Section Definition and 733 Threads

The section sign, §, is a typographical character for referencing individually numbered sections of a document; it is frequently used when citing sections of a legal code. It is also known as the section symbol, section mark, double-s, or silcrow.

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  1. H

    I Problem with section in Schwartz's QFT text

    Beginning of page 303 of Schawrtz's QFT text (section 16.1.1), there's a part on the renormalization of the scalar propagator in ##\phi^3## theory to second order in ##g## the bare coupling. He writes (quote begins): $$M(Q)=M^0 (Q)+M^1 (Q)=\frac{g^2}{Q^2}(1-\frac{1}{32 \pi^2}...
  2. Math Amateur

    MHB Directional Derivatives .... Apostol, Section 12.2, Example 4 ....

    I am reading Tom M Apostol's book "Mathematical Analysis" (Second Edition) ...I am focused on Chapter 12: Multivariable Differential Calculus ... and in particular on Section 12.2: The Directional Derivative ... ...I need help with part of Example 4, Section 12.2 ...Section 12.2, including the...
  3. José Ricardo

    Suggestion What sections are most popular on the PF forum?

    You guys could put the number of posts by each section, I think we would discover what interests more in the forum and what people study more.
  4. Math Amateur

    MHB Rel as a Category .... Awodey Section 1.4, Example 4, Pae 7 ....

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.4 Examples of Categories ... I need some further help in order to fully understand some aspects of the definition of the category Rel ... ... The definition of the category Rel ... reads as...
  5. parazit

    I The Maxwellian Averaged Cross Section

    Hi, Please forgive my ignorance but, can somebody please explain the Maxwellian Averaged Cross Section briefly and basically? Thank you in advance.
  6. CivilSigma

    Job Skills Should a resume include a "summary" section?

    I am a senior Civil Engineering student in my last study semester and I will begin to send out my resume in hopes of landing a job. I was wondering, is a "Professional Summary" section a standard practice for engineers looking for a job? Thank you in advance.
  7. Math Amateur

    MHB How can the product of two categories help us understand groups?

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.5 Isomorphisms ... I need some further help in order to fully understand some aspects of the definition of the product of two categories as it applies to the category Groups ... ... The definition...
  8. Math Amateur

    MHB Category Theory .... Groups and Isomorphisms .... Awodey, Section 1.5 .... ....

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.5 Isomorphisms ... I need some further help in order to fully understand some aspects of Definition 1.4, Page 12 ... ... The start of Section 1.5, including Definition 1.4 ... reads as...
  9. Math Amateur

    MHB Why Are Inverses Unique in a Category?

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.5 Isomorphisms ... I need some further help in order to fully understand some further aspects of Definition 1.3, Page 12, including some remarks Awodey makes after the text of the definition ... ...
  10. Math Amateur

    MHB Understanding Monoids as Categories: Awodey Section 1.4 Example 13

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.4 Examples of Categories ... I need some further help in order to fully understand some further aspects of Section 1.4 Example 13 ... Section 1.4 Example 13 reads as follows: In the above text by...
  11. Math Amateur

    MHB Monoids as Categories .... Awodey Section 1.4, Example 13 ....

    I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.4 Examples of Categories ... I need some help in order to fully understand some aspects of Section 1.4 Example 13 ... Section 1.4 Example 13 reads as...
  12. Alianos

    Emission cross section and laser performance

    How does the emission cross section of an emitting atom (such as Yb atoms in glass) affect the laser performance, namely the slope efficiency (signal power vs absorbed pump power) and laser threshold? Thanks a lot
  13. S

    Average Vector Acceleration Along a Curve and a Straight Section

    Homework Statement f f Homework Equations ##a = {v^2}{r}## ##d = vt## The Attempt at a Solution The way I do it is break it down into the curved and straight segment. The bicycle is always traveling at a constant speed. Curved portion: distance ##\frac{\pi R^2}{4}## acceleration ##=...
  14. Math Amateur

    MHB Another Question on Torsion Elements .... D&F Section 10.1, Exercise 8 ....

    I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an Exercise 8(c) of Section 10.1 ... Exercise 8 of Section 10.1 reads as...
  15. Math Amateur

    MHB How Can One Show That a Given Example is Not a Submodule?

    I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an Exercise 8(b) of Section 10.1 ... Exercise 8 of Section 10.1 reads as follows...
  16. shahbaznihal

    Testing Electricity and Magnetism section in GRE Physics

    Hi, I am taking GRE Physics this year and I am preparing from Conquering GRE Physics book and I have covered everything in that book on Electricity and Magnetism (yet to study Optics and Waves). My question: How much from Griffith Electrodynamics book do I need to study? Or is the material in...
  17. Math Amateur

    MHB Maximal Ideal .... Bland - AA - Example 2, Section 3.2.12 .... ....

    I am reading The Basics of Abstract Algebra by Paul E. Bland ... I am focused on Section 3.2 Subrings, Ideals and Factor Rings ... ... I need help with the proof of Example 2, Section 3.2.12, pages 147 to 148 ... ... Example 2, Section 3.2.12 reads as follows...
  18. S

    Finding errors in a section of microprocessor assembly code

    Hi guys, apparently I've got both a linear and a subroutine programming error in the code below from lines 20-35? Could someone point me in the right direction. I think one might be the 'CALL wait' instruction, which should be 'CALL delay'? Not really sure as new to this, any help would be much...
  19. J

    Radar Cross section Vs Reflection Coefficient

    I am working on HFSS and designing Antennas for LOW RCS , in all previous works they calculate the S11 parameter for the unit cell then make an array form this unit cell and calculate the RCS , my question is what is the relation between S11 and RCS and why we calculate S11 for the unit...
  20. Math Amateur

    MHB Generation of Modules .... Dummit and Foote, Section 10.3 .... ....

    I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an aspect of Dummit and Foote's Section 10.3 Basic Generation of Modules, Direct Sums and Free Modules ... ... The...
  21. Math Amateur

    MHB Endomorphism Rings .... Bland, Example 7, Section 1.1 .... ....

    I am reading Paul E. Bland's book, "Rings and Their Modules". I am focused on Section 1.1 Rings and need some help to fully understand the proof of part of Example 7 on page 10 ... ... Example 7 on page 10 reads as follows:In the above example from Bland we read the following: " ... ...
  22. M. M. Fahad Joy

    Find the Area of the Shaded Section in a Circle

    Known data: In the picture, CD = 10 cm. What is the area of shaded area? Equation: I know, Area of a circle = ##πr^2## Diameter of a circle = ##2πr## Attempt: Here, ## r = 10/2 = 5 ## So, diameter ## = 2πr = 2*3.1416*5 = 31.42 cm ## And area of the circle ## = πr^2 = 3.1416*5^2 = 78.54 cm^2...
  23. CDL

    Determining a Scattering Cross Section (Quantum Mechanics)

    Homework Statement Consider scattering of a particle of mass ##m## on the potential $$U(r) = \begin{cases} 0, & r \geq b\\ W, & r < b \\ \end{cases}$$ Where ##W## is some arbitrary chosen constant, and the radius ##b## is considered a small parameter. Find the cross section ##\sigma## in the...
  24. R

    Self-inductance of a toroid with a rectangular cross section

    I have found answers on how to calculate the self-inductance of toroid of rectangular cross section, however my question says that "The winding are seen as a thin homogeneous currentlayer around the core" (excuse the translation). What does that mean for N? Does it mean N=1?
  25. Math Amateur

    MHB Noetherian Modules - Bland, Example 3, Section 4.2 ....

    I am reading Paul E. Bland's book "Rings and Their Modules" ... Currently I am focused on Section 4.2 Noetherian and Artinian Modules ... ... I need some help in order to fully understand Example 3, Section 4.2 ... Example 3, Section 4.2 reads as follows: My questions are as...
  26. Math Amateur

    I Noetherian Modules - Bland, Example 3, Section 4.2 ....

    I am reading Paul E. Bland's book "Rings and Their Modules" ... Currently I am focused on Section 4.2 Noetherian and Artinian Modules ... ... I need some help in order to fully understand Example 3, Section 4.2 ... Example 3, Section 4.2 reads as follows: My questions are as...
  27. Math Amateur

    MHB Is \(\bigoplus_\Delta A_\alpha\) a Right Ideal of \(\prod_\Delta R_\alpha\)?

    I am reading Paul E. Bland's book: Rings and Their Modules and am currently focused on Section 2.1 Direct Products and Direct Sums ... ... I need someone to check my solution to Problem 2(b) of Problem Set 2.1 ... Problem 2(b) of Problem Set 2.1 reads as follows: My attempt at a solution...
  28. Math Amateur

    MHB Help with Problem 2(a), Rings & Modules, Paul E. Bland

    I am reading Paul E. Bland's book: Rings and Their Modules and am currently focused on Section 2.1 Direct Products and Direct Sums ... ... I need help with Problem 2(a) of Problem Set 2.1 ... Problem 2(a) of Problem Set 2.1 reads as follows: I am unsure of my solution to problem 2(a) and need...
  29. Math Amateur

    MHB External Direct Sums and Direct Products .... Bland Problem 1, Section 2.1 ....

    I am reading Paul E. Bland's book: Rings and Their Modules and am currently focused on Section 2.1 Direct Products and Direct Sums ... ... I need help with Problem 1(b) of Problem Set 2.1 ... Problem 1(b) of Problem Set 2.1 reads as follows: I have had difficulty in formulating a rigorous...
  30. Math Amateur

    MHB (R/I)-Modules .... Dummit and Foote Example (5), Section 10.1 ....

    I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an aspect of Example (5) of Section 10.1 Basic Definitions and Examples ... ... Example (5) reads as follows: I do...
  31. Math Amateur

    I (R/I)-Modules .... Dummit and Foote Example (5), Section 10.1

    I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an aspect of Example (5) of Section 10.1 Basic Definitions and Examples ... ... Example (5) reads as follows: I...
  32. ChrisVer

    A Question about a cross section from PDG

    Hi everyone, I was wondering, is the cross section at Eq 50.25 in http://pdg.lbl.gov/2017/reviews/rpp2017-rev-cross-section-formulae.pdf correct? Because I see a term in the denominator with \frac{1}{s\Gamma} whereas in several other references, the propagator term in the matrix element comes...
  33. CivilSigma

    Determining the Centroid of a 3D Section

    Homework Statement [/B] I am having a problem understanding a calculation performed as part of a bigger solution in the design of Slabs. That is, how to determine the centroid of the critical shear section, which consist of 3 planes intersecting to form a 3D model (please see attached...
  34. D

    Deflection of Tapered Beam with Elliptic Cross Section

    I am working on deriving expression for deflection of a tapered beam with an elliptic cross-section. Hence, area moment of inertia is a linear function of the beam length. The beam is fixed at one end, and a concentrated force F is applied on its tip at the free end. I am using the known...
  35. Ben2

    A Proving the Last Gauss Lemma for Real Numbers Using Induction

    Modified from Disquisitiones Arithmeticae, p. 10: Let "*" indicate multiplication and "^" indicate "to the power." For real numbers a, b, c,..., let [a] = a, [a,b] = b*a+1, [a,b,c] = c*[a,b]+[a], [a,b,c,d] = d*[a,b,c]+[a,b], etc. Prove that [a,b,...,l,m]*[b,c,...,l] - [a,b,...,l]*[b,c,...,m]...
  36. Math Amateur

    MHB Coordinate-Wise Convergence in R^n .... TB&B Chapter 11, Section 11.4 ....

    I am reading the book "Elementary Real Analysis" (Second Edition, 2008) Volume II by Brian S. Thomson, Judith B. Bruckner, and Andrew M. Bruckner ... and am currently focused on Chapter 11, The Euclidean Spaces \mathbb{R}^n ... ... I need with the proof of Theorem 11.15 on coordinate-wise...
  37. A

    Skew bending in a circular cross section (proof)

    Good day all I'm looking for the proof of stress generated in case of skew bending applied in acircular cross section ( I browsed internet the whole day without finding anything convincing) we use with many thanks in advance!
  38. S

    How to calculate total cross section from differential cross section

    I was doing the calculations for this: http://fermi.la.asu.edu/PHY531/cylinder/index.html But I can't figure out how to go from \frac{d\sigma}{d\phi} to the total cross section. My guess was that you did the integral from \phi=0 to \phi=2\pi, but that's not helping since I can't tell either how...
  39. nomadreid

    I Typographical question: the section sign

    I have seen the section sign \S mainly in legal documents. However, an acquaintance is writing a physics paper in which she uses this sign to refer to a section of another paper in which the section sign was not used (sections just being marked off by number), is it OK to use the section sign...
  40. Math Amateur

    MHB Complete Metric Spaces .... Conway, Analysis, Section 5.2 ....

    I am reading John B. Conway's book: Ä First Course in Analysis and am focused on Chapter 5: Metric and Euclidean Spaces ... and in particular I am focused on Section 5.2: Sequences and Completeness ... I need some help/clarification with Conway's defintion of completeness of a metric space ...
  41. B

    Resistance of a semicircular conductor with a rectangular cross section

    Homework Statement There is a conductor with the square-shaped area. the Radii are r1 , r2 with width b and resistivity ## \rho_R##. Find the resistance R between A and B 2. Homework Equations ##I = \iint_A\vec J \cdot d \vec A## ## \vec J = \kappa \vec E ## ## \vec E = \rho \vec J## ## V =...
  42. Y

    FORTRAN 90 How to plot the Poincaré section?

    Hi all, I'm writing a fortran 90 program to simulate the Duffing oscillator. I have it working and have produced a cos wave which I expected for D (the driving force) being set to 0. Here's the code: program rungekutta implicit none integer, parameter :: dp = selected_real_kind(15,300)...
  43. Math Amateur

    MHB Antisymmetry & Partial Orderings - H&J Ch.2 Section 5 | Peter's Help

    I am reading "Introduction to Set Theory" (Third Edition, Revised and Expanded) by Karel Hrbacek and Thomas Jech (H&J) ... ... I am currently focused on Chapter 2: Relations, Functions and Orderings; and, in particular on Section 5: Orderings I need some help with H&J's depiction of...
  44. Math Amateur

    MHB Understanding H&J's Section 3 on Invertible & One-to-One Functions: Q&A

    I am reading "Introduction to Set Theory" (Third Edition, Revised and Expanded) by Karel Hrbacek and Thomas Jech (H&J) ... ... I am currently focused on Chapter 2: Relations, Functions and Orderings; and, in particular on Section 3: Functions I need some help with H&J's depiction of...
  45. T

    News Moaning about Google science news section

    I usually read science section in Google news and it's really irritating how lately any time someone "predicts" the world will end they put it on top. But now they really seem to hit the rock bottom. Here's a screenshot and you can see first news is again about "end of the world" although this...
  46. Math Amateur

    MHB Cartesian Products and Families of Sets .... Searcoid, Section 1.2 .... ....

    I am reading Micheal Searcoid's book: "Elements of Abstract Analysis" ... ... I am currently focused on understanding Chapter 1: Sets ... and in particular Section 1.2 Relations and Functions ... I need some help in fully understanding some remarks by Searcoid in his sub-section on products...
  47. A

    MHB Problem 13 from section 16.1 of Taylor's PDE textbook.

    I was given as a task to solve this question by my teacher (heck if I had the time I would have solved every problem in both Taylor's and Evans's books on PDE); but didn't succeed to the teacher's satisfaction. In the following link there's a presentation of the problem, and in the attachment...
  48. Math Amateur

    MHB Why Does Lemma 8.4 Equal This Expression?

    The "Operator Norm" for Linear Transformations ... Browder, Lemma 8.4, Section 8.1, Ch. 8 ... ... I am reader Andrew Browder's book: "Mathematical Analysis: An Introduction" ... ... I am currently reading Chapter 8: Differentiable Maps and am specifically focused on Section 8.1 Linear Algebra...
  49. Math Amateur

    MHB Operator Norm for Linear Transformations: Browder Ch. 8, Section 8.1, Page 179

    The "Operator Norm" for Linear Transfomations ... Browder, page 179, Section 8.1, Ch. 8 ... ... I am reader Andrew Browder's book: "Mathematical Analysis: An Introduction" ... ... I am currently reading Chapter 8: Differentiable Maps and am specifically focused on Section 8.1 Linear Algebra...
  50. ChrisVer

    A What is a Fiducial Cross Section?

    I have come across the term quiet often, but I find it difficult to explain it to myself (or others) and even interpret it... So what is a fiducial cross section? Is it the measured cross section once you factor out the detector acceptance and the different cut-efficiencies (mainly motivated by...
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