The arrow of time paradox between quantum mechanics and thermodynamicsarises from the fundamental conflict between the time-symmetric evolution of thewave function and the irreversible increase of thermodynamic entropy. This pa?per introduces a ”small observer” model with quantum resolution capabilities andcombines quantum measurement theory with open quantum system dynamics toreveal the influence of observer scales on the perception of the arrow of time. Byestablishing a quantum master equation model for N coupled small observers, wedemonstrate the emergence of macroscopic thermodynamic entropy from micro?scopic quantum entropy production, providing a novel theoretical framework forunifying the understanding of the arrow of time. Numerical simulations based onthe quantum Darwinism framework validate the theoretical predictions.
The arrow of time paradox between quantum mechanics and thermodynamicsarises from the fundamental conflict between the time-symmetric evolution of thewave function and the irreversible increase of thermodynamic entropy. This pa?per introduces a ”small observer” model with quantum resolution capabilities andcombines quantum measurement theory with open quantum system dynamics toreveal the influence of observer scales on the perception of the arrow of time. Byestablishing a quantum master equation model for N coupled small observers, wedemonstrate the emergence of macroscopic thermodynamic entropy from micro?scopic quantum entropy production, providing a novel theoretical framework forunifying the understanding of the arrow of time. Numerical simulations based onthe quantum Darwinism framework validate the theoretical predictions.
I give an explanation of the thermodynamic arrow-of-time (namely entropy increases with time) within a quantum mechanical framework. This entails giving a solution to the Loschmidt paradox, i.e. showing how an irreversible macro-dynamics can arise from a reversible micro-dynamics. I argue that, in accordance to the reversible dynamics, both entropy-increasing and entropy-decreasing transformations take place, but entropy-decreasing transformations cannot leave any information of their having happened. This is indistinguishable from their not having happened at all. The second law of thermodynamics is then reduced to a tautology: the only transformations that can be seen are those where entropy does not decrease. However, typicality arguments seem to prevent this argument to be used as a complete solution to the arrow-of-time dilemma: it might still be necessary to postulate a low entropy initial state for the system under consideration.
The concept of time presents a profound challenge at the intersection of quantum mechanics and thermodynamics. While fundamental microscopic laws are largely time-symmetric, macroscopic phenomena universally exhibit a distinct thermodynamic arrow of time, characterized by increasing entropy. This paper explores the hypothesis that quantum entanglement plays a crucial role in the emergence of this thermodynamic arrow. We review how the entanglement between a quantum system and its environment leads to decoherence, effectively driving the system towards a state of higher entropy and classical-like behavior. By analyzing concepts such as von Neumann entropy, entanglement entropy, and the Page-Wootters mechanism, we propose a theoretical framework where the degradation and spreading of entanglement act as the underlying mechanism for the perceived unidirectional flow of time. This approach offers a potential resolution to the "problem of time" in quantum gravity and provides a unified perspective on the genesis of irreversibility from the inherently reversible laws of quantum mechanics. We discuss the implications of this entanglement-driven temporal emergence for our understanding of the universe's initial low-entropy state and the fundamental nature of reality.
We propose a speculative but quantitatively constrained phenomenological framework in which the thermodynamic arrow of time emerges from entropy-dependent decoherence in open quantum systems. Higher environmental entropy strengthens decoherence, preferentially de- stroying quantum coherence in one temporal direction, thus providing a microscopic mechanism for irreversibility. The formalism is constructed within an effective Lindblad master-equation approach, recovering unitary quantum mechanics and standard thermodynamics in appropriate limits. A toy two-level system illustrates the emergence of coherence decay and an effective microscopic arrow of time.
Why does time seem to have a direction when the microscopic laws do not? This paper gives a rigorous answer. We show that if you look at a system at a fixed resolution where its dynamics are reversible and satisfy a standard regularity condition (a log–Sobolev inequality), then there is no intrinsic arrow of time: entropy production is exactly balanced by an equal “ordering flux,” a state we call entropy–order balance (EOB). The arrow appears only when we observe the system through a lossy filter—such as averaging, ignoring variables, or tracing out an environment. Mathematically, this is a channel that merges many microscopic states into the same observed outcome and therefore forces a one-way loss of distinguishability. The main result is an Arrow Structure Theorem: an arrow of time exists at a given resolution if and only if the observation map is genuinely irreversible in a precise information-theoretic sense. We quantify its strength using a new, scale-dependent number—the arrow intensity As(O;t)∈[0,1]A_s(O;t) \in [0,1]As(O;t)∈[0,1]—which measures how much distinguishability is lost and behaves like a resource that can only increase under further coarse-graining. The same mechanism applies in both the classical and quantum cases and allows one to predict and measure how quickly an observed description forgets details, and to compare the strength of the arrow across platforms using a single information-theoretic yardstick. Conceptually, the work separates what the world does from what we access and provides a structural resolution of Loschmidt’s paradox: the arrow is not a property of the microscopic laws, but of the lossy channels through which we observe them.
The modern classical statistical physics, thermodynamics, quantum mechanics and gravity theory are developed and well-known theories. The described theories are developed and well studied for a long time. Nevertheless, it contains a number of paradoxes. It forces many scientists to doubt internal consistency of these theories. However, the given paradoxes can be resolved within the framework of the existing physics, without introduction of new laws. Further, in this paper we discuss the paradoxes underlying classical statistical physics, thermodynamics, quantum mechanics, and non-quantum and quantum gravities. We suggest the approaches to solution of these paradoxes on basis universal arrow of time. The first one relies on the influence of the external observer (environment), which disrupts the correlations in the system and results in time arrows alignment. The basis of the second one is the limits of self-knowledge of the system in case of the observed system; the external observer and the environment are included in the considered system. We introduce the concepts of observable dynamics, ideal dynamics, and unpredictable dynamics. We contemplate the phenomenon of complex (living) systems from the point of view of these dynamics. Perspectives of practical use of Unpredictable systems for artificial intellect are considered. c Chapter 1. The Universal Arrow of Time: Classical Mechanics. Abstract: Solution of paradox for the entropy increase in reversible systems. Statistical physics cannot explain why the thermodynamic time arrow does exist un- less very special and so it postulates unnatural initial conditions. However, we are ready to state that statistical physics is able to explain why the thermodynamic time arrow is
Abstract Quantum mechanics for describing the behavior of microscopic entities and thermodynamics for describing macroscopic systems exhibit separate time concepts. Whereas many theories of modern physics interpret processes as reversible, in thermodynamics, an expression for irreversibility and the so-called time arrow has been developed: the increase of entropy. The divergence between complete reversibility on the one hand and irreversibility on the other is called the paradox of time. Since more than hundred years many efforts have been devoted to unify the time concepts. So far, the efforts were not successful. In this paper a solution is proposed on the basis of matter-energy equivalence with an energetic distinction between matter and mass. By refraining from interpretations predominant in modern theoretical physics, the first and second laws of thermodynamics can be extended to fundamental laws of nature, which are also valid at quantum level.