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Zurab Silagadze
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According to 8.111 from Lewin's book "Polylogarithms and associated functions", it is expected that $$\int\limits_0^2\frac{\ln{(1-x)}\ln{(1+x)}}{x}\,dx=Li_3(-3)+\zeta(3)-2Li_3(3)+$$ $$\ln{3}\left[Li_2(-1)-Li_2(2)\right]+i\pi\left[Li_2(3)-Li_2(-1)-2\zeta(2)\right ], \tag{1} $$ as Lewin clarifies in his another book "for some choice of branches of $Li_3$, $Li_2$ and $\ln$" ("Structural properties of polylogarithms", p. 144). However, it seems numerical computation (at http://www.wolframalpha.com (and), as well as naive application of some polylogarithmpolylogarithmic functional identities to the r.h.s of (1), doesn't confirm (1) and requires an extra term in the imaginary part of the r.h.s., namely $-i\pi\ln^2(3)$. From where this extra term comes from?

According to 8.111 from Lewin's book "Polylogarithms and associated functions", it is expected that $$\int\limits_0^2\frac{\ln{(1-x)}\ln{(1+x)}}{x}\,dx=Li_3(-3)+\zeta(3)-2Li_3(3)+$$ $$\ln{3}\left[Li_2(-1)-Li_2(2)\right]+i\pi\left[Li_2(3)-Li_2(-1)-2\zeta(2)\right ], \tag{1} $$ as Lewin clarifies in his another book "for some choice of branches of $Li_3$, $Li_2$ and $\ln$" ("Structural properties of polylogarithms", p. 144). However, it seems http://www.wolframalpha.com (and naive application of some polylogarithm functional identities) doesn't confirm (1) and requires an extra term in the imaginary part of the r.h.s., namely $-i\pi\ln^2(3)$. From where this extra term comes from?

According to 8.111 from Lewin's book "Polylogarithms and associated functions", it is expected that $$\int\limits_0^2\frac{\ln{(1-x)}\ln{(1+x)}}{x}\,dx=Li_3(-3)+\zeta(3)-2Li_3(3)+$$ $$\ln{3}\left[Li_2(-1)-Li_2(2)\right]+i\pi\left[Li_2(3)-Li_2(-1)-2\zeta(2)\right ], \tag{1} $$ as Lewin clarifies in his another book "for some choice of branches of $Li_3$, $Li_2$ and $\ln$" ("Structural properties of polylogarithms", p. 144). However, it seems numerical computation (at http://www.wolframalpha.com), as well as naive application of some polylogarithmic functional identities to the r.h.s of (1), doesn't confirm (1) and requires an extra term in the imaginary part of the r.h.s., namely $-i\pi\ln^2(3)$. From where this extra term comes from?

Source Link
Zurab Silagadze
  • 16.5k
  • 1
  • 47
  • 94

Choice of branch cuts in logarithmic integral

According to 8.111 from Lewin's book "Polylogarithms and associated functions", it is expected that $$\int\limits_0^2\frac{\ln{(1-x)}\ln{(1+x)}}{x}\,dx=Li_3(-3)+\zeta(3)-2Li_3(3)+$$ $$\ln{3}\left[Li_2(-1)-Li_2(2)\right]+i\pi\left[Li_2(3)-Li_2(-1)-2\zeta(2)\right ], \tag{1} $$ as Lewin clarifies in his another book "for some choice of branches of $Li_3$, $Li_2$ and $\ln$" ("Structural properties of polylogarithms", p. 144). However, it seems http://www.wolframalpha.com (and naive application of some polylogarithm functional identities) doesn't confirm (1) and requires an extra term in the imaginary part of the r.h.s., namely $-i\pi\ln^2(3)$. From where this extra term comes from?