Recent content by Clear Mind

Thanks for the reply! So, summarizing up... if a radio telescope is capable to build directly an image (didn't know they can do it, i mean, not in a directly way), they may suffer of aberration (indeed I've found someone speaking about spherical aberration in the Arecibo radio telescope). But in...

I was studyng my exam of astrophysics laboratory, while treathing the optical aberration I've wondered: does radio telescope have aberration? Is a paraboloid antenna in a single dish affected by coma? and the radio telescope made by arrays of resonant structures? Maybe those are silly...

I've tryed to prove it, but i didn't succeed. By the way i think I've found a more directly way to show that ##H=[g_1 H]## if ## g_1 \in H##, but I'm stuck: Let's (## \forall g_1 , g_2 \in H##) build two left cosets, ##[g_1 H]## and ##[g_2 H]##, now, suppose that ##\exists \tilde{g}## so that...

Well, if ##g_1 \in H## than i suppose that ##\forall g_1## and ##\forall h \in H , g_1*h \in H## so my left coset ##[g_1 H]## it's a subgroup. Mumble ... i think that if ##g_1 \not\in H## than ##\forall h \in H##, ##\tilde{g_1}=g_1 * h \not\in [g_1 H]## (but ##\tilde{g_1} \in G##); so if you...

Hi, this week I've started to study group theory and there's a thing that i don't understand about cosets: Suppose to have a group ##\textit{G}## and a subgroup ##\textit{H}##, than ##\forall g \in \textit{G}## i can build my left coset ##[g \textit{H}]##. Now, here's my question: Once you have...

Ok, i see! Many thanks for the help :D

My question is about Force Free fields in the study of plasma stability (in MHD regime): Consider an isolated ideal plasma in an equilibrium state (where the effect of selfgravity is negligible), from the Navier-Stokes equation we get that: $$\vec{\nabla} P = \frac{1}{c} \vec{J} \times...

Thanks for the answers guys, you all make my day! I saw that you were discussing about internal resistance of the base. You can easily calculate the base resistance using the ##\pi##-hybrid or the ##T## model of BJT, they are both correct and their usance depends on the situation. For instance...

So we can affirm that (for small signal model) when ##C_E## is present the amplifier behave like a common emitter amplifier without ##R_e##. While if we remove ##C_E##, the amplifier behave like a common emitter with a emitter resistance ##R_e##?

Suppose to have a BJT Common Emitter amplifier like the one below: Now, if we send a signal ##V_{in}## with a frequency belonging to the midband frequency interval, we can consider ##C_1, C_2,## and ##C_E## as short circuit. Questions are: 1) What is the effect of ##C_E## (excluding its role...

Thank you very much for the help guys

The question it's easy. Suppose to have a black box circuit, it will have an input resistance ##R_{in}## and an output resistance ##R_{out}##, all the books and texts argue that it's good to have a big ##R_{in}## and a low ##R_{out}##, but why?

My apologies but I'm not understanfding what you mean, for example take the ##^{43}_{21}Sc_{22}##. It have 22 neutron (so we don't need to care about), and 21 proton which are filled until ##1f_{7 \backslash 2}##. There's only one proton unpaired so nuclear spin ##I## should be ##\frac{1}{2}##...

I was trying to calculate the ##^{19}_{9}F_{10}## nuclear spin using the nuclear shell method. From what i know the nuclear spin for a nucleous with odd ##A## is the total angular momentum ##J## of the stand-alone nucleon: P: ##(1d_{5 \backslash 2})^1## (stand-alone nucleon) N: ##(1d_{5...

As the title says, what is a pomeron? I thought it was a particle but i can't find anything on the PDG ... If is a particle what are its properties?