Artículos con la etiqueta ‘espacio-tiempo’

Constraints on Chronologies

Por • 25 ago, 2012 • Category: Filosofía

The time ordering of two spacelike separated events is arbitrary, when all inertial frames are taken into account, but for three or more events it is not generally so. We determine the structure of possible time orderings, or chronologies, for multiple events in any number of dimensions, analytically and exhaustively for three events in four space-time dimensions, algorithmically in other cases. We also formulate an alternative criterion, based on convexity, for determining the allowed chronologies of a set of events. We show how the metric of a Lorentz invariant spacetime can be partially reconstructed from a knowledge of the chronologies it supports. Finally, we propose a different but related criterion for allowed chronologies in curved spacetimes



Space-time crystals of trapped ions

Por • 27 jun, 2012 • Category: Opinion

Great progresses have been made in exploring exciting physics of low dimensional materials in last few decades. Important examples include the discovering and synthesizing of fullerenes (zero dimensional, 0D), carbon nanotubes (1D) and graphene (2D). A fundamental question is whether we can create materials with dimensions higher than that of conventional 3D crystals, for example, a 4D crystal that has periodic structures in both space and time. Here we propose a space-time crystal of trapped ions and a method to realize it experimentally by confining ions in a ring-shaped trapping potential with a static magnetic field. The ions spontaneously form a spatial ring crystal due to Coulomb repulsion. This ion crystal can rotate persistently at the lowest quantum energy state in magnetic fields with fractional fluxes. The persistent rotation of trapped ions produces the temporal order, leading to the formation of a space-time crystal. We show that these space-time crystals are robust for direct experimental observation. The proposed space-time crystals of trapped ions provide a new dimension for exploring many-body physics and emerging properties of matter.



A physical universe from the universe of codes

Por • 10 jun, 2012 • Category: Educacion

We investigate the most general phase space of configurations, consisting of the collection of all possible ways of assigning elementary attributes, «energies», to elementary positions, «cells». We discuss how this space defines a «universe» with a structure that can be approximately described by a quantum-relativistic physical scenario in three space dimensions. In particular, we discuss how the Heisenberg’s Uncertainty and the bound on the speed of light arise, and what kind of mechanics rules on this space.



Did the concepts of space and time change that much with the 1905 theory of relativity?

Por • 8 mar, 2012 • Category: Ciencia y tecnología

The advent of the 1905 theory of relativity is rightly considered as a breakthrough moment in the history of physics; in particular. it is widely accepted that it brought a new conception of space and time. The purpose of this work is to reevaluate to what point and in what sense can we consider that the conception of space and time went through a transformation when going from Newtonian mechanics to the theory of relativity



Extraction of timelike entanglement from the quantum vacuum

Por • 31 dic, 2011 • Category: Educacion

In January 2011, physicists said conventional entanglement links particles across space and pointed out that a similar effect links particles through time. Entanglement is the strange quantum phenomenon in which two or more particles become so deeply linked that they share the same existence. That leads to some counterintuitive effects, in particular, when two entangled particles become widely separated. When that happens, a measurement on one immediately influences the other, regardless of the distance between them. This «spooky-action-at-a-distance» has profound implications about the nature of reality but a clear understanding of it still eludes physicists. Today, they have something else to puzzle over. Jay Olson and Timothy Ralph at the University of Queensland in Australia say they’ve discovered a new type of entanglement that extends, not through space, but through time.



Exact Philosophy of Space-Time

Por • 4 oct, 2011 • Category: Filosofía

Starting from Bunge’s (1977) scientific ontology, we expose a materialistic relational theory of space-time, that carries out the program initiated by Leibniz, and provides a protophysical basis consistent with any rigorous formulation of General Relativity. Space-time is constructed from general concepts which are common to any consistent scientific theory and they are interpreted as emergent properties of the greatest assembly of things, namely, the world.



First Demonstration Of Time Cloaking

Por • 17 jul, 2011 • Category: Educacion

Time cloaking is possible because of a kind of duality between space and time in electromagnetic theory. In particular, the diffraction of a beam of light in space is mathematically equivalent to the temporal propagation of light through a dispersive medium. In other words, diffraction and dispersion are symmetric in spacetime. That immediately leads to an interesting idea. Just as its easy to make a lens that focuses light in space using diffraction, so it is possible to use dispersion to make a lens that focuses in time.



Philosophical problems of space-time theories

Por • 25 may, 2011 • Category: Filosofía

Emphasis is put on the ontological nature of space and time, the relation between determinism and predictability, the origin of irreversible processes in an expanding universe, and the compatibility of relativity and quantum mechanics. In particular, I argue for a Parmenidean view of time and change, I make clear the difference between ontological determinism and predictability, propose that the origin of the asymmetry observed in physical processes is related to the existence of cosmological horizons, and present a non-local concept of causality that can accommodate both special relativity and quantum entanglement.



Sudden vanishing and reappearance of nonclassical effects: General occurrence of finite-time decays and periodic vanishings of nonclassicality and entanglement witnesses

Por • 8 feb, 2011 • Category: Leyes

Recently, analyses of phenomena exhibiting finite-time decay of quantum entanglement have attracted much attention. Such decay is often referred to as sudden vanishing (sudden death) of entanglement, which can be followed by its sudden reappearance (sudden rebirth).



Complexity, Sustainability, Justice, and Meaning: Chronological Versus Dynamical Time

Por • 31 dic, 2010 • Category: Crítica

It is shown that time may be appreciated in at least two senses: chronological and dynamical. Chronological time is the time of our naïve acquaintance as transient beings. At its most extensive scale, it corresponds to history encompassing both the abiotic and the biotic universe. Dynamical time, deriving from classical mechanics, is the time embraced by most of the laws of physics.