Monday, 29 April 2013
Antimatter- Something Rather than Nothing
Like skis and skates, stuff came in pairs. Pairs that annihilated one another, shared mass but differed in charge and spin. It's the Jekyll and Hyde personality of particles that corresponds to the existence of matter and antimatter; Dirac envisaged a sea of negative energy levels, each filled with a pair of electrons of opposing spin with the positron appearing as a 'hole' in the sea as a state with a positive charge and energy. While Feynman and Stueckelberg likened negative energy particles moving backward in time to positive energy antiparticles moving forward in time. But the ultimate question remains the origin of the asymmetry of matter, and why unlike a world filled with antiparticles or emptiness, we are made of matter anyways; why there is something rather than nothing. Let's look back at the early universe, before primordial nucleosynthesis and into baryogenesis; the making of baryons and antibaryons. Sakharov noted three conditions necessary for the production of the baryon asymmetry namely; the violation of baryon number, violation of C and CP symmetry and a withdrawal from thermal equilibrium. Electroweak theory, the synthesis of the electromagnetic and weak interactions, incorporates gauge symmetries useful to explaining the matter asymmetry and fulfilling the Sakharov prerequisites; just like a hot iron ferromagnet with a series of randomly spinning electrons exhibiting rotational symmetry which may be broken and magnetised when cooled and aligning the spins, the weak symmetry breaks giving W and Z bosons mass via the Higgs field and preserves the electroweak symmetry keeping photons massless. So during the early epochs, the universe must have cooled down to a critical temperature like the ferromagnet, causing the electroweak phase transition out of thermal equilibrium to form like bubbles in boiling water, breaking the symmetry. At first sight, the electroweak interaction also seems to apparently conserve the baryon number but this may be violated in the current phase of broken symmetry via quantum tunneling but during the early universe, a barrier to fluctuation was not present and the baryon number was permitted to vary freely. But how can electroweak theory account for the differences between matter and antimatter? Like a roulette wheel likely to land in a spot of equal probability, a tilted wheel is biased toward a particular symmetry breaking much like the violation of charge conjugation (C) and parity (CP). Charge conjugation ensures the interchanging between particles and antiparticles while parity preserves spin but reverses direction; so here the CP symmetry can counteract particle production with antiparticles leading to annihilation, but how did a bit more matter than antimatter end up being made? The electromagnetic and strong interactions have C and P symmetries but the weak force violates it through the beta minus decay of kaons, thus the quark components of baryons should also be able to violate it through weak interactions and break the symmetry. Now that we've fulfilled the prerequisites via electroweak theory, it can be speculated that the initial early universe was full of a symmetric phase but as the phase transition broke the symmetry, bubbles formed and baryon number was violated out of thermal equilibrium; it may be further hypothesised that as the bubbles spread cross the universe via a plasma of particles and antiparticles, quarks were sealed in the bubbles, leaving their baryon number unscathed whereas the antiquarks were annihilated creating the asymmetry. However, the traditional Kobashi-Maskawa CP violation may prove inefficient as all quarks other than the 'top' are remarkably light compared the W boson; necessitating a new type of symmetry violation that will allow the weak interaction to manipulate the charge and flavour of all six quarks indiscriminate of their masses. A saga to be continued...
Saturday, 27 April 2013
Topology- From Euler to Poincaré
Turning a sphere inside out is one easy task. Simply poke a hole in it and yank it through. Or is it? Can it be done without poking a hole? And with a material that can bend, stretch and pass through itself? Enter topology; where doughnuts meet coffee mugs and where pretzels become nontrivial trefoils. It's way of looking at space with a sense of 'sameness' and connectivity, where even gravity is reduced to curvature on a trampoline. Indeed topology is the product of the cross fertilization of graph and knot theory, in 1736 Euler established the impossibility of the circuit round the seven bridges of Königsberg; by envisaging each plot of land as a vertex connected by lines, it became clear that an even number of edges was needed to cross each bridge once and fulfill the problem. But since the vertices all had odd numbers of edges, it was out of the question. More imaginary was the discovery of the Möbius strip, a surface with a single edge and a single side. Such a surface emerges via twisting a strip so that one side is reversed and formed into a closed loop, this introduced the notion of a non-orientable plane that confuses the sense of 'inside' and 'outside'. Attaching two Möbius strips together results in a Klein bottle, a closed surface lacking a defined boundary and may also be formed abstractly by gluing the remaining edges of a cylinder in opposite directions to make a torus. But to achieve this is everyday Euclidean space, the surface would have to go through itself to situate the edges. More intriguing was the Poincaré conjecture posited in 1904 and the topology of the sphere; simply put, the simplest object which is closed in any number of given dimensions. Any closed 3D manifold where a loop may be contracted to a single point is a 3D sphere, whereas loops on a torus fail to contract to a single point. But the central issue at large remained whether a closed 3D manifold could exist independent of the sphere but by considering Thurston's geometrisation theorem, where 8 types of manifolds could be sewn to form other 3D surfaces and Ricci flow, whereby irregular and lopsided spaces can be turned into uniform ones, the concept of a non-spherical closed manifold could be ruled out. Algebraic topology also introduces the idea of a vector bundle, considering spaces and structures described above a surface as opposed to within it; by designating a vector space to each point, followed by a fibre, a vector field is produced. Suppose a series of vectors lying tangent on a sphere, at least a single point will remain with a vector value of zero is inevitable making a hairy torus easily combable whereas a hairy ball will produce a crown at each pole. Moreover, at even the simplest topologies; the concept of homeomorphism forms a continuous transformation function between the torus and the coffee mug, both objects are said to be homotopic just as the 2D sphere and the horned sphere can be converted into one another without tearing or incising. Homotopy may also be applied when fine spaces or holes cannot be accounted by via homology or by examining features of the topological space that lack a boundary and are not boundaries in themselves.
Friday, 19 April 2013
Dark Matter- A Standard Model of Cosmology
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Tuesday, 16 April 2013
Morphic Resonance- The Presence of the Past
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