*Sweepstakes not currently available in all countries; visit echecs16.info for .. Chapter Our Universe — String Theory, Cosmology, and Astrophysics echecs16.info, for those who don't believe that these concepts are sci-. Five key ideas are at the heart of string theory. Become familiar with these key elements of string theory right off the bat. Read on for the very basics of these five . Schwarz and “String Theory in a Nutshell” by Kiritsis both deal with the bosonic .. unknown”, or because it is explained away as an environmental quantity as in .
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PDF | On Dec 1, , Stewart Bland and others published String Theory for Dummies. String theory is hardly the only possible approach to taming the graviton. ish kind fermions, the terms deriving from the names of the physicists who explained them. What exactly is this wave InABeginningTikkunpdf. Tegmark, Max. Doug Lowe has written a whole bunch of computer books, including more than 35 For Dummies books Networking for String Theory. Volume 1.
String Theory For Dummies Cheat Sheet - For Dummies Superpartners in String Theory String theorys concept of supersymmetry is a fancy way of saying that each particle has a related particle called a superpartner. Keeping track of the names of these superpartners can be tricky, so here are the rules in a nutshell. The superpartner of a fermion begins with an s, so the superpartner of an electron is the selectron and the superpartner of the quark is the squark. The superpartner of a boson ends in ino, so the superpartner of a photon is the photino and of the graviton is the gravitino. Use the following table to see some examples of the superpartner names.
Several models were constructed to show how this energy and pressure affected the expansion and contraction of space. When Einstein created his first model based on the general theory of relativity, he realized that it implied an expanding universe. At the time, no one had any particular reason to think the universe was expanding, and Einstein assumed that this was a flaw in his theory.
Einsteins general relativity equations allowed for the addition of an extra term while remaining mathematically viable. Einstein found that this term could represent a positive energy or negative pressure uniformly distributed throughout the fabric of space-time itself, which would act as anantigravity, or repulsive form of gravity.
This term was chosen to precisely cancel out the contraction of the universe, so the universe would be static or unchanging in time. In , the same year Einstein published his equations containing the cosmological constant, Dutch physicist Willem de Sitter applied them to a universe without matter, in which the only thing that exists is the energy of the vacuum the cosmological constant itself.
Even in a universe containing no matter at all, this means that space will expand. A de Sitter space has a positive value for the cosmological constant, which can also be described as a positive curvature of space-time.
A similar model with a negative cosmological constant or a negative curvature, in which expansion is slowing is called an anti-de Sitter space. In , the Russian physicist Aleksandr Friedmann turned his hand to solving the elaborate equations of general relativity, but decided to do so in the most general case by applying thecosmological principle which can be seen as a more general case of the Copernican principle , which consists of two assumptions: The universe looks the same in all directions its isotropic.
The universe is uniform no matter where you go its homogenous. With these assumptions, the equations become much simpler. Einsteins original model and de Sitters model both ended up being special cases of this more general analysis.
Each solution matches a certain geometry of space, which can be represented in a simplified way by the way space naturally curves in the universe, as shown in Figure Closed universe: There is enough matter in the universe that gravity will eventually overcome the expansion of space.
The geometry of such a universe is a positive curvature, such as the sphere in the leftmost image in the figure below.
This matched Einsteins original model without a cosmological constant. Open universe: There isnt enough matter to stop expansion, so the universe will continue to expand forever at the same rate.
This space-time has a negative curvature, like the saddle shape shown in the middle image in the figure below. Flat universe: The expansion of the universe and the density of matter perfectly balance out, so the universes expansion slows down over time but never quite stops completely.
When the theory was originally developed in the s, the filaments of energy in string theory were considered to be 1-dimensional objects: One-dimensional indicates that a string has only one dimension, length, as opposed to say a square, which has both length and height dimensions.
These strings came in two forms — closed strings and open strings. It was eventually found that these early strings, called Type I strings, could go through five basic types of interactions, as shown this figure.
This proved to be important, because the closed strings have properties that make physicists believe they might describe gravity. Instead of just being a theory of matter particles, physicists began to realize that string theory may just be able to explain gravity and the behavior of particles.
Over the years, it was discovered that the theory required objects other than just strings. These objects can be seen as sheets, or branes. Strings can attach at one or both ends to these branes. A 2-dimensional brane called a 2-brane is shown in this figure.
Modern physics has two basic scientific laws: These two scientific laws represent radically different fields of study. Quantum physics studies the very smallest objects in nature, while relativity tends to study nature on the scale of planets, galaxies, and the universe as a whole.
Obviously, gravity affects small particles too, and relativity accounts for this as well.
Theories that attempt to unify the two theories are theories of quantum gravity, and the most promising of all such theories today is string theory. Hand-in-hand with the question of quantum gravity, string theory attempts to unify the four forces in the universe — electromagnetic force, the strong nuclear force, the weak nuclear force, and gravity — together into one unified theory.
In our universe, these fundamental forces appear as four different phenomena, but string theorists believe that in the early universe when there were incredibly high energy levels these forces are all described by strings interacting with each other.
All particles in the universe can be divided into two types: String theory predicts that a type of connection, called supersymmetry, exists between these two particle types.
Under supersymmetry, a fermion must exist for every boson and vice versa.