Questions tagged [integrable-systems]
Liouville integrability means that there exists a regular foliation of the phase space by invariant manifolds such that the Hamiltonian vector fields associated to the invariants of the foliation span the tangent distribution: there exists a maximal set of Poisson-commuting invariants in phase space. May be used more broadly for systems possessing simple analytic solutions.
262 questions
0 votes
1 answer
89 views
Using conserved quantities as variables in Mechanics
I am currently taking a course in theoretical (classical) Mechanics, where I have learned about the Darboux theorem. My professor has also mentioned one can "reduce the system by symmetry", ...
3 votes
1 answer
117 views
Dynamical 2-cocycle condition for $sl_2$
I am reading these lecture notes https://arxiv.org/abs/math/9908064 on the dynamical Yang-Baxter equation and have a question regarding the dynamical 2-cocycle condition. (See also the book "The ...
2 votes
1 answer
190 views
Additional conserved currents and charges of the free scalar QFT
I'm following notations/conventions of Srednicki, chapter 3. My question relates to some conserved currents and charges of the free real scalar field, that arise in addition to the translation and ...
2 votes
0 answers
48 views
Invariants of the Kovalevskaya top and Lie groups
I read that the Kovalevskaya top has 4 invariants of motion: energy $H_K$ Kovalevskaya invariant $ K=\xi _{+}\xi$ angular momentum component in the $z$-direction $L_z$ magnitude of the $n$-vector: ${\...
2 votes
0 answers
176 views
Factor 4 in gauge fixing condition in Costello, Witten, Yamazaki paper "Gauge Theory and Integrability, I"
I'm trying to compute the propagators of the 4d Chern-Simons theory introduced in the paper "Gauge theory and Integrability, I" of Costello, Witten and Yamazaki. They pick a Lorenz like ...
0 votes
1 answer
119 views
What are the conserved quantities for the Euler top? And how does the symplectic formalism differ from the Poisson?
I am currently trying to explain why the free rigid body with a fixed point is an integrable system. My questions are the following: A $2n$-dimensional system is called integrable if there are $n$ ...
4 votes
2 answers
226 views
Infinitely many conserved currents in an (1+1)D free QFT
In a (1+1)D integrable quantum field theory (e.g. the sine-Gordon model), there is a tower of infinitely many conserved currents with increasing spins. During a scattering, the existence of such a ...
1 vote
2 answers
329 views
Is mass times velocity cubed $mv^3$ also conserved?
In many situations (e. g. elastic collisions) we have conservation of the quantities of momentum ($p=mv$) and kinetic energy ($K=\frac{1}{2}mv^{2}$). Does this extrapolate? Let's say in 1D for ...
3 votes
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Locality in QFT and energy density
I am reading this paper on twist fields in 2D integrable QFT: https://arxiv.org/abs/0706.3384 In page 3, the authors offer the following definition of locality in QFT, relativistic as well as ...
1 vote
0 answers
191 views
Can the 3-body problem be solved in a 1D simplified case?
The general 3-body problem is well-known to be unsolvable in closed form due to its chaotic nature. However, I am curious about a specific, simplified scenario: If we consider three particles, each ...
2 votes
1 answer
141 views
Integrable systems with explicit time dependence
Integrable systems are usually defined as those with an extensive amount of conserved charges. Now take one of these systems, and make one parameter time-dependent for all times, with e.g. an ...
2 votes
1 answer
477 views
What is the exact ground state energy of the 1D finite XY model in open boundary condition?
From what I understand, the XY model is exactly mapped to free fermions tight-binding approximation. I follow this lecture notes to find the formula for ground state of the model to be $$ k = \frac{2\...
4 votes
2 answers
514 views
Is there a classical Lagrangian system with essentially no cyclic coordinates?
Here is what I mean: In Lagrangian mechanics, we have the equation $$ \frac{\mathrm{d}}{\mathrm d t} \frac{\partial L}{\partial \dot q_i} = \frac{\partial L}{\partial q_i},\quad i = 1,2, \cdots, n. $$ ...
7 votes
2 answers
467 views
What is the need for angle-action variables in describing integrable systems?
I am currently reading Chapter 2 of Theoretical Astrophysics Vol 1 by T. Padmanabhan. Here he discusses integrable systems in Hamiltonian mechanics. The idea of angle action variables are introduced ...
7 votes
2 answers
675 views
How is the Yang-Baxter equation equivalent to the Braid equation?
Note: The origins of the Yang-Baxter equation is in physics, not mathematics. Let $V$ be a vector space. Let $R: V \otimes V \to V \otimes V$ be a linear operator. Consider a labelled (for notational ...