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The author of a book I'm reading defines the Dirac delta-function as

$$ \delta(\omega_0-\omega) = \frac{2}{\pi}\mathbf{Lt}_{t\rightarrow \infty} \frac{\sin^2\left(\frac 1 2 (\omega_0-\omega)t\right)}{(\omega_0-\omega)^2t}. $$

Does the symbol $\mathbf{Lt}$ have any special significance, or is it just a normal limit? I've never seen this notation before. The way he uses it, it seems to be just an ordinary limit, but since he doesn't use the universal $\lim_{x\rightarrow\infty} f(x)$ notation, I suspect it might have some additional significance?

The book is "The Quantum Theory of Light" by Loudon.

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Is this book in some specialized field like signals and systems or linear systems theory? Maybe provide the title of the book. Regards –  Amzoti Apr 26 '13 at 0:50
    
I added the name of the book. The field is quantum optics. –  Lasse Carstensen Apr 26 '13 at 0:53
    
Seeing as it's a Dirac delta, the limit probably denotes a nascent limit –  EuYu Apr 26 '13 at 1:01
    
A nascent limit is consistent with the development that comes after the above definition, EuYu is most likely right. –  Lasse Carstensen Apr 26 '13 at 2:09

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