Questions tagged [algorithms]
For questions about an algorithm as it relates to physics. DO NOT ask how to implement an algorithm, questions like that belong on Stack Overflow or Computational Science. DO NOT ask about the efficiency of an algorithm, or other such questions, questions like that belong on Computational Science.
56 questions with no upvoted or accepted answers
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Using a time-like boundary as a computer?
Question and Summary
Using classical calculations and the Robin boundary condition I show that one calculates the anti-derivative of a function within time $2X$ (I can compute an integral below)
$$\...
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Is the only difference between tDMRG and TEBD the way the central sites are shifted?
I have been reading up on time evolution methods using matrix product states. Reading from Schollwoeck's notes on the density matrix renormalization group, (https://arxiv.org/abs/1008.3477), I looked ...
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Textbooks on algorithms for the perturbative calculation of High energy physics
For the perturbative calculation of High energy physics, I have known some packages such as FeynArts, FeynCalc, MadGraph, CompHEP, GiNaC, and so on. But I am wondering whether there exists a textbook ...
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$N$-body gravity simulator: why does energy conservation break down when introducing an adaptive timestep?
I am playing with an N-body gravity simulator using the velocity-verlet algorithm. In the actual simulation I normalize everything so that it is nicely behaved numerically, but I'll express things in ...
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Multilateration of a light source in a medium whose index of refraction varies with position
Background
I have a set of $N$ receivers whose locations in $3D$ space are well-known. These receivers are immersed in a medium whose index of refraction (and thereby the velocity of light propagation)...
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Is there a proof for critical slow-down in Monte Carlo?
It is physically understood why the standard Metropolis-Hasting algorithm slows down near the critical temperature, since it doesn’t utilize the divergence of the correlation length. However, I’m ...
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Algorithm that checks if a subspace of states contains a product state
Suppose I have two identical qudits, the full Hilbert space is $\mathcal{H}=(\mathbb{C}^{d})^{\otimes 2}$. Say I'm given a supspace of states $\Lambda\subset \mathcal{H}$. What is the fastest ...
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Why is the boundary of friends-of-friends (FOF) halo corresponding to iso-density contour?
The friends-of-friends algorithm (hereafter FOF) is commonly used to find halos in cosmological simulations. (For more information, please refer to here and here)
I found that some literature argues ...
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Quantum machine learning and exponential compression
There is a statement related to Quantum Machine Learning video lectures in which I get stuck. The explanation is derived from Seth Lloyd class.
https://www.youtube.com/watch?v=Lbndu5EIWvI
He starts ...
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Why does the Quantum Approximate Optimization Algorithm work?
I am trying to understand the structure of the QAOA algorithm (see here) which is seen as one of the candidates to demonstrate early quantum supremacy. Yet Farhi, Goldstone and Gutmann only describe ...
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Phased non linear array antenna - First Sidelobe
I have a problem I cannot seem to solve and I REALLY need some help.
It's about phased-array antennas whose dipoles are not equally spaced, not equally phased, not equally fed (amplitude).
Let's ...
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Numerically computing induced magnetic field from current density
Let's say we have current density $J_i$ on a discretized grid with $(N_x \times N_y \times N_z)$ points. What is the best procedure to compute the induced magnetic field $(B_i)$ from the current ...
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Good algorithm for in-experiment 1-D optimization?
I'm running an experiment -- for the question, it doesn't matter which one, but I'm measuring an optical intensity $I$ as a function of two parameters: reflection angle $\theta$ and wavelength $\...
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Any quantum Monte-Carlo algorithm for calculating the lowest eigenenergy in each symmetry sector?
Suppose we have a hamiltonian which has the parity symmetry (e.g., the Heisenberg model with the open boundary condition). Is there any quantum Monte-Carlo algorithm which can be used to calculate the ...
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Fringe pattern and ripples in the fringe visibility plot from interferograms
I am using a lens testing interferometer, where I record 4 to 5 interferograms with a 90$^{\circ}$ phase step between consecutive interferograms. In addition to the interferometer, I have also created ...
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