# Tagged Questions

String theory is an research framework in particle physics that attempts to reconcile quantum mechanics and general relativity.

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### String-Theory: $1+2+3…=-\frac{1}{12}$

Probably almost everyone knows this formula: $$\sum_{k=1}^\infty k=1+2+3+4...=-\frac{1}{12}$$ Obviously it is just a bit magic. On one hand Numberphile has some arguments why it is true: http://www....
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### How many different subsequence in Thue-Morse sequence

Consider the Thue-Morse string. Suppose it has $n$ elements. My question is: how many different substrings(or subsequence) in this string. Actually I'm interest in bound of this value. Is it smth ...
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### What is spectral flow symmetry?

I can't find much about this, and am looking into this to satisfy personal curiosity. I will like to know what spectral flow is, and what spectral flow symmetry is. I tried looking for this on ...
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### Semi-infinite forms?

I am reading Vafa's paper 'Topological Mirros and Quantum Strings'(arXiv:hep-th/9111017). In this paper, the author says the Hilbert Space of a fermionic string theory corresponds to the space of semi-...
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### Image of ring homomorphism $\phi : \mathbb{Z}[t] \to \mathbb{Q}$?

Here is a problem I face practicing the theory of rings: Define $\phi : \mathbb{Z}[t] \to \mathbb{Q}$, a ring homomorphism (it does map $1$ to $1$). I'm trying to show that if $\phi(t)=\frac{u}{v}$...
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### (Soft Question) How active an area of research is Non-Commutative Geometry? [closed]

I am currently an undergraduate, but I am considering applying for a phd in algebraic geometry or a related field. I am quite interested in the link between non-commutative geometry and theoretical ...
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### How many bit strings of length 7 exist if the string remains unchanged if it is reversed?

How many bit strings of length 7 exist if the string remains unchanged if it is reversed ? 1 1 1 1 1 1 1 and 1 0 0 1 0 0 1 are an example that is unchanged if reversed. 0 0 0 0 0 0 0 and 0 1 1 0 1 1 ...
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### rigorous treatment of infinitesimal reparametrizations

my first post :) I am asking this directed to mathematicians or mathematical physicists since I don't like the usual physics approach. Reading some string theory books I always find that the ...
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### What is a good gentle introduction to the Virasoro algebra and its application in theoretical physics?

I am looking for an as gentle and pedagogical as possible introduction that explains the Virasoro algebra and its applications in theoretical physics; finally I am interested in its application in ...
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