Grand Unified Theory A Grand Unified Theory (GUT) is a model in particle physics in which at high energy, the three gauge interactions of the Standard Model which define the electromagnetic, weak, and strong interactions, are merged into one single interaction characterized by one larger gauge symmetry and thus one unified coupling constant. During the grand unification epoch, the gauge force separated from the gravitational force. Models that do not unify all interactions using one simple Lie group as the gauge symmetry, but do so using semisimple groups, can exhibit similar properties and are sometimes referred to as Grand Unified Theories as well. Unifying gravity with the other three interactions would provide a theory of everything (TOE), rather than a GUT. Nevertheless, GUTs are often seen as an intermediate step towards a TOE. History[edit] Motivation[edit] Unification of matter particles[edit] Schematic representation of fermions and bosons in SU(5) GUT showing 5+10 split in the multiplets. SU(5)[edit] If
String theory String theory was first studied in the late 1960s[3] as a theory of the strong nuclear force before being abandoned in favor of the theory of quantum chromodynamics. Subsequently, it was realized that the very properties that made string theory unsuitable as a theory of nuclear physics made it a promising candidate for a quantum theory of gravity. Five consistent versions of string theory were developed until it was realized in the mid-1990s that they were different limits of a conjectured single 11-dimensional theory now known as M-theory.[4] Many theoretical physicists, including Stephen Hawking, Edward Witten and Juan Maldacena, believe that string theory is a step towards the correct fundamental description of nature: it accommodates a consistent combination of quantum field theory and general relativity, agrees with insights in quantum gravity (such as the holographic principle and black hole thermodynamics) and has passed many non-trivial checks of its internal consistency.
Superstring theory 'Superstring theory' is a shorthand for supersymmetric string theory because unlike bosonic string theory, it is the version of string theory that incorporates fermions and supersymmetry. Since the second superstring revolution the five superstring theories are regarded as different limits of a single theory tentatively called M-theory, or simply string theory. Background[edit] The deepest problem in theoretical physics is harmonizing the theory of general relativity, which describes gravitation and applies to large-scale structures (stars, galaxies, super clusters), with quantum mechanics, which describes the other three fundamental forces acting on the atomic scale. The development of a quantum field theory of a force invariably results in infinite (and therefore useless) probabilities. Evidence[edit] Superstring theory is based on supersymmetry. Extra dimensions[edit] See also: Why does consistency require 10 dimensions? Number of superstring theories[edit] The five superstring interactions
Prenatal memory Prenatal memory, also called fetal memory, is important for the development of memory in humans. Many factors can impair fetal memory and its functions, primarily maternal actions. There are multiple techniques available not only to demonstrate the existence of fetal memory but to measure it. Fetal memory is vulnerable to certain diseases so much so that exposure can permanently damage the development of the fetus and even terminate the pregnancy by aborting the fetus. Background Information and Functions[edit] Fetal memory is integral to mother-infant attachment There is substantial evidence that fetal memory exists within the first and second trimester after conception when the egg is fertilized. Development[edit] The Central Nervous System (CNS) and memory in the fetus develop from the ectoderm following fertilization via a process called neurulation. Functions[edit] Measurement techniques[edit] There are considered to be three paradigms used to investigate fetal learning and memory.
M-theory M-theory is a theory in physics that unifies all consistent versions of superstring theory. The existence of such a theory was first conjectured by Edward Witten at the string theory conference at the University of Southern California in the summer of 1995. Witten's announcement initiated a flurry of research activity known as the second superstring revolution. Background[edit] Quantum gravity and strings[edit] One of the deepest problems in modern physics is the problem of quantum gravity. Number of dimensions[edit] In everyday life, there are three familiar dimensions of space (up/down, left/right, and forward/backward), and there is one dimension of time (later/earlier). Despite the obvious relevance of four-dimensional spacetime for describing the physical world, there are several reasons why physicists often consider theories in other dimensions. Dualities[edit] Main articles: S-duality and T-duality A diagram of string theory dualities. and winding number in the dual description. .
Antimatter In particle physics, antimatter is material composed of antiparticles, which have the same mass as particles of ordinary matter but have opposite charge and other particle properties such as lepton and baryon number. Encounters between particles and antiparticles lead to the annihilation of both, giving rise to varying proportions of high-energy photons (gamma rays), neutrinos, and lower-mass particle–antiparticle pairs. Setting aside the mass of any product neutrinos, which represent released energy which generally continues to be unavailable, the end result of annihilation is a release of energy available to do work, proportional to the total matter and antimatter mass, in accord with the mass-energy equivalence equation, E=mc2.[1] Antiparticles bind with each other to form antimatter just as ordinary particles bind to form normal matter. For example, a positron (the antiparticle of the electron) and an antiproton can form an antihydrogen atom. History of the concept Notation Positrons
Lattice gauge theory Basics[edit] In lattice gauge theory, the spacetime is Wick rotated into Euclidean space and discretized into a lattice with sites separated by distance and connected by links. In the most commonly considered cases, such as lattice QCD, fermion fields are defined at lattice sites (which leads to fermion doubling), while the gauge fields are defined on the links. That is, an element U of the compact Lie group G is assigned to each link. Yang–Mills action[edit] The Yang–Mills action is written on the lattice using Wilson loops (named after Kenneth G. There are many possible lattice Yang-Mills actions, depending on which Wilson loops are used in the action. . , making computations more accurate. Measurements and calculations[edit] This result of a Lattice QCD computation shows a meson, composed out of a quark and an antiquark. Quantities such as particle masses are stochastically calculated using techniques such as the Monte Carlo method. , where is the lattice action and . See also[edit]
Cosmogony Cosmogony (or cosmogeny) is any model concerning the coming-into-existence (i.e. origin) of either the cosmos (i.e. universe), or the so-called reality of sentient beings.[1][2] Developing a complete theoretical model has implications in both the philosophy of science and epistemology. Etymology[edit] The word comes from the Koine Greek κοσμογονία (from κόσμος "cosmos, the world") and the root of γί(γ)νομαι / γέγονα ("come into a new state of being").[3] In astronomy, cosmogony refers to the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the universe, the solar system, or the earth-moon system.[1][2] Overview[edit] The Big Bang theory is the prevailing cosmological model of the early development of the universe.[4] The most commonly held view is that the universe was once a gravitational singularity, which expanded extremely rapidly from its hot and dense state. Cosmologist and science communicator Sean M.
Lattice field theory Just as in all lattice models, numerical simulation gives access to field configurations that are not accessible to perturbation theory, such as solitons. Likewise, non-trivial vacuum states can be discovered and probed. The method is particularly appealing for the quantization of a gauge theory. Most quantization methods keep Poincaré invariance manifest but sacrifice manifest gauge symmetry by requiring gauge fixing. See also[edit] References and external links[edit]
What Wavelength Goes With a Color? Colors We Can't See There are many wavelengths in the electromagnetic spectrum the human eye cannot detect. Energy with wavelengths too short for humans to see Energy with wavelengths too short to see is "bluer than blue". How do we know this light exists? Energy with wavelengths too long for humans to see Energy whose wavelength is too long to see is "redder than red". How do we know this kind of light exists? Very long wavelengths of infrared light radiate heat to outer space. Effective field theory The renormalization group[edit] Presently, effective field theories are discussed in the context of the renormalization group (RG) where the process of integrating out short distance degrees of freedom is made systematic. Although this method is not sufficiently concrete to allow the actual construction of effective field theories, the gross understanding of their usefulness becomes clear through a RG analysis. Examples of effective field theories[edit] Fermi theory of beta decay[edit] The best-known example of an effective field theory is the Fermi theory of beta decay. BCS theory of superconductivity[edit] Another famous example is the BCS theory of superconductivity. Effective Field Theories in Gravity[edit] General relativity itself is expected to be the low energy effective field theory of a full theory of quantum gravity, such as string theory. Other examples[edit] Presently, effective field theories are written for many situations. See also[edit] References[edit] External links[edit]