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REVIEW 4 major objections 4 minor 47 references

This paper argues that the derivative expansion of the exact renormalization group is a divergent series in every dimension, but with a specific asymptotic structure that explains its practical success.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

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2026-08-01 15:30 UTC pith:LPU3PUZA

load-bearing objection The perturbative two- and three-loop divergence results are solid and significant, but the nonperturbative extrapolation is argued rather than proven, and the abstract overstates the categorical conclusion. the 4 major comments →

arxiv 2607.18397 v1 pith:LPU3PUZA submitted 2026-07-20 hep-th cond-mat.stat-mech

Asymptotic behaviour of the derivative expansion in the ERG

classification hep-th cond-mat.stat-mech PACS 11.10.Hi
keywords derivative expansionexact renormalization groupfunctional renormalization groupasymptotic seriesdivergent seriesloop expansionmassless scalar field theorycutoff function
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

This paper aims to settle why the derivative expansion—the most widely used approximation in the exact renormalization group—works so well in practice while failing in principle. Working in massless lambda-phi-fourth theory, it shows that from two loops onward the expansion cannot converge for most vertices: the two- and four-point vertices still converge for any dimension and derivative order, the six-point vertex converges only for d below 10 minus twice the derivative order, and the eight-point and higher vertices diverge in every dimension. The mechanism is a factorial growth generated by integrating powers of loop momentum against the cutoff, which cancels the factorial suppression of the one-loop Taylor coefficients. Despite the divergence, the expansion is asymptotic in a concrete sense: for the leading large-order terms the exact result always lies between successive partial sums, so the best accuracy is obtained by truncating just short of the smallest term. If the argument goes through, it explains the numerical success of low-order truncations and sets a limit on how far they can be pushed.

Core claim

The paper shows that the derivative expansion of the flow equation for the Legendre effective action cannot converge beyond one loop. At two loops the dominant large-order contributions scale as (−c_m)^n n^{r−m+d/2−2}, with c_m = (m+1)/4 for odd m and m(m+2)/(4(m+1)) for even m; convergence requires c_m < 1, leaving only the two-point and four-point vertices convergent for all dimensions d and derivative orders r. At three loops a further insertion of a cutoff loop makes every vertex divergent, with leading terms shaped like a polylogarithm outside its radius of convergence. The paper proves that this leading series brackets the exact answer between successive partial sums, so the series is

What carries the argument

The central object is the two-loop 'sewn' diagram obtained by tying the momentum-carrying legs of a one-loop 2m-point vertex to a Gaussian cutoff factor K(q) = (2/Lambda^3) exp(−q^2/Lambda^2). The identity ∫ d^d q (q+p)^{2n} e^{−q^2/Lambda^2} ∝ sum_r Γ(n+d/2)/Γ(r+d/2) binomial(n,r) (p^2)^r turns derivative-expansion orders into numerical series; the large-n behaviour is read off by saddle-point analysis at the corner of the Feynman-parameter space. The sign of convergence is carried by the coefficient c_m, and the bracketing property of the resulting polylogarithm −Li_ς(−x), with an exact remainder integral, is what elevates a divergent series to an asymptotic one.

Load-bearing premise

The whole non-perturbative conclusion rests on the unproven claim that the derivative expansion of the full theory cannot converge better than its loop expansion, i.e., that the two expansions commute with the ℏ → 0 limit, so a two-loop divergence necessarily implies non-perturbative divergence.

What would settle it

Compute the exact coefficient of O(∂^{2n}) for the two-loop eight-point vertex at zero momentum in d = 3 with the exponential cutoff, out to n = 50; the leading formula predicts a minimum near n = 21 and a subsequent exponential rise. If the coefficients keep decreasing past n = 40, the assumed dominance of this diagram fails. Alternatively, a non-perturbative calculation in d = 3 at O(∂^20) and O(∂^22) for the effective potential should show a minimum term around O(∂^18); if the series still decreases at O(∂^20), the picture is wrong.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • The derivative expansion cannot converge non-perturbatively for any 2m-point vertex with m ≥ 4 in any dimension; φ^6 needs d < 10, and φ^4 and φ^2 are the only safe sectors at two loops.
  • Optimal use of the expansion is to truncate at one order before the smallest term; for the effective potential in d = 3,4 this means retaining terms up to O(∂^18) at two loops and O(∂^10) at three loops before divergence sets in.
  • Truncations of the renormalization group flow to finite sets of local operators—a subset of the derivative expansion—inherit the divergence and cannot be convergent either.
  • With generic smooth cutoffs in the literature, two-loop coefficients grow factorially and the series takes the standard n! g^n asymptotic form; accuracy is still achievable by optimal truncation, with the radius of convergence of the cutoff propagator controlling the working range.
  • The loop expansion and the derivative expansion are linked: the non-perturbative derivative expansion cannot do better than the loop expansion, so the two-loop failure already determines the non-perturbative fate.

Where Pith is reading between the lines

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

  • If the bracketing property holds for the whole series and not just the leading terms, standard techniques for improving alternating asymptotic series beyond optimal truncation could be systematically applied, potentially recovering accurate values beyond the critical order.
  • The sharp dimension thresholds (for example d < 10 − 2r for φ^6) suggest a test in O(N) models: changing N or adding a mass term should shift the thresholds but not remove the divergence; numerical derivative expansions beyond O(∂^6) could verify the pattern.
  • The factorial mechanism is generic to any smooth cutoff, so one should expect the divergence to persist in theories with fermions or gauge fields, where the loop-momentum integrals have the same large-n structure; the thresholds would differ but the asymptotic nature would not.
  • For state-of-the-art calculations at O(∂^6), the paper predicts that apparent convergence is real because the critical order is still far away; physical observables dominated by high-point vertices, such as equation-of-state quantities involving φ^8, may be the first place the divergence becomes visible.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

4 major / 4 minor

Summary. The paper studies the derivative expansion (DE) of the functional renormalization group for massless λφ^4 theory, with a smooth exponential cutoff and then more general smooth cutoffs. It computes the large-order O(∂^{2n}) behavior of selected one-, two-, and three-loop contributions to 2m-point vertices in arbitrary dimension d. The central claim is that the DE is a divergent series for all d and for all vertices beyond the six-point case at two loops, and indeed for all vertices at three loops, but that the divergent series is asymptotic in a non-Poincaré sense: successive partial sums initially approach the exact result up to a critical order n_cr and then diverge exponentially. The perturbative calculations are checked against the known two-loop beta function in d=4 and against an exact two-loop eight-point calculation (Fig. 5.4).

Significance. If the perturbative large-order results are correct, the paper provides a concrete mechanism for the eventual divergence of the DE and explains the empirical success of low-order truncations. The explicit analytic control of infinite classes of diagrammatic contributions, the Schwinger-parameter large-n techniques, and the exact checks are valuable technical contributions that go well beyond the earlier work in [10]. The paper also corrects several typos in [10]. However, the paper's headline nonperturbative conclusion—that the DE of the exact FRG is divergent—is not established by the perturbative two- and three-loop computations, because the argument that the DE must converge order-by-order in the loop expansion relies on an unproven analyticity/commutativity assumption.

major comments (4)
  1. [Sec. 1, third paragraph; Sec. 7, Eq. (7.1)] The statement 'If the derivative expansion truly converges, then it must also do so in the loop expansion' is used as the bridge from perturbative divergence to nonperturbative divergence. This is not a theorem: a function of ℏ can be finite at ℏ=1 while its Taylor coefficients around ℏ=0 diverge, and the DE coefficients a_n(ℏ) need not be analytic in ℏ uniformly in n. Eq. (7.1) is an identity, not a bound; it does not rule out cancellations between loop orders. Thus the categorical abstract claim that the derivative expansion 'is a divergent series' is stronger than demonstrated. The paper's own Sec. 7 caveat ('full confirmation ... requires going beyond these leading order calculations') is in tension with this claim. Please either prove the required analyticity/uniformity or state the nonperturbative conclusion as conditional on it.
  2. [Sec. 5.2, Eqs. (5.10)-(5.17)] The contribution of Fig. 5.2 is introduced with '∋' and 'we expect this to be the dominant contribution', but no complete classification of two-loop diagrams is provided. To prove that the full two-loop DE diverges, one must show either that this contribution dominates in absolute value over all other two-loop terms at large n, or that no cancellation can occur. The leading term oscillates as (-c_m)^n, so sign cancellations are not a priori excluded. Sec. 5.6 checks only a subclass of subleading diagrams (Fig. 5.5), not all two-loop topologies. This is a load-bearing gap for the two-loop divergence claim.
  3. [Secs. 5.7-5.8, Eqs. (5.39), (5.43)] The three-loop conclusion that 'all vertices now have a divergent derivative expansion' rests on the same dominance assumption. The argument that Fig. 5.6 gives 'the weakest convergence obtainable' is heuristic ('we have now run out of legs'). Sec. 5.8 analyzes only one other class. A systematic bound on all other three-loop contributions, or a proof that the chosen class cannot be cancelled, is needed before the three-loop divergence can be asserted for the full DE.
  4. [Sec. 5.4, Watson's lemma] Watson's lemma is invoked with g=1 fixed, where the lemma does not yield an asymptotic expansion in the usual sense. The paper acknowledges this, but then states that 'this is also true as a general non-perturbative statement'. The preceding polylogarithm bracketing proof (Sec. 5.3) applies only to the leading-order series treated in isolation, not to the full DE. The nonperturbative asymptotic claim is therefore not supported by Watson's lemma.
minor comments (4)
  1. [Sec. 5.2, Eq. (5.10) and passim] The '∋' notation for 'this is one of a number of contributions' is unusual; please define it explicitly at first use and consider a more standard notation such as 'contains the contribution'.
  2. [Fig. 5.4] The horizontal axis is described as 'O(∂^2) up to O(∂^80)' in the caption; clarify whether this means n=1,...,40 in the coefficient of (p^2/Λ^2)^n, since derivative order 2n would make O(∂^{80}) correspond to n=40.
  3. [Sec. 5.3, Eq. (5.21)] The polylogarithm Li_ς(x) is not defined; add a definition or reference for readers unfamiliar with the notation.
  4. [Sec. 4.2, Eq. (4.21)] The statement that 'all the series in (4.21) have radius of convergence Δ=2' should specify that this is the radius in the bookkeeping parameter Δ, not in p^2/Λ^2. This is clear from context but could be stated more explicitly.

Circularity Check

0 steps flagged

No significant circularity: the divergence claim is computed from the flow equation, with one unproven commutativity premise that is a correctness risk, not a circular reduction.

full rationale

The derivation chain is not circular. The two- and three-loop contributions whose large-n behaviour is shown to diverge are computed from the flow equation (2.3) via explicit Schwinger-parameter integrals and saddle-point estimates (e.g. (5.6), (5.14), (5.19), (5.39)), not imported from the conclusion. The two-loop beta-function check in Sec. 4.3 matches the known universal result (4.37), providing an external benchmark. Earlier results of the author, refs. [10,34], are rederived in Sec. 4 and App. A rather than merely assumed, and the paper corrects typos and a sign error in [10], so self-citation is not load-bearing. The main nonperturbative step rests on the premise (Sec. 1 and Sec. 7) that convergence of the derivative expansion would imply convergence in the loop expansion; this is an unproven commutativity/analyticity assumption, and the paper itself states that 'full confirmation ... requires going beyond these leading order calculations' (Sec. 7). That is a limitation or correctness risk, not a circular reduction: no equation or parameter is defined in terms of the target conclusion, and no fitted value is relabelled as a prediction.

Axiom & Free-Parameter Ledger

0 free parameters · 4 axioms · 0 invented entities

No numbers were fitted to data; λ(Λ) runs via the beta function but is treated as an input coupling. The counting parameter Δ is a bookkeeping device set to 1. The cutoff parameter α for general smooth cutoffs is taken from the literature, not fitted here. No new physical entities are introduced; the 'broadened asymptotic series' is a definition, not an entity.

axioms (4)
  • domain assumption Convergence of the nonperturbative derivative expansion would imply convergence of the derivative expansion at each order of the loop expansion (the expansions commute with the expansion in ℏ).
    Used in Sec. 1 paragraph 3 and Sec. 7 to extend perturbative divergence to the full ERG; not proven.
  • domain assumption Massless λφ⁴ theory with the exponential cutoff (3.1) is representative for the convergence properties of the derivative expansion in general smooth-cutoff FRG applications.
    The paper generalizes to smooth cutoffs in Sec. 6 but only for leading large-n behaviour; the detailed two- and three-loop proofs use the exponential cutoff.
  • domain assumption The identified one-loop, two-loop and three-loop diagram classes (figs 5.2 and 5.6) are the dominant contributions at large O(∂^{2n}) and are not cancelled by other diagrams.
    Argued in Secs. 5.6 and 5.8 via asymptotic comparisons; not proven as a bound for all m and n.
  • domain assumption The leading large-n Schwinger-parameter saddle-point calculation yields the true leading asymptotic behaviour of the integrated vertex coefficients.
    Standard in asymptotic analysis; verified numerically for one case (fig 5.4) and for known cases, but not in general.

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0 comments
read the original abstract

We show that the derivative expansion of the exact (functional) renormalization group is a divergent series in any dimension, both for an exponential cutoff and more general smooth cutoffs. We prove this by showing that within massless $\lambda\varphi^4$ perturbation theory, such divergences arise first at two loops. From several lines of theoretical argument and by analysing infinite classes of two- and three-loop contributions, we conclude that the derivative expansion is an asymptotic series that initially converges towards the exact result before divergent behaviour takes over.

Figures

Figures reproduced from arXiv: 2607.18397 by Tim R. Morris.

Figure 4.1
Figure 4.1. Figure 4.1: The one-loop six-point vertex. By momentum conservation [PITH_FULL_IMAGE:figures/full_fig_p013_4_1.png] view at source ↗
Figure 5.1
Figure 5.1. Figure 5.1: One-loop Feynman diagrams that contribute to Γ [PITH_FULL_IMAGE:figures/full_fig_p022_5_1.png] view at source ↗
Figure 5.2
Figure 5.2. Figure 5.2: A two-loop Feynman diagram contribution to the flow of the (2 [PITH_FULL_IMAGE:figures/full_fig_p024_5_2.png] view at source ↗
Figure 5.3
Figure 5.3. Figure 5.3: The filled circles give the dimensions d in which six-point 2r-derivative operators have convergent derivative expansions at two loops. The line with no derivatives, viz. ∂ 0 , thus corresponds to the φ 6 operator. The open circles mark special cases where the derivative expansion series is purely oscillatory at leading order in n and thus no longer converges. For all other values of d and r, the derivat… view at source ↗
Figure 5.4
Figure 5.4. Figure 5.4: The graph on the left displays the magnitude of derivative expansion contributions, [PITH_FULL_IMAGE:figures/full_fig_p031_5_4.png] view at source ↗
Figure 5.5
Figure 5.5. Figure 5.5: A two-loop Feynman diagram contribution to the flow of the (2 [PITH_FULL_IMAGE:figures/full_fig_p034_5_5.png] view at source ↗
Figure 5.6
Figure 5.6. Figure 5.6: A three-loop Feynman diagram contribution to the flow of the (2 [PITH_FULL_IMAGE:figures/full_fig_p036_5_6.png] view at source ↗
Figure 5.7
Figure 5.7. Figure 5.7: A three-loop Feynman diagram contribution where the loop momentum flows are not [PITH_FULL_IMAGE:figures/full_fig_p038_5_7.png] view at source ↗

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Reference graph

Works this paper leans on

47 extracted references · 29 linked inside Pith

  1. [1]

    Wilson and John B

    K.G. Wilson and John B. Kogut. The Renormalization group and the epsilon expansion. Phys.Rept., 12:75–200, 1974

  2. [2]

    J. F. Nicoll and T. S. Chang. An Exact One Particle Irreducible Renormalization Group Generator for Critical Phenomena.Phys. Lett., A62:287–289, 1977

  3. [3]

    Exact evolution equation for the effective potential.Phys.Lett., B301:90– 94, 1993

    Christof Wetterich. Exact evolution equation for the effective potential.Phys.Lett., B301:90– 94, 1993

  4. [4]

    Tim R. Morris. The Exact renormalization group and approximate solutions.Int.J.Mod.Phys., A 09:2411–2450, 1994, hep-ph/9308265

  5. [5]

    Dupuis, L

    N. Dupuis, L. Canet, A. Eichhorn, W. Metzner, J. M. Pawlowski, M. Tissier, and N. Wschebor. The nonperturbative functional renormalization group and its applications.Phys. Rept., 910:1– 114, 2021, 2006.04853. 46

  6. [6]

    Tim R. Morris. Derivative expansion of the exact renormalization group.Phys.Lett., B329:241– 248, 1994, hep-ph/9403340

  7. [7]

    Tim R. Morris. The Renormalization group and two-dimensional multicritical effective scalar field theory.Phys.Lett., B345:139–148, 1995, hep-th/9410141

  8. [8]

    Tim R. Morris. Three-dimensional massive scalar field theory and the derivative expansion of the renormalization group.Nucl.Phys., B495:477–504, 1997, hep-th/9612117

  9. [9]

    Morris and Michael D

    Tim R. Morris and Michael D. Turner. Derivative expansion of the renormalization group in O(N) scalar field theory.Nucl. Phys., B509:637–661, 1998, hep-th/9704202

  10. [10]

    Morris and John F

    Tim R. Morris and John F. Tighe. Convergence of derivative expansions of the renormalization group.JHEP, 08:007, 1999, hep-th/9906166

  11. [11]

    Daniel F. Litim. Optimized renormalization group flows.Phys.Rev., D64:105007, 2001, hep- th/0103195

  12. [12]

    Optimization of the derivative expansion in the nonperturbative renormalization group.Phys

    Leonie Canet, Bertrand Delamotte, Dominique Mouhanna, and Julien Vidal. Optimization of the derivative expansion in the nonperturbative renormalization group.Phys. Rev. D, 67:065004, 2003, hep-th/0211055

  13. [13]

    Nonperturbative renormalization group approach to the Ising model: A Derivative expansion at order∂ 4.Phys

    Leonie Canet, Bertrand Delamotte, Dominique Mouhanna, and Julien Vidal. Nonperturbative renormalization group approach to the Ising model: A Derivative expansion at order∂ 4.Phys. Rev. B, 68:064421, 2003, hep-th/0302227

  14. [14]

    Convergence of Nonperturbative Approximations to the Renormalization Group.Phys

    Ivan Balog, Hugues Chat´ e, Bertrand Delamotte, Maroje Marohni´ c, and Nicol´ as Wschebor. Convergence of Nonperturbative Approximations to the Renormalization Group.Phys. Rev. Lett., 123(24):240604, 2019, 1907.01829

  15. [15]

    Precision calculation of critical exponents in theO(N) universality classes with the nonperturbative renormalization group.Phys

    Gonzalo De Polsi, Ivan Balog, Matthieu Tissier, and Nicol´ as Wschebor. Precision calculation of critical exponents in theO(N) universality classes with the nonperturbative renormalization group.Phys. Rev. E, 101(4):042113, 2020, 2001.07525

  16. [16]

    Conformal invariance and composite operators: A strategy for improving the derivative expansion of the nonperturbative renormalization group.Phys

    Bertrand Delamotte, Gonzalo De Polsi, Matthieu Tissier, and Nicol´ as Wschebor. Conformal invariance and composite operators: A strategy for improving the derivative expansion of the nonperturbative renormalization group.Phys. Rev. E, 109(6):064152, 2024, 2401.02517. 47

  17. [17]

    Tim R. Morris. The Derivative expansion of the renormalization group.Nucl. Phys. B Proc. Suppl., 42:811–814, 1995, hep-lat/9411053

  18. [18]

    T. R. Morris. Properties of derivative expansion approximations to the renormalization group. Int. J. Mod. Phys., B12:1343–1354, 1998, hep-th/9610012

  19. [19]

    Nonperturbative renormalization flow in quantum field theory and statistical physics.Phys

    Juergen Berges, Nikolaos Tetradis, and Christof Wetterich. Nonperturbative renormalization flow in quantum field theory and statistical physics.Phys. Rept., 363:223–386, 2002, hep- ph/0005122

  20. [20]

    Morris and John F

    Tim R. Morris and John F. Tighe. Convergence of derivative expansions in scalar field theory. Int. J. Mod. Phys., A16:2095–2100, 2001, hep-th/0102027

  21. [21]

    An Introduction to the nonperturbative renormalization group.Lect

    Bertrand Delamotte. An Introduction to the nonperturbative renormalization group.Lect. Notes Phys., 852:49–132, 2012, cond-mat/0702365

  22. [22]

    Bonanno and Emiliano M

    Alfio M. Bonanno and Emiliano M. Glaviano. Gravitationally Induced UV Completion of an O(N) Scalar Theory. 2601.20820

  23. [23]

    Scaling solutions for gauge invariant flow equations in dilaton quantum gravity.Phys

    Yadikaer Maitiniyazi, Christof Wetterich, and Masatoshi Yamada. Scaling solutions for gauge invariant flow equations in dilaton quantum gravity.Phys. Rev. D, 113(10):106023, 2026, 2512.14009

  24. [24]

    Anisotropic scale invariance and the uniaxial Lifshitz point from the nonperturbative renormalization group.Phys

    Gonzalo De Polsi and Pawel Jakubczyk. Anisotropic scale invariance and the uniaxial Lifshitz point from the nonperturbative renormalization group.Phys. Rev. E, 113(5):054120, 2026, 2511.21004

  25. [25]

    Conformal invariance constraints in the O(N) models: A study within the nonperturbative renormalization group.Phys

    Santiago Cabrera, Gonzalo De Polsi, and Nicol´ as Wschebor. Conformal invariance constraints in the O(N) models: A study within the nonperturbative renormalization group.Phys. Rev. E, 111(5):054126, 2025, 2412.16388

  26. [26]

    Vladimir V. Skokov. Two lectures on Yang-Lee edge singularity and analytic structure of QCD equation of state.SciPost Phys. Lect. Notes, 91:1, 2025, 2411.02663

  27. [27]

    Numerical accuracy of the derivative-expansion-based functional renormal- ization group.J

    Andrzej Chlebicki. Numerical accuracy of the derivative-expansion-based functional renormal- ization group.J. Stat. Mech., 2024(9):093204, 2024, 2404.18707

  28. [28]

    Two-Pomeron Interaction.Universe, 10(3):103, 2024

    Luis Cancino Arancibia and Carlos Contreras. Two-Pomeron Interaction.Universe, 10(3):103, 2024. 48

  29. [29]

    Effect of droplet config- urations within the functional renormalization group of the Ising model approaching the lower critical dimension.Phys

    Ivan Balog, Lucija Nora Farkaˇ s, Maroje Marohni´ c, and Gilles Tarjus. Effect of droplet config- urations within the functional renormalization group of the Ising model approaching the lower critical dimension.Phys. Rev. E, 113(3):034128, 2026, 2506.23415

  30. [30]

    Robustness of the deriva- tive expansion in asymptotic safety.Phys

    Alessio Baldazzi, Kevin Falls, Yannick Kluth, and Benjamin Knorr. Robustness of the deriva- tive expansion in asymptotic safety.Phys. Rev. D, 113(2):026005, 2026, 2312.03831

  31. [31]

    Tim R. Morris. Elements of the continuous renormalization group.Prog.Theor.Phys.Suppl., 131:395–414, 1998, hep-th/9802039

  32. [32]

    J. F. Nicoll, T. S. Chang, and H. E. Stanley. Approximate Renormalization Group Based on the Wegner-Houghton Differential Generator.Phys. Rev. Lett., 33:540–543, 1974

  33. [33]

    Marco D’Attanasio and Tim R. Morris. Large N and the renormalization group.Phys. Lett., B409:363–370, 1997, hep-th/9704094

  34. [34]

    Papenbrock and C

    T. Papenbrock and C. Wetterich. Two loop results from one loop computations and nonpertur- bative solutions of exact evolution equations.Z. Phys. C, 65:519–535, 1995, hep-th/9403164

  35. [35]

    R. B. Dingle.Asymptotic expansions: their derivation and interpretation. Academic Press, New York-London, 1973

  36. [36]

    F. W. J. Olver.Asymptotics and special functions. Academic Press, New York-London, 1974. Computer Science and Applied Mathematics

  37. [37]

    Bender and Steven A

    Carl M. Bender and Steven A. Orszag.Advanced Mathematical Methods for Scientists and Engineers I: Asymptotic Methods and Perturbation Theory. Springer-Verlag, New York, 1999

  38. [38]

    G. N. Watson. A theory of asymptotic series.Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character, 211:279–313, 1912

  39. [39]

    Graduate studies in mathematics; 75

    Peter D Miller.Applied asymptotic analysis. Graduate studies in mathematics; 75. AMS, 2006

  40. [40]

    Quantum field theory and critical phenomena.Int

    Jean Zinn-Justin. Quantum field theory and critical phenomena.Int. Ser. Monogr. Phys., 113:1–1054, 2002

  41. [41]

    M. V. Berry and C. J. Howls. Hyperasymptotics.Proceedings: Mathematical and Physical Sciences, 430(1880):653–668, 1990. 49

  42. [42]

    Regulator dependence in the functional renormal- ization group: A quantitative explanation.Phys

    Gonzalo De Polsi and Nicol´ as Wschebor. Regulator dependence in the functional renormal- ization group: A quantitative explanation.Phys. Rev. E, 106(2):024111, 2022, 2204.09170

  43. [43]

    Geoffrey R. Golner. Exact renormalization group flow equations for free energies and N point functions in uniform external fields. hep-th/9801124

  44. [44]

    Bagnuls and C

    C. Bagnuls and C. Bervillier. Exact renormalization group equations. An Introductory review. Phys.Rept., 348:91, 2001, hep-th/0002034

  45. [45]

    Gerald V. Dunne. An all orders derivative expansion.Int. J. Mod. Phys. A, 12:1143–1152, 1997, hep-th/9611019

  46. [46]

    Dunne and Theodore M

    Gerald V. Dunne and Theodore M. Hall. Borel summation of the derivative expansion and effective actions.Phys. Rev. D, 60:065002, 1999, hep-th/9902064

  47. [47]

    Sommerfield, and Eyvind H

    Robert Karplus, Charles M. Sommerfield, and Eyvind H. Wichmann. Spectral Representations in Perturbation Theory. 1. Vertex Function.Phys. Rev., 111:1187–1190, 1958. 50