* Astronomy

Members Login
Post Info
TOPIC: Superstrings


L

Posts: 130250
Date:
RE: Superstrings
Permalink  
 




__________________


L

Posts: 130250
Date:
String theory
Permalink  
 


String theory is one of the most famous ideas in modern physics, but it is also one of the most confusing.
At its heart is the idea that the fundamental particles we observe are not point-like dots, but rather tiny strings that are so small that our best instruments cannot tell that they are not points.
It also predicts that there are extra dimensions to space beyond the obvious length, breadth and depth, but we do not experience them because they are bunched up in tiny spaces.

Read more

__________________


L

Posts: 130250
Date:
RE: Superstrings
Permalink  
 


Edward Witten, a leading architect of string theory, works at the cutting edge of mathematics and physics in his quest for a "theory of everything". Matthew Chalmers met up with him to ask how it feels to work in an area so rarefied that it's a problem simply conveying to other people what he's up to
Read more

__________________


L

Posts: 130250
Date:
Permalink  
 


In clear, nontechnical language, string theorist Brian Greene explains how our understanding of the universe has evolved from Einstein's notions of gravity and space-time to superstring theory, where minuscule strands of energy vibrating in 11 dimensions create every particle and force in the universe. (This mind-bending theory may soon be put to the test at the Large Hadron Collider in Geneva.)


__________________


L

Posts: 130250
Date:
Permalink  
 

Title: "Black Universe" epoch in String Cosmology
Authors: Alex Buchel, Lev Kofman

String theory compactification involves manifolds with multiple warp factors. For cosmological applications, one often introduces a short, high-energy inflationary throat, and a long, low-energy Standard Model throat. It is assumed that at the end of inflation, the excited Kaluza-Klein modes from the Inflationary throat tunnel to the SM throat and reheat Standard Model degrees of freedom, which are attached to probe brane(s). However, the huge hierarchy of energy scales can result in a highly dynamic transition of the throat geometry. We point out that in such a cosmological scenario the Standard Model throat (together with SM brane) will be cloaked by a Schwarzschild horizon, produced by the Kaluza-Klein modes tunnelling from the short throat. The Black Brane formation is dual to the first order chiral phase transition of the cascading gauge theory. We calculate the critical energy density corresponding the formation of the BH horizon in the long throat. We discuss the duality between "Black Universe" cosmology and an expanding universe driven by the hot gauge theory radiation. We address the new problem of the hierarchical multiple-throat scenarios: SM brane disappearance after the decay of the BH horizon.

Read more (25kb, PDF)

__________________


L

Posts: 130250
Date:
New dimensions
Permalink  
 


The universe as we currently know it is made up of three dimensions of space and one of time, but researchers in the Department of Physics and the Department of Electrical and Computer Engineering at Virginia Tech are exploring the possibility of an extra dimension.
Sound like an episode from the Twilight Zone? Almost, but not quite; according to John Simonetti, associate professor of physics in the College of Science and Michael Kavic, graduate student and one of the investigators on the project, whose research was featured in a recent edition of Nature News Online and in New Scientist Magazine.

Read more

__________________


L

Posts: 130250
Date:
Extra Dimensions
Permalink  
 


Title: Constraints on the Size of Extra Dimensions from the Orbital Evolution of Black-Hole X-Ray Binaries
Authors: Tim Johannsen (Arizona), Dimitrios Psaltis (Arizona), Jeffrey E. McClintock (Harvard)

One of the plausible unification schemes in physics considers the observable universe to be a 4-dimensional surface (the "brane") embedded in a higher-dimensional curved spacetime (the "bulk"). In such braneworld gravity models with infinitely large extra dimensions, black holes evaporate through the emission of the additional gravitational degrees of freedom, resulting in lifetimes of stellar-mass black holes that are significantly smaller than the Hubble time. We show that the predicted evaporation rate leads to a change in the orbital period of X-ray binaries harbouring black holes that is observable with current instruments. We obtain an upper limit on the rate of change of the orbital period of the binary A0620-00 and use it to constrain the asymptotic curvature radius of the extra dimension to a value comparable to the one obtained by table-top experiments.

Read more (38kb, PDF)

__________________


L

Posts: 130250
Date:
RE: Superstrings
Permalink  
 


When the world's most powerful particle accelerator starts up later this year, exotic new particles may offer a glimpse of the existence and shapes of extra dimensions.
Researchers from the University of Wisconsin-Madison and the University of California-Berkeley say that the telltale signatures left by a new class of particles could distinguish between possible shapes of the extra spatial dimensions predicted by string theory.
String theory, which describes the fundamental particles of the universe as tiny vibrating strings of energy, suggests the existence of six or seven unseen spatial dimensions in addition to the time and three space dimensions that we normally see.

Read more

__________________


L

Posts: 130250
Date:
String Theory
Permalink  
 




__________________


L

Posts: 130250
Date:
Superstrings
Permalink  
 


Ancient light absorbed by neutral hydrogen atoms could be used to test certain predictions of string theory, say cosmologists at the University of Illinois. Making the measurements, however, would require a gigantic array of radio telescopes to be built on Earth, in space or on the moon.
String theory a theory whose fundamental building blocks are tiny one-dimensional filaments called strings is the leading contender for a theory of everything. Such a theory would unify all four fundamental forces of nature (the strong and weak nuclear forces, electromagnetism, and gravity). But finding ways to test string theory has been difficult.
Now, cosmologists at the U. of I. say absorption features in the 21-centimetre spectrum of neutral hydrogen atoms could be used for such a test.

Read more


__________________
«First  <  1 2 3 4 59  >  Last»  | Page of 9  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard