamics should incorporate causal connections between elements of the belief system and the possibility that belief systems are influenced by exogenous factors. These necessary components can be satisfied by conceptualizing an individual’s belief system as a network of causally connected attitudes and identities which, via the interactions between the elements and the push of exogenous influences, produces the disparate phenomena in the belief systems literature. We implement this belief systems as networks theory in a dynamic Ising model and demonstrate that the theory can integrate at least six otherwise unrelated phenomenon in the political belief systems literature, including work on attitude consistency, cross-pressures, spillover effects, partisan cues, and ideological differences in attitude consensus. Our findings suggest that belief systems are not just one thing, but emerge from the interactions between the attitudes and identities in the belief system. All code is available: https://osf.io/aswy8/?view_only=99aff77909094bddabb5d382f6db2622 .

Evaluating Belief System Networks as a Theory of Political Belief System Dynamics

A theory of political belief system dynamics should incorporate causal connections between elements of the belief system and the possibility that belief systems are influenced by exogenous factors. These necessary components can be satisfied by conceptualizing an individual’s belief system as a network of causally connected attitudes and identities which, via the interactions between the elements and the push of exogenous influences, produces the disparate phenomena in the belief systems literature. We implement this belief systems as networks theory in a dynamic Ising model and demonstrate that the theory can integrate at least six otherwise unrelated phenomenon in the political belief systems literature, including work on attitude consistency, cross-pressures, spillover effects, partisan cues, and ideological differences in attitude consensus. Our findings suggest that belief systems are not just one thing, but emerge from the interactions between the attitudes and identities in the belief system. All code is available: https://osf.io/aswy8/?view_only=2bebd3d0eabd4bc3b44fc1890bbf115e

Monte Carlo Simulations of Short-Time Critical Dynamics

Monte Carlo simulations of the short-time critical dynamics are reviewed. The short-time universal scaling behavior of the dynamic Ising model and Potts model are discussed in detail, while extension and application to more complex systems as the XY model, the fully frustrated XY model and other dynamic systems are also presented. The investigation of the universal behavior of the short-time dynamics not only enlarges the fundamental knowledge on critical phenomena but also, more interestingly, provides possible new ways to determine not only the new critical exponents θ and θ1, but also the traditional dynamic critical exponent z as well as all static critical exponents.