AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy | Gravity, black holes and physics |
Appendix B
UNITARY FIELD THEORY
AND QUANTUM GRAVITY
B.1. The process
of unification in physics
B.2. Einstein's visions of
geometric unitary field theory
B.3. Wheeler's
geometrodynamics. Gravity and
topology.
B.4. Quantum
geometrodynamics
B.5. Gravitational
field quantization
B.6. Unification
of fundamental interactions. Supergravity.
Superstrings.
B.7. General
principles and perspectives of unitary field theory
B.1. The process of unification in physics
Naturalists and
especially physicists are deeply convinced of the comprehensibility of the world , especially nature. He
therefore strives to find a uniform explanation of the basic
building blocks of matter and the interactions between them. The
basis of scientific thinking is unification : in the vast diversity of
phenomena and events, to seek general
laws and a common
essence , to try to explain the diversity of phenomena on the
basis of as few basic laws as possible. It is based on the idea
that " nature is rich in forms,
but poor in laws
".
Thoughtful people have always longed for a
theory that would describe and understand all the observed
complexity and diversity of nature. The ultimate ideal is (if
possible) to explain all the laws of nature using a single universal principle - to create a definitive final
theory or a unified " theory of everything
" ( TOE
- Theory Of Everything ) ; to reveal a
single law clarifying all the phenomena of the world.
Unitarization efforts are based on the belief in the material unity of the world , which
is now the basis of all science. That there is some hidden universal structure in the Universe or the law on the basis of which
the whole universe works. And it is physics that examines the
most basic laws of nature that has a unifying
role among
all the natural sciences. In the course of development, with the
discovery of ever new phenomena and laws, physics seems more and
more complex, demanding and complex. However, this is only a
partial external view. Within physics, in fact, there is an integration process , the aim of which is to give a uniform description of physical phenomena.
Unitary
"theory of everything": the end of physical research?
Sometimes we encounter the opinion (especially in the
scientific-popularization literature) that the successful
construction of a unitary theory of the field, the "theory
of everything", would mean the end of physics and
even perhaps the whole of science - there would be nothing new to
discover! This view is wrong for at least two
reasons :
1. Quantum relations of uncertainty
, if the new unitary theory did not overcome them in any way
(which does not seem probable), fundamentally limit the
possibilities of predicting phenomena.
2. We cannot solve the relevant equations
accurately, except in the simplest and idealized cases. With the
number of degrees of freedom (the number of bodies and particles)
this becomes completely impossible, an attempt to make an
accurate prediction necessarily dissolves into chaotic
behavior (see §3.1, section " Determinism
- chance - chaos? ").
So there is still a lot of intellectual work
left, how to derive and understand the behavior of
systems in complex and realistic situations from basic principles
and laws. Due to its fundamentality, complexity and heuristic
significance , this work does not compete with revealing
the principles of unitary field theory.
Basic
stages of unitarization
The basic stages of unification in physics are shown in Fig.B.1.
The first stage of unitarization actually
took place in the very beginnings of physics as a science: it was
a unification of " terrestrial
" and " celestial
" mechanics . Thanks to Galileo, Copernicus
and Kepler, it became clear that the laws of nature observed here on
Earth also apply elsewhere in the universe (the
first more concrete confirmation of this was Galileo's
observation of "mountains" on the surface of the Moon) . For real "father of
unification" can be considered to I.Newtona that before
about 300 year those formulated the law
of universal gravitation and showed that the force of the Earth's
gravity causing bodies to fall is identical to the force of
keeping planets in orbit around the Sun, i.e., cosmic gravity.
The "classical" period
of unitarization of physics can also include the unification of mechanics and thermals in the kinetic theory of heat,
according to which the essence of thermal phenomena (formerly considered separate) is the kinetic energy of disordered and
oscillating motion of molecules and atoms in matter.
A great example of unitarization
in physics is the unification of
electric and magnetic forces which previously seemed to be
quite different forces of nature. In the first third of the 19th
century, Faraday and Ampér discovered that magnetic forces
(known until then only from permanent magnets) are created by the
movement of electric charges. And changes in the magnetic field
cause an electric field. This knowledge was further developed and
generalized by JCMaxwell in his electromagnetic field theory
(§1.5). The consequence of the unity of electricity and
magnetism in Faraday-Maxwell electrodynamics is the existence of electromagnetic waves , which are emitted during the
accelerated motion of electric to tric charges.
The properties of these
electromagnetic waves proved to be identical to the properties of
light: in addition, optical and electromagnetic phenomena
were unified. . Radio waves, heat radiation,
light, X-rays and gamma rays, together with the classical and
relativistic effects of electricity and magnetism, are therefore
just different manifestations of electromagnetic
interaction
.
Fig.Bl Basic stages of unification of
natural laws.
Weak and strong interactions and
unification of individual types of interactions are not yet
included in this scheme; the continuation of the scheme of
unitarization in the field of unitary field theories is shown in
Fig.B.8 in §B.6 " Unification of fundamental
interactions. Supergravity. Superstrings. ".
The development of atomistics and quantum
mechanics
in the first third of the 20th century showed that all the
diversity of chemical phenomena can be explained by
electromagnetic interactions and quantum laws in the electronic shells of atoms of individual elements; the same
applies to the physical properties of solids (crystal lattices - elasticity, strength, dislocation) , liquids and gases. Thus,
chemistry was in fact "absorbed" by physics, at least
as far as the foundations are concerned - see §1.1 "Atoms and Atomic
Nuclei", section " Interaction of Atoms " of the book " Nuclear Physics and Physics of Ionizing
Radiation "
.
The other two stages of unitarization are
already related torelativity theory . In his special theory of
relativity Einstein unified space
and time
into a single space-time continuum, in his
general theory of
relativity he unified space-time
and gravity
- he showed that Newtonian gravity and inertia are a common
manifestation of geometric properties (curvature) of space-time,
which has a dynamic character (Chapter 2) .
The last stage of
unitarization takes place in the area of "elementary"
particles . A huge amount of experimental
knowledge about the properties and interactions of elementary
particles, obtained in the 50s-80s, processed and unified in the
spirit of a number of quantum-theoretical concepts, resulted in
the so-called Standard Model of Elementary Particlesand
their interactions (it is discussed in more
detail in §1.5 " Elementary particles and accelerators
", passage " Standard
model - unified understanding of elementary particles " of the book " Nuclear physics and
physics of ionizing radiation ") .
All matter in nature in its deepest interior consists of only 2
"families" of basic (elementary) particles - 6 leptons
and 6 quarks , between which 4 fundamental forces
(interactions) act: strong, electromagnetic, weak and
gravitational . The first three of these interactions are
described by exchanges of intermediate bosons with spin 1: strong
interaction is mediated by gluons , electromagnetic
interaction by photons, weak interaction by heavy
intermediate bosons charged (W +, - ) and neutral
(Z o ).
Quantum theory for the gravitational interaction has not yet been
completed, but can be described by intermediate gravitons
(spin 2). The modern
unitary theories that try to unify the various types of
interactions between elementary particles, will be mentioned at
the end of this chapter (§B.6 " Unification
of fundamental interactions. Supergravity. Superstrings. ") .
But before that, let's talk about geometric
unitary theories that are most closely related to the
subject of this book.
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A. Mach's principle | B.2. Einstein's visions of geometric unitary field theory |
Gravity, black holes and space-time physics : | ||
Gravity in physics | General theory of relativity | Geometry and topology |
Black holes | Relativistic cosmology | Unitary field theory |
Anthropic principle or cosmic God | ||
Nuclear physics and physics of ionizing radiation | ||
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