Hi everybody, it's my first post on here but as i seem to have hit a brick wall with my work i'm hoping somebody might be able to help me :)(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

I'm looking at how the planck scale is reduced in higher dimensions (ADD theories) and i've managed to reproduce an expression relating the 4-d gravitational constant [tex]G_{4}[/tex] and a fundamental gravitational constant [tex]G_{4+n}[/tex] by invoking gauss's law for gravity in extra dimensions around a line/plane of mass (due to the compactification of the extra dimensions). Here n represents the number of extra dimensions. With this i've had no problems and the answer I get seems to match the answers found in the literature.

The issue i'm having is with relating this change of gravitational constant to a change in planck length. I've just been using the normal relation for converting G into [tex]M_{pl}[/tex] i.e [tex]M_{4+n}=\sqrt{\frac{\hbar c^5}{G_{4+n}}}[/tex] but all the papers on the subject use the relation [tex]M_{4+n}^{2+n}\approx G_{4+n}^{-1}[/tex] with this relation I get all the right answers but I can't for the life of me figure out where it comes from. Can anyone let me know where the extra factor of [tex]M_{4+n}^n[/tex] arises?

Thanks for your time!

Nathan

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Planck scale in extra dimensions

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**