REVIEW 3 major objections 5 minor 86 references
Gauss-Bonnet holographic superconductors in exponential nonlinear electrodynamics
T0 review · 3 major / 5 minor · reviewed 2026-08-14 · deepseek-v4-flash
Pith's one-line read In Einstein-Gauss-Bonnet gravity with exponential nonlinear electrodynamics, higher curvature and nonlinear parameters lower the critical temperature of the holographic superconductor, while the condensation value rises and the critical…
desk verdict Useful incremental extension with a solid Tc cross-check; condensation and conductivity sections need numerical verification and the printed formulas need cleanup. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The argument runs on the Sturm-Liouville eigenvalue method applied to the scalar-field equation near the critical temperature. The gauge-field profile is written through a Lambert W function, and the nonlinear parameter is handled by a perturbative iterative procedure with step size 0.05, evaluating $b\lambda^2$ at each step from the previous value. The trial function $F(z)=1-az^2$ is inserted, and minimizing the Sturm-Liouville expression fixes $\lambda$, hence $T_c$. The same machinery is then expanded to second order in the condensation to obtain the coefficient $\beta$ and the universal exponent $1/2$, and a linearized fluctuation equation for $A_x$ with holographic renormalization yields the optical conductivity.
What would settle it
Compute the same critical-temperature coefficient for $d=5$, $\alpha=0.06$, and the nonlinear parameter $b=0.15$ by solving the full boundary-value problem directly without the iterative step approximation, and compare it with the analytic value $0.139\rho^{1/3}$; a disagreement beyond the few-percent level quoted in the table would show the approximation is responsible for the reported numbers.
Extended reading notes
Core claim
The central discovery is a set of monotonicity results for $d$-dimensional s-wave holographic superconductors with exponential nonlinear electrodynamics. For fixed charge density, the critical temperature decreases when the Gauss-Bonnet parameter or the nonlinear parameter increases, while for sufficiently low charge density it increases with spacetime dimension. The scalar condensation value at fixed $T/T_c$ grows with all three of these quantities. The critical exponent stays $1/2$ regardless of the Gauss-Bonnet or nonlinear corrections, the mean-field value. In the conductivity spectrum the superconducting energy gap widens with the Gauss-Bonnet parameter and narrows with the nonlinear parameter, with the expected delta function at zero frequency and the high-frequency power-law $\mathrm{Re}[\sigma] \propto \omega^{d-4}$.
Load-bearing premise
The load-bearing premise is that the perturbative iterative approximation for $b\lambda^2$, which replaces the value at each step of 0.05 by the value at the previous step, is accurate enough at the largest nonlinear parameters studied; the paper itself notes that a smaller step size improves the approximation.
Editorial extensions
If this is right
- The transition becomes harder to achieve as either correction grows: for fixed charge density, $T_c$ shifts downward with both the Gauss-Bonnet and nonlinear parameters.
- At fixed $T/T_c$, the condensate is larger for larger Gauss-Bonnet parameter, nonlinear parameter, or spacetime dimension, so these effects strengthen the ordered state below $T_c$.
- The universal exponent $1/2$ means the phase transition remains of the mean-field type despite higher-curvature and nonlinear gauge corrections.
- The optical conductivity develops a superconducting energy gap below $T_c$, with the gap growing with the Gauss-Bonnet parameter and shrinking with the nonlinear parameter.
- In arbitrary dimensions the high-frequency conductivity follows $\mathrm{Re}[\sigma] \propto \omega^{d-4}$, and the dimension dependence of $T_c$ flips with the charge-density regime.
Reading between the lines
- If the $1/2$ exponent survives backreaction and other matter couplings, the correction terms change the location and strength of the transition but not its mean-field universality class.
- Since the gauge-field equation for exponential nonlinear electrodynamics agrees with Born-Infeld electrodynamics to first order in the nonlinear parameter, at least the leading shifts in $T_c$ and condensate reported here should also appear in a Born-Infeld version of the same model.
- A direct numerical solution without the iterative step approximation would separate genuine physical effects from approximation artifacts; this is within reach of standard shooting methods.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies d-dimensional s-wave holographic superconductors in the probe limit, combining Einstein-Gauss-Bonnet gravity with exponential nonlinear electrodynamics. Using the Sturm-Liouville eigenvalue method, it derives analytic expressions for the critical temperature Tc ~ rho^{1/(d-2)}, the condensation value <O+> ~ (1 - T/Tc)^{1/2}, and the optical conductivity, and it reports numerical shooting results for Tc in d=5. The central qualitative claims are that Tc decreases with increasing Gauss-Bonnet coupling or nonlinear parameter, while it increases with spacetime dimension at sufficiently low charge density; that the condensation value increases with all three; and that the critical exponent remains 1/2 independently of these deformations.
Significance. If the results hold, this is a useful but incremental extension of holographic superconductor phenomenology to a motivated higher-curvature and nonlinear-electrodynamics setting. The paper has the virtue of not fitting parameters to target outcomes: the variational coefficient is optimized through the Sturm-Liouville functional, and the Tc comparison in Table I provides a genuine numerical cross-check for d=5. The qualitative trends are plausible and consistent with earlier GB and Born-Infeld-type studies. However, the quantitative condensation and conductivity predictions rest on an uncontrolled iterative approximation and on printed formulas that contain sign and integrand inconsistencies, so the contribution currently needs repair before its quantitative claims can be relied upon.
major comments (3)
- [Section III, Eq. (31)] The perturbative iterative procedure replaces b*lambda^2 at each step by its value at the previous b-step, with step size Delta b = 0.05, and the paper states only that smaller steps improve accuracy. No convergence study is presented. Because lambda_min determines the coefficient gamma in Eq. (39), and the same b*lambda^2 enters the integrand for A in Eq. (62) and hence the condensation and conductivity plots, the quantitative results of Figs. 2-7 are not yet supported. Please demonstrate convergence by rerunning with smaller step sizes or by solving the fixed-point equation for b*lambda^2, and add a numerical check for <O+> or the optical gap analogous to the Tc check in Table I.
- [Section IV, Eqs. (58) and (61)] As printed, Eq. (58) gives beta proportional to sqrt(-lambda (d-2)! / chi^{(d-3)}(0)). Since lambda > 0 and chi'(z) > 0 from Eq. (54), chi^{(d-3)}(0) is positive, so the argument of the square root is negative and beta would be imaginary. The final expression Eq. (61) drops both the minus sign and lambda and is positive. This sign inconsistency must be resolved; otherwise the derivation of the condensation coefficient is not reproducible as written. If Eq. (61) is the formula actually used for the plots, that should be stated explicitly and Eq. (58) corrected.
- [Section III, Eqs. (25), (28), (30), (62)] The printed integrands are mutually inconsistent. Eq. (25) as typeset appears to place the factor sqrt(b)*tilde z in the denominator, while Eqs. (30) and (62) effectively use sqrt(b)*tilde z^2. The b -> 0 limit xi = 1 - z^{d-3} and the second-order expansion in Eq. (28) both select the tilde z^2 form. The authors should reconcile these expressions, since the Sturm-Liouville functional in Eq. (38) and the coefficient A in Eq. (62) are evaluated with the tilde z^2 denominator.
minor comments (5)
- [Section IV, Eq. (51)] Equation (51) is stated as 'we find' with no derivation. It follows from Eq. (24) by expanding to the stated order in b, but a one-line derivation or an explicit reference would improve reproducibility.
- [Throughout] There are several typographical errors, including 'sapcetime' in the conclusion, 'dimesnional' in the introduction, and 'This can been seen' in Section III. Please copyedit the manuscript.
- [Figures 2-7] The axis labels in the figures are rendered in a nonstandard notation that is difficult to parse; please rewrite them using conventional mathematical notation, for example <O+>^{1/Delta_+}/T_c versus T/T_c.
- [Section V] The numerical conductivity results are presented only for d=5, while Eqs. (71)-(73) give expressions for d=5,6,7. Please clarify whether the higher-dimensional formulas are used anywhere or are included only for completeness.
- [Section III, text near Table I] The statement that the analytic and numerical results are in 'very good agreement' is somewhat stronger than the table suggests: the b=0.1 and b=0.15 rows differ by about 4-7 percent, which is acceptable but should be described as moderate agreement.
Circularity Check
No circular derivation; central claims are variational/numerical outputs from stated inputs, with only a non-load-bearing self-citation.
full rationale
The derivation chain is self-contained. The Sturm-Liouville functional (38) is minimized over the stated trial function F(z)=1-a z^2, with no parameter fitted to the target observables; the eigenvalue lambda_min then enters the algebraic scaling relation (39) for T_c, and beta is obtained from the perturbative expansion of phi in <O_+> (Eqs. (49)-(62)). The iterative b*lambda^2 procedure in Eq. (31) is an explicitly acknowledged fixed-point approximation with step-size dependence, not a fit of T_c or <O_+> to data. The analytical T_c is benchmarked against an independent shooting method in Table I. The only same-author citation, Ref. [76], appears in a general list of prior GB-superconductor works and is not load-bearing; no uniqueness theorem or ansatz is imported from it. The manuscript's own caveat that smaller Delta b improves accuracy is a numerical-convergence limitation, and the sign/printing inconsistencies around Eqs. (58) and (61) are internal-consistency concerns, not circularity.
Assumptions & free parameters
free parameters (5)
- b (nonlinear parameter) =
0, 0.05, 0.1, 0.15 (varied)
- α (Gauss-Bonnet coupling) =
0.02, 0.04, 0.06 (also 0.001, 0.005, 0.01, 0.05, 0.08 in figures)
- a (trial function coefficient) =
0.784748 for d=5, α=0.05, b=0; 0.834335 for b=0.05
- Δb (step size) =
0.05
- m² (scalar mass squared) =
-2 or -3
assumptions (6)
- domain assumption Probe limit: matter fields' backreaction on the geometry is neglected, T_μν ≃ 0, fixing the background as a planar GB AdS black hole.
- domain assumption Planar GB AdS black hole metric (Eqs. 7-8) is taken from Ref. [77] and assumes α ≥ 0 and α̃ ≤ l²/4 for a real solution.
- domain assumption The matter Lagrangian Lm = (1/b)(e^{-bF}-1) - |Dψ|² - m²|ψ|² is postulated, following Ref. [44].
- standard math Sturm-Liouville eigenvalue method: the eigenvalue functional Eq. (38) is minimized over trial functions to obtain the lowest eigenvalue λ².
- standard math Lambert W function properties are used to solve the gauge field equation at T_c (Eq. 25).
- domain assumption AdS/CFT dictionary and holographic renormalization are used to read off chemical potential, charge density, operator expectation values, and conductivity.
Cite this review
Pith. "Pith review of Gauss-Bonnet holographic superconductors in exponential nonlinear electrodynamics." pith.science (2026). https://pith.science/paper/Z7ONJ4RH
@misc{pith2026190806711,
author = {Pith},
title = {Pith review of: Gauss-Bonnet holographic superconductors in exponential nonlinear electrodynamics},
year = {2026},
howpublished = {\url{https://pith.science/paper/Z7ONJ4RH}},
note = {Machine review of arXiv:1908.06711}
}
abstract
The low-energy limits of the string theory lead to the higher-order curvature corrections for Einstein gravity. Also, they give the higher-order derivative corrections for the Maxwell or linear electrodynamics, which suggests the nonlinear electrodynamics. Inspired by this, in this paper we investigate $d$-dimensional holographic superconductors in the probe limit in the framework of Einstein-Gauss-Bonnet gravity and exponential nonlinear electrodynamics. Based on the Sturm-Liouville eigenvalue method, we compute the critical temperature, the condensation value, and the critical exponent. It is observed that the critical temperature decreases when the Gauss-Bonnet (GB) parameter or the nonlinear parameter increases, but it increases with the higher dimension of the spacetime at the efficiently low charge density. In addition, we found that the condensation value becomes larger as increasing the GB parameter, the nonlinear parameter as well as the spacetime dimension. Finally, we calculate the optical conductivity and study the effects of the GB term and exponential nonlinear electrodynamics on superconducting energy gap.
Figures
Figures from the paper (4 more)
Reference graph
Works this paper leans on
- [74]
-
[1]
φ →λ1φ, ψ →λ1ψ, q →λ−1 1 q, b →λ−2 1 b
-
[2]
Using these scaling symmetries, one can set q = l = 1
φ →λ2φ, ψ →λ1/2 2 ψ, b →λ−2 2 b ~α →λ−1 2 ~α, l →λ−1/2 2 l, m →λ1/2 2 m. Using these scaling symmetries, one can set q = l = 1. In order to solve Eqs. (14) and (15) and obtain the behavior of the gauge field and scalar field, first we need to impose the appropriate boundary conditions for φ(r) and ψ(r) at the event horizon r+. The matter fields are regular at...
2000
-
[3]
Bardeen, L
J. Bardeen, L. N. Cooper, and J. R. Schrieffer, Phys. Rev. 108, 1175 (1957)
1957
-
[4]
J. M. Maldacena, Adv. Theor. Math. Phys. 2, 231 (1998)
1998
-
[5]
Witten, Adv
E. Witten, Adv. Theor. Math. Phys. 2, 253 (1998)
1998
-
[6]
S. S. Gubser, I. R. Klebanov, and A. M. Polyakov, Phys. Lett. B 428, 105 (1998)
1998
-
[7]
O. Aharony, S. S. Gubser, J. M. Maldacena, H. Ooguri, and Y. Oz , Phys. Rept. 323, 183 (2000)
work page 2000
Show all 86 references
-
[8]
S. A. Hartnoll, C. P. Herzog, and G. T. Horowitz, Phys. Rev. Let t. 101, 031601 (2008)
2008
-
[9]
S. A. Hartnoll, C. P. Herzog, and G. T. Horowitz, JHEP 0812, 015 (2008)
2008
-
[10]
S. S. Gubser, Class. Quant. Grav. 22, 5121 (2005)
2005
-
[11]
S. S. Gubser, Phys. Rev. D 78, 065034 (2008)
2008
-
[12]
G. T. Horowitz and M. M. Roberts, Phys. Rev. D 78, 126008 (2008)
2008
-
[13]
Franco, A
S. Franco, A. Garcia-Garcia, and D. Rodriguez-Gomez, JHEP 04, 092 (2010)
2010
-
[14]
Siopsis and J
G. Siopsis and J. Therrien, JHEP 05, 013 (2010)
2010
-
[15]
X.-H. Ge, B. Wang, S.-F. Wu, and G.-H. Yang, JHEP 08, 108 (2010)
2010
-
[16]
Chen and M.-F
C.-M. Chen and M.-F. Wu, Prog. Theor. Phys. 126, 387 (2011)
2011
-
[17]
H.-B. Zeng, X. Gao, Y. Jiang, and H.-S. Zong, JHEP 1105, 002 (2011)
2011
-
[18]
Cai, H.-F Li, and H.-Q
R.-G. Cai, H.-F Li, and H.-Q. Zhang, Phys. Rev. D 83, 126007 (2011)
2011
-
[19]
R.-G. Cai, L. Li, L.-F. Li, R.-Q. Yang, Sci China Phys. Mech. Astro n. 58, 060401 (2015)
2015
-
[20]
Amoretti, A
A. Amoretti, A. Braggio, N. Maggiore, N. Magnoli, and D. Musso, JHEP 1401, 054 (2014)
2014
-
[21]
Nakonieczny and M
/suppress L. Nakonieczny and M. Rogatko, Phys. Rev. D90, 106004 (2014)
2014
-
[22]
Nakonieczny, M
/suppress L. Nakonieczny, M. Rogatko, and K. I. Wysokinski, Phys. Rev. D 91, 046007 (2015)
2015
-
[23]
Nakonieczny, M
/suppress L. Nakonieczny, M. Rogatko, and K. I. Wysokinski, Phys. Rev. D 92, 066008 (2015)
2015
-
[24]
Y. Peng, Q. Pan, and Y. Liu, Nucl. Phys. B 915, 69 (2017)
2017
-
[25]
Natsuume, Phys
M. Natsuume, Phys. Rev. D 50, 3949 (1994)
1994
-
[26]
Y. Kats, L. Motl, and M. Padi, JHEP 0712, 068 (2007)
2007
-
[27]
Cai, Z.-Y
R.-G. Cai, Z.-Y. Nie, and Y.-W. Sun, Phys. Rev. D 78, 126007 (2008)
2008
-
[28]
J. T. Liu and P. Szepietowski, Phys. Rev. D 79, 084042 (2009)
2009
-
[29]
Anninos and G
D. Anninos and G. Pastras, JHEP 0907, 030 (2009)
2009
-
[30]
Ritz and R
A. Ritz and R. Delbourgo, Int. J. Mod. Phys. A 11, 253 (1996)
1996
-
[31]
J. Jing, Q. Pan, and S. Chen, JHEP 11, 045 (2011)
2011
-
[32]
Gangopadhyay and D
S. Gangopadhyay and D. Roychowdhury, JHEP 05, 156 (2012). 21
2012
-
[33]
Roychowdhury, Phys
D. Roychowdhury, Phys. Rev. D 86, 106009 (2012)
2012
-
[34]
Z. Zhao, Q. Pan, S. Chen, and J. Jing, Nucl. Phys. B 871, 98 (2013)
2013
-
[35]
Banerjee, S
R. Banerjee, S. Gangopadhyay, D. Roychowdhury, and A. La la, Phys. Rev. D 87, 104001 (2013)
2013
-
[36]
C. Lai, Q. Pan, J. Jing, and Y. Wang, Phys. Lett. B 749, 437 (2015)
2015
-
[37]
Sheykhi, F
A. Sheykhi, F. Shaker, Phys. Lett. B 754, 281 (2016)
2016
-
[38]
Ghorai and S
D. Ghorai and S. Gangopadhyay, Eur. Phys. J. C 76, 146 (2016)
2016
-
[39]
J. Jing, L. Jiang, and Q. Pan, Class. Quant. Grav. 33, 025001 (2016)
2016
-
[40]
Sheykhi, H
A. Sheykhi, H. R. Salahi, and A. Montakhab, JHEP 04, 058 (2016)
2016
-
[41]
Y. Liu, Y. Gong, and B. Wang, JHEP 02, 116 (2016)
2016
-
[42]
Sheykhi, A
A. Sheykhi, A. Ghazanfari, and A. Dehyadegari, Eur. Phys. J. C 78, 159 (2018)
2018
-
[43]
Sheykhi, D
A. Sheykhi, D. H. Asl, A. Dehyadegari, Phys. Lett. B 781, 139 (2018)
2018
-
[44]
Boillat, J
G. Boillat, J. Math. Phys. 11, 941 (1970); 11, 1482 (1970)
1970
-
[45]
G. W. Gibbons and D. A. Rasheed, Nucl. Phys. B 454, 185 (1995)
1995
-
[46]
S. H. Hendi, JHEP 03, 065 (2012)
2012
-
[47]
S. H. Hendi, Ann. Phys. 333, 282 (2013)
2013
-
[48]
S. H. Hendi, Ann. Phys. 346, 42 (2014)
2014
-
[49]
Sheykhi and A
A. Sheykhi and A. Kazemi, Phys. Rev. D 90, 044028 (2014)
2014
-
[50]
S. H. Hendi, A. Sheykhi, M. S. Rad, and K. Matsuno, Gen. Rel. Gr av. 47, 117 (2015)
2015
-
[51]
S. I. Kruglov, Europhys. Letters 115, 60006 (2016)
2016
-
[52]
S. I. Kruglov, Ann. Phys. 378, 59 (2017)
2017
-
[53]
Hajkhalili and A
S. Hajkhalili and A. Sheykhi, Int. J. Mod. Phys. D 27, 1850075 (2018)
2018
-
[54]
Zwiebach, Phys
B. Zwiebach, Phys. Lett. B 156, 315 (1985)
1985
-
[55]
D. J. Gross and E. Witten, Nucl. Phys. B 277, 1 (1986)
1986
-
[56]
D. J. Gross and J. H Sloan, Nucl. Phys. B 291, 41 (1987)
1987
-
[57]
R. R. Metsaev and A. A. Tseytlin, Phys. Lett. B 185, 52 (1987); 191, 354 (1987); Nucl. Phys. B 293, 385 (1987)
1987
-
[58]
M. C. Bento and O. Bertolami, Phys. Lett. B 368, 198 (1996)
1996
-
[59]
Gregory, S
R. Gregory, S. Kanno, and J. Soda, JHEP 0910, 010 (2009)
2009
-
[60]
Q. Pan, B. Wang, E. Papantonopoulos, J. Oliveira, and A. B. Pav an, Phys. Rev. D 81, 106007 (2010)
2010
-
[61]
Pan and B
Q. Pan and B. Wang, Phys. Lett. B 693, 159 (2010)
2010
-
[62]
Barclay, R
L. Barclay, R. Gregory, S. Kanno, and P. Sutcliffe, JHEP 1012, 029 (2010)
2010
-
[63]
Cai, Z.-Y
R.-G. Cai, Z.-Y. Nie, and H.-Q. Zhang, Phys. Rev. D 82, 066007 (2010)
2010
-
[64]
Li, R.-G
H.-F. Li, R.-G. Cai, and H.-Q. Zhang, JHEP 04, 028 (2011)
2011
-
[65]
Barclay, R
L. Barclay, R. Gregory, S. Kanno, and P. Sutcliffe, JHEP 1012, 029 (2010),
2010
-
[66]
Kanno, Class
S. Kanno, Class. Quant. Grav. 28, 127001 (2011)
2011
-
[67]
J. Jing, L. Wang, Q. Pan, and S. Chen, Phys. Rev. D 83, 066010 (2011)
2011
-
[68]
Cai, Z.-Y
R.-G. Cai, Z.-Y. Nie, and H.-Q. Zhang, Phys. Rev. D 83, 066013 (2011). 22
2011
-
[69]
Barclay, JHEP 10, 044 (2011)
L. Barclay, JHEP 10, 044 (2011)
2011
-
[70]
Q. Pan, J. Jing, and B. Wang, JHEP 11, 088 (2011)
2011
-
[71]
J. Jing, Q. Pan, and S. Chen, Phys. Lett. B 716, 385 (2012)
2012
-
[72]
R.-G. Cai, L. Li, L.-F. Li, H.-Q. Zhang, and Y.-L. Zhang, Phys. Rev . D 87, 026002 (2013)
2013
-
[73]
Cui and Z
S.-L. Cui and Z. Xue, Phys. Rev. D 88, 107501 (2013)
2013
-
[75]
Cai, L.-Li, and L.-F
R.-G. Cai, L.-Li, and L.-F. Li, JHEP 1401, 032 (2014)
2014
-
[76]
Dey and A
S. Dey and A. Lala, Annals Phys. 354, 165 (2014)
2014
-
[77]
Parai, S
D. Parai, S. Gangopadhyay, D. Ghorai, Ann. Phys. 403, 59 (2019)
2019
-
[78]
C. H. Nam, arXiv: 1908.05031
1908 arXiv
-
[79]
Cai, Phys
R.-G. Cai, Phys. Rev. D 65, 084014 (2002)
2002
-
[80]
Breitenlohner and D
P. Breitenlohner and D. Z. Freedman, Ann. Phys. 144, 249 (1982)
1982
-
[81]
Breitenlohner and D
P. Breitenlohner and D. Z. Freedman, Phys. Lett. B 115, 197 (1982)
1982
-
[82]
Abramowitz and I
M. Abramowitz and I. A. Stegun, Handbook of mathematical functions (Dover, New York, 1972)
1972
-
[83]
Skenderis, Class
K. Skenderis, Class. Quant. Grav. 19, 5849 (2002)
2002
-
[84]
Barclay, R
L. Barclay, R. Gregory, S. Kanno, and P. Sutcliffe, JHEP 12, 29 (2010)
2010
-
[85]
J. R. Sun, S. Y. Wu, and H. Q. Zhang, Phys. Rev. D 87, 086005 (2013)
2013
-
[86]
Tong, Lectures on holographic conductivity , Presented at Cracow School of Theoretical Physics,(2013)
D. Tong, Lectures on holographic conductivity , Presented at Cracow School of Theoretical Physics,(2013)
2013
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