What is Gaussian: Definition and 771 Discussions

Gaussian is a general purpose computational chemistry software package initially released in 1970 by John Pople and his research group at Carnegie Mellon University as Gaussian 70. It has been continuously updated since then. The name originates from Pople's use of Gaussian orbitals to speed up molecular electronic structure calculations as opposed to using Slater-type orbitals, a choice made to improve performance on the limited computing capacities of then-current computer hardware for Hartree–Fock calculations. The current version of the program is Gaussian 16. Originally available through the Quantum Chemistry Program Exchange, it was later licensed out of Carnegie Mellon University, and since 1987 has been developed and licensed by Gaussian, Inc.

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  1. A

    Free particle has a Gaussian wave packet wave function.

    Homework Statement This is problem 2.22 from D.J. Griffiths Introduction to Quantum Mechanics A free particle has the initial wave function: \Psi(x,0)=Ae^{-ax^{2}} Find \Psi(x,t). Hint Integrals of the form: \int_{-\infty}^{\infty}e^{-(ax^{2}+bx)}dx can be handled by completing the square...
  2. F

    Sub-quotients and Gaussian Integer rings

    This has to do with number theory along with group and set theory, but the main focus of the proof is number theory, so forgive me if I'm in the wrong place. I've been struggling to understand a piece of a proof put forth in my book. I know what the Gaussian integers are exactly, and what a...
  3. F

    Gaussian integers and norms

    Show that N(a+bi) = even => a+bi divisible by 1+i So, N(a+bi) = a2+b2 = even so 2 divides a2+b2 Write 2 = (1+i)(1-i) so we have 1+i divides a2+b2 so 1+i divides either (a+bi) or (a-bi) if 1+i divides a+bi we are done what if 1+i divides a-bi though? Thats where I'm stuck!
  4. J

    Characteristic Function of Joint Gaussian Distribution

    This is inspired by Kardar's Statistical Physics of Particles, page 45, and uses similar notation. Homework Statement Find the characteristic function, \widetilde{p}(\overrightarrow{k}) for the joint gaussian distribution: p(\overrightarrow{x})=\frac{1}{\sqrt{(2\pi)^{N}det...
  5. A

    Weakly stationary Gaussian process?

    X = (Y(t))^2 where Y(t) is zero mean Gaussian process and correlation function R_YY = exp(-λ|τ|) i want to check if X is weakly stationary.So i guess for the first part, i checked if mean is constant σ^2=R_YY = exp(-λ|0|) = 1 E(X^2) = μ^2+ σ^2 = 1 since μ is zero and σ = 1 I wanted to check if...
  6. Z

    Gaussian Elimination rules - apply to rows only?

    Homework Statement In this video; the uploader states at 0:47 that there are three rules. 1. Can swap rows 2. Can multiply a row by a constant 3. Can add a multiple of one row to another Do these rules apply only to rows? Can they be applied to columns? The uploader has not stated...
  7. K

    Why I doubt the generality of Gauss' law: A Gaussian sphere 1 light year across

    Let's say I have a Gaussian sphere 1 light year across with synchronized clocks and sensors all over its surface. All clocks are co-moving, not accelerating, and the spatial curvature is negligible. If I have only one charge inside the Gaussian sphere, 1 centimeter from its surface for an entire...
  8. K

    Time-retarded E-field and Gaussian surface integral

    If I have an oscillating charge inside of a sphere, will the integral of E(t), where t=proper time of the sphere, over the sphere's surface area result in a value of electric flux equal to the value of the charge?
  9. lonewolf219

    Can Gauss' Law Be Applied to a Non-Uniformly Charged Solid Sphere?

    Question: A solid sphere of radius R has a non-uniform charge distribution of p=Ar^2, where A is constant. Find total charge Q within the volume of the sphere. p=roe p=Q/dV EdA=qenclosed/Enaught Can you use Gauss' Law for this problem when sphere is solid? If so, how? Since p...
  10. K

    One-Dimensional Gaussian Wave Packet

    Homework Statement Consider a one-dimensional wave packet with \phi(p) = A \Theta ((h/2\pi) / d -|p-p0|) Determine the constant A and find the spatial wave function ψ(x). Ignore temporal evolution. Homework Equations The Attempt at a Solution Honestly this is a little embarrassing, but the...
  11. G

    Gaussian process with linear correlation

    Hi I have a stationary gaussian process { X_t } and I have the correlation function p(t) = Corr(X_s, X_(s+t)) = 1 - t/m, where X_t is in {1,2,..,m}, and I want to simulate this process. The main idea is to write X_t as sum from 1 to N of V_i, X_t+1 as sum from p+1 to N+p V_i and so on, where...
  12. L

    How to show integral identity involving gaussian over x

    So I have come across this integral identity in Krall's Principles of Plasma Physics (right after equ. 6.4.4 in the 1st edition) and I have not been able to show the identity is true. The reason that I would like to understand the integral is that I am trying to solve a similar problem to the...
  13. K

    Relativistic corrections to E-fields of charges bounded inside a Gaussian surface

    If I have a spread of electrical charges contained inside a Gaussian surface, and if I cause those electrical charges to move at relativistic speeds, the electric fields of those charges should be subject to relativistic contraction. What happens then to electric flux that cuts through that...
  14. A

    Bounded/Truncated Gaussian distribution

    Dear all, I have a problem in understanding how to bound a Gaussian distribution. LEt me describe the problem at hand: Let's say that we have a Gaussian distribution in the x-coordinate and a Gaussian distribution in the y-coordinate. Further, assume that the independent random variables x...
  15. A

    MATLAB Curl of Gaussian image derivatives matlab

    Hi guys, I am trying to create a magnetic field from an image contour and an attempt to create an active contour model. I have a function which takes the image derivative via a Guassian: function J=ImageDerivatives2D(I,sigma,type) % Gaussian based image derivatives % %...
  16. K

    Why is Gaussian Packet the lower limit?

    Dear all: When I was just reading about how Gaussian wave packets allow us to derive(because it has) the lowest limit on uncertainty. So what would be the (mathmetical?) derivation to just obtain that limit before proving/identifying that it's true for Gaussian packet?
  17. H

    Surfaces with Same Gaussian Curvature: Hedi's Ques.

    Hi, are there two non isomorphic surfaces with the same gaussian curvature? thank's Hedi
  18. S

    Gaussian Wavepacket: Position-Momentum Uncertainty

    how can the gaussian wavepacket presents a physical picture of the origin of position-momentum uncertainty?
  19. N

    What is the method for solving the Gaussian integral?

    Homework Statement Find the Gaussian integral: I = \int_{-\infty}^{\infty} e^{-x^2-4x-1}dx (That's all the information the task gives me, minus the I=, I just put it there to more easily show what I have tried to do) 2. The attempt at a solution I tried to square I and get a double...
  20. S

    Understanding Gaussian Elimination Matrices for Solving Linear Equations

    Homework Statement What is the Gaussian elimination matrix for the vector for the vector v=(2,-10,16,2)? The Attempt at a Solution I don't understand the question. What is a "Gaussian elimination matrix for a vector?" I know that Gaussian elimination is a method for solving a system of...
  21. D

    Comparing Chance of Observing Event w/ Gaussian Variables

    I am not sure how to do the following homework question: Suppose X1, X2, ... are independent Gaussian variables with mean zero and variance 1. Consider the event that X1 + X2 + ... + X2n ≥ 2na wth a > 0 Compare the chance of observing this event in the following two ways: (i) by...
  22. A

    Show that a Gaussian Distribution Corresponds to a CTS random variable.

    Going over my Lecture Notes my Lecturer as Started with Show that a Gaussian Distribution Corresponds to a CTS random variable. Then she has i) Taken the f(x) = [p.d.f] and shown a) f(x) >= 0 for all x member of real numbers. b) Integral over all real numbers = 1 ii) Found the M.G.F then...
  23. V

    What is the basic difference between Maxwell and Gaussian Distribution?

    Can anyone tell me the basic difference between Maxwell and Gaussian distribution? Thanks in Advance
  24. R

    Gaussian emission lines

    Homework Statement The spectroscopic observation of an interstellar gas cloud shows emission lines H (λ=6563 A), Hβ λ=4862 A) e OI (λ=1304 A), each one with a gaussian profile of the kind: g(\nu)=A e^[-\frac{(\nu-\nu_0)^2}{2\sigma^2}] Per Hα si osserva σ_{Hα} = 1.2 \times 10^{10} Hz...
  25. M

    Question of units of B, H in Gaussian system

    In "Classical Theory of Fields", by Landau & Lifgarbagez, they give, for example, the force on a charged particle by a magnetic field as: F = \frac{ev}{c} x H where H is the magnetic field intensity. Now, normally written in SI units, this expression would use B and no factor of 1/c...
  26. A

    Why the Gaussian curvature is extrinsic ?

    Hi all! Let's start from the begin to see where I get lost. Extrinsic curvature defines the way an object relates to the radius of curvature of circles that touch the object (a couple of further nicer definitions come from physics, for the moments I am not mentioning them), and intrinsic...
  27. M

    Help with integral of a gaussian function

    Hi all! I'm curious as to how one would go about actually computing this integral \int_0^\pi \exp(\frac{-x^2}{2c^2})\sin(\frac{m\pi x}{2}) dx I start off by using integration by parts but I am unsure how to solve this integral v = \int_0^\pi \exp(\frac{-x^2}{2c^2}) dx Any help...
  28. Z

    Is E constant in simple Gaussian diagram?

    Homework Statement If you have a simple Gaussian diagram of spherical shape, and arrows pointing out from the centre indicating [E] how do you know if [E] is constant or if it varies? Is it because the arrows are of slightly different lengths? (Though all eminating from the centre and...
  29. A

    Estimation of X in Gaussian Noise

    Given {X}=[x_1 x_2 ... x_n]^T where {x_i} \in \{ 0, a_1, a_2, a_3 \}^n, a_i \in \mathbb{C} and Z = \{z_1 z_2,...,z_n \} where z_i ~ N(0,\sigma^2) is a Complex Gaussian RV with mean 0 and variance sigma^2. Suppose we observe Y Y = HX+Z where H is known and its elements are independent...
  30. U

    Variational Method - Gaussian Trial Wavefucntion

    Homework Statement Use the variational method with a gaussian trial wavefunction ψ(x) = Ae^{\frac{-a^{2}x^{2}}{2}} to prove that in 1 dimension an attractive potential of the form shown, no matter how shallow, always has at least 1 bound state. *Figure is of a potential V(x) that has a minimum...
  31. D

    Calculating the gaussian curvature of a surface

    Let x(u,v) be a coordinate patch. Define a new patch by y(u, v) = c x (u, v) where c is a constant. Show that K_y = \frac {1}{c^2}K_x where K_x is the gaussian curvature calculated using x(u, v) and K_y is the gaussian curvature calculated using y(u, v). my book expects us to use the...
  32. V

    Solving PDE involving Gaussian fields.

    I need to solve three coupled differential equations. The equations are as follows: dE1/dz = f(E2,E3) dE2/dz = f(E1,E3) dE3/dz = f(E1,E2) Where E1,E2,E3 represents field amplitudes. In case of plane waves these amplitudes will be constant in the transverse direction therefore i can...
  33. J

    Solving the Gaussian Integral for Variance of Gaussian Distribution

    How to show that the variance of the gaussian distribution using the probability function? I don't know how to solve for ∫r^2 Exp(-2r^2/2c^2) dr .
  34. A

    Expectation Value/ Evaluating Gaussian Integral

    Homework Statement I'm re-hashing a problem from my notes; given the wave function \psi(x)=Ne^{-(x-x_0)/2k^2} Find the expectation value <x>. Homework Equations The normalization constant N for this is in my notes as N^2=1/\sqrt{2 \pi k^2} N=1/(2\pi k^2)^{(1/4)} It should be...
  35. X

    Gaussian Distribution Question.

    I am studying the Gaussian distribution and am doing one of the problems for practice. The problem states that the standard deviation is equal to 15 and the actual value recorded in the experiment is 385.0. It then asks what is the probability that a single measurement lies in the range of the...
  36. M

    Solving via Gaussian Elimination

    Homework Statement Solve the following system of equations using Gaussian Elimination: -2a+5c=1 a+2b-c=2 3a-2b=3 Homework Equations N/A The Attempt at a Solution Augmented matrix (-2 0 5 | 1) R2 → R2 +R1/2 (1 2 -1 | 2) R3 → R3 - 3R2 (3 -2 0 | 3) (-2 0 5 | 1) Swap R2 and...
  37. P

    Help with the 3D gaussian function

    Hi, I need help with the gaussian function in 3D. I'm using the form: z=A*exp( (x-xo)^2/(2σx^2)+(y-yo)^2/(2σy^2)) I know that A is the amplitude and xo,yo are the center coordinate. I found that formula on http://en.wikipedia.org/wiki/Gaussian_function and they say that σx and σy are...
  38. N

    Gaussian wavefunction; expectation energy

    Homework Statement Homework Equations The Attempt at a Solution The issue I'm having here is that the problem should be able to be done rather quickly. I can see how to solve for <H> using the operator, but there's a quick way that I'm not picking up on. I thought about solving <H> = <p^2> /...
  39. Z

    Understanding Gaussian Beam Contraction and Divergence in Optics

    I am new to lasers. In the expression for q parameter, 1/q = 1/R - j(λ/πw^2) how did we come to know that w(z) is a measure of decrease in field amplitude E with distance? I can't feel it. Does the gaussian beam itself contract to the minimum diameter? Shouldn't a lens be required for this...
  40. N

    Gaussian Elimination, is this method OK?

    Homework Statement A= <1, -3, -1, 1> <2, -5, 0, 1> <-3, 5, -6, 3> What I did was Row2 = 2*Row1 - Row2 which renders Row2 as: <0, -1, -2, 1> However in the solutions, Row2 was given as: <0, 1, 2, -1>, which appears to be R2 = -2R1 + R2 I'm guessing it makes no real difference...
  41. D

    Inverse fourier transform of gaussian

    well, i have to prove that the inv. Fourier transform of a gaussian (e^(-(k^2/2)) is a gaussian, i know some elementary complex analysis(never actually taken a class in it), not well enough, it seems, to find the solution to this. I tried to integrate over a circular contour, and let the radius...
  42. X

    Online tools for Gaussian elimination / LU decomposition ?

    I can not find any useful online tool that solves you a system of equations using Gaussian elimination and LU decomposition. So just a system like: -3X+4X+9X+4x=-2 9X+2X+1X-5X=2 etc. Just about 4 lines. several lines. So basically an online tool where you can just plug in the...
  43. A

    What's the kinetic energy uncertainty for gaussian wave packet?

    What's the kinetic energy uncertainty for gaussian wave packet ψ(x)=((α/pi)^(1/4))exp(-αx^2/2)?
  44. A

    Expectation Value for Gaussian Wave Packet.

    Homework Statement Calculate <x> for the Gaussian wave packet \psi(x)=Ne-(x-x0)/2k2 Homework Equations \left\langle x \right\rangle = \int dx x|\psi(x)|2 The Attempt at a Solution So I've been reviewing for the up-coming midterm and I've had the painful realization that I'm...
  45. W

    Magnus Expansion and gaussian stochastic process?

    Hi, I do some calculations on a rf-pulse controlled Spin-1/2 system influenced by noise given by a normal distributed random variable n(t) (which is, I guess, a gaussian stochastic process, as n(t) is a gaussian distributed random variable for all t). Using the Magnus-Expansion...
  46. G

    Gaussian Elimination Solve for variable

    Homework Statement Determine the value of k for which the system x + y + 2z = 3 x + 2y -4z = -3 2 + 8 + kz = -29 has no solutions. Homework Equations None The Attempt at a Solution Converting to a matrix 1 1 2 3 1 2 -4 -3 2 8 k -29 r2=r2-r1 1 1 2 3 0 1 -6 0 2 8 k -29...
  47. E

    Calculate focused spot size - Gaussian FWHM

    http://www.calctool.org/CALC/phys/optics/f_NA Does anyone know how they calculate the spot size (Gaussian FWHM) at this website? For a plane wave, the focused spot size it approx=2*wavelength*f/(pi*d0) f=focal length of lens d0=collimated beam diameter before lens but how do you...
  48. A

    Integration limits for Gaussian surface

    Homework Statement Say you have a nonconducting spherical shell. A is the inner radius and B is the outer radius. If you wanted to set up an integral to find the flux, would the gaussian surface include B, or be just inside it? That is, would the limits of integration go from A to B? If...
  49. R

    Intuitive Expl. of Gaussian Wave Packets & $\Delta x \Delta p = \frac{\hbar}{2}$

    Is there an intuitive way to see why Gaussian wave packets are the only ones that satisfy \Delta x \Delta p = \frac{\hbar}{2}?
  50. J

    Gaussian surface line charge

    Homework Statement A uniformly charged, straight filament 7.00 m in length has a total positive charge of 2.00 \muC. An uncharged cardboard cylinder 2.00 cm in length and 10.0 cm in radius surrounds the filament at its center, with the filament as the axis of the cylinder. Using reasonable...
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