Gamma Summation
1. **State the problem:** We are given the function
$$G_{q,\nu,r}[a,t] = \sum_{j=0}^\infty \frac{\Gamma(1-r)(-a)^j t^{(r+j)q-\nu-1}}{\Gamma(1+j)\Gamma(1-j-r)\Gamma((r+j)q-\nu)},$$
with conditions \(\text{Re}(qr-\nu)>0\), \(\text{Re}(s)>0\), and \(\left|\frac{a}{s^q}\right|<1\).
2. **Laplace transform given:**
$$L \{ G_{q,\nu,r}[a,t] \} = \frac{s^\nu}{(s^q - a)^r},$$
with \(\text{Re}(qr-\nu)>0\), \(\text{Re}(s)>0\), and \(\left|\frac{a}{s^q}\right|>0\).
3. **Gamma function identities:**
- For integer \(n\geq 0\),
$$\Gamma(x-n) = \frac{\Gamma(x)}{(x-1)(x-2) \cdots (x-n)} = \frac{(-1)^n \Gamma(x)}{(1-x)_n},$$
where \((1-x)_n\) is the Pochhammer symbol.
- Specifically,
$$\Gamma(1-j-r) = \frac{\Gamma(1-r)}{(-r)(-1-r) \cdots (1-r-j)} = \frac{(-1)^j \Gamma(1-r)}{(r)_j},$$
for \(j=1,2,\ldots\).
4. **Rewrite the summand using the identity for \(\Gamma(1-j-r)\):**
Substitute into the summand denominator:
$$\Gamma(1-j-r) = \frac{(-1)^j \Gamma(1-r)}{(r)_j} \implies \frac{1}{\Gamma(1-j-r)} = \frac{(r)_j}{(-1)^j \Gamma(1-r)}.$$
5. **Simplify the summand:**
The summand is
$$\frac{\Gamma(1-r)(-a)^j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma(1-j-r) \Gamma((r+j)q-\nu)} = \frac{\Gamma(1-r)(-a)^j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma(1-j-r) \Gamma((r+j)q-\nu)}.$$
Replace \(\frac{1}{\Gamma(1-j-r)}\) with the expression above:
$$= \frac{\Gamma(1-r)(-a)^j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma((r+j)q-\nu)} \cdot \frac{(r)_j}{(-1)^j \Gamma(1-r)} = \frac{(-a)^j t^{(r+j)q-\nu-1} (r)_j}{\Gamma(1+j) \Gamma((r+j)q-\nu) (-1)^j}.$$
6. **Simplify the powers of \(-1\):**
Note that \((-a)^j = (-1)^j a^j\), so
$$\frac{(-a)^j}{(-1)^j} = a^j.$$
7. **Final simplified summand:**
$$\frac{a^j (r)_j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma((r+j)q-\nu)}.$$
8. **Interpretation:**
The summation becomes
$$G_{q,\nu,r}[a,t] = \sum_{j=0}^\infty \frac{a^j (r)_j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma((r+j)q-\nu)}.$$
9. **Summary:**
We used the Gamma function identity to rewrite the summand in a simpler form involving the Pochhammer symbol \((r)_j\) and powers of \(a\) and \(t\).
10. **Graphical expression:**
The numerator of the summand includes the product \((-r)(1-r) \cdots (1-j-r) (-a)^j t^{(r+j)q-\nu-1}\), which corresponds to the Pochhammer symbol \((r)_j\) times \(a^j t^{(r+j)q-\nu-1}\).
**Final answer:**
$$G_{q,\nu,r}[a,t] = \sum_{j=0}^\infty \frac{a^j (r)_j t^{(r+j)q-\nu-1}}{\Gamma(1+j) \Gamma((r+j)q-\nu)}.$$