After some passage of time, the string interactions cause the symmetry of the universe to spontaneously break, causing three of the nine dimensions to expand.
The other six are left stunted at the Planck length. “The time when the symmetry is broken is the birth of the universe,” says Nishimura..
Cosmic strings are hypothetical 1-dimensional topological defects which may have formed during a symmetry-breaking phase transition in the early universe when the topology of the vacuum manifold associated to this symmetry breaking was not simply connected..
String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter physics, and it has stimulated a number of major developments in pure mathematics..
Instead of treating subatomic particles as the fundamental building blacks of matter, string theory says that everything is made of unbelievably tiny strings, whose vibrations produce effects that we interpret as atoms, electrons and quarks..
Summary. — In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different initial conditions are possible, and not necessarily unlikely..
String theory posits that at the beginning of the universe (up to 10−43 seconds after the Big Bang), the four fundamental forces were once a single fundamental force..
This approach can be dated back to a paper by Gabriele Veneziano that shows how an inflationary cosmological model can be obtained from string theory, thus opening the door to a description of pre- Big Bang scenarios.
The idea is related to a property of the bosonic string in a curve background, better known as nonlinear sigma model.
[Submitted on 8 Mar 2023 ( v1 ), last revised 5 May 2023 (this version, v2)] We review applications of string theory to cosmology, from primordial times to the present-day accelerated expansion.
String cosmology appears to have difficulties in explaining this transition.
This is known in the literature as the graceful exit problem .
An inflationary cosmology implies the presence of a scalar field that drives inflation.
In string cosmology, this arises from the so-called dilaton field.
According to some calculations, the cosmos might have cooled so quickly that the fabric of space-time became fractured, creating a network of whisper-thin tubes filled by pure energy that stretch across the breadth of the observable universe.
This is one possible origin story of cosmic strings.
This approach can be dated back to a paper by Gabriele Veneziano that shows how an inflationary cosmological model can be obtained from string theory, thus opening the door to a description of pre-Big Bangscenarios.
The idea is related to a property of the bosonic string in a curve background, better known as nonlinear sigma model.
First calculatio.
This section presents some of the relevant equations entering into string cosmology.
The starting point is the Polyakov action, which can be written as.
1) S 2 = 1 4 π α ′ ∫ d 2 z γ [ γ a b G μ ν ( X ) ∂ a X μ ∂ b X ν + α ′ ( 2 ) R Φ ( X ) ] , {\\displaystyle S_{2}={\\frac {1}{4\\pi \\alpha '}}\\int d^{2}z{\\sqrt {\\gamma }}\\left[\\gamma ^{ab}G_{\\mu \ u }(X.
Speculative feature of the early universe
