The letter submitted is an executive summary of our previous paper. To solve the Einstein Podolsky Rosen “paradox” the two boundary quantum mechanics is taken as self consistent interpretation of quantum dynamics. The difficulty with this interpretation is to reconcile it with classical physics. To avoid macroscopic backward causation two “corresponding transition rules” are formulated which specify needed properties of macroscopic observations and manipulations. The apparent classical causal decision tree requires to understand the classically unchosen options. They are taken to occur with an “incomplete knowledge” of the boundary states typically in macroscopic considerations. The precise boundary conditions with given phases then select the actual measured path and this selection is mistaken to happen at the time of measurement. The apparent time direction of the decision tree originates in an assumed relative proximity to the initial state. Only the far away final state allows for classically distinct options to be selected from. Cosmologically the picture could correspond to a big bang initial and a hugely extended final state scenario. It is speculated that it might also hold for a big bang/big crunch world. If this would be the case the Born probability postulate could find a natural explanation if we coexist in the expanding and the correlated CPT conjugate contracting world.
The letter submitted is an executive summary of our previous paper. To solve the Einstein Podolsky Rosen “paradox” the two boundary quantum mechanics is taken as self consistent interpretation of quantum dynamics. The difficulty with this interpretation is to reconcile it with classical physics. To avoid macroscopic backward causation two “corresponding transition rules” are formulated which specify needed properties of macroscopic observations and manipulations. The apparent classical causal decision tree requires to understand the classically unchosen options. They are taken to occur with an “incomplete knowledge” of the boundary states typically in macroscopic considerations. The precise boundary conditions with given phases then select the actual measured path and this selection is mistaken to happen at the time of measurement. The apparent time direction of the decision tree originates in an assumed relative proximity to the initial state. Only the far away final state allows for classically distinct options to be selected from. Cosmologically the picture could correspond to a big bang initial and a hugely extended final state scenario. It is speculated that it might also hold for a big bang/big crunch world. If this would be the case the Born probability postulate could find a natural explanation if we coexist in the expanding and the correlated CPT conjugate contracting world.
Modern physics is built on the assumption that time only moves one way, beginning at the initial boundary (or initial condition), fixed effectively at the Big Bang. Our theories begin at that starting point and evolve from there. Yet the laws of nature work both forward and backward. This one-way view lies at the root of many of physics’ biggest puzzles, like wavefunction collapse, quantum “spookiness,” the arrow of time, and the clash between quantum mechanics and relativity. Two-Boundary Theory (2BT) proposes a minimal correction: the universe is a unique four-dimensional history jointly constrained by two real temporal boundaries, an initial (α) and a final (Ω). No new dynamics or hidden variables are added; the same lawful evolution operates in both directions, and the realized world is the intersection of the forward image of α with the backward image of Ω. From within time, partial knowledge of α and ignorance of Ω make outcomes appear stochastic and the future “open,” though the underlying history is globally deterministic and locally causal. This two-sided admissibility resolves the major paradoxes in a single move: Bell-level correlations arise from whole-trajectory consistency rather than superluminal influence; measurement collapse becomes an epistemic update, not a physical jump; and the arrow of time reflects asymmetric boundary information, not asymmetric law. The analysis preserves unitarity, covariance, and conservation principles intact. The paper confines itself to the conceptual and ontological core of the framework; later work develops the informational field Φ(t) and weighted-operator formalism that implement the same constraint mathematically. The result is an Ockham-minimal, time-symmetric completion of the scientific worldview: one reversible law, two boundaries, one consistent universe.
The conventional explanation of delayed-choice experiments appears to violate our causal intuition at the quantum level. I reanalyze these experiments using time-reversed and time-symmetric formulations of quantum mechanics. The time-reversed formulation does not give the same experimental predictions. The time-symmetric formulation gives the same experimental predictions but actually violates our causal intuition at the quantum level. I explore the reasons why our causal intuition may be wrong at the quantum level, suggest how conventional causation might be recovered in the classical limit, propose a quantum analog to the classical block universe viewpoint, and speculate on implications of the time-symmetric formulation for cosmological boundary conditions.
This article explores models of causality of the physical universe which extend beyond the usual quantum and classical descriptions. To facilitate discussion of this topic, a brief review of relevant areas of modern physics is included. Although mathematical logic is not directed in time, the causal description of the physical universe is classically performed in terms of temporal determinism, an initial-value problem in which subsequent states are determined through the action of differential equations, thus avoiding the paradox of effects preceding their causes. Quantum mechanics has reduced this description to the status of a stochastic-causal theory, in which individual future states of a system are not predictable because the probability interpretation of the wave function prevents a complete knowledge of a single reduction of the wave packet. The transactional interpretation of quantum mechanics provides a basis for examining the workings of stochastic causality in terms of time-symmetri c advanced and retarded waves. Cosmic symmetry-breaking provides a contrasting description in which time-directed phenomena derive their explanation. Dual-time supercausality replaces the stochastic model with one in which two complementary causal processes, symmetric- time and directed-time are operating. The mode of interaction of these avoids temporal paradox in the time- directed description, and also explains why quantum mechanics provides an incomplete stochastic model. An important role for supercausal processes in the structural evolution of the universe is proposed, including the emergence of biosystems, biological evolution, and consciousness. 1 : CAUSALITIES AND SUPERCAUSALITIES Since the development of calculus and the Newtonian model of the universe, the evolution of dynamical events has been described through the directional application of time as a parameter. The evolution of a classical system can in principle be causally described in terms of the initial conditions and the differential equations governing its action. In the classical Laplacian universe, the initial conditions and the dynamical equations taken together completely specify the ongoing state at subsequent times. We will refer to this model as temporal determinism. The classical Hamiltonian and Lagrangian dynamical equations are both expressed as differential equations expressing generalized coordinates in terms of increasing time, where = T - V and in the case of a potential, = T + V, giving the total ( T kinetic & V potential ) energy :
This preprint is part of a three-paper series exploring physical realization as a temporally organized process constrained by relativistic causality. The present paper addresses quantum outcome realization. Standard quantum mechanics provides a complete and accurate description of state evolution but does not specify how physical outcomes are realized within an already structured world. In this work, a strict separation is made between quantum dynamics and realization. No modification of the Schrödinger equation, operators, or measurement formalism is introduced. A minimal global temporal constraint, T= L / c, is proposed as an organizational condition on realization, arising directly from finite causal connectivity. Quantum states are interpreted as spaces of possible realizations, while actual outcomes emerge through selection constrained by global phase compatibility with previously realized structure. Within this framework, the Born rule appears as the unique statistically stable distribution of realizations required for consistency across composite systems, rather than as a postulate of dynamics. The approach preserves quantum indeterminacy, introduces no hidden variables, and provides a unified account of realization across quantum and macroscopic regimes.
Modern physics faces a constellation of foundational puzzles: the Big Bang singularity, time's arrow, dark matter and dark energy, the cosmological constant problem, fine-tuning, quantum measurement, and quantum gravity unification. This Perspective proposes a unified resolution grounded in complexity-driven selection from diverse quantum paths. Prior to the Big Bang, reality comprises a pre-temporal quantum substrate (lacking classical time coordinate but governed by unitary quantum evolution), evolving reversibly across multiple trajectories—including opposing time arrows. The Big Bang marks an emergence threshold (λ) where decoherence locks spacetime parameters, yielding our classical universe as a "survivor" of local emergence rather than a closed totality. Dark matter and dark energy represent unevolved quantum paths—residuals exerting gravitational influence without full manifestation. This framework reframes cosmology as the study of layered emergence, dissolving "why" questions into "when/how" selection dynamics, with testable predictions in CMB perturbations, quantum decoherence experiments, and gravitational wave observations. By shifting from reductionism to emergentism, it suggests a universal pattern: threshold-gated emergence from diverse substrates, applicable from the cosmos to consciousness.
Quantum mechanics has achieved unparalleled success as an operational theory, describing a wide range of experiments to remarkable accuracy. However, the physical foundations on which it rests remain as puzzling as they were a century ago, and a concise statement of the physical principles that underlie quantum mechanics is still outstanding. One promising approach holds that these principles should be formulated in terms of information, since many of the counter-intuitive effects in quantum theory concern questions such as what one can know about a quantum system and how the information encoded therein can be processed and distributed between parties. Another challenging feature of quantum theory is its incompatibility with the other cornerstone of modern physics, general relativity. In order to reconcile the two, one must identify and retain only the essential concepts and principles of each theory, and in the case of general relativity, causality has been identified as such a concept. This raises the question of how our classical understanding of causality must change when quantum theory is taken into account. In order to address these questions about information, knowledge and causality, I turn to the framework of causal models. In classical statistics, causal models explain the relations among a set of variables in terms of causal influences, which makes them a powerful tool for structuring our knowledge about complex systems and developing strategies for interacting with them. More importantly, the framework provides the conceptual underpinnings and mathematical methods for addressing questions about causation, information and knowledge in a rigorous manner. In this thesis, I develop a version of the classical causal models framework that is compatible with quantum theory and explore its physical implications. \n \n \nA first step is to define quantum versions of fundamental elements such as variables, conditionals and belief propagation rules. This allows one to consider the question of what one can come to know about a quantum variable from the point of view of causal modelling. The conditionals relating quantum variables are found to have a richer structure than their classical counterparts, which can be exploited for the task of discerning causal relations given limited data -- a central problem in classical causal modelling. The mathematical properties of quantum conditionals also establish a correspondence between various classes of two-party correlations, such as bound and distillable entanglement, and the types of causal structures that can give rise to them, which may become a useful tool for entanglement theory and quantum information processing. In the context of open quantum systems dynamics, quantum causal models provide a clear physical explanation of not completely positive maps and, more broadly, of non-Markovian quantum dynamics. Finally, I consider the possibility of non-classical effects in the way that different causal mechanisms are combined -- that is, non-classical causal structures. For the simple case of two causally ordered variables, I propose indicators that witness different classes of combinations of causal mechanisms, including a non-classical mixture, and describe an experiment realizing examples of the different classes. \n \n \nAs these results illustrate, the framework of quantum causal models provides both greater conceptual clarity and a comprehensive mathematical formalism for studying a diverse set of problems, ranging from foundational questions to applications in open systems dynamics and the exploration of non-classical causal structures, which are likely to feature in a future theory of quantum gravity. The material presented in this thesis is intended as a foundation and inspiration for further applications of quantum causal models.