Elements Definition and 984 Threads

I am curious how stars form elements heavier than iron. I have read that it generally occurs in the supernova death of a star or when neutron stars collide but have not read anything much more specific. I have read the wiki link on Nucleosynthesis but it doesn't have much in the way of...

Heavier elements like gold, uranium etc. are formed at the end of a star's life. As the star explodes into a supernova, it gives rise to nebula which is the birthplace of new stars. But as the star has already fused lighter elements into heavier elements, where does the new hydrogen required for...

All sources I have found on the web give the abundance of the elements on Earth measured by weight. By that oxygen is number one or iron, depending on where you look. But when counting just the number of atoms wouldn't that make hydrogen number one? thanks

Good evening all, first post here, and I'm hoping I've come to the right place to find some answers. I'm a math teacher at a small private school, and I've been debating about what to do for my Honors Geometry class next year. I have this strong desire to use Euclid's Elements as our primary...

Hello everybody/reader, Thank you for reading my post, i have been known to be long winded but i put a abridged version of my question and sectional labels so it can be skimmed easily for relevant information. note: I Wrote a very explanatory post, which had sections and was written...

I'm trying to determine the elements that are present in the human body. Online I'm finding inconsistent determinations. I'm reading that some lanthanoids are present, then on another site, none are present, though I see no reason that all lanthanoids would be present to some miniscule degree...

Hi, I was wondering if I could test my understanding on the S-matrix and its role in evolving initial states of systems to final states (after some scattering process has occurred). Would it be correct to say the following: Given a system in an initial state \vert i \rangle, the final...

Definition of maximal, greatest, minimal and least elements of a set: http://i.stack.imgur.com/PnI9V.png Since c is a minimal element but c is not a least element, this implies that there is one element that is not comparable to c. What is that element? What about d and i?

Hi all, I have a couple questions about radiation from radioactive elements. I've read a lot of articles on the different types of radiation given off by elements undergoing nuclear decay (alpha, beta, and gamma) but I haven't been able to answer the following question: What is the...

The definition for volume element is simples, is ##dV=dxdydz##, ok. But, if you integrate this you'll have problems, because ##\int dV = \int dxdydx## no make sense in the right side of equation and, on the other hand, ##\iiint dV =\iiint dxdydx## no make sense in the left side of equation...

Here is the problem I have faced recently that I cannot deal with yet and I need some help: Given is the - list of elements (numbered): e.g. [1,2,3,4,6,7,8] - the count and size of groups, which can be used to cover the given set of numbers, e.g. groups with group size 2. - I need to find...

Is cardnality of a set refers to the number of elements that set has?

So let's say I have 2 matrices A and B. I need to solve 2 eqns involving specific elements of each matrix. e.g. A(1)+B(2)=4; A(1)-B(2)=2. Is there any way to do this? My efforts with Fsolve and solve have failed. Here's what I've done so far: function F=myfun(A,B)...

For matrix element ##(a)_{i,j}## ##j## represent column. Is this always the case? For example in case of linear harmonic oscillator ##(\hat{a}^+)_{1,0}=\langle 1|\hat{a}^+|0 \rangle =1##. It is easier to me to see this in Dirac notation, because kets are columns and bras are rows.

what type of sold elements will not burn...even in the highest heat temperature..

Reading this wiki article http://en.wikipedia.org/wiki/Atomic_electron_configuration_table I was surprized to see they predicted 172 elements. Now, since the speed of the electron of Hydrogen is vH = 2,18816 (C/137), and since speed in further elements is multiplied by z (number od protons)...

Dear all I'm trying to find the separative work units (SWU) required to enrich isotopically Tungsten. I've come across the SWU equation (http://www.fas.org/programs/ssp/nukes/effects/swu.html) SWU = P·V(Np) + W·V(Nw) – F·V(Nf) where V(x)=(2x-1)ln(x/(1-x)) and x is the...

We define by recursion the set of sets {An:n∈ℕ} this way: A_0=∅ A_n+1=A_n ∪ {A_n}. I want to prove by induction that for all n∈ℕ, the set A_n has n elements and that A_n is transitive (i.e. if x∈y∈A_n, then x∈A_n). My thoughts: for n=0, A_1 = ∅∪ {∅} = {∅} then, for n+1: A_n+2...

Question about monoisotopic elements... Of the 80 elements with at least one stable isotope, 26 have only one single stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes that occur for a single...

Homework Statement The whole problem: If ##(B \cap C) \subseteq A## then ##[(B \cup C)-A] \subseteq [(B \cup C)-(B \cap C)]##Homework Equations ##A-B=A\cap \bar{B}## ##N \subseteq M=\bar{M} \subseteq \bar{N}##The Attempt at a Solution Initially I'm having troubles with ##[(B \cup C)-(B \cap...

Hi, Hopefully this is the right place for this question. I'm wondering whether a 100lb ball of lead would roll down a ramp (assuming a 35 degree slope) at the same speed as 100lb ball of copper. Would there be a difference in force while they are rolling down? Thanks,

Well I am not sure if this thread belongs here or in mathematics/groups but since it also has to do with physics, I think SR would be the correct place. An element of the Euclidean group E(n) can be written in the form (O,\vec{b}) which acts: \vec{x} \rightharpoondown O\vec{x}+\vec{b} With O...

Hello I would like to understand the resonance phenomenon that can occurs when we deals with satellite's orbits. Here what it is said about it : KAULA - Theory of satellite geodesy - p. 49...

This is a concise question, so the title pretty much says it all. Also, this is not a HW question, but the idea has subtly popped up in two homework problems that I have done in the past. I cannot justify why the entire set would be bounded, because we know nothing of the nature of the...

What are the "matrix elements" of the angular momentum operator? Hello, I just recently learned about angular momentum operator. So far, I liked expressing my operators in this way: http://upload.wikimedia.org/math/8/2/6/826d794e3ca9681934aea7588961cafe.png I like it this way because it...

we know that elements are formed in the core of stars where fusion occurs. The stars collapse on the formation of iron, if it so how come element after iron like cobalt, gold, silver were produced...?

Hello, this is my first post(so, hopefully I'm not breaking any decorum). Something that I've always been puzzled about. I understand that a star will keep fusing elements until it hits iron. What I'm curious of, is why? Why does iron take so much more energy to create fusion than other...

Hi, I wondered what is the maximal ionization of a given element when it is free (not bound into a molecule). I'd assume it is possible to strip off all electrons of a given element (given sufficient ionizing radiation) so the maximal positive charge should be +Z (Z being the atomic number)...

I want to know what causes this specificity of reactions in between elements. Why does carbon only react with X elements? What are the factors that come into play to cause this specificity? From what I understand every element has the potential to bond with every other element but a lot of...

Homework Statement Find ##(g_ig_j)^{-1}## for any two elements of group ##G##. Homework Equations For matrices ##(AB)^{-1}=B^{-1}A^{-1}## The Attempt at a Solution I'm not sure how to show this? I could show that for matrices ##(AB)^{-1}=B^{-1}A^{-1}##. And that for numbers...

Homework Statement Show that if a set has 3 elements, then we can find 8 relations on A that all have the same symmetric closure. Homework Equations Symmetric closure ##R^* = R \cup R^{-1} ## The Attempt at a Solution If the symmetric closures of n relations are the same then...

Hello I have N couples of real numbers higher than 1. Let's call them like (a0,b0), (a1,b1),...,(aN,bN) I have a number R <= N. I need the sum of all the possible products of N elements, chosing one from each couple but exactly R times the "b" element and N-R times the "a" element...

Homework Statement Let G be a finite complex matrix group: G \subset M_{n\times n}. Show that, for g \in G, |\text{tr}(g)| \le n and |\text{tr}(g)| = n only for g = e^{i\theta}I. 2. The attempt at a solution Since G is finite, then every element g \in G has a finite order: g^r = I for some...

I have a question that I feel I am going about in a roundabout way, and would like some help on. I am preparing for an exam. **Problem:** Let $G$ be a group with $|G|=150.$ Let $H$ be a non-normal subgroup in $G$ with $|H|=25$. (a) How many elements of order 5 does $G$ have? (b) How many...

Homework Statement Evaluate the matrix element <U210|z|U100> where by |Unlm> we mean the hydrogen atom orbital with it's quantum numbers. Homework Equations The Attempt at a Solution So where I'm getting stuck is on the integral, because the "U" portion of the wave function is...

Greetings, For a homomorphism \varphi, I'm trying to show that elements of a fiber, say the fiber above a, X_a, are writable as a given element of X_a times an element of the kernel K. So, if a\in X_a and b\in X_a, then \exists k\in K such that b=ak. I want to do this without using the...

http://img17.imageshack.us/img17/3937/vjj6.png I don't understand the very last bit, where it says a and b are central and so c is, hence a is not irreducible. Basically what replaces the "hence"? I can't seem to figure out the link between c being central meaning a isn't irreducible. a...

First a little warm up problem. Suppose g:\mathbb{R}^N\to\mathbb{C} is some fixed function, and we want to find f:\mathbb{R}^N\to\mathbb{C} such that g(x) = u\cdot\nabla_x f(x) holds, where u\in\mathbb{R}^N is some constant. The problem is not extremely difficult, and after some work...

Hi to all. I am programing a new code for some calculation and i have detected a strange issue. I have my all arrays strictly defined for example real, dimension(-2:2,-3:2) A, B complex, dimension(-2:2,1:2) C In my time dependend calculations i expect the matrix element C(-2,1) to...

Today in 9th grade ADV Biology, we learned about how the two Hydrogen atoms in a Water molecule are relatively positive compared to the Oxygen atom. This is because the Oxygen's pull on Hydrogen's electron is greater than the Hydrogen's, or that its Electronegativity is greater. This unequal...

I am having lots of trouble doing this problem because I have particularly poor visualization skills. (Or maybe haven't developed them well yet). I would appreciate any help on this math problem. Here is the question: Suppose a cube is oriented before you so that from your point of view there...

I'm preparing for an upcoming exam, and as I see one of the typical questions that is frequently asked in our exams is about finding the number of elements that have a particular order in a group like Sn. I searched on google and came up with some such problems with solutions. To be honest...

Hi, i would like to have a hint for the following problem: Let $$v_1, v_2 \&\ v_3 $$ in a vector space V over a field F such that$$ v_1+v_2+v_3=0$$, Show that $\{v_1,v_2\}$ spans the same subspace as $\{v_2,v_3\}$ Thanks in advance

Hello this is not a homework, just studying for the exam, and : Homework Statement Consider E a linear space with dot product (.,.) and the norm ||x|| = sqrt(x,x) a and b two orthogonals elements of E Find the value of ||a+ b|| et||a- b|| and ||a+ b||-||a- b|| Homework Equations...

Hello all, I am struggling with this relatively simple task. In a university with 88 students, each student can choose to participate in 3 afternoon activities: activity A, activity B and activity C. Each student can choose to participate in some activities, all or none. 33 students...

I'm trying to understand how Hamiltonian matrices are built for optical applications. In the excerpts below, from the book "Optically polarized atoms: understanding light-atom interaction", what I don't understand is: Why are the \mu B parts not diagonal? If the Hamiltonian is \vec{\mu} \cdot...

In a matrix the sum of element of a matrix in a row times it's co factor of that elemt gives the determinant value, but why does the sum of element of a matrix times cofactor of different row is always zero?

In quantum mechanics, observable variables are represented by operators, and thus can be replaced by matrix in a certain basis. If we have H|n>=E(n)|n>, where |n> are eigenfunctions of Hamilton matrix. Here is the problem: what's the physical meaning of <m|P|n>, namely off-diagonal elements of...

Homework Statement b(B) = cls(B) \ Int(B) where b(B) is the boundary, cls is the closure, and int is the interior of set B. This was not hard for me to prove by picking elements and showing that the sets were contained in one another. However, I decided it would be fun to try to derive it by...

Homework Statement Prove that a set with n elements has \frac{n(n-1)(n-2)}{6} subsets containing exactly three elements whenever n is an integer greater than or equal to 3. Our professor wants us to use Induction. Homework Equations P(n) = \frac{n(n-1)(n-2)}{6} n \geq 3 The...