Inverse Laplace Sum
1. **State the problem:** We want to find the inverse Laplace transform of the function given by the infinite sum
$$F(s) = \sum_{m=0}^\infty \frac{\Gamma(m+1)}{\Gamma(\alpha m + \beta)} s^{m+1}.$$
2. **Rewrite the sum:** Recall that $\Gamma(m+1) = m!$. So the function is
$$F(s) = \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} s^{m+1}.$$
3. **Express the inverse Laplace transform:** The inverse Laplace transform $f(t)$ is given by
$$f(t) = \mathcal{L}^{-1}\{F(s)\}(t) = \mathcal{L}^{-1}\left\{ \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} s^{m+1} \right\}(t).$$
4. **Use linearity of inverse Laplace transform:** We can interchange sum and inverse transform (assuming convergence):
$$f(t) = \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} \mathcal{L}^{-1}\{ s^{m+1} \}(t).$$
5. **Find inverse Laplace transform of $s^{m+1}$:** Recall that for $n > -1$,
$$\mathcal{L}\{ t^n \}(s) = \frac{\Gamma(n+1)}{s^{n+1}} \implies \mathcal{L}^{-1}\{ s^{-k} \}(t) = \frac{t^{k-1}}{\Gamma(k)}.$$
Here, $s^{m+1} = s^{-( -m -1)}$, so the exponent is positive, which is not a standard Laplace transform form. Usually, Laplace transforms involve negative powers of $s$.
6. **Rewrite $s^{m+1}$ as $s^{-( -m -1)}$:** This corresponds to the Laplace transform of a fractional derivative or distribution, which is complicated. Instead, consider the function as a formal power series in $s$.
7. **Alternative approach:** Consider the function
$$G(s) = \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} s^{m}$$
so that
$$F(s) = s G(s).$$
8. **Inverse Laplace transform of $F(s)$:** Using the property
$$\mathcal{L}^{-1}\{ s G(s) \}(t) = \frac{d}{dt} \mathcal{L}^{-1}\{ G(s) \}(t).$$
9. **Find inverse Laplace transform of $G(s)$:**
$$G(s) = \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} s^{m} = \sum_{m=0}^\infty \frac{\Gamma(m+1)}{\Gamma(\alpha m + \beta)} s^{m}.$$
10. **Recognize $G(s)$ as a generalized Mittag-Leffler function:** The generalized Mittag-Leffler function is defined as
$$E_{\alpha, \beta}(z) = \sum_{m=0}^\infty \frac{z^m}{\Gamma(\alpha m + \beta)}.$$
Here, the numerator is $m!$ instead of 1, so rewrite $m! = \Gamma(m+1)$ and consider the function
$$H(z) = \sum_{m=0}^\infty \frac{\Gamma(m+1)}{\Gamma(\alpha m + \beta)} z^m.$$
11. **Express $\Gamma(m+1)$ as an integral:** Using the integral representation
$$\Gamma(m+1) = \int_0^\infty x^m e^{-x} dx,$$
we can write
$$H(z) = \sum_{m=0}^\infty \frac{z^m}{\Gamma(\alpha m + \beta)} \int_0^\infty x^m e^{-x} dx = \int_0^\infty e^{-x} \sum_{m=0}^\infty \frac{(x z)^m}{\Gamma(\alpha m + \beta)} dx.$$
12. **Recognize the inner sum as $E_{\alpha, \beta}(x z)$:** So
$$H(z) = \int_0^\infty e^{-x} E_{\alpha, \beta}(x z) dx.$$
13. **Therefore, the inverse Laplace transform of $G(s)$ is related to the inverse Laplace transform of $H(s)$:** This integral representation is complicated, but the key insight is that
$$f(t) = \frac{d}{dt} \mathcal{L}^{-1}\{ G(s) \}(t) = \frac{d}{dt} g(t),$$
where
$$g(t) = \mathcal{L}^{-1}\{ G(s) \}(t).$$
14. **Summary:** The inverse Laplace transform of the original function is
$$f(t) = \frac{d}{dt} \left( \mathcal{L}^{-1} \left\{ \sum_{m=0}^\infty \frac{m!}{\Gamma(\alpha m + \beta)} s^m \right\} (t) \right).$$
15. **Final note:** Without additional constraints on $\alpha, \beta$, or $s$, the inverse Laplace transform involves generalized Mittag-Leffler functions and their integral representations. The problem is advanced and typically requires special function theory for explicit closed forms.
**Answer:** The inverse Laplace transform is
$$f(t) = \frac{d}{dt} \left( \int_0^\infty e^{-x} E_{\alpha, \beta}(x t) dx \right),$$
where $E_{\alpha, \beta}$ is the generalized Mittag-Leffler function.