1 Introduction
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A well-known result of Gay [11, Theorem 3.1] asserts local 2n-step q-quadratic convergence of Broyden’s method under appropriate assumptions. We show under the same assumptions that if \(n-d\) of the equations are affine and the corresponding \(n-d\) rows of \(B_0\) agree with the corresponding \(n-d\) rows of \(F^{\prime }\), then Broyden’s method is locally 2d-step q-quadratically convergent.
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We provide high-precision numerical experiments that confirm the improved convergence speed and observe that it is lost if the relevant rows of \(B_0\) are perturbed.
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The experiments suggest that Broyden’s method enjoys a q-order of convergence no smaller than \(2^{1/(2d)}\). This is the first time that the q-order of Broyden’s method is studied numerically, and even for \(d=n\) the conjecture that a q-order larger than one may exist is novel.
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may converge \((2d-1)\)-step q-quadratically for \(d\in \{2,\ldots ,n\}\) (which, if true, implies an r-order of convergence no smaller than \(2^{\frac{1}{2d-1}}\)),
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may exhibit a q-order of convergence [30, Sect. 9.1] larger than one,
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may admit the lower bound \(2^{1/(2d)}\) for their q-order for \(d\in \{1,\ldots ,n\}\).
2 A subspace property of Broyden’s method
3 Improved convergence for mixed linear–nonlinear systems
4 Numerical experiments
4.1 Design of the experiments
4.1.1 Implementation and accuracy
4.1.2 Known solution and random initialization
rand
, which produces uniformly distributed random numbers, and satisfies \(u^0\in \bar{u}+[-10^{-3},10^{-3}]^n\). For \(B_0\) we choose \(B_0=F^{\prime }(u^0)+\hat{\alpha }\Vert F^{\prime }(u^0)\Vert R\), where \(\hat{\alpha }\in \{0,10^{-30},10^{-10},10^{-3}\}\) and where \(R\in \mathbb {R}^{n\times n}\) is a random matrix whose entries belong to \([-1,1]\), but that has a particular structure in which many entries are zero. Specifically, we use two schemes for R: Either R affects only those rows of \(B_0\) that correspond to nonlinear components of F, in which case \(R^j=0\) for all \(j\in J\) (cf. Assumption 1 for notation), or it affects only those rows that correspond to affine components, in which case \(R^j=0\) for all \(j\in \{1,\ldots ,d\}\). In the first case we want to demonstrate that the perturbation has essentially no effect, so we allow R to be nonzero in the entire rows, i.e., for each \(j\in \{1,\ldots ,d\}\) the row \(R^j\) is randomly drawn from \([-1,1]^n\). In the second case the aim is to show that even minimal perturbations significantly decrease the order of convergence, so we modify only one entry of \(B_0\) per row, i.e., for each \(j\in J\) all entries of \(R^j\) except one are zero. The nonzero entry is taken to be a random number in \([-1,1]\) and its position within the row is random, too. We denote \(\hat{\alpha }=\hat{\alpha }_n\) (nonlinear) in the first case and \(\hat{\alpha }=\hat{\alpha }_l\) (linear) in the second.4.1.3 Quantities of interest
4.1.4 Single runs and cumulative runs
4.2 Numerical examples
4.2.1 Example 1 a
k | \(||F_k||\) | \(\rho _k^1\) | \(\rho _k^4\) | \(\rho _k^3\) | \(\rho _k^2\) | \(C_k^4\) | \(C_k^3\) | \(C_k^2\) |
---|---|---|---|---|---|---|---|---|
0 | 4.4e−3 | −1 | −1 | −1 | −1 | −1 | −1 | −1 |
1 | 2.4e−6 | 2.08 | −1 | −1 | −1 | −1 | −1 | −1 |
2 | 2.4e−9 | 1.44 | −1 | −1 | 3.01 | −1 | −1 | 1.1e−3 |
3 | 6.4e−13 | 1.38 | −1 | 4.15 | 1.99 | −1 | 4.6e−7 | 1.2 |
4 | 2.2e−16 | 1.28 | 5.32 | 2.55 | 1.77 | 1.6e−10 | 4.1e−4 | 111 |
5 | 2.2e−22 | 1.38 | 3.53 | 2.44 | 1.77 | 4.1e−10 | 1.1e−4 | 600 |
6 | 3.4e−31 | 1.41 | 3.44 | 2.49 | 1.94 | 1.7e−13 | 9.2e−7 | 7.6 |
7 | 2.7e−41 | 1.33 | 3.32 | 2.59 | 1.87 | 7.2e−17 | 6.0e−10 | 600 |
8 | 6.0e−52 | 1.26 | 3.27 | 2.36 | 1.68 | 1.3e−20 | 1.4e−8 | 5.7e9 |
9 | 2.7e−67 | 1.30 | 3.07 | 2.18 | 1.64 | 6.0e−24 | 2.5e−6 | 4.2e14 |
10 | 6.2e−91 | 1.35 | 2.96 | 2.22 | 1.76 | 5.9e−30 | 9.8e−10 | 1.9e12 |
11 | 5.8e−120 | 1.32 | 2.94 | 2.33 | 1.79 | 9.1e−39 | 1.8e−17 | 9.2e13 |
12 | 2.3e−151 | 1.26 | 2.94 | 2.26 | 1.67 | 7.1e−49 | 3.6e−18 | 6.5e29 |
13 | 1.0e−192 | 1.27 | 2.88 | 2.13 | 1.61 | 1.6e−59 | 2.9e−12 | 3.4e46 |
14 | 2.5e−255 | 1.33 | 2.82 | 2.13 | 1.69 | 7.1e−75 | 8.2e−17 | 5.3e46 |
15 | 5.0e−337 | 1.32 | 2.82 | 2.23 | 1.75 | 1.7e−98 | 1.1e−35 | 5.5e47 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.20 | 1.29 | 2.76 | 2.90 | 1.99 | 2.21 | 1.50 | 1.69 | 1e−50 | 2e−36 | 3e−20 | 27.0 | 2e44 | 9e106 |
1.20 | 1.30 | 2.73 | 2.92 | 1.99 | 2.22 | 1.50 | 1.69 | 1e−53 | 4e−31 | 3e−20 | 71.8 | 9e43 | 3e111 |
4.2.2 Example 1 b
k | \(||F_k||\) | \(\rho _k^3\) | \(\rho _k^2\) | \(\rho _k^1\) | \(C_k^3\) | \(C_k^2\) | \(C_k^1\) |
---|---|---|---|---|---|---|---|
0 | 5.2e−3 | −1 | −1 | −1 | −1 | −1 | −1 |
1 | 3.0e−6 | −1 | −1 | 1.97 | −1 | −1 | 1.2 |
2 | 7.0e−9 | −1 | 2.88 | 1.46 | −1 | 2.9e−3 | 1.1e3 |
3 | 1.8e−14 | 4.81 | 2.45 | 1.67 | 7.6e−9 | 2.9e−3 | 533.0 |
4 | 1.1e−22 | 3.9 | 2.66 | 1.59 | 1.7e−11 | 3.3e−6 | 4.7e5 |
5 | 1.8e−36 | 4.32 | 2.58 | 1.62 | 5.2e−20 | 7.5e−9 | 2.0e8 |
6 | 1.7e−58 | 4.17 | 2.62 | 1.61 | 7.4e−31 | 2.0e−14 | 7.7e13 |
7 | 2.7e−94 | 4.24 | 2.61 | 1.62 | 3.1e−50 | 1.2e−22 | 1.3e22 |
8 | 4.2e−152 | 4.22 | 2.62 | 1.62 | 1.8e−80 | 1.9e−36 | 7.9e35 |
9 | 9.9e−246 | 4.23 | 2.62 | 1.62 | 4.6e−130 | 1.9e−58 | 8.1e57 |
10 | 3.6e−397 | 4.23 | 2.62 | 1.62 | 6.9e−210 | 3.0e−94 | 5.2e93 |
\(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(\rho _1^-\) | \(\rho _1^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) | \(C_1^-\) | \(C_1^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|
4.18 | 4.23 | 2.60 | 2.62 | 1.61 | 1.62 | 2e−65 | 4e−40 | 1e−29 | 2e−18 | 4e75 | 2e122 |
4.11 | 4.23 | 2.59 | 2.62 | 1.61 | 1.62 | 2e−65 | 1e−39 | 1e−29 | 5e−18 | 4e75 | 2e122 |
1.99 | 2.21 | 1.51 | 1.69 | 1.20 | 1.30 | 5e−20 | 23.1 | 2e43 | 2e102 | 1e99 | 3e246 |
2.04 | 2.25 | 1.53 | 1.71 | 1.21 | 1.30 | 2e−25 | 4e−5 | 2e40 | 2e81 | 1e99 | 2e223 |
2.00 | 2.27 | 1.37 | 1.63 | 1.16 | 1.24 | 4e−29 | 3.05 | 1e52 | 1e98 | 1e99 | 8e217 |
4.2.3 Example 1 c
k | \(||F_k||\) | \(\rho _k^1\) | \(\rho _k^4\) | \(\rho _k^3\) | \(\rho _k^2\) | \(C_k^4\) | \(C_k^3\) | \(C_k^2\) |
---|---|---|---|---|---|---|---|---|
0 | 5.1e−3 | −1 | −1 | −1 | −1 | −1 | −1 | −1 |
1 | 2.4e−6 | 2.09 | −1 | −1 | −1 | −1 | −1 | −1 |
2 | 3.5e−9 | 1.44 | −1 | −1 | 3.01 | −1 | −1 | 1.2e−3 |
3 | 9.2e−13 | 1.43 | −1 | 4.31 | 2.06 | −1 | 2.1e−7 | 0.41 |
4 | 4.4e−16 | 1.27 | 5.45 | 2.61 | 1.81 | 1.0e−10 | 2.0e−4 | 45.0 |
5 | 2.6e−22 | 1.39 | 3.64 | 2.52 | 1.77 | 1.2e−10 | 2.7e−5 | 855.0 |
6 | 4.5e−31 | 1.40 | 3.53 | 2.47 | 1.95 | 4.5e−14 | 1.4e−6 | 6.2 |
7 | 1.4e−43 | 1.41 | 3.47 | 2.74 | 1.97 | 4.6e−19 | 2.0e−12 | 5.6 |
8 | 1.8e−56 | 1.30 | 3.56 | 2.55 | 1.83 | 2.4e−25 | 6.9e−13 | 2.4e5 |
9 | 7.0e−72 | 1.27 | 3.25 | 2.33 | 1.65 | 2.7e−28 | 9.4e−11 | 9.3e14 |
10 | 1.2e−95 | 1.33 | 3.10 | 2.20 | 1.70 | 1.6e−34 | 1.6e−9 | 1.1e17 |
11 | 2.1e−129 | 1.35 | 2.98 | 2.30 | 1.80 | 2.8e−43 | 1.8e−17 | 1.2e14 |
12 | 1.0e−167 | 1.30 | 2.98 | 2.34 | 1.76 | 8.8e−56 | 5.6e−25 | 1.9e23 |
13 | 1.9e−211 | 1.26 | 2.95 | 2.21 | 1.64 | 1.1e−68 | 3.6e−21 | 1.2e47 |
14 | 2.3e−274 | 1.30 | 2.87 | 2.12 | 1.64 | 4.3e−84 | 1.4e−16 | 6.2e60 |
15 | 1.2e−365 | 1.33 | 2.83 | 2.18 | 1.73 | 7.4e−108 | 3.2e−31 | 8.5e56 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.20 | 1.29 | 2.70 | 2.96 | 1.99 | 2.21 | 1.51 | 1.68 | 2e−51 | 2e−34 | 6e−21 | 24.1 | 7e44 | 4e104 |
1.20 | 1.30 | 2.76 | 2.93 | 1.99 | 2.23 | 1.50 | 1.69 | 1e−51 | 5e−31 | 7e−20 | 20.5 | 4e41 | 9e110 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _5^-\) | \(\rho _5^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(C_5^-\) | \(C_5^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.13 | 1.20 | 2.25 | 2.57 | 1.84 | 2.10 | 1.54 | 1.74 | 8e−43 | 5e−17 | 3e−12 | 4e24 | 8e39 | 3e103 |
1.14 | 1.20 | 2.29 | 2.66 | 1.87 | 2.17 | 1.56 | 1.76 | 9e−50 | 2e−24 | 1e−16 | 1e24 | 3e37 | 2e97 |
1.13 | 1.20 | 2.43 | 2.84 | 1.93 | 2.20 | 1.57 | 1.82 | 2e−82 | 4e−54 | 2e−31 | 2e11 | 2e31 | 4e79 |
4.2.4 Example 2
k | \(||F_k||\) | \(\rho _k^1\) | \(\rho _k^4\) | \(\rho _k^3\) | \(\rho _k^2\) | \(C_k^4\) | \(C_k^3\) | \(C_k^2\) |
---|---|---|---|---|---|---|---|---|
0 | 0.01 | −1 | −1 | −1 | −1 | −1 | −1 | −1 |
1 | 9.3e−7 | 1.61 | −1 | −1 | −1 | −1 | −1 | −1 |
2 | 3.0e−8 | 1.33 | −1 | −1 | 2.13 | −1 | −1 | 0.43 |
3 | 1.4e−11 | 1.57 | −1 | 3.35 | 2.08 | −1 | 1.6e−4 | 0.42 |
4 | 1.6e−14 | 1.31 | 4.37 | 2.72 | 2.05 | 2.1e−7 | 5.5e−4 | 0.49 |
5 | 2.2e−17 | 1.23 | 3.35 | 2.53 | 1.61 | 7.8e−7 | 6.9e−4 | 5.1e3 |
6 | 2.8e−22 | 1.32 | 3.34 | 2.12 | 1.63 | 9.0e−9 | 0.066 | 3.8e4 |
7 | 1.1e−30 | 1.42 | 3.01 | 2.31 | 1.88 | 2.7e−10 | 1.5e−4 | 77 |
8 | 4.1e−39 | 1.30 | 3.00 | 2.43 | 1.84 | 5.5e−13 | 2.8e−7 | 1.6e3 |
9 | 1.2e−47 | 1.23 | 2.99 | 2.27 | 1.60 | 8.2e−16 | 4.8e−6 | 3.0e11 |
10 | 5.2e−61 | 1.29 | 2.93 | 2.07 | 1.59 | 2.1e−19 | 0.013 | 9.9e14 |
11 | 1.1e−82 | 1.37 | 2.83 | 2.18 | 1.77 | 2.7e−24 | 2.1e−7 | 2.4e10 |
12 | 2.2e−108 | 1.32 | 2.88 | 2.34 | 1.81 | 4.2e−33 | 4.8e−16 | 2.6e11 |
13 | 6.9e−134 | 1.24 | 2.90 | 2.24 | 1.64 | 1.5e−41 | 8.2e−15 | 1.9e29 |
14 | 9.7e−169 | 1.26 | 2.83 | 2.07 | 1.57 | 1.1e−49 | 2.6e−6 | 6.3e45 |
15 | 1.8e−225 | 1.34 | 2.77 | 2.10 | 1.70 | 4.9e−63 | 1.2e−11 | 1.2e40 |
16 | 1.6e−298 | 1.33 | 2.79 | 2.25 | 1.78 | 1.0e−84 | 1.0e−33 | 5.4e36 |
17 | 3.2e−375 | 1.26 | 2.83 | 2.24 | 1.67 | 2.1e−110 | 1.1e−40 | 3.0e73 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.20 | 1.29 | 2.66 | 2.88 | 1.97 | 2.19 | 1.50 | 1.68 | 3e−48 | 6e−24 | 3e−18 | 314.0 | 3e44 | 9e110 |
1.19 | 1.29 | 2.64 | 2.90 | 1.94 | 2.19 | 1.47 | 1.68 | 3e−38 | 7e−24 | 1e−14 | 4e4 | 2e45 | 8e111 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.08 | 1.19 | 2.07 | 3.02 | 1.78 | 2.49 | 1.55 | 2.07 | 3e−49 | 3e−7 | 7e−33 | 8e42 | 5e−9 | 6e100 |
1.09 | 1.19 | 2.19 | 3.15 | 1.83 | 2.60 | 1.55 | 2.11 | 7e−68 | 3e−15 | 2e−46 | 3e31 | 1e−11 | 5e98 |
1.10 | 1.18 | 2.34 | 3.59 | 1.93 | 2.86 | 1.61 | 2.21 | 4.e−101 | 4e−54 | 8e−75 | 5e13 | 1e−32 | 4e81 |
4.2.5 Example 3
k | \(||F_k||\) | \(\rho ^1_k\) | \(\rho _k^5\) | \(\rho _k^4\) | \(\rho _k^3\) | \(C_k^5\) | \(C_k^4\) | \(C_k^3\) |
---|---|---|---|---|---|---|---|---|
0 | 4.6e−3 | −1 | −1 | −1 | −1 | −1 | −1 | −1 |
1 | 6.0e−7 | 2.28 | −1 | −1 | −1 | −1 | −1 | −1 |
2 | 2.5e−11 | 1.75 | −1 | −1 | −1 | −1 | −1 | −1 |
3 | 7.7e−15 | 1.34 | −1 | −1 | 5.36 | −1 | −1 | 1.1e−9 |
4 | 3.5e−18 | 1.21 | −1 | 6.48 | 2.85 | −1 | 1.1e−12 | 7.1e−6 |
5 | 9.1e−22 | 1.20 | 7.75 | 3.41 | 1.94 | 4.5e−16 | 2.9e−9 | 4.2 |
6 | 5.3e−26 | 1.20 | 4.10 | 2.34 | 1.74 | 1.7e−13 | 2.4e−4 | 4.9e3 |
7 | 7.6e−36 | 1.39 | 3.26 | 2.43 | 2.01 | 3.5e−14 | 7.1e−7 | 0.67 |
8 | 1.3e−46 | 1.31 | 3.18 | 2.63 | 2.20 | 1.3e−17 | 1.2e−11 | 7.2e−5 |
9 | 2.6e−56 | 1.21 | 3.19 | 2.67 | 2.22 | 2.3e−21 | 1.4e−14 | 4.1e−6 |
10 | 4.0e−66 | 1.18 | 3.14 | 2.61 | 1.87 | 2.2e−24 | 6.4e−16 | 3.1e4 |
11 | 6.4e−77 | 1.17 | 3.04 | 2.18 | 1.67 | 1.0e−26 | 4.9e−7 | 1.6e15 |
12 | 5.9e−91 | 1.19 | 2.59 | 1.97 | 1.63 | 4.5e−21 | 14.0 | 3.9e20 |
13 | 7.1e−115 | 1.27 | 2.50 | 2.06 | 1.75 | 1.7e−23 | 4.7e−4 | 1.9e16 |
14 | 4.9e−145 | 1.26 | 2.61 | 2.21 | 1.90 | 3.3e−34 | 1.3e−14 | 5.3e7 |
15 | 4.5e−175 | 1.21 | 2.68 | 2.29 | 1.94 | 1.2e−44 | 4.9e−23 | 5.8e5 |
16 | 1.3e−205 | 1.18 | 2.70 | 2.28 | 1.80 | 1.4e−53 | 1.7e−25 | 1.2e23 |
17 | 3.7e−237 | 1.15 | 2.63 | 2.07 | 1.64 | 4.8e−57 | 3.3e−9 | 6.7e51 |
18 | 5.1e−276 | 1.16 | 2.42 | 1.91 | 1.58 | 4.5e−48 | 9.3e12 | 1.1e73 |
19 | 6.8e−338 | 1.23 | 2.34 | 1.94 | 1.65 | 1.2e−49 | 1.5e11 | 1.7e72 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _5^-\) | \(\rho _5^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(C_5^-\) | \(C_5^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.13 | 1.20 | 2.29 | 2.60 | 1.85 | 2.12 | 1.56 | 1.74 | 3e−45 | 2e−21 | 3e−12 | 3e29 | 6e32 | 6e100 |
1.13 | 1.19 | 2.24 | 2.51 | 1.83 | 2.08 | 1.53 | 1.73 | 9e−37 | 5e−18 | 7e−8 | 7e18 | 3e37 | 2e94 |
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _8^-\) | \(\rho _8^+\) | \(\rho _7^-\) | \(\rho _7^+\) | \(\rho _6^-\) | \(\rho _6^+\) | \(C_8^-\) | \(C_8^+\) | \(C_7^-\) | \(C_7^+\) | \(C_6^-\) | \(C_6^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.06 | 1.14 | 1.96 | 3.15 | 1.76 | 2.77 | 1.60 | 2.36 | 1e−63 | 1100 | 4e−48 | 2e21 | 7e−30 | 3e54 |
1.06 | 1.15 | 2.24 | 3.30 | 1.96 | 2.91 | 1.74 | 2.49 | 1e−75 | 2e−16 | 2e−57 | 1644 | 6e−36 | 1e25 |
1.08 | 1.14 | 3.01 | 3.84 | 2.49 | 3.29 | 2.04 | 2.72 | 8e−119 | 6e−77 | 2e−94 | 3e−65 | 1e−63 | 2e−7 |
4.2.6 Example 4
\(\rho _1^-\) | \(\rho _1^+\) | \(\rho _4^-\) | \(\rho _4^+\) | \(\rho _3^-\) | \(\rho _3^+\) | \(\rho _2^-\) | \(\rho _2^+\) | \(C_4^-\) | \(C_4^+\) | \(C_3^-\) | \(C_3^+\) | \(C_2^-\) | \(C_2^+\) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.20 | 1.30 | 2.77 | 2.93 | 1.98 | 2.23 | 1.50 | 1.71 | 3e−51 | 2e−34 | 3e−21 | 46.3 | 2e44 | 3e104 |