martillo,
I'd just like to point out something: The Minkowski product of any two four-vectors is invariant (this is why you'll sometimes hear Lorentz boosts called "rotations" in space-time), so you can see immediately that a relation like $$\Psi = e^{i \vec{k} \cdot \vec{r}}$$ is Lorentz invariant. This is why Minkowski's formalism is so popular - it allows laws to be expressed in a form that emphasizes their invariance using terms that are Lorentz scalars. There are also invariant equivalents to the classical gradient, divergence, and laplacian operators.
If you have an object at rest at the origin in $$K'$$ ($$x_1' = 0$$) and another at $$ x_2' = L'$$, then for object #1:
For #2:
The difference $$L = x_2 - x_1$$ gives:
I'm sure you can extend this reasoning to see what happens to the relationship between $$L$$ and $$L'$$ if objects #1 and #2 are not stationary in $$K'$$.
Happy thinkingI accept the change of the minus sign in the equation. You would have it in that way if you had started with the equation cos(kx-wt) for the wave.
I must recognize you have found a very good point with your reasoning.
This will make me think more about.
I'd just like to point out something: The Minkowski product of any two four-vectors is invariant (this is why you'll sometimes hear Lorentz boosts called "rotations" in space-time), so you can see immediately that a relation like $$\Psi = e^{i \vec{k} \cdot \vec{r}}$$ is Lorentz invariant. This is why Minkowski's formalism is so popular - it allows laws to be expressed in a form that emphasizes their invariance using terms that are Lorentz scalars. There are also invariant equivalents to the classical gradient, divergence, and laplacian operators.
You can derive the length contraction formula from the Lorentz transformation by considering the worldlines of two objects stationary in one frame.I still wonder: if the wavelenght is a lenght (a distance) in the x axis why it does not transform as a normal lenght contraction λ=λ'/γ? I think that in principle it should do.
If you have an object at rest at the origin in $$K'$$ ($$x_1' = 0$$) and another at $$ x_2' = L'$$, then for object #1:
$$x_1' = \gamma ( x_1 - v t ) = 0$$
$$\Rightarrow x_1 = v t$$
For #2:
$$ x_2' = \gamma ( x_2 - v t ) = L'$$
$$\Rightarrow x_2 = vt + \frac{L'}{\gamma}$$
The difference $$L = x_2 - x_1$$ gives:
$$L' = \gamma L$$
I'm sure you can extend this reasoning to see what happens to the relationship between $$L$$ and $$L'$$ if objects #1 and #2 are not stationary in $$K'$$.
On its own $$\vec{F} = \frac{d \vec{p}}{d \tau}$$ has no predictive power. To make real predictions you need another law that determines $$\vec{F}$$ (electromagnetism, gravity, etc.). While it's true that you can introduce centrifugal forces and the like to keep $$\vec{F} = \frac{d \vec{p}}{d \tau}$$ invariant, this comes at the expense of making the laws determining the force variant.Returning to other subject:
But the concept of the "fictitius"forces enables for exmple the motion law: F=dp/dt have the same form. Is just that the forces are different when seen from different frames.
This is why I asked for an example. In which cases a law would take different form?
Note that if this is the case you are pointing to a possible inconsistency in Relativity Theory.