I wanted to ask a quick question about the complex scalar field. My question is that does the scalar field need to be complex in order to include the part for anti-particles or do you regards the scalar field for particles and anti-particles seperate. I saw this specifically when you second quantization to quantize the scalar field that satisfies the Klein-Gordon equation. Are there any advantages and disadvantages of making the scalar field complex if it really doesn't apply to what I mentioned above? Thanks in advance for anybody who can clarify this question.