Mahler has written many papers on the geometry of numbers. Arguably, his most influential achievements in this area are his compactness theorem for lattices, his work on star bodies and their critical lattices, and his estimates for the successive minima of reciprocal convex bodies and compound convex bodies. We give a, by far not complete, overview of Mahler’s work on these topics and their impact.

Whereas for many truths, truthmaker theory offers a plausible account, there are certain kinds of truths for which the theory seems less helpful: principally (though not exclusively) analytic truths. I argue that an augmentation of the usual idea of truthmakers can solve this problem. Moreover that once solved we are able to look afresh at the nature of mathematics, whether conceived as analytic or synthetic, necessary or contingent, and reduce the ontological options. I also argue that it was Quine’s reformulation of analyticity, deployed in place of the correct Leibniz-Wolff-Kant account, which led to his holistic account of knowledge and pragmatist account of scientific revisability.

Our collective views regarding the question “what is fundamental?” are continually evolving. These ontological shifts in what we regard as fundamental are largely driven by theoretical advances (“what can we calculate?”), and experimental advances (“what can we measure?”). Rarely (in my view) is epistemology the fundamental driver; more commonly epistemology reacts (after a few decades) to what is going on in the theoretical and experimental zeitgeist.

In The Hitchhiker’s Guide to the Galaxy, by Douglas Adams, the Answer to the Ultimate Question of Life, the Universe, and Everything is found to be 42 — but the meaning of this is left open to interpretation. We take it to mean that there are 42 fundamental questions which must be answered on the road to full enlightenment, and we attempt a first draft (or personal selection) of these ultimate questions, on topics ranging from the cosmological constant and origin of the universe to the origin of life and consciousness.

We argue that dualities offer new possibilities for relating fundamentality, levels, and emergence. Namely, dualities often relate two theories whose hierarchies of levels are inverted relative to each other, and so allow for new fundamentality relations, as well as for epistemic emergence. We find that the direction of emergence typically found in these cases is opposite to the direction of emergence followed in the standard accounts. Namely, the standard emergence direction is that of decreasing fundamentality: there is emergence of less fundamental, high-level entities, out of more fundamental, low-level entities. But in cases of duality, a more fundamental entity can emerge out of a less fundamental one. This possibility can be traced back to the existence of different classical limits in quantum field theories and string theories.

En este artículo intentamos dar cuenta de la relevancia de la tesis de Turing sobre el concepto de cálculo efectivo en relación con la tesis de Church sobre el mismo tema. Si bien ambas tesis son extensionalmente equivalentes y proporcionan, por lo tanto, una misma solución al Entscheidungsproblem de Hilbert, hay una especie de acuerdo en considerar que la formulación de Turing es la más satisfactoria o la más convincente. La pregunta es por qué se da tal acuerdo. En respuesta a esta pregunta destacamos la complejidad del Entscheidungsproblem e indagamos en qué medida las propuestas de Church y Turing captan dicha complejidad.

Modern mathematics is known for its rigorous proofs and tight analysis. Math is the paradigm of objectivity for most. We identify the source of that objectivity as our knowledge of the physical world given through our senses. We show in detail, for the core of modern mathematics, how modern mathematical formalism encapsulates deep realities about extension into a system of symbols and axiomatic rules. In particular, we proceed from the foundations in our senses to the natural numbers through integers, rational numbers, and real numbers, including introducing the concept of a field. An appendix shows how the formalism of complex numbers arises.

The notion of contextuality, which emerges from a theorem established by Simon Kochen and Ernst Specker (1960-1967) and by John Bell (1964-1966), is certainly one of the most fundamental aspects of quantum weirdness. If it is a questioning on scholastic philosophy and a study of contrafactual logic that led Specker to his demonstration with Kochen, it was a criticism of von Neumann’s “proof” that led John Bell to the result. A misinterpretation of this famous “proof” will lead them to diametrically opposite conclusions. Over the last decades, remarkable theoretical progresses have been made on the subject in the context of the study of quantum foundations and quantum information. Thus, the graphic generalizations of Cabello-Severini-Winter and Acin-Fritz-Leverrier-Sainz raise the question of the connection between non-locality and contextuality. It is also the case of the sheaf-theoretic approach of Samson Abramsky et al., which also invites us to compare contextuality with the logical structure of certain classical logical paradoxes.

We consider two generalizations of the Recursion Theorem, namely Visser’s ADN Theorem and Arslanov’s Completeness Criterion, and we prove a joint generalization of these theorems.

We present arguments to the effect that time and temperature can be viewed as a form of quantum entanglement. Furthermore, if temperature is thought of as arising from the quantum mechanical tunneling probability this then offers us a way of dynamically “converting” time into temperature based on the entanglement between the transmitted and reflected modes. We then show how similar entanglement-based logic can be applied to the dynamics of cosmological inflation and discuss the possibility of having observable effects of the early gravitational entanglement at the level of the universo.