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arxiv: 2605.04823 · v2 · pith:2VYI4APV · submitted 2026-05-06 · hep-th · cond-mat.stat-mech

Expectation values after an integrable boundary quantum quench

Zolt\'an Bajnok , D\'avid F\"ulepi , M\'at\'e Lencs\'es This is my paper

Reviewed by Pith T0 review T1 audit T2 compute T3 formal T4 kernel 2026-06-30 23:34 UTCgrok-4.3pith:2VYI4APVrecord.jsonopen to challenge →

classification hep-th cond-mat.stat-mech
keywords integrable boundary quenchform factorsLee-Yang modelreal-time dynamicsboundary-changing operatorstruncated conformal space approachexpectation values
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0 comments X

The pith

Form factors of bulk and boundary-changing operators determine the real-time dynamics after an integrable boundary quench.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper develops a general framework to analyze real-time dynamics after switching one integrable boundary condition to another. The framework relies on form factors of bulk and boundary-changing operators to express the evolution of the pre-quench vacuum. It is applied first at the conformal point of the Lee-Yang model and then to the massive perturbation. Analytic results for vacuum-to-vacuum matrix elements of local operators are obtained and checked numerically with an adapted truncated conformal space approach. A sympathetic reader would care because this supplies a concrete calculational tool for post-quench observables in solvable models.

Core claim

We develop a general framework for analyzing the resulting real-time dynamics based on form factors of bulk and boundary-changing operators. We first study the problem at the conformal point of the Lee-Yang model and then extend the analysis to its massive perturbation, where we examine the time evolution of the pre-quench vacuum and compute the vacuum-to-vacuum matrix elements of local operators inserted after the quench. The analytical results are validated by numerical calculations using the truncated conformal space approach adapted to boundary-changing situations.

What carries the argument

The form factors of bulk and boundary-changing operators that allow expansion of the post-quench state in a basis suitable for computing time-dependent local expectations.

If this is right

  • The time evolution of the pre-quench vacuum is expressible via form factor sums in the Lee-Yang model.
  • Vacuum-to-vacuum matrix elements of local operators after the quench follow from the same expansion.
  • The framework works both at criticality and in the massive regime.
  • The analytic predictions match numerical results from the adapted truncated conformal space approach.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The framework may apply to other two-dimensional integrable models with known form factors.
  • Boundary-changing operators could help analyze a wider class of boundary quenches.
  • The success in the massive regime indicates the method is not limited to the critical point.

Load-bearing premise

The form factors of bulk and boundary-changing operators suffice to capture the complete real-time dynamics after the boundary quench.

What would settle it

A mismatch between the form-factor predictions and independent numerical or exact results for the time-dependent expectation values in the massive Lee-Yang model.

read the original abstract

We investigate an integrable boundary quench, in which one integrable boundary condition is suddenly switched to another. We develop a general framework for analyzing the resulting real-time dynamics based on form factors of bulk and boundary-changing operators. We first study the problem at the conformal point of the Lee-Yang model and then extend the analysis to its massive perturbation, where we examine the time evolution of the pre-quench vacuum and compute the vacuum-to-vacuum matrix elements of local operators inserted after the quench. The analytical results are validated by numerical calculations using the truncated conformal space approach adapted to boundary-changing situations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 2 minor

Summary. The manuscript develops a general framework for real-time dynamics after an integrable boundary quench, based on form factors of bulk and boundary-changing operators. It first treats the conformal point of the Lee-Yang model, then extends the analysis to the massive perturbation by computing the time evolution of the pre-quench vacuum and the vacuum-to-vacuum matrix elements of local operators inserted after the quench. Analytic results are validated numerically with a boundary-adapted truncated conformal space approach (TCSA).

Significance. If the central claims hold, the work supplies a systematic form-factor method for boundary quenches that extends existing techniques to boundary-changing operators and supplies explicit, testable expressions in a concrete model. The combination of analytic derivations with reproducible numerical checks via adapted TCSA is a concrete strength.

minor comments (2)
  1. The notation for boundary-changing form factors is introduced without an explicit comparison table to the corresponding bulk form factors; adding such a table in §3 would improve readability.
  2. Figure 4 caption does not state the truncation level used in the TCSA data; this detail should be added for reproducibility.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our work on the form-factor framework for integrable boundary quenches in the Lee-Yang model, including the analytic derivations and numerical validation via adapted TCSA. We are pleased that the referee recommends acceptance.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper constructs a form-factor framework for real-time dynamics after an integrable boundary quench in the Lee-Yang model, first at the conformal point and then in the massive perturbation, with explicit vacuum-to-vacuum matrix elements and numerical validation via boundary-adapted TCSA. No derivation step reduces by construction to a fitted input, self-citation loop, or renamed ansatz; the analytic results rest on standard integrable-model techniques whose inputs (form factors) are independently computable and the numerics provide external falsifiability outside any fitted parameters. The derivation chain is therefore self-contained.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no information on free parameters, axioms, or invented entities.

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discussion (0)

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Reference graph

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