Strings and the size of particles

In summary: Etc.In summary, string theory is a misnomer, current theory work with branes, and the only known vibration modes are supersimmetric modes. There is no evidence for the existence of other vibrational modes that coincide with known particles of the standard model.
  • #1
Moneer81
159
2
Hi,

If elementary particles are nothing but a mode of vibration of a string, and if strings are on the order of Planck's length, then how did we end up with particles that are as big as 10^20 times Planck's length?
 
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  • #2
In the Standard Model the particles start out as massless and dimensionless. They acquire mass through the Higgs mechanism. The proton and neutron have size because they are multiparticle systems with lots of space between the three quarks and an "ocean" of massless virtual gluons flying around holding it all together. As quantum particles they are defined by their wave functions. So the quarks and gluons could well be vibration modes of tiny strings which BTW are not the size of the PLanck length but somewhat bigger.
 
  • #3
Moneer81 said:
Hi,

If elementary particles are nothing but a mode of vibration of a string, and if strings are on the order of Planck's length, then how did we end up with particles that are as big as 10^20 times Planck's length?

Unfortunately

i) there is no link between particles and strings. Except methaphysical ones.

ii) string theory is a misnomer, since current theory work with branes and would be called brane theory. In fact, is callled brane theory in research papers but "string theory" in popular talks and books. Emphasizing the myth around string theory.

iii) The only "well-known" vibration modes are masless supersimmetric modes. There is a belief that would explain hypotetical particles like the graviton, but no prooof.

iv) Nobody has found nonsupersimmetric nonzero mass modes of vibrations that coincide with known particles of the standard model.

v) Nobody know if strings (or branes) are of the order of Planck's length.

vi) Etc
 
  • #4
Juan R. said:
Unfortunately

i) there is no link between particles and strings. Except methaphysical ones.

ii) string theory is a misnomer, since current theory work with branes and would be called brane theory. In fact, is callled brane theory in research papers but "string theory" in popular talks and books. Emphasizing the myth around string theory.

iii) The only "well-known" vibration modes are masless supersimmetric modes. There is a belief that would explain hypotetical particles like the graviton, but no prooof.

iv) Nobody has found nonsupersimmetric nonzero mass modes of vibrations that coincide with known particles of the standard model.

v) Nobody know if strings (or branes) are of the order of Planck's length.

vi) Etc

(i) through (iv) are absolutely correct and I didn't deny them.


On (v), string (and brane and M-) theorists assume they have a spacetime continuum available to them and that motion, implied in the worldsheet, is unproblematical. Furthermore they (mostly) treat gravity as negligible. This implies their dimensions are large compared to the Planck length where the Compton radius equals the Schwartzschild radius.
 
  • #5
I vote for (vi).
 
  • #6
ohwilleke said:
I vote for (vi).

I think she's pretty cute too.
 
  • #7
selfAdjoint said:
On (v), string (and brane and M-) theorists assume they have a spacetime continuum available to them and that motion, implied in the worldsheet, is unproblematical. Furthermore they (mostly) treat gravity as negligible. This implies their dimensions are large compared to the Planck length where the Compton radius equals the Schwartzschild radius.

Thanks!

Regarding (v) I mean that in proper formulation of string or brane theory there is nothing fixing really the scale of the string or branes. Whereas in other alternatives a Planck scale arise naturally, string or brane theorist choose the tension parameter which in last instance fix really the size of the string. The situation is similar to the status of 'hidden' dimensions, each author chooses a size: Planck scale (or several orders of magnitude larger, as you correctly note), mm range, cosmological, etc.

I also was expresing idea that in cosmology is supposed that strings (branes) are of cosmological scale. For example in brane cosmology is assumed that 4D spacetime is a brane of size more large that radius of observed universe. This is 'explained' from dualities.

I simply desired to express with my previous points that is said in popular books, talks, and magazines is very, very different is said in research articles on the topic.
 
Last edited:

1. What are strings in relation to particles?

Strings are one-dimensional objects that are believed to make up the smallest building blocks of matter. They are thought to vibrate at different frequencies and create different particles based on their vibrations.

2. How do strings affect the size of particles?

The size of a particle is determined by the length of the string it is made up of. The longer the string, the larger the particle. Different vibrations of the string can also create particles with different sizes.

3. What is the significance of string size in particle physics?

The size of strings is a crucial factor in understanding the fundamental structure of matter. By studying string size and its effects on particles, scientists can gain insight into the underlying laws and principles that govern the universe.

4. Can strings be observed or measured?

Currently, strings cannot be directly observed or measured due to their incredibly small size. However, scientists can study their effects on particles and make predictions based on mathematical models and experiments.

5. How does string theory differ from traditional particle physics?

In traditional particle physics, particles are thought to be point-like objects with no internal structure. String theory, on the other hand, proposes that particles are made up of strings, which have length and vibrate at different frequencies. This theory aims to provide a more comprehensive explanation of the fundamental nature of matter.

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