In the novel I'm planning the human characters that inhabit the world are all clones of each other. Man and woman. They aren't given names when born, instead they are given serial numbers that also work like IDs. But given the fact that they still have diferent personalities and many even have different appearances due to tattoos, scars, dyed hairs, etc... How could I deal with them? How would they interact with each other? Aliases are a go, but as society grow numerous also does the necessity to be known in order to be recognized by his or her alias.
Your characters may not have names, but they have to have some identifiers.
Other examples in fiction:
- Star Trek's Borg use designations which specify where each drone (individual) is in the hierarchy of its group, and where that group is attached to. Seven of Nine, Tertiary Adjunct to Unimatrix 01 means that this drone is the third most important (9 of 9 is the most) but her specific task is teritary to the lead drone (so not super critical), and her group is attached to a specific location (Unimatrix 01, the center of Borg "society").
- Larry Niven's Kzinti are addressed by their family relationships and then jobs and have to earn a name.
- In Ayn Rand's novella Anthem, individuals are called by a combination of a word plus a number, and are raised in collective groups. Each individual refers to him- or herself with plural pronouns.
- In Ira Levin's This Perfect Day, people are using fewer and fewer names; there are something like four names for men and four for women when the story starts. The protagonist's actual name is a string of characters, but his nickname is "Chip."
- I haven't read it, but in Margaret Atwood's The Handmaid's Tale, the protagonist is "Offred," meaning of Fred, belonging to Fred. Handmaidens are all given designations like this.
- In The Bees by Laline Paull, the characters (all actual bees) are from various groups named after flowers and then given a number; the protagonist is Flora 717.
- In The Force Awakens, we learn that stormtroopers are stolen from their families as children and raised in groups, and given only numerical designations. John Boyega's character originally had the designation FN-2187; it's Poe Dameron who later gives him the name Finn.
People will come up with ways to address one another. You as the author need to figure out how to delineate your characters so the reader can distinguish them. Nicknames, shortened versions of lengthy alphanumeric strings, epithets like The Gunslinger, The Doctor, the man with the thistledown hair — just be consistent in how you address each individual, and you'll be fine.
A name is not actually an invariant property of a person or object. A name is an expression of the relationship between a person and another or between a person and an object. Thus the same person may be "mom", "grandma", "aunty", "Joan", "Joanie", "Joan Smith", "Mrs. Smith", "the woman in the green dress", "Smitty", "Junebug", and "234 782 189" in relationship to different people and institutions.
Pretty much every modern state assigns its citizens a serial number these days (in Canada we call it a Social Insurance Number), so a state which takes no interest in the subject;s names other than the serial number is not really so far from reality. But people will still acquire names based on other relationships. Names are fundamental to language and our relationships with the world. We can claim and project a name, and we often do, but people will assign a name to us for their own purposes, or select from the variety of names we project. The fact that that people in your story are not assigned a name by the state would actually make little difference to the process by which people assign names to things or accept the names that people claim for themselves.
If they have numbers, then the number is effectively a name. But human beings have a hard time remembering numbers. If your characters refer to each other as 1892463, 1984236, 3894361, and 4896324, the reader is going to have a hard time keeping track of them.
If it's hard to keep track in a story, that's probably because it would be hard to keep track in real life. Rather than ask, "How can I make this work in my story?", try asking, "How would this work in real life?" If your world was real, how would people refer to each other? If you can come up with something that would plausibly work in real life, it will probably work in the story.
I'd guess that in real life, people would give each other names of some sort. If not what we think of as names, they might call each other by job titles or relationships or physical descriptions. Just like we do today. ("Sarge", "Mom", "Shorty", etc.)
People will name themselves and one another. It seems to be more or less hardcoded into our DNA. Once you have a concept of yourself, you have a concept of something other than you, and the need for a label to distinguish the two emerges.
You could do worse than to check out the animated series Star Wars: The Clone Wars, which among other things spends quite a bit of time with groups of characters who are all physically identical, and formally known only by their ID numbers. They develop individual personalities, decorate their armour to distinguish themselves from one another, decorate themselves with tattoos and hairstyles, and they adopt nicknames - either chosen by themselves, or by their 'brothers'.
These nicknames often come from elements of the clone's personality or experiences. For example:
CT-5555 is known as "Fives" "Heavy" prefers heavy weaponry "Echo" tends to repeat orders for everyone "Dogma" believes what his superiors tell him, and toes the party line "Chatter" was a comms tech "Fixer" was a tech specialist
Your clones would likely be in a similar situation - If there's an easy pattern in a person's number, that might be referenced. If they show a particular interest or aptitude in some sphere of endeavour, that would give them a name. Some unusual experience could be referenced ("Crock" if someone once stepped on an alligator, for example).