- #1
dumbperson
- 77
- 0
This is actually not a homework problem, but a problem I'm encountering while working on a little project and I'm not sure if it's even solvable or if it makes sense what I'm doing
1. Homework Statement
First, I have the equation
$$p_{ij} = \frac{1}{2}\left( \tanh{(-\frac{\theta_i + \theta_j}{2} + 2Kp_{ij} )} + 1 \right)$$
where ##1 \leq i,j \leq N##. ##N## and ##K## are known quantities and ##\theta_i, \theta_j## are unknown.
The ##N## equations are $$C_i = \sum_{j\neq i}p_{ij}^* = \frac{N-1}{2} + \frac{1}{2}\sum_{j\neq i} \tanh{\left( - \frac{\theta_i + \theta_j}{2} + 2Kp_{ij}^* \right)}$$
where ##C_i## is a known quantity and ##p_{ij}^*## is the solution to the equation in the problem statement.
I want to solve for ##\theta_i, \theta_j##.
I don't necessarily need to solve this exactly, it can be done numerically.
I first tried to solve this problem by expanding the tanh to first order, which simply gives me a system of ##N## linear equations.
I feel as if this system of equations is only solvable if instead of the ##2Kp_{ij}^*## in the argument of the tanh, I had ##2K\sum_{j\neq i}p_{ij}##. This way, I would have the value of ##\sum_{j\neq i}p_{ij}^* = C_i (\textrm{given})## for every ##i##, I could plug this value into the tanh, and then solve for ##\theta_i##.
Is this problem solvable? Or do I not have enough information. To me it seems that I have ##N## unknown quantities (##\theta_i##) and ##N## equations, which should be doable. or am I missing something?
1. Homework Statement
First, I have the equation
$$p_{ij} = \frac{1}{2}\left( \tanh{(-\frac{\theta_i + \theta_j}{2} + 2Kp_{ij} )} + 1 \right)$$
where ##1 \leq i,j \leq N##. ##N## and ##K## are known quantities and ##\theta_i, \theta_j## are unknown.
Homework Equations
The ##N## equations are $$C_i = \sum_{j\neq i}p_{ij}^* = \frac{N-1}{2} + \frac{1}{2}\sum_{j\neq i} \tanh{\left( - \frac{\theta_i + \theta_j}{2} + 2Kp_{ij}^* \right)}$$
where ##C_i## is a known quantity and ##p_{ij}^*## is the solution to the equation in the problem statement.
I want to solve for ##\theta_i, \theta_j##.
The Attempt at a Solution
I don't necessarily need to solve this exactly, it can be done numerically.
I first tried to solve this problem by expanding the tanh to first order, which simply gives me a system of ##N## linear equations.
I feel as if this system of equations is only solvable if instead of the ##2Kp_{ij}^*## in the argument of the tanh, I had ##2K\sum_{j\neq i}p_{ij}##. This way, I would have the value of ##\sum_{j\neq i}p_{ij}^* = C_i (\textrm{given})## for every ##i##, I could plug this value into the tanh, and then solve for ##\theta_i##.
Is this problem solvable? Or do I not have enough information. To me it seems that I have ##N## unknown quantities (##\theta_i##) and ##N## equations, which should be doable. or am I missing something?