Problems
Although bosonic string theory has many attractive features, it falls short as a viable physical model in two significant areas and is forced to posit a 26 dimensional spacetime to remedy inconsistencies.
First, it predicts only the existence of bosons whereas many physical particles are fermions.
Second, it predicts the existence of a mode of the string with imaginary mass, implying that the theory has an instability to a process known as "tachyon condensation".
In addition, bosonic string theory in a general spacetime dimension displays inconsistencies due to the conformal anomaly. But, as was first noticed by Claud Lovelace, in a spacetime of 26 dimensions (25 dimensions of space and one of time), the anomaly cancels. This high dimensionality is not necessarily a problem for string theory, because it can be formulated in such a way that along the 22 excess dimensions spacetime is folded up to form a small torus or other compact manifold. This would leave only the familiar four dimensions of spacetime visible to low energy experiments.
Read more about this topic: Bosonic String Theory
Famous quotes containing the word problems:
“...I have wanted to believe people could make their dreams come true ... that problems could be solved. However, this is a national illness. As Americans, we believe all problems can be solved, that all questions have answers.”
—Kristin Hunter (b. 1931)
“An interesting play cannot in the nature of things mean anything but a play in which problems of conduct and character of personal importance to the audience are raised and suggestively discussed.”
—George Bernard Shaw (1856–1950)
“It’s so easy during those first few months to think that the problems will never end. You feel as if your son will never sleep through the night, will always spit up food after eating, and will never learn to smile—even though you don’t know any adults or even older children who still act this way.”
—Lawrence Kutner (20th century)