Hemeroteca de la sección ‘Leyes’

Contextuality, Witness of Quantum Weirdness

Por • 23 abr, 2018 • Category: Leyes

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.

Generalizations of the Recursion Theorem

Por • 18 abr, 2018 • Category: Leyes

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.

Time, (Inverse) Temperature and Cosmological Inflation as Entanglement

Por • 11 abr, 2018 • Category: Leyes

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.

Articulating Space in Terms of Transformation Groups: Helmholtz and Cassirer

Por • 1 abr, 2018 • Category: Leyes

Hermann von Helmholtz’s geometrical papers (1868–1878) have been typically deemed to provide an implicitly group-theoretical analysis of space, as articulated later by Felix Klein, Sophus Lie, and Henri Poincaré. However, there is less agreement as to what properties exactly in such a view would pertain to space, as opposed to abstract mathematical structures, on the one hand, and empirical contents, on the other. According to Moritz Schlick, the puzzle can be resolved only by clearly distinguishing the empirical qualities of spatial perception from those describable in terms of axiomatic geometry. This paper offers a partial defense of the group-theoretical reading of Helmholtz along the lines of Ernst Cassirer in the fourth volume of The Problem of Knowledge of 1940.

Balanced Black and White Coloring Problem on knights chessboards

Por • 30 mar, 2018 • Category: Leyes

Graph anticoloring problem is partial coloring problem where the main feature is the opposite rule of the graph coloring problem, i.e., if two vertices are adjacent, their assigned colors must be the same or at least one of them is uncolored. In the same way, Berge in 1972 proposed the problem of placing b black queens and w white queens on a n×n chessboard such that no two queens of different color can attack to each other, the complexity of this problem remains open. In this work we deal with the knight piece under the balance property, since this special case is the most difficult for brute force algorithms.

The Bronstein hypercube of quantum gravity

Por • 25 mar, 2018 • Category: Leyes

We argue for enlarging the traditional view of quantum gravity, based on “quantizing GR”, to include explicitly the non-spatiotemporal nature of the fundamental building blocks suggested by several modern quantum gravity approaches (and some semi-classical arguments), and to focus more on the issue of the emergence of continuum spacetime and geometry from their collective dynamics. We also discuss some recent developments in quantum gravity research, aiming at realising these ideas, in the context of group field theory, random tensor models, simplicial quantum gravity, loop quantum gravity, spin foam models.

Spacetime is as spacetime does

Por • 19 mar, 2018 • Category: Leyes

Theories of quantum gravity generically presuppose or predict that the reality underlying relativistic spacetimes they are describing is significantly non-spatiotemporal. On pain of empirical incoherence, approaches to quantum gravity must establish how relativistic spacetime emerges from their non-spatiotemporal structures. We argue that in order to secure this emergence, it is sufficient to establish that only those features of relativistic spacetimes functionally relevant in producing empirical evidence must be recovered. In order to complete this task, an account must be given of how the more fundamental structures instantiate these functional roles. We illustrate the general idea in the context of causal set theory and loop quantum gravity, two prominent approaches to quantum gravity.

Hilbert’s Sixth Problem: the endless road to rigour

Por • 12 mar, 2018 • Category: Leyes

Introduction to the special issue of Phil. Trans. R. Soc. A 376, 2018, `Hilbert’s Sixth Problem’. The essence of the Sixth Problem is discussed and the content of this issue is introduced. In 1900, David Hilbert presented 23 problems for the advancement of mathematical science. Hilbert’s Sixth Problem proposed the expansion of the axiomatic method outside of mathematics, in physics and beyond. Its title was shocking: “Mathematical Treatment of the Axioms of Physics.” Axioms of physics did not exist and were not expected. During further explanation, Hilbert specified this problem with special focus on probability and “the limiting processes, … which lead from the atomistic view to the laws of motion of continua”. The programmatic call was formulated “to treat, by means of axioms, those physical sciences in which already today mathematics plays an important part.”

Demolishing prejudices to get to the foundations

Por • 18 feb, 2018 • Category: Leyes

Commonly accepted views on foundations of science, either based on bottom-up construction or top-down reduction of fundamental entities are here rejected. We show how the current scientific methodology entails a certain kind of research for foundations of science, which are here regarded as insurmountable limitations. At the same time, this methodology allows to surpass the bounds classically accepted as fundamental, yet often based on mere “philosophical prejudices”. Practical examples are provided from quantum mechanics and biophysics.

Why Is There Something, Rather Than Nothing?

Por • 9 feb, 2018 • Category: Leyes

It seems natural to ask why the universe exists at all. Modern physics suggests that the universe can exist all by itself as a self-contained system, without anything external to create or sustain it. But there might not be an absolute answer to why it exists. I argue that any attempt to account for the existence of something rather than nothing must ultimately bottom out in a set of brute facts; the universe simply is, without ultimate cause or explanation.