String thoery - extra dimensions

In summary, string theory requires 26 dimensions when incorporating quantum mechanics and 10 dimensions when including fermionic strings. This is due to a mathematical requirement involving a central term that only vanishes for specific dimensions. The underlying physical reason for this remains unclear and is often worked around by compactifying the extra dimensions.
  • #1
kashiark
210
0
Why does string theory need so many dimensions? i know in our 3 it would break special relativity but i don't know why
 
Physics news on Phys.org
  • #2
First of all, note that "classical" string theory in 3 dimensions is no problem at all. The requirement for 26 dimensions only comes when you try to fit in quantum mechanics, i.e. you try to canonically quantize your strings. When you include fermionic strings as well, you "only" need 10 dimensions.

The mathematical reason, although the calculations are usually categorized in "advanced mathematics", can in principle be traced. (If it means anything to you: there is some algebra involving a central term which depends on the dimension d of space-time and only vanishes for a special choice of d = 10, 11 or 26 - depending on the theory you're looking at).
The physical reason why it should only work in that particular number of dimensions is, AFAIK, not so clear. At least I've never really heard any good reason why it is like it is, people just accept it and devise ways around it (e.g. compactifying the extra dimensions).
 
  • #3


String theory is an attempt to provide a unified theory that combines the principles of general relativity and quantum mechanics. This theory proposes that the fundamental building blocks of the universe are not particles, but tiny, vibrating strings. In order for string theory to be consistent with both general relativity and quantum mechanics, it requires a total of 10 dimensions.

One of the main reasons for the need for extra dimensions in string theory is that it allows for the unification of the four fundamental forces of nature - gravity, electromagnetism, strong nuclear force, and weak nuclear force. In our 3-dimensional world, it is difficult to explain how these forces can coexist and interact with each other. However, in higher dimensions, these forces can be described in a more elegant and unified way.

Furthermore, string theory also requires extra dimensions in order to solve the problem of ultraviolet divergences in quantum field theory. In our 3-dimensional world, these divergences arise when trying to calculate the behavior of particles at extremely small distances. However, in higher dimensions, these divergences disappear, making the theory more mathematically consistent.

It is important to note that these extra dimensions are not physical dimensions that we can observe or experience. They are compactified, meaning they are curled up and hidden from our perception. This is why we do not perceive more than three dimensions in our everyday lives.

In summary, string theory requires extra dimensions in order to unify the fundamental forces of nature and to solve mathematical inconsistencies within the theory. While it may seem counterintuitive to our 3-dimensional perception, these extra dimensions are essential for the development of a complete and consistent theory of the universe.
 

1. What is string theory and how does it explain extra dimensions?

String theory is a theoretical framework in physics that aims to unify all known fundamental forces in nature. It suggests that the fundamental building blocks of the universe are not particles, but tiny, one-dimensional strings. These strings vibrate at different frequencies and create different particles, which give rise to the four fundamental forces (gravity, electromagnetism, strong nuclear force, and weak nuclear force) that we observe. String theory also allows for the existence of additional dimensions beyond the three spatial dimensions (length, width, and height) and one temporal dimension (time) that we experience in our everyday lives.

2. How many extra dimensions does string theory predict?

String theory predicts the existence of six or seven extra dimensions in addition to the four dimensions we already know. However, the exact number and size of these dimensions are still a subject of debate and have not been experimentally confirmed.

3. Can we physically observe these extra dimensions?

No, we cannot physically observe these extra dimensions because they are too small for our current technology to detect. According to string theory, these dimensions are "curled up" or compactified at the subatomic level, making them inaccessible to our senses.

4. What implications do these extra dimensions have on the universe?

The existence of extra dimensions could help explain some of the mysteries of the universe, such as the unification of the four fundamental forces and why gravity is weaker than the other forces. It could also potentially provide insights into phenomena like dark matter and dark energy, which make up a significant portion of the universe but cannot be explained by our current understanding of physics.

5. Is string theory the only theory that proposes extra dimensions?

No, there are other theories such as Kaluza-Klein theory and brane theory that also propose extra dimensions. However, string theory is the most well-known and extensively studied among them. It is also the only theory that attempts to incorporate all four fundamental forces into a single framework.

Similar threads

  • Beyond the Standard Models
Replies
2
Views
2K
  • Beyond the Standard Models
Replies
5
Views
2K
  • Beyond the Standard Models
Replies
2
Views
2K
  • Beyond the Standard Models
Replies
1
Views
1K
  • Beyond the Standard Models
Replies
1
Views
1K
  • Beyond the Standard Models
Replies
31
Views
2K
  • Beyond the Standard Models
Replies
1
Views
1K
  • Beyond the Standard Models
Replies
1
Views
1K
  • Beyond the Standard Models
Replies
2
Views
2K
  • Beyond the Standard Models
Replies
1
Views
1K
Back
Top