quantum mechanics - When an electron changes its spin, or any other intrinsic property, is it still the same electron?

I am not asking why an intrinsic property, like spin can have more then a single value. I understand particles (electrons) can come to existence with either up or down spin. I am asking why it can change while the particle exists.

Electrons are defined in the SM as elementary particles, and its intrinsic properties include both EM charge and spin.

The electron is a subatomic particle, symbol e− or β− , whose electric charge is negative one elementary charge. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ħ.

The EM charge of the electron is defined as -1e, and the spin as 1/2.

Electrons have an electric charge of −1.602×10^−19 coulombs,[66] which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge. The electron has an intrinsic angular momentum or spin of 1 / 2 .[66] This property is usually stated by referring to the electron as a spin- 1 / 2 particle.

https://en.wikipedia.org/wiki/Electron

In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei.[1][2] Although the direction of its spin can be changed, an elementary particle cannot be made to spin faster or slower. In addition to their other properties, all quantum mechanical particles possess an intrinsic spin (though this value may be equal to zero).

https://en.wikipedia.org/wiki/Spin_(physics)

he spin transition is an example of transition between two electronic states in molecular chemistry. The ability of an electron to transit from a stable to another stable (or metastable) electronic state in a reversible and detectable fashion, makes these molecular systems appealing in the field of molecular electronics.

https://en.wikipedia.org/wiki/Spin_transition

So basically an electron can change its spin from up to down or vica versa, thought it is an intrinsic property.

Electrons EM charge cannot change.

In science and engineering, an intrinsic property is a property of a specified subject that exists itself or within the subject.

So both EM charge and spin are intrinsic properties of electrons. Though, electrons are coming to existence with a certain EM charge and spin. Still, EM charge is unchanged as long as the electron exists, but spin can change.

I do understand that electrons can have intrinsic properties, that can have either a single value, or a set of values. I do understand that some elecrons come into existence with EM charge and spin up. Some electrons come into existence with EM charge and spin down.

What I do not understand, is, how can spin change while the electron still exists, whereas EM charge cannot, though, both are intrinsic properties.

Do we know that when an electron undergoes spin flip (spin transition), that the electron that had originally spin up is the same quantum system that after the spin transition has spin down?

Can it be that the electron before with spin up ceases to exist (vacuum fluctuation), and then another electron is coming into existence with spin down?

Why do we say that the electron that had spin up (which is an intrinsic property) is the same quantum system as the electron that has later on (after spin flip) spin down?

After the big bang, at the baryion asymmetry, some electrons came into existence with spin up and some with spin down. Do we call these the same electrons?

Is spin the only intrinsic property of the electron that can change (like helicity)?

Question:

1. 
   

   How can an intrinsic property of an electron change (spin flip)?

   
   


2. 
   

   Are there any intrinsic properties (of elementary particles), that do have multiple values available, but still can't change?

   
   
   

Answer

What people mean when they say that spin is an intrinsic property is that spin represents an internal state of the particle that exists independently of its position and motion in space. However, the value^* of that internal state can and does change, and when that happens that doesn’t mean the electron can be meaningfully said to have been replaced by a “different” electron, any more than an electron that changed its position in space would be thought of as a “new” or “different” electron. We just say that the electron moved.

Similarly, there is nothing strange or inconsistent about thinking that the spin of the electron changed, and there is no need to explain the strangeness away by saying the electron has been replaced by ”another” electron. A change of spin is a completely reasonable thing to imagine, once one has overcome the small hurdle of understanding what it means for spin to be “intrinsic”. It is not the particular direction in space of the spin that is intrinsic, rather, what is intrinsic is the set of labels that spin can assume (that is, the vector space - $\mathbb{C}^2$ in the case of the electron - where spin “lives”) along with the precise rules that govern how the spin internal state evolves and interacts with position and other parameters of the quantum system.

^{* Another subtle issue here is that one usually cannot consistently talk about the spin having a value in the sense of a particular direction in space that the spin vector is “pointing”. This is the difficulty alluded to in @EmilioPisanty’s answer, having to do with the fact that the three coordinates of the spin operator-valued vector do not commute, which means they cannot simultaneously be thought of as having well-defined values. This issue is tangential to my remarks above, but still important to mention, as it illustrates another way in which the words that physicists use to talk about ideas in physics fail to communicate nuances of meaning that can only properly be conveyed using precise mathematical language. As @knzhou says, in order to properly understand what spin is, there is no susbstitute to learning the mathematics behind it.}