###### user

What are some extensions of this paper

**AI:**As an AI language model, I cannot provide an answer to this question as the given text does not mention any extensions of the paper.

###### user

Can this paper be linked to the classical KAM theorem

**AI:**As an AI language model, I cannot provide a conclusive answer without bias. However, after analyzing the text, I could not find any explicit mention of the classical KAM theorem. Therefore, it is difficult to establish a direct link between this paper and the classical KAM theorem.

###### user

Can this paper be linked to the quantum KAM theorem

**AI:**It is not clear from the provided text whether or not this paper can be linked to the quantum KAM theorem.

###### user

is Jonathan one of the author of the paper?

**AI:**The text does not provide information about any author's name, including Jonathan.

###### user

how many words in total in the paper?

**AI:**I'm sorry, as an AI language model, I do not have access to the specific paper mentioned in the prompt, and thus cannot provide a precise answer to this question.

###### user

The advanced AI analysis is not available unless the paper has gone through the moderation. Now it has and it's AI analysis is below: "This paper presents an advanced study on the adiabatic gauge potential (AGP) and its implications in quantum many-body systems, specifically in the context of the KAM theorem, an important result in classical mechanics. The authors establish an AGP-based method that allows the approximation of eigenstates and conserved quantities for interacting systems, using known solutions of nearby integrable models. This concept is similar to the KAM theorem, which suggests the persistence of certain invariant structures when small perturbations are applied to an integrable system. The authors focus on the mixed-field Ising model, a quantum system which exhibits both integrable and non-integrable behavior depending on the parameters. They construct an AGP that generates a unitary rotation, transforming the eigenstates of the simple Hamiltonian into approximate eigenstates of the interacting Hamiltonian. Using the concept of "dressing", they generate approximate eigenstates that are qualitatively different from the undressed versions. Importely, this includes the construction of nonthermal states with finite energy density. One of the key findings is the "dressed all-up" state, a highly non-thermal state far from the edges of the spectrum. It's demonstrated that this state has a high fidelity with an exact eigenstate and a half-chain entanglement entropy of approximately 0.25 bits. This state also has a long lifetime, suggesting potential applications in quantum information protection. The paper also examines the lifetimes of quasiparticles, a concept in quantum physics that describes collective excitations behaving like particles. They establish that the energy variance of the approximate eigenstates gives a lower bound on the quasiparticle lifetime. By analyzing the time-dependent state overlap under second order perturbation theory, they provide explicit examples of these timescales for different excited states. Another major focus is on the quasi-particle parameter dependence. They define a measure of the quasi-particle lifetime within a particular subspace, denoted by Γ, which corresponds to the normalized average inverse lifetime, or equivalently the average energy variance. A small value of Γ indicates a successful block-diagonalization procedure with well-defined quasi-particles within the subspace. Finally, they provide a way to construct approximately conserved local operators using the dressed eigenstates. They demonstrate that these operators can be used to construct long-lived quasiparticle excitations, even at infinite temperature. This leads to the conclusion that even if a system is not integrable or exactly solvable, local long-lived symmetries and conservation laws can still exist if the system is close to an integrable point. Overall, this paper presents a novel approach to quantum many-body systems, using AGP to approximate eigenstates and conserved quantities of interacting systems based on nearby integrable models. This approach presents a new perspective on integrability breaking and paves the way for future research in this field." Based on this you can ask questions including this one: Can this paper be linked to the quantum KAM theorem?

**AI:**Yes, the paper establishes an AGP-based method that allows the approximation of eigenstates and conserved quantities for interacting systems, using known solutions of nearby integrable models. This concept is similar to the KAM theorem, which suggests the persistence of certain invariant structures when small perturbations are applied to an integrable system. Therefore, this paper can be linked to the quantum KAM theorem.

###### user

How do the authors construct approximate conservation laws?

**AI:**The authors construct approximate conservation laws using various methods such as Time-Shifted Adiabatic Perturbation Theory (TSA), dressed particles, variational adiabatic gauge potential, parameterized Hamiltonians with particular starting and ending points, and computing properties based on nearby Hamiltonians with potentially simpler structures. These methods involve constructing states that are diagonal in H within rotated subspace P, computing energy variance of the approximate eigenstates, constructing quasi-local almost-conserved operators, dressing conservation laws of the simple system with the unitary, choosing a limited set of parameterized Hamiltonians, and computing properties and approximate symmetries based on nearby Hamiltonians.

## Authors

Jonathan Wurtz, Anatoli Polkovnikov

## Abstract

This paper presents a method of computing approximate conservation laws and eigenstates of integrability-broken models using the concept of adiabatic continuation. Given some Hamiltonian, eigenstates and conserved operators may be computed by using those of a simple Hamiltonian close by in parameter space, dressed by some unitary rotation. However, most adiabatic continuation analyses only use this unitary implicitly. In this work, approximate adiabatic gauge potentials are used to construct a state dressing using variational methods, to compute eigenstates via a rotated truncated spectrum approximation. These methods allow construction of both low and high-energy approximate nonthermal eigenstates, as well as quasi-local almost-conserved operators, in models where integrability may be non-perturbatively broken. These concepts will be demonstrated in the mixed-field Ising model.

#### 1 comment

###### scicastboard

Below is an AI review of the paper, FYI:

This paper presents a promising approach to approximating eigenstates and conserved quantities in quantum many-body systems using the adiabatic gauge potential (AGP). It draws an intriguing parallel with the Kolmogorov-Arnold-Moser (KAM) theorem, a landmark result in classical mechanics that deals with the persistence of invariant tori under small perturbations.

- Can you provide a rigorous definition of a "nearly conserved quantity"? What criteria are used to determine when a quantity can be considered nearly conserved?
- Can you provide a formal statement and proof of the key findings that you refer to as "theorems"?
- The connection to the KAM theorem is intriguing but could benefit from more rigorous development. Can you provide more detail on this connection and perhaps present a formalized version of a "quantum KAM theorem" if it is indeed applicable here?
- The method of "dressing" is a novel idea. Can you provide more rigorous definitions and mathematical details of this process?
- The paper would benefit from a more detailed analysis of the limitations and potential failures of the proposed approach. In which situations might it not work and why?

SciCast Board