What is Delta: Definition and 1000 Discussions

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position.

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  1. M

    Delta function defined for complez values

    is there a form to define the dirac delta function for complex values ? i mean \delta (x-a-bi) or \delta (-ix) using 'test functgions' i get that they converge nowhere (always infinite) which makes no sense at all, using scalling properties we could define \delta (ix) = \delta(x)...
  2. F

    Dirac delta in curved spacetime

    Does anyone know what the Dirac delta function would look like in a space with curvature and torsion? The Dirac delta function is a type of distribution. But that distribution might look differently in curved spacetime than in flat spacetime. I wonder what it would look like in curved spacetime...
  3. P

    Convolution of a dirac delta function

    Alright...so I've got a question about the convolution of a dirac delta function (or unit step). So, I know what my final answer is supposed to be but I cannot understand how to solve the last portion of it which involves the convolution of a dirac/unit step function. It looks like this: 10 *...
  4. M

    Dirac Delta Function Potential (One Dimension)

    Alright, I'm in my first QM course right now, and one of the topics we've looked at is solving the one-dimensional time-independent Schrodinger equation for various potentials, such as the harmonic oscillators, infinite and finite square wells, free particles, and last, but not least, the dirac...
  5. A

    Solving Dirac Delta Cosx: Find Range of n and a_n, x_n

    Homework Statement The function \delta(cosx) can be written as a sum of Dirac delta functions: \delta(cosx)=\sum_{n} a_{n}\delta(x-x_{n}) Find the range for n and the values for a_{n} and x_{n} The Attempt at a Solution Well, taking the integral of \delta(cosx), we only get spikes when...
  6. R

    What does Delta mean in this case

    Homework Statement R = { (X,Y) \epsilon P(A) x P(A) / (X\DeltaY) \subseteq B} (X\DeltaY) \subseteq B - what does delta mean? Homework Equations The Attempt at a Solution
  7. P

    Proving the Delta Function Property: \delta(ax) = {\delta(x) \over {|a|}}

    Homework Statement I would like to prove that \delta(ax)={\delta(x) \over {|a|}}. My problem is that I don't know how the absolute value brackets arise. Homework Equations \int_{-\infty}^{\infty} \delta(x)dx = 1The Attempt at a Solution I start from \int_{-\infty}^{\infty} \delta (ax) dx, and...
  8. E

    Delta Function Limits: Solving Integrals from 0 to 1

    with limits from 0 to 1 \int delta(x) * cos(x) dx does this delta function integral even make sense from 0 to 1?
  9. G01

    Quick Question on the Dirac Delta Function

    The Dirac delta function, \delta (x) has the property that: (1) \int_{-\infty}^{+\infty} f(x) \delta (x) dx = f(0) Will this same effect happen for the following bounds on the integral: (2) \int_{0}^{+\infty} f(x) \delta (x) dx = f(0)...
  10. S

    Finding Rest Energy of Delta (0 charge & 0 strangeness)

    Hello, I'm having trouble finding the rest energy of delta, on the internet. Can anyone give me this value please. It's delta zero. i.e. its charge is 0 and strangeness is 0 too. Thanks a lot for your time From Steven
  11. Y

    Prove a delta function identity

    Hi, I'm stuck with the last proof I need to do Homework Statement I need to prove that f(x)delta(g(x)) = f(x) delta (x-x0)/abs(g'(x)) By delta I mean the Dirac delta function here. (I'm new to this forum, so i don't know how to write it all nicely like so many of you do!) Homework...
  12. D

    Proof ε-δ: Epsilon Delta Proof of lim x->a of ((3x²-3a²)/(x-a)) = 6a

    I’m going to say from the beginning that I need to hand this problem in. I'm not looking for the answer, I think I already have it, just want a critical eye. I need someone to look over this problem and tell me if it's good. Not just if it's right but if it's perfect. I always get the...
  13. G

    Calculus, Delta- Epsilon Proof Of Limits

    Homework Statement Is this the right direction to prove Given that , prove that . Using the delta epsilon definition to prove that means that, for any arbitrary small there exists a where as: If we choose any constant for (x) called C, as long as C does not equal zero, the...
  14. C

    Dirac Delta function and charge density.

    I have a line charge of length L and charge density /lambda on the Z-axis. I need to express the charge density in terms of the Dirac Delta function of theta and phi. How would I go about doing this?
  15. M

    Exploring Epsilon-Delta Proofs for Continuity: What's the Name of This Proof?

    Homework Statement i have a couple of questions to anser and they start 'Give epsilon - delta proofs that the following functions are continuous at the indicated points.' im guessing its not going to be too hard but what is the name of this epsilon - delta proof so i can search for and...
  16. O

    Integrating the Dirac Delta Function

    I am trying to evaluate the following integral. \int_{-\infty}^{\infty}{\delta(2t-3)\sin(\pi t) dt} where delta represents the Dirac delta function. I am told that the answer is -1. However, when I evaluate it in MATLAB and Maple 11, I get an answer of -1/2. What is the correct way...
  17. A

    Proving Delta Function: Help with Homework Equation | Attachment Included

    Homework Statement Can u pls help me to prove delta function. Here is the problem in attachment. Homework Equations The Attempt at a Solution
  18. M

    What is the Proof for the Limit of Square Root Function?

    Homework Statement Prove: \lim_{x \to a} \sqrt{x} = \sqrt{a}, if a>0 Homework Equations |f(x)-L| < \epsilon |x-a| < \delta The Attempt at a Solution |\sqrt{x}-\sqrt{a}| < \epsilon, when |x-a| < \delta |x - 2\sqrt{x}\sqrt{a}-a| < \epsilon^2, when |x-a| < \delta From here I...
  19. S

    Properties of Dirac delta function

    Homework Statement I'm trying to prove that \delta'(y)=-\delta'(-y). Homework Equations The Attempt at a Solution I'm having trouble getting the LHS and the RHS to agree. I've used a test function f(y) and I am integrating by parts. For the LHS, I have...
  20. B

    The Impact of Delta Protein Expression on Aging Cells

    Can you force older cells to express more delta protein? Would the cells expressing more delta protein be good or bad?
  21. L

    Walkthrough of Epsilon Delta Limits Question

    Could someone please give me a walkthrough of the following question(and answer)?? I really can't understand it... lim x^2 = 9 x->3 if 0<|x-c|<delta then |f(x) - L|< epsilon so... x^2 - 9 = (x+3)(x-3) |x^2 - 9| = |x+3||x-3| Here's the problem.The book states: An...
  22. J

    Integral involving delta distribution

    Homework Statement Solving a problem about the variational method I came across one nasty integral. Here goes: \bar{H} := \frac{ < \hat{0} | H | \hat{0} > }{< \hat{0} | \hat{0} >} Homework Equations H = -\frac{ \hbar^2 }{2m} \frac{\partial ^2}{\partial x^2} + \frac{1}{2} m...
  23. D

    Help me im in WAS and i need to know Delta V. .

    help me please I am in WAS and i need to know Delta V. please please please. ok i am curently in WAS(wa arowspace scolars) I am a bad speller but i could care less also I am new hear. i know what the formula for delta v is but i do not understand it. i am interested in learning but please putin...
  24. J

    What is the integral of a square of Dirac delta function?

    Homework Statement Hi there, I'm stuck at a problem where I have (sorry i don't know how to use mathtype so I'll try my best at making this clear) the integral of a dirac delta function squared: int[delta(x*-x)^2] between minus infinity and infinity (x*=constant) I know that the function...
  25. F

    Dirac delta, math of implication?

    So what we have so far is that any and all subsets are implied by a set. If there exist a set, then all the subsets within it are implied to exist also. This includes the elements of a set. The elements of a set are implied by the existence of a set. One of the most natural things to do with...
  26. M

    How to Solve an IVP Involving Dirac Delta Function?

    Dirac Delta Function: If, at time t =a, the upper end of an undamped spring-mass system is jerked upward suddenly and returned to its original position, the equation that models the situation is mx'' + kx = kH delta(t-a); x(0) = x(sub zero), x'(0) = x(sub 1), where m is the mass, k is the...
  27. S

    The actual meaning of delta in these circumstances

    Homework Statement Please don't make fun of my question, I just want to have a strong understanding of the meaning and it's use My textbook just pops these symbols out at me without explanation. Maybe it just expects I know this stuff In the equation Vs = \Delta d / \Delta t
  28. L

    Delta function in spherical coords

    Homework Statement If we have a delta function in cartesian coords, how do we convert it into spherical. for example : delta (r) = delta(x-x0) delta(y-y0) delta(z-z0) Homework Equations The Attempt at a Solution I used delta (r) = delta(r-r0) delta(cos{theta}-cos{theta0}) delta...
  29. S

    Solving Dirac Delta Function Beam Problem

    1. The ProblemHomework Statement 4 Parts to the Assignment. Finding the Displacement of a beam assuming w to be constant. 1. Cantilever beam, free at one end. Length =l, Force P applied concentrated at a point distance rl from the clamped end. Boundary Conditions y(0)=0, y'(0)=0, y"(l)=0, and...
  30. E

    Change of variables for Delta distribution

    Hello everybody First I'd like to thank for the work all of you are developing with this forum. I found it for casuality but I'm sure since now it will be a perpetual partner. I'm a Spanish Physics graduate and I am working about microwave guides and connectors for devices components in...
  31. S

    Contour integral and delta function

    I have two related questions. First of all, we have the identity: \int_{-\infty}^{\infty} e^{ikx} dk = 2 \pi \delta(x) I'm wondering if it's possible to get this by contour integration. It's not hard to show that the function is zero for x non-zero, but the behavior at x=0 is bugging...
  32. M

    Calculating Delta Heat of Formation: Alternatives and Limitations

    Currently I am enrolled in college level General Chemistry course, and at this time we are working on a project to figure out the delta heat for formation of a specific reaction. The equation is this H2 + CuSO4(aq) ---> Cu(s) + H2SO4. We have gone through and determined the half...
  33. J

    Solving simple dirac delta function

    [b]1. Homework Statement \int x[delta(x)-delta(x/3+4)] dx Homework Equations so I'm supposed to use this principle: \int f(x)delta(x-xo)dx=f(xo) The Attempt at a Solution So it seems simple but I just want to make sure that I'm applying the above principle correctly. I...
  34. B

    How Does a Delta Wing Create Lift?

    I understand how an ordinary wing works but I cannot find anything on how a delta wing works, the only thing I know is that it creates vortices on the upper wing surface, but how do these vortices create lift?
  35. D

    Delta Function Well and Uncertainty Principle

    [SOLVED] Delta Function Well and Uncertainty Principle Homework Statement Griffiths Problem 2.25. I need to calculate < p^{2}> for the Delta Function Well. The answer given is: < p^{2}> = (m\alpha/\hbar)^2 The wave function given by the book is...
  36. M

    Calculate Current in 5-Resistor Wye-Delta Circuit

    calculate the current through circuit which contain 5 resistors,3 of them shape y network thier values are 220 ohm's,330 ohm's,680 ohm's. the other 2 resistors are in parallel with them and they are 1Kohm's. the voltage sourse give 10V.
  37. J

    Help converting dirac delta function

    Homework Statement SO I'm given a dirac delta function, also known as a unit impulse function. d(t-t'_=(1/P) sum of e^[in(t-t')], for n from negative to positive infinity. I need to graph this. Homework Equations I understand that at t', there is a force made upon the system which...
  38. S

    Calculate ΔG for Dilution of HCl from 0.89M to 0.253M

    1. Calculate ΔG for the dilution of aqueous HCl from 0.89 M to 0.253 M at 25°C. data 2. The process you are considering is: H+(aq) + Cl-(aq)® H+(aq) + Cl-(aq) (for which ΔG°=0 i.e. standard states all round--both sides are the same). Now use ΔG=ΔG° + RTln(Q). (Use the actual...
  39. P

    Understanding the Delta Function Well in Quantum Mechanics

    So I'm studying that part right now. I only get parts of it though, it seems. The first thing the book goes over (This is intro to QM by Griffiths) is a potential that has the form -A*deltafunction. Okay, that's just something he plucked for simplicity. But then if the potential is lower...
  40. E

    Delta function potential problem

    Homework Statement Why does it make sense that a negative delta function potential represents a highly localized attractive force and a positive delta function potential represents a highly localized repulsive force? How do you explain that using -dV/dx = f(x) ? I guess I am confused about...
  41. 1

    2-D Delta function question

    I'm trying to plot the function f(x,y) = DiracDelta[r-r0]and then take the Fourier transform. Is this a radial delta function? I'm having trouble understanding the significance of this "function" . Thanks!
  42. E

    Understanding the Dirac Delta Function: Solving the Integral of Delta(x-b)

    Q: Integral of Delta(x-b)dx and the lower limit is (-) infinity and upper is a Please help me in steps tried my best to solve.Note this is not homework I was doing the book problems or my practice Thanks
  43. C

    Finding Delta to Satisfy |f(x)-l|<ε for 0<|x-a|<δ

    Homework Statement Find a delta such that |f(x)-l|< epsilon for all x satisfying 0<|x-a|< delta f(x)=(x^4)+(1/x); a=1; l=2 Homework Equations Lemma Theorem The Attempt at a Solution 0<|x-1|<delta; |(x^4)+(1/x)-2|<epsilon |x^4-1|<epsilon/2 and |(1/x)-1|<epsilon/2 Then I...
  44. Z

    Convolution of delta function

    for linear time invariant system, y(t)=h(t)*x(t) where y(t) is the output , x(t) is the input and h(t) is the impulse response.(* is the convolution) The definition of convolution is y(t)=integration from -infinity to +infinity (h(tau)x(t-tau)d(tau) p/s: i don't know how to use...
  45. A

    Delta Sign Confusion: Solving Depth of Grand Canyon

    Homework Statement Hans stands at the of the Grand Canyon and yodels down to the bottom. He hears his yodel echo back from the canyon floor 5.20s later. Assume that the speed of sound in air is 340.0m/s. How deep is the canyon at this location? I made a chart. Velocity Original = 340...
  46. E

    How Do You Correctly Integrate the Delta Function in This Equation?

    Homework Statement Evaluate: \int_{-3}^{5} e^{-2t} sin(t-3) \delta(t-5) dt Homework Equations \int_{-\infty}^{\infty} f(t) \delta(at-t_0) dt = \frac{1}{|a|}f(\frac{t_0}{a}) The Attempt at a Solution e^{-2(5)} sin (5-3) = e^{-10} sin (2) The solution given by the professor...
  47. E

    Proving the Limit of Dirac Delta from Normal Distribution

    Homework Statement How would one show that dirac delta is the limit of the normal distribution? http://en.wikipedia.org/wiki/Dirac_delta using the definition \delta(k) = 1/(2\pi)\int_{-\infty}^{\infty}e^{ikx}dx Homework Equations The Attempt at a Solution
  48. nicksauce

    Does the delta function integral still hold true for non-continuous functions?

    Evaluate: \int^{\infty}_{-\infty} f(x)\delta(x-x_0)dx Where f(x)=ln(x+3), x_0=-2 Ordinarily, you would just evaluate f(x_0), so it would be 0, but in this case, since f(x) is -\infty at x=-3, does that make a difference?
  49. C

    Understanding the Kronecker Delta function

    Homework Statement I'm having some trouble understanding the Kronecker Delta function and how it is used. I understand the basics of it, if i=j, delta=1, if not, delta=0. However, I don't understand why: \delta_{ii}=3 and \delta_{ij}\delta_{ij}=3Homework Equations \delta_{ij}=...
  50. U

    [EE - Signals] Question about Discrete-Time Impulse/Discrete-Time Delta

    Quick question about a discrete unit impulse. If I were to draw delta[n+1], at ... etc n = -2 ... the point would be at location: 0 n = -1 ... the point would be at location: 1 n = 0 ... the point would be at location: 0 n = 1 ... the point would be at location: 0 n = 2...
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