Would "No one has arrived" be "personne n'est pas arrivé" or "personne n'est arrivé"? In which case will the "pas" absorbed by personne as in "Personne ne me connaît ici"? Or "personne" never goes with "pas" because it already carry/equivalent to a negative meaning, such as "Je ne connais personne ici"?
Google translate gives me "personne n'a arrivés". If it is correct, why "n'a arrivés" and not "n'est arrivés", and why plural "arrivés" for "personne"? I thought it has a singular meaning.
The correct translation is indeed
Personne n'est arrivé
And as you correctly deducted, "personne" already has a negative meaning so you shouldn't combine it with "pas" (but keeping the ne or in this case n'). If you do so, it's called a double négation. Double negations are usually tricky and therefore used very rarely and most of the time to induct confusion.
As in mathematics, double negation turns out to be positive.
Personne n'est pas arrivé (Nobody hasn't arrived)
means
Tout le monde est arrivé (Everybody has arrived)
or, if you want to use a plural ("Tout le monde" having a singular meaning being seen as one whole group)
Toutes les personnes sont arrivées (All the people have arrived)
where you should be careful not to mix up la personne/les personnes the noun , meaning "the people" and personne the pronoun meaning "nobody".
The Google translation you mention is indeed completely wrong but would be understood if ever you express it that way.
When refering to things instead of people, rien (nothing) should be used instead of personne (nobody). The grammatical use would be almost the same, at least regarding negation :
Tu n'as rien compris
... no "pas" in this sentence, rien conveying negative meaning.
Note that in this case rien comes between auxialiary and verb. "Tu n'as compris rien" isn't correct. I couldn't give a technical explanation about why though... I think your confusion might come from the fact rien is actually translated differently in English depending you're speaking positively or negatively. Actually as I think about it I guess it's more correct in English too to use "not ... anything" than just "nothing". I already heard sentences like "I didn't do nothing", but it's not how I was taught English...
Would "No one has arrived" be "personne n'est pas arrivé" or "personne n'est arrivé"?
No one has arrived is translated with Personne n'est arrivé.
In which case will the "pas" absorbed by personne as in "Personne ne me connaît ici"? Or "personne" never goes with "pas" because it already carry/equivalent to a negative meaning, such as "Je ne connais personne ici"?
The word personne (in French) is twofold. In your question the nature of personne is the second in the list:
personne (indefinite pronoun) in the sense of nobody is very common.
personne (indefinite pronoun) with the meaning of anybody/anyone/somebody/someone is less common. Examples:
You don't use personne and pas together to emphasize a stronger negation for example. I have never seen that in a sentence.
Laurent gave a good example of the usage of double negation in his answer (excellent mention).
Google translate gives me "personne n'a arrivés". If it is correct, why "n'a arrivés" and not "n'est arrivés", and why plural "arrivés" for "personne"? I thought it has a singular meaning.
Google Translate uses probability theory and statistics. The translations are fallible at times, not like a dictionary for example. I suggest not to rely on Google Translate and use dictionaries or site like this one.
