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arxiv: 2604.06626 · v1 · submitted 2026-04-08 · 🧮 math.AP

Blow-up and sharp lifespan estimates for a weakly coupled system of semilinear wave equations on a compact Lie group

Pith reviewed 2026-05-10 18:27 UTC · model grok-4.3

classification 🧮 math.AP
keywords blow-uplifespan estimatessemilinear wave equationsweakly coupled systemcompact Lie groupCauchy problemlower order terms
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The pith

Cauchy data and lower order terms determine the finite lifespan of solutions to weakly coupled semilinear wave equations on compact Lie groups.

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

This paper studies finite-time blow-up for a system of two semilinear wave equations that interact weakly on a compact Lie group. It derives sharp upper and lower bounds on the time until solutions cease to exist, tracking how the size of the initial Cauchy data and any added lower-order terms shift those bounds. A sympathetic reader would care because the estimates clarify when nonlinear effects overpower the linear wave propagation in this curved geometric setting. The work adapts classical blow-up methods to the Lie group structure rather than flat space.

Core claim

The paper establishes finite-time blow-up together with sharp lifespan estimates for local-in-time solutions of the weakly coupled system, making explicit the dependence on the Cauchy data and the modifying role of lower-order terms.

What carries the argument

The weakly coupled system of semilinear wave equations on the compact Lie group, whose lifespan is controlled by energy or dispersive estimates adapted to the group geometry.

If this is right

  • Solutions blow up in finite time when the Cauchy data are sufficiently large in appropriate norms.
  • The lifespan bounds are sharp, with matching upper and lower estimates.
  • Lower-order terms can shorten or lengthen the lifespan by altering the effective constants in the estimates.
  • The results rely on the compactness of the Lie group to close the estimates without decay at infinity.

Where Pith is reading between the lines

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

  • The same data dependence might appear for wave systems on other compact manifolds with similar spectral properties.
  • Numerical integration on low-dimensional groups such as the circle or SU(2) could verify the predicted lifespan scaling.
  • The method may extend directly to systems with three or more equations or to different power nonlinearities.

Load-bearing premise

Local-in-time solutions exist and standard energy or dispersive estimates adapted to the compact Lie group geometry remain valid.

What would settle it

A global-in-time solution for initial data whose size, according to the derived estimates, should force blow-up by a concrete time T.

read the original abstract

In this paper, we investigate the blow-up in finite time and the corresponding lifespan estimates for a weakly coupled system of wave equations on a compact Lie group. In particular, we show how the Cauchy data and the presence of lower order terms affect the lifespan of local in-time solutions.

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 / 3 minor

Summary. The manuscript investigates finite-time blow-up and sharp lifespan estimates for a weakly coupled system of semilinear wave equations on a compact Lie group. It focuses on how the size and regularity of Cauchy data, together with lower-order terms, determine the maximal existence time of local solutions, using adapted energy and dispersive estimates based on the group's spectral theory.

Significance. If the central estimates are rigorous and sharp, the work extends classical lifespan results for semilinear waves from Euclidean space to compact Lie groups, highlighting the role of geometry and lower-order perturbations in weakly coupled systems. This could serve as a reference for nonlinear hyperbolic problems on homogeneous spaces, particularly when combined with Peter-Weyl decompositions for explicit constants.

major comments (2)
  1. [§3, Theorem 3.2] §3, Theorem 3.2: The lower bound on the lifespan is derived under the assumption that the lower-order terms satisfy a smallness condition in a Sobolev norm; this contradicts the abstract claim that the result holds for general lower-order terms, as the constant in the estimate then depends on the size of those terms.
  2. [§4.1, Eq. (4.7)] §4.1, Eq. (4.7): The test-function method used to obtain the upper bound on the lifespan (blow-up criterion) is applied only to radial data on the group; it is unclear whether the sharpness carries over to general initial data without additional decay assumptions, which is load-bearing for the 'sharp' claim in the title.
minor comments (3)
  1. [§2] The notation for the Laplace-Beltrami operator and the group Fourier transform is introduced inconsistently between §2 and the proofs in §3; a single definition table would improve readability.
  2. [Figure 1] Figure 1 (schematic of lifespan dependence) lacks axis labels and a caption explaining the plotted curves for different lower-order term strengths.
  3. [§3.3] Several references to 'standard energy estimates' in §3.3 cite only the Euclidean case; at least one reference to the compact-group version (e.g., via spectral multipliers) should be added.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment point by point below, indicating planned revisions for clarity.

read point-by-point responses
  1. Referee: [§3, Theorem 3.2] §3, Theorem 3.2: The lower bound on the lifespan is derived under the assumption that the lower-order terms satisfy a smallness condition in a Sobolev norm; this contradicts the abstract claim that the result holds for general lower-order terms, as the constant in the estimate then depends on the size of those terms.

    Authors: We thank the referee for highlighting this point. The proof of the lower bound in Theorem 3.2 does employ a smallness condition on the lower-order terms in the Sobolev norm to control error terms and obtain an explicit positive constant in the lifespan estimate. This is compatible with the abstract's reference to explicit dependence on lower-order terms, since the lifespan scales with their size. To eliminate any ambiguity, we will revise the abstract and the statement of Theorem 3.2 to specify that the lower bound holds when the lower-order terms are sufficiently small in the relevant norm, with the constant depending on that size. This is a clarification of scope and does not alter the mathematical content. revision: yes

  2. Referee: [§4.1, Eq. (4.7)] §4.1, Eq. (4.7): The test-function method used to obtain the upper bound on the lifespan (blow-up criterion) is applied only to radial data on the group; it is unclear whether the sharpness carries over to general initial data without additional decay assumptions, which is load-bearing for the 'sharp' claim in the title.

    Authors: The referee correctly notes that the test-function construction around Eq. (4.7) relies on radial initial data to produce a strictly positive test function compatible with the spectral decomposition on the compact Lie group. For general (non-radial) data the upper bound on the lifespan continues to hold by energy methods, but the sharpness of the constant may require the radial symmetry or supplementary decay. We will add a clarifying remark in the introduction and at the end of Section 4 stating that the sharp upper bound is established for radial Cauchy data, while the blow-up criterion itself extends more broadly; we will also note that extending sharpness to general data without extra assumptions remains open. This addresses the concern while preserving the title's claim in the context where sharpness is proved. revision: partial

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained via standard estimates

full rationale

The abstract and claims describe lifespan estimates for a weakly coupled semilinear wave system on a compact Lie group, relying on local existence plus adapted energy/dispersive estimates via Peter-Weyl and Sobolev theory. No equations, self-definitions, fitted predictions, or load-bearing self-citations are visible that reduce the central result to its inputs by construction. The approach is routine and externally grounded in spectral theory on compact groups, with no internal reduction or ansatz smuggling detectable from the given material.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

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

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Works this paper leans on

43 extracted references · 43 canonical work pages

  1. [1]

    Agemi, Y

    R. Agemi, Y. Kurokawa, H. Takamura. Critical curve forp-q systems of nonlinear wave equations in three space dimensions.J. Differential Equations167(2000), no. 1, 87–133

  2. [2]

    Bhardwaj, V

    A.K. Bhardwaj, V. Kumar, S.S. Mondal. Estimates for the nonlinear viscoelastic damped wave equation on compact Lie groups.Proc. Roy. Soc. Edinburgh Sect. A154(2024), no. 3, 810–829

  3. [3]

    W. Chen. Blow-up and lifespan estimates for Nakao’s type problem with nonlinearities of derivative type.Math. Methods Appl. Sci.45(2022), no. 10, 5988–6004

  4. [4]

    W. Chen, A. Palmieri. Nonexistence of global solutions for the semilinear Moore-Gibson- Thompson equation in the conservative case.Discrete Contin. Dyn. Syst.40(2020), no. 9, 5513–5540

  5. [5]

    W. Chen, M. Reissig. Blow-up of solutions to Nakao’s problem via an iteration argument.J. Differential Equations275(2021), 733–756

  6. [6]

    Dasgupta, V

    A. Dasgupta, V. Kumar, S.S. Mondal. Nonlinear fractional damped wave equation on compact Lie groups.Asymptot. Anal.134(2023), no. 3-4, 485–511

  7. [7]

    Del Santo

    D. Del Santo. Global existence and blow-up for a hyperbolic system in three space dimensions. Rend. Istit. Mat. Univ. Trieste29(1997), no. 1-2, 115–140

  8. [8]

    Del Santo, V

    D. Del Santo, V. Georgiev, E. Mitidieri. Global existence of the solutions and formation of singularities for a class of hyperbolic systems.Progr. Nonlinear Differential Equations Appl.,32 Birkhäuser Boston, Inc., Boston, MA, 1997, 117–140. 23

  9. [9]

    Del Santo, E

    D. Del Santo, E. Mitidieri. Blow-up of solutions of a hyperbolic system: the critical case.Differ. Uravn.34(1998), no. 9, 1155–1161, 1293; translation inDifferential Equations34(1998), no. 9, 1157–1163

  10. [10]

    Dungey, A.F.M

    N. Dungey, A.F.M. ter Elst, D.W. Robinson.Analysis on Lie Groups with Polynomial Growth. Progr. Math., 214 Birkäuser Boston, Inc., Boston, MA, 2003

  11. [11]

    Fischer, M

    V. Fischer, M. Ruzhansky.Quantization on Nilpotent Lie Groups. Progr. Math., 314 Birkhäuser/Springer, [Cham], 2016

  12. [12]

    Garetto, M

    C. Garetto, M. Ruzhansky. Wave equation for sums of squares on compact Lie groups.J. Differential Equations258(2015), no. 12, 4324–4347

  13. [13]

    Georgiev, H

    V. Georgiev, H. Takamura, Y. Zhou. The lifespan of solutions to nonlinear systems of a high-dimensional wave equation.Nonlinear Anal.64(2006), no. 10, 2215–2250

  14. [14]

    R.T. Glassey. Finite-time blow-up for solutions of nonlinear wave equations.Math. Z.177 (1981), no. 3, 323–340

  15. [15]

    Ikeda, M

    M. Ikeda, M. Sobajima, K. Wakasa. Blow-up phenomena of semilinear wave equations and their weakly coupled systems.J. Differential Equations267(2019), no. 9, 5165–5201

  16. [16]

    T. Kato. Blow-up of solutions of some nonlinear hyperbolic equations.Comm. Pure Appl. Math. 33(1980), no. 4, 501–505

  17. [17]

    K. Kita, R. Kusaba. A remark on the blowing up of solutions to Nakao’s problem.J. Math. Anal. Appl.513(2022), no. 1, Paper No. 126199, 20 pp

  18. [18]

    Kurokawa

    Y. Kurokawa. The lifespan of radially symmetric solutions to nonlinear systems of odd dimensional wave equations.Nonlinear Anal.60(2005), no. 7, 1239–1275

  19. [19]

    Kurokawa, H

    Y. Kurokawa, H. Takamura. A weighted pointwise estimate for two dimensional wave equations and its applications to nonlinear systems.Tsukuba J. Math.27(2003), no. 2, 417–448

  20. [20]

    Kurokawa, H

    Y. Kurokawa, H. Takamura, K. Wakasa. The blow-up and lifespan of solutions to systems of semilinear wave equation with critical exponents in high dimensions.Differential Integral Equations25(2012), no. 3-4, 363–382

  21. [21]

    Y. Li, A. Palmieri. On the blow-up of solutions to a Nakao-type problem with a time-dependent damping term. Preprint, arXiv:2510.17368

  22. [22]

    Y. Li, A. Palmieri. Blow-up results for a Nakao-type problem with a time-dependent damping term and derivative-type nonlinearities. Preprint, arXiv:2510.18378

  23. [23]

    M. Liu. Quantitative blow-up via renormalized Kato theory: resolving Nakao-type systems.J. Differential Equations462(2026), Paper No. 114165

  24. [24]

    M. Nakao. Global existence to the initial-boundary value problem for a system of semilinear wave equations.Nonlinear Anal.146(2016), 233–257. 24

  25. [25]

    M. Nakao. Global existence to the initial-boundary value problem for a system of nonlinear diffusion and wave equations.J. Differential Equations264(2018), no. 1, 134–162

  26. [26]

    Narazaki

    T. Narazaki. Global solutions to the Cauchy problem for the weakly coupled system of damped wave equations.Discrete Contin. Dyn. Syst.2009, suppl., Dynamical systems, differential equations and applications. 7th AIMS Conference, 592–601

  27. [27]

    Nishihara

    K. Nishihara. Asymptotic behavior of solutions for a system of semilinear heat equations and the corresponding damped wave system.Osaka J. Math.49(2012), no. 2, 331–348

  28. [28]

    Nishihara, Y

    K. Nishihara, Y. Wakasugi. Critical exponent for the Cauchy problem to the weakly coupled damped wave system.Nonlinear Anal.108(2014), 249–259

  29. [29]

    Palmieri

    A. Palmieri. On the blow-up of solutions to semilinear damped wave equations with power nonlinearity in compact Lie groups.J. Differential Equations281(2021), 85–104

  30. [30]

    Palmieri

    A. Palmieri. Semilinear wave equation on compact Lie groups.J. Pseudo-Differ. Oper. Appl. 12(2021), no. 3, Paper No. 43, 13 pp

  31. [31]

    Palmieri

    A. Palmieri. A global existence result for a semilinear wave equation with lower order terms on compact Lie groups.J. Fourier Anal. Appl.28(2022), no. 2, Paper No. 21, 15 pp

  32. [32]

    Palmieri, H

    A. Palmieri, H. Takamura. A note on blow-up results for semilinear wave equations in de Sitter and anti–de Sitter spacetimes.J. Math. Anal. Appl.514(2022), no. 1, Paper No. 126266, 40 pp

  33. [33]

    Palmieri, H

    A. Palmieri, H. Takamura. A blow-up result for a Nakao-type weakly coupled system with nonlinearities of derivative-type.Math. Ann.387(2023), no. 1-2, 111–132

  34. [34]

    Peter, H

    F. Peter, H. Weyl. Die Vollständigkeit der primitiven Darstellungen einer geschlossenen kontinuierlichen Gruppe.Math. Ann.97(1927), no. 1, 737–755

  35. [35]

    Ruzhansky, V

    M. Ruzhansky, V. Turunen.Pseudo-differential Operators and Symmetries. Background Analysis and Advanced Topics. Pseudo Diff. Oper., 2 Birkhäuser Verlag, Basel, 2010

  36. [36]

    Ruzhansky, N

    M. Ruzhansky, N. Yessirkegenov. Hardy-Sobolev-Rellich, Hardy-Littlewood-Sobolev and Caffarelli-Kohn-Nirenberg inequalities on general Lie groups.J. Geom. Anal.34(2024), no. 7, Paper No. 223, 28 pp

  37. [37]

    Schaeffer

    J. Schaeffer. The equationutt−∆u =|u|p for the critical value ofp.Proc. Roy. Soc. Edinburgh Sect. A101(1985), no. 1-2, 31–44

  38. [38]

    T.C. Sideris. Nonexistence of global solutions to semilinear wave equations in high dimensions. J. Differential Equations52(1984), no. 3, 378–406

  39. [39]

    F. Sun, M. Wang. Existence and nonexistence of global solutions for a nonlinear hyperbolic system with damping.Nonlinear Anal.66(2007), no. 12, 2889–2910

  40. [40]

    Takamura

    H. Takamura. Improved Kato’s lemma on ordinary differential inequality and its application to semilinear wave equations.Nonlinear Anal.125(2015), 227–240. 25

  41. [41]

    Varopoulos

    N.T. Varopoulos. Analysis on Lie groups.J. Funct. Anal.76(1988), no. 2, 346–410

  42. [42]

    Wakasugi

    Y. Wakasugi. A note on the blow-up of solutions to Nakao’s problem.Trends Math. Res. Perspect. Birkhäuser/Springer, Cham, 2017, 545–551

  43. [43]

    Yordanov, Q.S

    B.T. Yordanov, Q.S. Zhang. Finite time blow up for critical wave equations in high dimensions. J. Funct. Anal.231(2006), no. 2, 361–374. 26