# Bound on the string tension of cosmic strings

+ 7 like - 0 dislike
448 views

Many GUT theories contain cosmic strings with string tension near GUT scale. I would like to ask: what is the upper bound of such a string tension from, say,  cosmic microwave background and the recent BICEP2 observation?

FYI, $SO(10)$ GUT energy scales (one example): $SO(10) \to Z_2\rtimes [SO(6)\times SO(4)] \sim_{\text{as Lie alg}} SU(4)\times [SU(2)\times SU(2)]$ $\to SU(3)\times SU(2)\times U(1)$. The first breaking [by Higgs in $54$ representation of the $SO(10)$] happens at $3.5\times 10^{15}$ GeV, and the second (by Higgs in $126$ and $126^*$ representations) around $10^{11}$ GeV. ($M_P=1.2\times 10^{19}$ GeV.)

We also have $10\times 10 =1_s +45_a +54_s$ and $16\times 16 = 10_s + 120_a +126_s$. For $SO(10) \to SU(4)\times SU(2)\times SU(2)$: $10\to (1,2,2)+(6,1,1)$ and $16\to (4,2,1)+(4^*,1,2)$.

edited Apr 7, 2014

+ 4 like - 0 dislike

Here are old bounds (without BICEP2):

http://arxiv.org/abs/1005.0479 gives $G\mu < 3\times 10^{-7}$ or $\sqrt{\mu} < 5\times 10^{-4} M_P$

http://arxiv.org/abs/1309.6637 gives $G\mu < 3\times 10^{-9}$ or $\sqrt{\mu} < 5\times 10^{-5} M_P$

Due to the unbroken $Z_2$ which leads to a cosmic string at $10^{15}$GeV, the above bound nearly rule out the breaking path $SO(10) \to Z_2\rtimes [SO(6)\times SO(4)] \sim_{\text{as Lie alg}} SU(4)\times [SU(2)\times SU(2)]$ .

answered Apr 6, 2014 by (3,485 points)
edited Apr 19, 2014

 Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead. To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL. Please consult the FAQ for as to how to format your post. This is the answer box; if you want to write a comment instead, please use the 'add comment' button. Live preview (may slow down editor)   Preview Your name to display (optional): Email me at this address if my answer is selected or commented on: Privacy: Your email address will only be used for sending these notifications. Anti-spam verification: If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:p$\hbar$ysicsOve$\varnothing$flowThen drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds). To avoid this verification in future, please log in or register.