Difficulties with behaviour of other PhD students in group I'm in my first year of a PhD at a top UK university. I am part of a cohort of students, most of whom have come straight from an undergraduate degree and never had any "real-world" experience. I am half a decade older than them due to getting some life experience and working in teaching for a few years before realising where my academic interests lie and deciding to give it another go.

I have realised that some of the students on my cohort are, to put it politely, not the sorts of people I would actively choose to work with. They may be very able STEM students with excellent academic credentials, but they have tendencies which are getting on my nerves and making them less pleasant to be around. These include:


Giving correct albeit unhelpful advice - for example, one of my fellow students emphatically smacked a couple of equations she wrote on the board during a group project, and proceded to have a go at me for not working through them myself, rather than politely explaining how she got them
Intellectual arrogance - for example, one student goes around, stands behind other students' computers and offers them assistance with their work regardless of whether they asked for it or not, almost as though trying to create an impression of omnipotence and undermining the merits of others
Resistance towards work of a different format to what students have been accustomed to in the past - for example, writing reports as opposed to doing problem sheets, which may not require a complete understanding of the concepts but are more akin to what an industrial role might expect
Self-opinionated behaviour from some students and attempts to attack my own opinions because they do not line up with their own.
Defeatist and entitled attitude - one student who has done poorly in his assignments takes a negative attitude towards work, constantly complains about it and tries to convince others why the work is a waste of time and why there is little to be gained from it.


I can't help but feel a bit despirited at these traits others are expressing, considering how I am rusty on some things having taken a gap from academia and yet asking some questions seems to lead to unnecessarily hostile responses. It is also despiriting to realise how much of a maturity gap there is between me and the other students, and (unlike in my previous job) I am not in a position of authority to reprimand them for their behaviour or place them on any sort of misconduct procedure.

How can I explain to these other students that their behaviour is having a negative impact on me, and how can I improve my working relationship with them?
In my experience it is not uncommon for people in your situation to not "gel" perfectly with the rest of their cohort. You are used to an industrial way of working, which is, or at least should be, quite professional and focused on a common goal (e.g., shipping some product). You are also used to fairly clear management structures, as indicated by your usage of "reprimand" and "misconduct procedure". Academia typically does not work like that. As user2768 aptly observes, a PhD study is an individual project - you are not all together shipping some common product, but you are all working on your individual research (or, in the worst case, you are directly competing for papers, grants, and future positions). That does not mean that you can't or shouldn't be friends with the people in your cohort, but it certainly gives the interactions a different dynamic.

I have found the following to be a good mental model for working in a research lab: envision yourself as a one-person (or two-person, you and your supervisor) early-stage start-up company working in an incubator or shared office space with other start-ups in a similar position. Sure, you want to have a nice relationship with these other "start-ups", and often it will help to collaborate on this and that, but ultimately you don't need to work with any of them. If you feel it is more productive to do things on your own, do so - and, conversely, don't feel that they are obligated to help you with anything specific you need.

As for how to deal with the specific behaviors you mention: essentially, my tip for all of them is to tell the respective students (more or less friendly, depending on your personality and whether you would like to build up or retain a friendly personal relationship) to bugger off and annoy somebody else. You don't need to listen to them giving you unwanted feedback, you don't need to convince them of your opinions, and they don't need to explain how they arrived at a specific solution. If a specific student annoys you or is categorically unhelpful, stop interacting with them.

With all that said, I feel there is also a good chance that parts of the conflict are also related to your own mindset. I think it would help you to stop seeing yourself as mature and them as immature and in need of correction. While I am (based on your descriptions) convinced that some of your colleagues are indeed not the nicest of people, you won't be able to change them. It is more productive for you to take a hard look at your own behaviors, and whether you are potentially not as adapted to being back at university as you would like. Maybe letting go of a notion of superiority and maturity, and making some corrections in how you deal with your colleaguesm will also help normalize your relationships.

Edit:
Some specific advise on dealing with defeatist people. Yes, those are a problem. Avoid very negative students at all costs. Nothing kills your motivation to do challenging research quicker than a friend who talks about nothing else than how pointless their research, your research, and a PhD in general is. Make very clear that you are not interested in that kind of conversation, and if they persist stop interacting with them.