Modern and Theoretical Physics

Can somebody tell me what the differences between P-type & N-type Si Wafer?? If i want to use it as a substrate to be coated with a metallic coating, which one should i preferred to choose? and why?. Thanks

I am interested in the following information so I can study further, what is the history of dark 'stuff'? What I mean by this is, to the best of my knowledge there is dark matter, dark energy and dark flow. When and how did these come about exactly please? Did they come about together or did one follow the other? Thanks.

I guess the title is the question, is space polymorphic? Or is it a background on which things occur?

I am an engineering student, but I would like to perform some experiments unrelated to my studies. I originally thought that getting liquid nitrogen would require a license, but a relative who works in the liquid air industry said that was not the case. So now that I can get my hands on liquid nitrogen fairly inexpensively, I just need the wire material. I would like something flexible enough to shape when room temperature, that only needs liquid nitrogen to become superconducting. My search has only led me to wires that need liquid helium. Any help, like a particular material to look for or a company to look at, would be appreciated. Thanks in advance

As someone with a classical music background who has studied golden ratio and such mathematical universe once stumbled on something called the rosslyn motet, though questionable it did open up a new way of thinking about musical logic and sound. After a long time of testing theory i came to the conclusion that im sure others have made before me (sadly i had no access to library's of this nature so had to figure it out myself) that sound has physical property wich may explain why when its vibrations resonate through us we can discern 'correct' patterns/chords/note correleance and 'false' ones. Afterall, each note has a tremor frequency wich may or may not resonate wit…

Hi, i'm studying a robot arm i have done davenit and direct geometric model and i obtain this equations system J'ai essayé par des substitutions du type cos=1-u²/1+u² mais le système devient rapidement inextricable.... system eq1=335*cos(t2)* sin(t3) -77*sin(t2)-260*sin(t2)*sin(t4)+260*cos(t2)*cos(t3)*cos(t4)+85=x; eq2=335*cos(t3)-260* sin(t3)*cos(t4)=y; eq3=0-335*sin(t2)* sin(t3) -77*cos(t2) -260*cos(t2)*sin(t4)-260*sin(t2)*cos(t3)*cos(t4) =z; which is equal to (1)S+(2)*C2 =>eq1=260*sin(2*t2)*sin(t4)== 8-x*sin(t2)-z*cos(t2); eq2=335*cos(t3)-260*sin(t3)*cos(t4)-y==0; eq3=0-335*sin(t2)* sin(t3) -77*cos(t2) -260*cos(t2)*sin(t4)-260*sin(t2)*cos(t3)*cos(t4) =z; avec …

I have a .top and .crd files of a receptor-ligand system in a cubic box of water created with Amber and xLeap. It's not me who created the system and I would like to know if the .top file specifies the water model used ? I looked for keywords like 'WATER' and 'MODEL' in the .top file but didn't find matches.

I'm newer to this so please don't attack my ignorance towards things. A thought I had a little while ago while trying to fall asleep, if you understand how gravity works with the example of the fabric of space (if not search gravity visualized on youtube its the first video) then think of a black hole as a rip or dent in that fabric (part of my theory). if you look at black holes you see there is a super massive black hole at the center of every galaxy. so why not expand that to the universe? we know there was the big bang, and we know when there is a explosion with great mass a black hole follows. so that would say the big bang would create a hypermassive (idk what other…

Hi, I have, albeit reluctantly, almost come round to accepting what appears to be a fairly widespread view in the scientific community: that monopoles do not exist, at least according to the current models we have about the universe, post Big Bang. This is to say that the likes of Ampere, Gauss and Maxwell have thus far proved correct, over that of Curie and Dirac. Nonetheless, part of me has always wondered if this will be the full story on the subject of monopoles. I'm also extremely wary about scientists making negative pronouncements before all the the evidence has been examined - or even discovered. Clarke's First Law ("When a distinguished but elderly scientist …

Hello scienceforums, I would like to hear your opinion on this idea about "nothing" (This is inspired by question "Why there is something rather than nothing??") - in an absolute way "nothing" doesn't have any response (can't be proven), it doesn't contain any space, and can't occupy any space, so it can't be "stored" within existing phenomena -> this would mean that "nothing" is just a concept our mind created, and that "something" and "nothing" are just completely different entities, which simultaneously denies "existence" of each other - so if our world is "something", there can't be any "nothing", so it means that our environment can't have any b…

Can photons travel infinitely in a vacuum? What happens to time inside a black hole? What happens to photons inside a black hole? How can it be that energy has always existed?

Why is it the speed of light in vacuum is not affected by relative clock speed

I am attaching 3 figures from a well known book (Electronic Devices by Thomas L. Floyd). How does a multimeter measure µV and mV on Figures 4-39 a and f? How does this part of the transistor behave as a floating voltage point? And also how does it measure 3V on the base side and 2.5V or more on the ground side of the transistor on Fig. 4-44? Floating voltage points.pdf

Hi, I recently had to think a bit about the property of the Fourier Transform being sort of a rotation in the frequency-time (or more generally, q-dq) domain. That got me thinking of symmetry groups. I also recalled that the Fourier operator is unitary. This fits very nicely into gauge theory. This reminded me of the Fractional Fourier transform. So it's even a continuous rotation, a Lie group. Moreover, this transformation is extremely connected to Hilbert space, the underpinning of QM, connecting the position operator with the momentum operator (also later for fields in QFT). So we have under our noses a continuous-unitary-Hilbert rotation operator, which tran…

link removed Fe, Cu,....

What is the outcome of a collision between a photon and an electron ? Please opine.

Is there something like zero time. What does it mean. Prove it in nature . What would be the consequence of existence of this kind of time. For instance you can say hey zero time is at the verry begining of the universe. The moment of creation . The big bang . But it is not clear is there a creation at all and what if for instance the universe have existed forever. So in the second scenario there is no zero time.

Hi All, Sorry for being so lengthy, I was trying to be as precise as possible, and efficiently bunch up all of my questions on this topic in this one post. Most of this post is just a review. I am not a physicist, so if there are errors, please point them out so I can learn from them. My questions follow. [latex]\tilde{A}[/latex] is the EM potential one-form such that [latex]F_{\mu\nu}=(d\tilde{A})_{\mu\nu}[/latex] using the exterior derivative. [latex]\vec{\Psi}[/latex] is a wave-function (wave-vector). It is a function of space-time coordinates, with its "vectorness" values being in fiber coordinates. This distinction in coordinates means that [latex]\mu…

Do photons obey the equation : m = m0 / sq.rt (1 - v2/c2) since for photons v ~ c.

Hi all I am wanting to discuss a different first cause from the original view of Big Bang. Now I understand that science questions itself as to whether Big Bang was one event or a series of big bangs so this is really about expansion of energy. What if , rather than losing energy via expansion which is rather like turning on a hose and letting all the energy out, The singularity which is said to be the size of a pin head , lost energy and what we could see if we took step one and step two , was simply different states of the singularity. Step one original singularity Step two original singularity minus one measure of energy. Step three original singular…

Will the emitted radiation and / or particles change if say two neutrons are collided inside an accelerator at different speeds ? eg) 0.95 c versus 0.99c

What is the closest proximity that electrons and positrons can co-exist without annihilating ?

This topic was started two years ago, on a different forum website. The rules there were restrictive, to say the least. Please note that while there are responses to this question on the original website, this is a sort of 'starting anew'. The older responses are NOT considered null and void. They are simply being set aside as a snapshot of how responders would reply two years ago, before recent theory and concepts arose. With this in mind, please avoid repeating any of those responses here. They have already been noted and apreciated. Here it goes... Two years ago: "As a tenth grader with electronics on the mind, ionocraft is probably one of the most interesting top…

Which force balances centripetal force . For example if we are rotating a ball tied with a string then centripetal force is acting inwards . Then which force balances it . And the centrifugal force is pseudo force.

If 1 thousand small drops of WA ter each of radius combined to form one single large drop then what should be the energy . If the surface tension is equal to 0.07 N/m . I think the surface area should decrease as energy is released , but how will we find the energy. Or how can we find radius of large drop to find , A= surface area