# Which equations of 5 string theories show that elementary particles formed by strings?

It is commonly said that

"elementary particles are indeed formed by strings."

(from E Witten interview)

Which equations of string theory show that elementary particles are indeed formed by strings (2d string worldsheets)?

How to see elementary particles in equations of each version of string theory?

• In Type I?
• In Type IIA?
• In Type IIB?
• In Type SO(32)?
• In Type $$E_8 \times E_8$$?

Can we take electrons and $$u,d$$ quarks as examples?

• Well, particles arising in the spectrum of a string can be seen in even the simpler model of the bosonic string, if that general mechanism is what you are after. – JamalS Jul 26 '20 at 15:07
• It is commonly said that <YouTube link> Questions on PSE are expected to be self-contained and not require watching videos. Please edit your question to explain what is commonly said. – G. Smith Jul 26 '20 at 16:36
• done -sorry I missed a sentennce – annie marie heart Jul 26 '20 at 20:02

"that elementary particles formed by strings?"

Elementary particles are described theoretically by the standard model a well developed and flexible quantum field theory, with the group structure of SU(3)xSU(2)xU(1).

The interest in string theories arises because this group structure can be embedded in the group behavior of the vibrations of a string. Automatically all the success of the standard model can be reproduced by string theories in their mathematical construction, assuming that the elementary particles are vibrations on a string,( of any type as long as they can carry the group structure).

In a sense , if strings had been studied before the experimental observation of SU(3)xSU(2)xU(1) , they could have predicted it.

It is not in the equations , but in the solutions, elementary particles are identified with the vibrations of the string of any type.

• But where do we see SU(3)xSU(2)xU(1) from string theory and where do we see quarks and leptons from string theory? – annie marie heart Jul 26 '20 at 20:00
• excuse me, I am hoping more details to show the spectra of elementary particles. – annie marie heart Jul 26 '20 at 20:10
• the groups structure exists in string theories, the spectra, if you mean the masses depend on the type of theory one chooses and the energy . If at very high energies all masses are zero (in specific theories for cosmology for example). we just try to map the theoretical map on the data, and it fits because the same groups appear. It isongoing research. justthe possibility exists. see these talks physics.ox.ac.uk/pp/seminars/String%20Phenomenology.pdf nikhef.nl/~t58/Presentations/VU_26_2.pdf for the progress – anna v Jul 27 '20 at 4:28
• quarks and lepton spectra experimentally are organized in the symmetries of SU(3)xSU(2)xU(1) , those are the spectra at low energies the symmetries are broken and we see a different mass. the group structure of the spectra is expected to persist at high energies, and that is why any theory of everything has to embed SU(3)xSU(2)xU(1) – anna v Jul 27 '20 at 5:25
• just saw this , and it might interest you to see how the particle spectrum appears in a specific model arxiv.org/abs/2007.13248 – anna v Jul 28 '20 at 8:23