information

The Reversibility Problem

March 1, 2022

This is my exploration into formalizing the reversibility problem, i.e. the question “Which processes are reversible?” My long term goals are to, formally define what it means for any process to be reversible, regardless of equilibrium considerations; clarify the connection between information and reversibility (and by extension the connection between information and entropy); clarify (make well defined) the meaning of statements like “breaking a glass is irreversible because the entropy of the broken glass is higher than the entropy of the unbroken glass,” and “the entropy of the universe is monotonically increasing.” …

Why Doesn't Uncopying Defeat The 2nd Law?

February 17, 2022

In Is The Szilard Cycle Reversible? I pondered whether uncopying a bit of information at the end of the Szilard cycle makes the full cycle reversible, apparently getting around the 2nd law. This “loophole” is more much pervasive to thermodynamics than the Szilard engine. I will go through its generalization in #Maxwell’s Superdemon. I assume the 2nd law holds, so in #Slaying The Superdemon I consider some possible reasons why this loophole doesn’t work. …

Is The Szilard Cycle Reversible?

February 9, 2022

This is a long-winded attempt at formulating a question about thermodynamics. I will first give a high level #Overview of what this post is about, and then go through the technical details in the subsequent sections. Feel free to otherwise skip directly to #Part I Uncopying if you’d rather jump right in. The question is stated at the bottom: #Question. …

Redundancy And Copying

June 23, 2021

Information in our universe can be copied, as evidenced by the ubiquitous copying of computer memory, books and paper everywhere, and our ability to non-destructively see and hear everything around us. Information is copied (or cloned) when the state of one system, the target, becomes correlated with the state of another system, the source, without destructively altering the state of the source. Information is moved, on the other hand, when the state of the source is transferred to the target in a way that leaves the source’s state erased or overwritten with something else. In general, information copying between two systems is a special case of increasing information redundancy between two systems. …

Causality And Information

May 23, 2021

In Causality For Physics, I introduced Pearlian interventions for physical systems that evolve over time. In Physical Information, I defined what it means for a system to have information. Here, I will merge these threads and talk about what it means for a system to have causal effect, and the connection with information. …

Physical Information

May 14, 2021

I will apply to abstract physics the same information algebra I introduced in Bayesian information theory and further developed in Information Algebra. Bayesian information is just information from the perspective of an agent that may have or not have particular information. Below, I will introduce the notion of a physical system having or not having information about itself or other systems (regardless of whether or not it has agenty attributes), and the same information algebra will apply. The only difference is a shift from the 1st person to 3rd person perspective. …