The flow of time from the past to the future is a central feature of the world we experience.But exactly how this phenomenon, known as the arrow of time, arises from microscopic interactions between particles and cells remains a mystery – researchers at the CUNY Graduate Center for Theoretical Sciences (ITS) program are helping to solve the problem. Open a new paper in the journal Physical Review Letters. These findings could have important implications for multiple disciplines including physics, neuroscience and biology.
Fundamentally, the arrow of time stems from the second law of thermodynamics: the principle by which the microscopic arrangement of physical systems tends to increase in randomness, from order to disorder. The more disordered a system is, the harder it is to get back into order, and the more powerful the arrow of time is. In short, the chaotic tendency of the universe is the fundamental reason why we experience the flow of time in one direction.
“Two questions for our team are, if we look at a particular system, can we quantify the strength of its arrow of time, and whether we can sort out how it emerges from the microscopic scale, where cells and neurons interact, The whole system?” said Christopher Lynn, lead author of the paper and a postdoctoral researcher in the ITS program. “Our findings provide the first step in understanding how the arrow of time that we experience in our daily lives emerges from these more microscopic details.”
To begin answering these questions, the researchers explored how to break down the arrow of time by looking at specific parts of the system and how they interact. For example, these parts may be neurons that function within the retina.Looking at a moment, they show that the arrow of time can be broken down into different parts: parts that result from parts that work individually, in pairs, triplets, or more complex configurations
With this method of breaking down the arrows of time, the researchers analyzed existing experiments on how salamander retinal neurons responded to different movies. In one film, an object moves randomly across the screen, while another depicts the full complexity of a scene in nature. In both films, the researchers found that the arrows of time came from simple interactions between pairs of neurons, rather than large, complex groups. Surprisingly, the team also observed that when viewing random motion, the retina showed a stronger arrow of time than in natural scenes. The latter finding raises the question of how our internal perception of the arrow of time aligns with the external world, Lynn said.
“These results may be of particular interest to neuroscience researchers,” Lynn said. “For example, they could come to an answer as to whether the arrow of time functions differently in atypical neuronal brains.”
“Chris’s decomposition of local irreversibility — also known as the arrow of time — is an elegant general framework that can shed new light on the exploration of many high-dimensional, non-equilibrium systems,” said David, professor of physics and biology Schwab said. Graduate Center and Principal Investigator of the study.
Characterizing the “arrow of time” in open quantum systems
Decompose local time arrows in interactive systems, Physical Review Letters (2022). journals.aps.org/prl/accepted/… 6a8ee4316350b055c80c, open Arxiv: arxiv.org/abs/2112.14721v1
Courtesy of the CUNY Graduate Center
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