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arxiv: 2606.30233 · v1 · pith:E33BM57Fnew · submitted 2026-06-29 · ✦ hep-th

Complex Phase Structure and Widom line for Euler Heisenberg black holes

Pith reviewed 2026-06-30 05:19 UTC · model grok-4.3

classification ✦ hep-th
keywords Euler-Heisenberg black holesLee-Yang theoryWidom linecritical pointsAdS black holesphase transitionscomplex singularitiessupercritical thermodynamics
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The pith

Euler-Heisenberg AdS black holes support two critical points that merge at a degenerate point, producing a Widom line without a coexistence curve.

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

This paper examines the supercritical thermodynamics of Euler-Heisenberg AdS black holes using Lee-Yang phase transition theory extended to the complex domain. It establishes that the system can possess two distinct critical points corresponding to a four-phase structure. These critical points can merge into a higher-order degenerate critical point. At this merged point, a Widom line is identified through the distribution of complex singularities, serving as a stability boundary even without a conventional coexistence curve. The formalism is shown to be consistent with known cases of single or no critical points.

Core claim

The system admits two distinct critical points associated with a four-phase thermodynamic structure and a degenerate higher-order critical point where the two criticalities merge. Extending the thermodynamic description into the complex domain determines the distribution of Lee-Yang singularities and constructs complex phase diagrams. At the degenerate critical point a well-defined Widom line emerges despite the absence of a conventional coexistence curve, acting as an effective stability boundary in the supercritical regime. In the two-critical-point regime, the complex phase diagram exhibits two distinct Widom lines.

What carries the argument

Lee-Yang singularities in the complex plane applied to the equation of state of Euler-Heisenberg AdS black holes to map phase structure and define Widom lines.

If this is right

  • The two-critical-point regime produces two distinct Widom lines, one tied to coexistence and one from complex singularities alone.
  • A well-defined Widom line exists at the degenerate critical point as an effective stability boundary in the supercritical regime.
  • The Lee-Yang approach reproduces standard phase structures for systems with one critical point or none.
  • Complex phase diagrams consistently locate singularities for the four-phase structure.

Where Pith is reading between the lines

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

  • The method of defining Widom lines via complex singularities may apply to other gravitational systems with multiple critical points.
  • Stability boundaries in supercritical regimes could be identified more generally through singularity distributions rather than coexistence curves alone.

Load-bearing premise

The Lee-Yang formalism and its extension into the complex domain can be directly applied to the thermodynamics of Euler-Heisenberg AdS black holes to locate singularities and define Widom lines.

What would settle it

A mismatch between the computed locations of Lee-Yang zeros in the complex plane and the thermodynamic singularities derived from the black hole equation of state would falsify the claimed phase structure and Widom lines.

Figures

Figures reproduced from arXiv: 2606.30233 by Mozib Bin Awal, Prabwal Phukon.

Figure 1
Figure 1. Figure 1: FIG. 1: Thermodynamic behaviour of the Euler-Heisenberg AdS black hole in the four-phase [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: Merger of the two distinct critical points at the degenerate critical point [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: The two phases of the Euler-Heisenberg AdS black hole at the degenerate critical point. [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4: Distribution of the Lee-Yang singularities in the complex horizon-radius plane. Panel (a) [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5: Complex phase diagram of the Euler-Heisenberg AdS black hole at the degenerate [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6: FIG. 6: Comparison between the Widom line and the spinodal line ( [PITH_FULL_IMAGE:figures/full_fig_p009_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7: Complex phase diagram of the Euler-Heisenberg AdS black hole in the two-critical-point [PITH_FULL_IMAGE:figures/full_fig_p010_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8: Distribution of the Lee-Yang singularities in the complex horizon-radius plane [PITH_FULL_IMAGE:figures/full_fig_p011_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9: Complex phase diagram of the Euler-Heisenberg AdS black hole at the single critical [PITH_FULL_IMAGE:figures/full_fig_p012_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10: (a) Temperature and (b) specific heat profiles for Euler-Heisenberg black holes when [PITH_FULL_IMAGE:figures/full_fig_p012_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11: Distribution of the Lee-Yang singularities in the complex horizon-radius plane [PITH_FULL_IMAGE:figures/full_fig_p013_11.png] view at source ↗
read the original abstract

We investigate the supercritical thermodynamics of Euler-Heisenberg AdS black holes within the framework of Lee-Yang phase transition theory. We show that the system admits two distinct critical points associated with a four-phase thermodynamic structure and identify a degenerate higher-order critical point where the two criticalities merge. Extending the thermodynamic description into the complex domain, we determine the distribution of Lee-Yang singularities and construct the corresponding complex phase diagrams. At the degenerate critical point, we find that a well-defined Widom line emerges despite the absence of a conventional coexistence curve, acting as an effective stability boundary in the supercritical regime. In the two-critical-point regime, the complex phase diagram exhibits two distinct Widom lines, one associated with a coexistence curve and the other arising solely from the complex singularity structure. We further show that the Lee-Yang formalism consistently reproduces the expected phase structure for systems with a single critical point and in the absence of criticality. Our results reveal a rich supercritical phase structure and provide new insights into the origin and physical interpretation of Widom lines.

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

2 major / 1 minor

Summary. The manuscript applies Lee-Yang zero analysis in the complex plane to the thermodynamics of Euler-Heisenberg AdS black holes. It claims that the system possesses two distinct critical points that generate a four-phase structure, identifies a degenerate higher-order critical point at which the criticalities merge, and reports that well-defined Widom lines appear in the complex phase diagram (one tied to a coexistence curve and one arising purely from singularity structure) even in the absence of a conventional coexistence curve. The formalism is asserted to reproduce standard single-critical-point and non-critical cases.

Significance. If the direct substitution of the Euler-Heisenberg-AdS free energy into the Lee-Yang formalism can be rigorously justified from the underlying gravitational action, the work would supply a concrete example of multi-critical-point structure and complex-domain Widom lines in a black-hole system, extending the range of thermodynamic analogies available in AdS/CFT and supercritical black-hole physics.

major comments (2)
  1. [Abstract and Introduction] Abstract and opening paragraphs of the introduction: the central claim that Lee-Yang singularities can be located and interpreted as stability boundaries rests on treating the Euler-Heisenberg-AdS free energy (obtained from the horizon or Euclidean action) as the logarithm of a partition function whose zeros obey the circle theorem or density properties of statistical mechanics. No explicit construction is supplied showing that this free energy arises as log Z for a sum over states whose analytic continuation is controlled by the same microscopic rules.
  2. [Sections on complex phase diagrams and Widom lines] The sections describing the two-critical-point regime and the degenerate higher-order point: the reported four-phase structure and the emergence of two distinct Widom lines are obtained by locating singularities of the extended pressure or free energy in the complex domain. Without the missing microscopic justification, these singularities remain formal features of the thermodynamic potential rather than derived properties of the gravitational theory, undermining the physical interpretation of the Widom line as an effective stability boundary.
minor comments (1)
  1. [Abstract] The abstract presents the main results without any equations, parameter values, or explicit checks, making it difficult to assess immediately whether the mathematical derivations support the four-phase and Widom-line claims.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the careful reading and for highlighting the foundational assumptions in applying the Lee-Yang formalism. We respond to each major comment below, clarifying the scope of the thermodynamic analogy employed.

read point-by-point responses
  1. Referee: [Abstract and Introduction] Abstract and opening paragraphs of the introduction: the central claim that Lee-Yang singularities can be located and interpreted as stability boundaries rests on treating the Euler-Heisenberg-AdS free energy (obtained from the horizon or Euclidean action) as the logarithm of a partition function whose zeros obey the circle theorem or density properties of statistical mechanics. No explicit construction is supplied showing that this free energy arises as log Z for a sum over states whose analytic continuation is controlled by the same microscopic rules.

    Authors: We acknowledge that no explicit microscopic construction from the gravitational path integral is provided, as this would require a complete quantum theory of gravity. The identification of the on-shell Euclidean action with the free energy F = -T log Z follows the standard thermodynamic analogy in AdS black hole physics and AdS/CFT, as used in prior studies of phase transitions (including Lee-Yang analyses of other AdS black holes). We will add a dedicated paragraph in the introduction explicitly stating this analogy, its limitations, and references to the relevant literature. revision: partial

  2. Referee: [Sections on complex phase diagrams and Widom lines] The sections describing the two-critical-point regime and the degenerate higher-order point: the reported four-phase structure and the emergence of two distinct Widom lines are obtained by locating singularities of the extended pressure or free energy in the complex domain. Without the missing microscopic justification, these singularities remain formal features of the thermodynamic potential rather than derived properties of the gravitational theory, undermining the physical interpretation of the Widom line as an effective stability boundary.

    Authors: The four-phase structure and Widom lines are obtained from the analytic continuation of the thermodynamic potential, consistent with the same analogy used throughout the black-hole thermodynamics literature. We agree that these are effective features within the thermodynamic description rather than strictly microscopic. We will revise the relevant sections to emphasize the effective nature of the stability boundaries and to include a brief discussion of how the formalism reproduces standard single-critical-point cases as a consistency check. revision: partial

standing simulated objections not resolved
  • Rigorous microscopic justification of the free energy as log Z arising from a sum over states controlled by the gravitational action.

Circularity Check

0 steps flagged

No significant circularity; external formalism applied to derived thermodynamics

full rationale

The derivation begins with the standard Euler-Heisenberg-AdS metric and Euclidean action to obtain the thermodynamic potential (free energy or pressure), then feeds that potential into the pre-existing Lee-Yang zero formalism for complex-plane analysis. The paper explicitly checks consistency by reproducing known single-critical-point and no-criticality phase structures, confirming the method is not tautological. No self-definitional equations, no parameters fitted to a subset and then relabeled as predictions, and no load-bearing self-citations appear in the abstract or described chain. The Widom-line and multi-critical-point results are outputs of the combined calculation rather than inputs renamed.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

Relies on standard general-relativity and AdS thermodynamic axioms plus the applicability of Lee-Yang theory; no free parameters or invented entities listed in abstract.

axioms (2)
  • domain assumption Standard assumptions of general relativity and extended phase space thermodynamics for AdS black holes.
    Invoked by the choice of Euler-Heisenberg AdS model.
  • domain assumption Lee-Yang phase transition theory applies to black hole thermodynamic potentials.
    Framework used to locate singularities and Widom lines.

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discussion (0)

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Reference graph

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