I propose a summary of the definition: String Theory.
¬ Albert Einstein devoted the last thirty years of his life in search of so-called "unified field theory" that is, the theory that would unify the laws of gravity and electromagnetism in order to allow a unified description of natural phenomena. His plan failed, but in no case could be successful because at that time there were many gaps concerning knowledge of the physical world. When Einstein set out on his attempt to unify for example, only three were known elementary particles (electron, proton and photon) and were known only two interactions core (electromagnetism and gravity).
Currently there are over one hundred elementary particles: an even number in excess of what is necessary to explain the cosmic order so that when it was discovered the muon, a particle like the electron but 200 times heavier than it, the Nobel Prize Isaac Rabi received the new discovery with an upset: "Who ordered that?" The fundamental forces meanwhile have become four, and their union has become the central objective of the research end of the century. The methods of investigation that are taken now are original and there seems to be a clear progress in this field of research even though in reality the unification of gravitation with the other three forces has not yet been realized. Physicists, however, believe that you have chosen the right path that leads to the formulation of that one theory can explain all that exists in the universe. The new theory on which you are working is called superstring.
1. Superstring theory
As you know, there are two pillars on which modern physics: general relativity was founded by Albert Einstein and quantum mechanics founded by Max Planck. The first place in the wonderful task of explaining the behavior of large objects (stars, galaxies, galaxy clusters, etc..) Present Universe, the second allows us to understand the atomic and subatomic world (molecules, atoms, electrons, quarks, etc.).. These two theories, which have allowed extraordinary progress of physics in the last century, but has a defect insurmountable: they are not mutually compatible.
this incompatibility physicists have never given because the field investigation of the two theories is very different and when there was a need to study small objects and light is made use of quantum mechanics without worrying about what relativity says while, when there was a need to study large and heavy objects, you use the laws of relativity general without addressing the utterances of the other theory: never happened in the past it was necessary to use both theories simultaneously. Lately, however, things have changed: the holes are heavy objects such as blacks, but at the same time very small and the universe would emerge from an infinitely small particle is both extremely heavy and hot. On these objects would then the simultaneous application of two theories.
Today, as we mentioned, there is a theory called superstring able to reconcile quantum mechanics and general relativity. It would explain the behavior of matter, the forces that hold together objects materiali, e forse anche dello spazio e del tempo. Secondo questa teoria tutto ciò che esiste nell’Universo non sarebbe altro che la manifestazione di “energia vibratoria”. Cerchiamo di spiegare di cosa si tratta.
La nuova teoria prese l’avvio nel 1968 da un’osservazione del fisico italiano Gabriele Veneziano, a quel tempo ricercatore presso il Cern di Ginevra. Egli stava analizzando una serie di dati sperimentali riguardanti la forza nucleare forte quando notò che una formula utilizzata per descrivere una classe di curve geometriche, la cosiddetta “funzione beta”, inventata 200 anni prima dal matematico svizzero Leonhard Euler (meglio noto con il nome latinizzato di Eulero), forniva un’utile mathematical system of the subject he was studying.
Veneziano's insight was later expanded and it was discovered that if the elementary particles were treated as vibrating wire (called strings or cords, in English string) rather than point to entities without internal structure as suggested by the so-called Standard Model ( conceptual tool that was used in the course of the twentieth century to explain the behavior of elementary particles) would describe the beta function with equal consistency interactions between particles.
strings (do not let the name fool you) is infinitely short and thin wires so that would be invisible even if they were examined instruments billion times more powerful than those currently available: they are long-millionth of a billionth of a billionth of a billionth of a centimeter (billion billion times smaller than an atomic nucleus) and a thickness of zero. These are structures whose dimensions are close to the so-called Planck length (10-33 cm) the smallest conceivable physical, but with a force that is stretched incredibly large: up to 1039 tons. It is precisely this enormous power to determine the frequency of vibration: the more it is, the greater is the mass of the particle associated and consequently the greater the force of gravity that it exerts on other particles. This would be the clue for which the superstring theory would link the gravity described by general relativity with the structure of elementary particles described by quantum mechanics.
There is a substantial difference between the theories of gravity of Newton and Einstein and the one that comes from superstring theory. Their theories with Newton and Einstein simply explain a phenomenon of which already had direct experience in the case of string theory gravity is instead directly incorporated into its theoretical core so that even if there had been no previous experience of this strength, it would emerge as a consequence of the theory itself. In other words, the superstring theory predicts the existence of gravity because it emerge spontaneously all four mediators particles (or messengers) of fundamental interactions and their unification comes naturally.
modes of vibration of these wires are very thin and often very short closed loop generate all the elementary particles that make up our universe a bit 'like a violin string, more or less tense (but never applied it to forces such as those provided by the theory Superstring!) generates an infinite number of musical tones. The prefix super was added to the string theory when it was discovered that the theory had a supersymmetry, ie when it was realized that to every particle of matter correspond to a particle of strength and vice versa.
To understand what it is you need to know that elementary particles are divided in two groups: fermions "(named after the Italian physicist Enrico Fermi) and" boson "(named after the Indian physicist Satyendra Bose). Are part of the first family matter particles such as electrons and quarks, the particles of the second mediating forces like photons and gravitons. Well, supersymmetry says that every known particle there is another aspect of the unknown but similar behavior, these particles, although no one has ever seen, has also been named: for example, symmetric the photon (the carrier particle of electromagnetic force) is the photino (material particle), the symmetric partner of the quark (a fermion) is the boson s-quark, and so on.
2. The M-theory
Superstring theory includes five variants known as type I, type IIA, type IIB, heterotic heterotic E and O, all theories are very similar but not identical to each other. Similar examples include the fact that they all require nine dimensions of space (in addition to time) within which to act and not just the three of which we have direct perception. Of these a total of six ten dimensions are invisible, resulting in tightly curled inward (With technical term is compactified say, a shame lexicon) because "strangled" by the strings that wrap around them (as if they were rubber bands that bind the inner tube of a bicycle) preventing them from expanding.
The addition of hidden dimensions to those observed what may seem a bizarre and unprovable, but in reality it is a good hypothesis: experimental observations in fact do not need to confirm if this hypothesis can be useful to provide a clear description of physical world. Something similar had already happened in the past when an unknown Polish mathematician named Theodor Kaluza sent Einstein a paper in which advanced the belief that the universe could have had a fourth spatial dimension in addition to time already included in his theory of relativity. Kaluza noted that the presence of an extra dimension gave rise to a series of equations in addition to those given by Einstein that were nothing more than the formulated from Maxwell equations to describe the electromagnetic theory. In other words in a five-dimensional space are unified gravitation and electricity.
The five subtypes of superstring theory but also show some substantial differences. Differ from each other for the way they incorporate supersymmetry or strings of the form: the theory of Type I, for example, unlike the other provides for the presence of open strings, ie with the free end, as well as closed strings ring.
In 1995 the theoretical physicist Edward Witten found that the five superstring theories were intimately related to each other so that they can be grouped into a single conceptual framework which was given the name M-theory, where M would be for mother, then it would be the "mother of all theories." This new discovery could lead to the much sought after theory of everything (TOE, as they call the Anglo-Saxons, Theory of everything), but many of its properties have not yet been fully understood.
The M-theory exhibits some characteristics additional to those present in the superstring. First, it postulates that the size shift from ten to eleven at nine spatial dimensions and one time in the theory of superstrings is added and then another whose presence enables to carry out exact calculations and not just those who were approximated as obtained previously. A second feature of the M-theory is that it contains, in addition to one-dimensional structures that have been said, other elements that can be extended in several dimensions: in all these objects are called branes (a term derived from mem-branes). Using this new terminology and the original strings are called 1-brane, the 2-branes are membranes or two-dimensional surfaces, but there are small masses three-dimensional (tribrane) and other multi-dimensional objects in all frantic and constant vibration. Due to the presence of objects larger strings, the M-theory is also called "membrane theory", but at this point the most malicious assign the letter M theory the meaning of "mystery".
3. The theory explains the origin of the universe
One of the problems that have always plagued the human mind and the origin of the universe. The currently most widely accepted scientific theory, that of the big bang, says that the Universe, in the early moments of her life was incredibly small in size but at the same time extremely dense and hot. To analyze scientific terms such extreme conditions would need a quantum theory of gravity, but as we have seen, such a theory does not exist. For this reason the so-called standard cosmological model is forced to describe the evolution of the universe from an elementary particle of this minimum size at time t = 10-43 seconds from the beginning (called the Planck time).
In fact, extrapolating backwards the equations of general relativity can be seen that the Universe is getting smaller and at the same time sempre più caldo e più denso fino a scomparire del tutto quando si raggiunge il tempo zero, mentre temperatura e densità in quello stesso istante assumono valori infiniti. Ovviamente queste conclusioni lasciano gli astrofisici fondamentalmente insoddisfatti e perplessi.
Ora, la teoria delle superstringhe sembra poter risolvere queste contraddizioni e dare una risposta più precisa e convincente al problema relativo all’origine dell’Universo anche se per la verità la strada da percorrere non solo è lunga, ma anche accidentata. La modifica più sostanziale che la nuova teoria apporta al Modello cosmologico standard è quella riguardante le dimensioni che avrebbe assunto l’Universo all’inizio dei tempi: they could not fall below a minimum value. Superstring theory in other words does not include the so-called Singularity that is the fact that the universe can be reduced until it reached zero size. The other key aspect of the theory is related to the size not more than four (according to the Standard Model) but eleven, and this implies the need to track trends over time for all of them this size.
Just when you follow the evolution of the multiple dimensions of the universe using the equations contained in the superstring theory is observed that when they fall below the Planck length, rather than fall further, to grow and take over the temperature goes hand in hand the variation of the size of the universe: that is, reached a maximum value, it begins to decrease.
Based on the results which leads to string theory have been developed some new cosmological models one of which predicts the existence of a cyclic universe with no beginning and no end in time, in an uninterrupted succession of contractions and expansions. It would be contained within two-dimensional membrane (we can imagine two identical thick cardboard flat and parallel) that evolve over time (ie in the fourth dimension), and fluctuate in a fifth dimension by which you feel gravity while the other six, as usual, would be small and rolled up within the plot space. The particles that are within the two membranes evolve independently but may also interact via the carrier particle of gravity, the graviton, which not only act within the membrane may pass from one universe to another moving along spiral around one of many extra dimensions. The particles of one of the two membranes behave like dark matter to the other, in addition, dark energy (an additional form of matter known) that the standard model was not justified by theory, the new model has a fundamental role in driving the accelerated expansion of the Universe seems to be the subject.
The two membranes may also collide with each other at the end of the long run-up but then you bounce and turn away to return later to approach in an endless process.
The problem now is to see if the model is well adapted to reality, but it does not seem easy because the model itself relies on theories that in turn require experimental verification. To study the superstrings in the laboratory would need to have some energy trillions of times more than at present, to create what you should build a synchrotron as large as the galaxy.
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