Properties Definition and 1000 Threads

Does anybody know about a comprehensive list of cosmological models and their properties? E.g. FRW, dS, AdS, ... Goedelspacetime, ... with metrics g, Christoffel symbols, Riemann tensors, Ricci, Ricci scalar, Kretschmann scalar, ... Tom

I have looked everywhere to find a simple, easy test to find whether a wave is longitudinal or transverse, I've read my textbook and I think it may be to do with polarisation but I am not quite sure how, or someone said that passing the wave through a vacuum would determine the type of wave. any...

Suppose that limx->c f(x) = infinity and limx->c g(x)=l where l is a real number. Prove the following. limx->c[f(x)+g(x)]= infinity limx->c[f(x)g(x)]= infinity if l > 0 limx->c[f(x)g(x)]= -infinity if l < 0 I have the proof for these already, but I couldn't understand them, would someone please...

Homework Statement \sqrt{\sum}x^{2}_{i}\leq\sum|x_{i}|\leq\sqrt{n}\sqrt{\sum}x^{2}_{i} *The sums are all from i=1 to n.* Homework Equations The Attempt at a Solution I'm very new to proof-based math, and just looking for some help to get started with this one. Thanks in advance.

Hello I am having a problem with the following question. Homework Statement Determine which statements are true in 3. (Select all that apply.) (a) Two lines parallel to a third line are parallel. (b) Two lines perpendicular to a third line are parallel. (c) Two planes parallel to a...

Hello all! :smile: I am (painfully) going through the first chapter of Spivak's Calculus. At one point he introduces the property: if a, b, and c are any numbers, then a\cdot(b+c) = a\cdot b +a\cdot c. He then uses this property in an example in which he shows that the only time that a - b =...

Hi, I was wondering if I correctly applied the properties of the supremum of a set to solve the following proof. I feel like I "cheated" in the sense that I said, "Let s = Sup(B) - epsilon. Homework Statement If \sup A < \sup B, then show that there exists an element b \in B that is an upper...

PBS will split unpolarized light into beams of differing polarization, but what will it do to linearly polarized light?

Homework Statement ∫(from pi/4 to pi/2)sin x/x ≤ 1/√2. Homework Equations The Attempt at a Solution I know the pi/4≤x≤pi/2 and so 1/√2 ≤ sin x ≤ 1 and i have tried to manipulate this to no end and it has annoyed the living daylights out of me

I'm mainly looking for how "real" life properties are explained. I'm looking for a book on the properties of matter. Something that covers the why liquids flow, the detailed properties of water, how different colors come about, etc, properties of solids, etc. Why are soft things soft? Stuff...

Hi, I need a hand with my reasoning on the following question. I have answered all the questions, but not too sure weather they are correct. Please guide me or point me on the right direction if they are not correct. Regards 1. A system defined by the following equation y(t)=[x(t-2)]^2...

For reference, let \mathbb N^{\infty} denote the set of all \infty-tuples of the form (n_{1}, n_{2}, \dots) with n_{i}\in \mathbb N ,\,\forall i, and let \mathbb N^{*}=\{1,2,3,\dots\}. Let n\in\mathbb N^{*}. Then by the Fundamental Theorem of Arithmetic, we can represent n as a unique...

Let's say we have the statement \sum^{\infty}_{0}f(x)=\frac{\sum^{\infty}_{0}g(x)}{\sum^{\infty}_{0}h(x)} does this imply that \int^{\infty}_{0}f(x)=\frac{\int^{\infty}_{0}g(x)}{\int^{\infty}_{0}h(x)}? Also if \sum^{\infty}_{0}f(x)=\sum^{\infty}_{0}g(x) does this imply that f(x)=g(x), or...

Consider an ARCH(1) model: Xt = σtZt, where Zt~ i.i.d. N(0,1) σt2 = w0 + w1 Xt-12 Find (i) E(Xt) and (ii) the autocovariance function γX(h) for h=0,1,2,3,..., assuming the process is second-order stationary. Solution: (i) E(Xt) = E[E(Xt|σt2)] =E[E(σtZt|σt2)] =E[σtE(Zt|σt2)] =...

Hi all, i'm trying to devise an experiment for measuring the thermal conductivity and other properties of a layer of glaze (~5mm thick, glaze is similar to that used in pottery and tiling). At this stage, the only samples of the glaze I have access to are fixed to a small clay tile (roughly...

Greeting Physics Forums; my first post here. Thanks in advance for your time! Approximately how many soundwaves compose what we can say is a single noise, like a drumbeat? I know there are multiple frequencies involved and our brain interprets this in it's own way. There is interference...

Do gravitational forces discriminate against chemical energy potential? Could the gravitational forces of three substances, equal in density, but differing in chemical properties affect each other differently based on their differences in chemical energy potential? Take two separate bodies of...

hello, I'am stuying the laplace transform and have problems with understanding the follow thing my course says: lim s->+inf F(s)=lim t->0 f(t) lim s->0 F(s)=lim t->+inf. f(t) I would like to understand it because I have the feeling that this are important properties. Thank you very...

Homework Statement I'm self-studying Abstract Algebra from baby Herstein. This is an exercise in its problem sets: Suppose that G is closed under an associative operation such that 1. given a,y in G, there is an x in G such that ax = y, and 2. given a,w in G, there is a u in G such that ua =...

Homework Statement Suppose we are given the following information about a continuous-time periodic signal with period 3 and Fourier coefficients a_{k} 1. a_{k} = a_{k+2} 2. a_{k} = a_{-k} 3. \int_{-0.5}^{0.5}x(t)dt = 1 4. \int_{0.5}^{1.5}x(t)dt = 2 Determine x(t) Homework Equations if x(t)...

¿ Can diff. EM frequencies create diff. magnetic fields with diff. properties ? I understand that a magnetic field is generated via moving charged particles . Electricity and magnetism are linked through electromagnetism . Electromagnetism can be in different wavelengths and frequencies but...

Homework Statement List the 4 properties and characteristics of electric field lines. Homework Equations I was not able to get them all and the ones that I did get I am confused that if it is really a characteristic or a property The Attempt at a Solution 1. Characteristic...

The Supergolden ratio is the solution of x3=x2+1. \psi = \left({{\sqrt{31}}\over{2\ \times 3^{{{3}\over{2}}}}} {{29}\over{54}} \right)^{{{1}\over{3}}} {{1}\over{9\,\left({{\sqrt{31}}\over{2\ \times3^{ {{3}\over{2}}}}} {{29}\over{54}}\right)^{{{1}\over{3}}}}} {{1}\over{ 3}}\approx...

Is it true that every material can be attracted by a magnetic field provided that the magnetic field is STRONG enough?

I am an ameteur physicist (i actually have my degree in meteorology), and i have some questions about the EM properties of liquid metals or ferrous liquids when in spherical form. I understand if you are too busy or if i sound off, but if you do have the time to answer a few questions, it would...

A physics hobbyist such as myself, trying to understand high-energy experiments from the recent decades, often hears about symmetries in the model, conservation laws, Feynman diagrams and so on. These are all intuitive properties but very far from a basic world view of "what happens...

Dear All, I am curious to know about some materials listed below- Mumetals, Permalloy, Supermalloy, Permendur, Perminvar and Sendust. I am interested to study there magnetic properties like permeability, hysteresis, temp. dependence of magnetism etc, if possible coefficient of...

Homework Statement Determine which, if any, of the following functions have the properties of auto-correlation functions. Justify your determination. http://rndpakistan.com/projects/hswhs/images/ques.jpg Homework Equations [PLAIN][PLAIN]http://rndpakistan.com/projects/hswhs/images/autop.jpg...

Hello guys I've asked to prove following equation on determinants, here it is; Using the properties of determinants & without expanding prove that, see attachment, I need to verify my answer can some one tell me whether is this correct or not?:smile:

Homework Statement my textbook mentions the following as properties of lines of forces among other things They do not pass through a conductor. They contract longitudinally. They exert a lateral pressure on each other. I want clarification on these points i) Why lines of force do...

Hi, Can anyone tell me at what temperature a 25micron sulphuric acid anodic coating will start to breakdown. I have noticed that after exposure to 135°C the electrical properties of the coating have dropped drastically. Regards Dan

Homework Statement Determine if the system y(t) = sin(x(t)) is time invariant, linear, causal, and/or memoryless. Homework Equations None. The Attempt at a Solution The system is time invariant and is non-linear, but I don't understand why it is causal and has memory.

Does anyone know if steel is still magnetic at over it's melting temp? If it does lose it's magnetic properties as a liquid, at what point does it happen? Gradual or at a certain temp?

Hello, I am nearing the end of my first year. I will have 1-2 months of vacation. I am really interested in getting grasp at least a little around magnetic phenomena. If somebody could recommend me a book where this issue is addressed hard. Where magnetism is explained, but not on the...

If the speed of light were (slightly) different, how would that affect the chemical properties of atoms, if so?

Hi, All: Could someone please tell me or give me a ref. on the basic properties of Gl(n,R) ; R a ring; possibly a division ring, and Gl(n,R) the group (under composition) of matrices invertible over R ? (I imagine we need a ring R with 1 , to talk about invertibility). I...

Which properties of the photon/quantum are random? Spin - Yes Position (within the "range/orbital") - Yes Momentum - Yes Phase - No Polarization - No Coherence (derivative of phase) - No Is the above correct? Please add the properties I missed

In supersymmetry, particles are said to have symmetric partners or something(dont remember what it was called) and those partners where exactly the same but they spun slower, so they had different properties, so why does different spin give different properties of particles?

Please help me prove that the following properties are equivalent Nested Interval Property Bolzano-Wierstrass theorem Monotonic sequence property LUB property Heine-Borel theorem archimedean property and cauchy sequence line connectedness...

1. What properties (that we are aware of/discovered) can be entangled? - spin, polarization etc 2. Can we entangled/disentangled additional properties (between a two photon pair) at any particular time? for example can we have both spin and polarization entangled at same time? - can we...

Homework Statement A sound goes up one octave, from 256 Hz to 512 Hz. What happens to the, period, frequency, amplitude, pitch, and speed? (choices are increase decrease or stay same) Why? Homework Equations N/A The Attempt at a Solution N/A

Homework Statement I have some hypothetical questions. Question 1 There is a conductor with a single electron and proton inside of it. If we try to charge the conductor by induction, we might put a proton close to the conductor. The electron will go towards that proton while the proton in...

Homework Statement the displacement of a wave traveling in the negative x-direction is given by y(x,t)=(5.2cm)cos(5.5x/m+72t/s) where x is in metres, t is in seconds, calculate: i)the frequency ii) the wavelength iii) the speed of this wave) The Attempt at a Solution i have...

I have a question concerning what has been proven about the properties of light over billions of years and billions of light years. Specifically, is it assumed/proven that light waves stay the same over billions of years as they travel through space? (Disregarding the other influences like...

Homework Statement State three conditions that must be satisfied by the wave-function of a particle that is in a bound state of a potential well. Homework Equations The Attempt at a Solution Not sure what the three are!? I can only think of one: the wavefunction must be...

Homework Statement The graph of f goes through the origin; f is increasing at an increasing rate on the interval (0,1) and at a decreasing rate on (6, Infinity); f is constant on the interval (2,4); f is decreasing at an increasing rate for all other positive values of x; f(1)=2, f(3)=1...

Identify the style property (or properties) and corresponding value(s) required to achieve the following: a.) Red, bold, italic lettering. b.) Quarter inch letters in Monotype Corsiva font. c.) A dotted blue line above and below, but not on either side. d.) Table cells with solid lines...

Firstly be easy on me, I'm 17 and still in high school and English is not my first language so go easy on the heavy vocabulary. I was wondering the other day, what is it that gives atoms its properties? If air would be densed to as thick as water, would it have the same properties? I don't...

Hello, I'v been taking an interest to astronomical spectroscopy lately and I have some questions about that. In order to get myself going I wanted to get as much information about Sirius A and Sirius B using the distance, obtained by using parallax(I didn't do that but imagine I did) , and...

i need help to find : 1) a surface area and volume of a c60 molecule. Assume the structure is a truncated icosahedron (Faces=32, Edges=90 and Vertices=60). The mean c60 diameter is 0.68nm but Van der Waals diameter is closer to 1nm. 2) electronic properties of c60 molecule, like how many...