#14: Supermaterial Gets Supersized | Materials Science. #26: How Matter Defeated Antimatter | Subatomic Particles. The Big Bang theory has a Big Problem. The leading models of cosmology imply that the universe should have begun with equal quantities of matter and antimatter. But when the two meet, they annihilate each other, so an equal balance would have yielded an empty cosmos. In May, physicists at the Tevatron particle accelerator in Illinois singled out a strange particle that could help explain the conundrum. Studying nearly eight years’ worth of high-speed smashups between protons and antiprotons, Guennadi Borissov of Lancaster University in the U.K. and other members of the Tevatron team focused on the B meson, a short-lived particle that emerges from the collisions. During its brief life, this particle rapidly oscillates between matter and antimatter: One moment it’s a B meson, the next it’s an anti-B meson. Follow-up experiments planned for this year at both the Tevatron and the Large Hadron Collider will test the team’s findings.
#63: Ghost Particles Shake Physics | Subatomic Particles. #70: The Proton Gets Small(er) | Subatomic Particles. Quantum triviality. In a quantum field theory, charge screening can restrict the value of the observable "renormalized" charge of a classical theory. If the only allowed value of the renormalized charge is zero, the theory is said to be "trivial" or noninteracting. Thus, surprisingly, a classical theory that appears to describe interacting particles can, when realized as a quantum field theory, become a "trivial" theory of noninteracting free particles. This phenomenon is referred to as quantum triviality. Strong evidence supports the idea that a field theory involving only a scalar Higgs boson is trivial in four spacetime dimensions,[1] but the situation for realistic models including other particles in addition to the Higgs boson is not known in general.
Nevertheless, because the Higgs boson plays a central role in the Standard Model of particle physics, the question of triviality in Higgs models is of great importance. The situation becomes more complex in theories that involve other particles however. Dark energy. Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations. Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe.[8] Nature of dark energy[edit] Many things about the nature of dark energy remain matters of speculation. The evidence for dark energy is indirect but comes from three independent sources: Distance measurements and their relation to redshift, which suggest the universe has expanded more in the last half of its life.[9]The theoretical need for a type of additional energy that is not matter or dark matter to form our observationally flat universe (absence of any detectable global curvature).It can be inferred from measures of large scale wave-patterns of mass density in the universe.
Effect of dark energy: a small constant negative pressure of vacuum[edit] . Holographic principle. In a larger sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon[clarification needed], such that the three dimensions we observe are an effective description only at macroscopic scales and at low energies. Cosmological holography has not been made mathematically precise, partly because the particle horizon has a finite area and grows with time.[4][5] The holographic principle was inspired by black hole thermodynamics, which conjectures that the maximal entropy in any region scales with the radius squared, and not cubed as might be expected. In the case of a black hole, the insight was that the informational content of all the objects that have fallen into the hole might be entirely contained in surface fluctuations of the event horizon.
Black hole entropy[edit] An object with entropy is microscopically random, like a hot gas. Black hole information paradox[edit] Limit on information density[edit] Entropic gravity. Entropic gravity is a hypothesis in modern physics that describes gravity as an entropic force; not a fundamental interaction mediated by a quantum field theory and a gauge particle (like photons for the electromagnetic force, and gluons for the strong nuclear force), but a probabilistic consequence of physical systems' tendency to increase their entropy. The proposal has been intensely contested in the physics community but it has also sparked a new line of research into thermodynamic properties of gravity.
Origin[edit] The probabilistic description of gravity has a history that goes back at least to research on black hole thermodynamics by Bekenstein and Hawking in the mid-1970s. These studies suggest a deep connection between gravity and thermodynamics, which describes the behavior of heat. Erik Verlinde's theory[edit] Criticism and experimental tests[edit] Even so, entropic gravity in its current form has been severely challenged on formal grounds. See also[edit] References[edit] Loop quantum gravity. More precisely, space can be viewed as an extremely fine fabric or network "woven" of finite loops. These networks of loops are called spin networks. The evolution of a spin network over time is called a spin foam.
The predicted size of this structure is the Planck length, which is approximately 10−35 meters. According to the theory, there is no meaning to distance at scales smaller than the Planck scale. Therefore, LQG predicts that not just matter, but also space itself has an atomic structure. Today LQG is a vast area of research, developing in several directions, which involves about 50 research groups worldwide.[1] They all share the basic physical assumptions and the mathematical description of quantum space.
Research into the physical consequences of the theory is proceeding in several directions. History[edit] General covariance and background independence[edit] In mathematics, a diffeomorphism is an isomorphism in the category of smooth manifolds. And. . . , we have where 2. 3. . .