Could anyone recommend introductory books on Green's functions with applications in the framework of classical electrodynamics?
For a physics major, what are the best books/references on Greens functions for self-studying?  My mathematical background is on the level of Mathematical Methods in the physical sciences by Mary Boas.
On my homepage, I'm using this method to hide my email from spam bots:  &lt;a href="admin [at] example.com"    rel="nofollow"    onclick="this.href='mailto:' + 'admin' + '@' + 'example.com'"&gt;Contact me&lt;/a&gt;   What do you think about it? Is it effective? What other methods do you know or use? How prove this equation $\alpha=\aleph_{0}\alpha$ Question:     let $\alpha$ be a infinite cardinal , show that:   $$\alpha=\aleph_{0}\alpha$$   where $\aleph_{0}$ is the cardinality of the natural numbers is denoted aleph-null   this equation is from a book,and I can't prove it,and the author say this is important equation,and can't prove it.Thank you for you help I would like to have a similar biblatex behaviour as described , i.e. separate bibliographies for different publication types, each bibliography should 1) be prefixed with a corresponding label (C for conference publications, J for journals etc), 2) sorted so that the newest entry is at the top (defined by the publication year) and 3) with reference numbers sorted in descending order per bibliography, i.e. the newest entry should have the highest number.  Journal articles ---------------- [J3]    reference from 2017 [J2]    reference from 2016 [J1]    reference from 2015  Conference publications ----------------------- [C4]    reference from 2017 [C3]    reference from 2017 [C2]    reference from 2016 [C1]    reference from 2015   I currently have the following:  \usepackage[backend=biber,         isbn=true,         giveninits=true,         style=numeric,         maxnames=99,         sorting=ydnt,         defernumbers=true,         autocite=superscript]{biblatex}  \subsection*{Journal articles} \begin{refcontext}[labelprefix=J] \printbibliography[type=article] \end{refcontext}  \subsection*{Conference publications} \begin{refcontext}[labelprefix=C] \printbibliography[type=inproceedings]   Separate bibliographies works fine, labelprefix also works as desired, sorting by year in descending order as well. However, if I try the solution mentioned in the above question I get very high reference numbers (in the 500s).  Is the above behaviour possible at all and, if yes, what is the most elegant solution using current biblatex etc.?  Thanks a lot in advance! Possible to get type of an aliased type in c#? Type.GetType("System.String")   Is there a lookup for the aliases available somewhere?  Type.GetType("string")   returns null. Can Yahoo! Messenger be used with Ubuntu? How to print a date in a regular format? This is my code:  import datetime today = datetime.date.today() print(today)   This prints: 2008-11-22 which is exactly what I want.  But, I have a list I'm appending this to and then suddenly everything goes "wonky". Here is the code:  import datetime mylist = [] today = datetime.date.today() mylist.append(today) print(mylist)   This prints the following:   [datetime.date(2008, 11, 22)]   How can I get just a simple date like 2008-11-22? Prove that for any prime p, there is a complete set of mod p residues {q1, . . . , qp}, where each qi is prime. I used the theorem {a, a+n, a+ 2n, . . .} contains infinitely many primes if gcd(a, n) = 1 but haven't got much progress. Any comment will be helpful! I have an internet connection that I'd like to be enabled only during the day. With multiple household internet devices, this would need to be something disabled at the level of the router.  I don't believe the router offers this sort of functionality, but I'm reasonably familiar with setting up web servers and the like, and I'm wondering if I can set up some sort of proxy server on the internet that the router must go through and have that proxy only active at certain times of day.  It's a bit vague I know, but is something like this even possible?  If not, are there other solutions to the problem? Separate long math text under sum symbol into different lines? checking apt-get update lock file Linear regression with non-symmetric cost function? I want to predict some value $Y(x)$ and I am trying to get some prediction $\hat Y(x)$ that optimizes between being as low as possible, but still being larger than $Y(x)$. In other words: $$\text{cost}\left\{ Y(x) \gtrsim \hat Y(x) \right\}  &gt;&gt; \text{cost}\left\{ \hat Y(x) \gtrsim Y(x) \right\}  $$  I think a simple linear regression should do totally fine. So I somewhat know how to implement this manually, but I guess I'm not the first one with this kind of problem. Are there any packages/libraries (preferably python) out there doing what I want to do? What's the keyword I need to look for?  What if I knew a function $Y_0(x) &gt; 0$ where $Y(x) &gt; Y_0(x)$. What's the best way to implement these restrictions? Check Constraint with Case Statement I want to add a check constraint on a column if entered value for column is greater than 3 than it should be saved as 1 else entered value. For that scenario I am using below query but on insertion of data it shows an error message.  create table tblTestCheckConstraint  ( id int, NewColumn int )   alter table tblTestCheckConstraint add constraint chk_tblTestCheckConstraint_NewColumn1 CHECK   (     CASE         WHEN NewColumn &gt;4 THEN 1         ELSE NewColumn     END = 1 )   Insert Statement:   insert into tblTestCheckConstraint values ( 1,5) insert into tblTestCheckConstraint values ( 1,2)   Error Message:   Msg 547, Level 16, State 0, Line 1 The INSERT statement conflicted with the CHECK constraint "chk_tblTestCheckConstraint_NewColumn1". The conflict occurred in database "DBName" , table "dbo.tblTestCheckConstraint", column 'NewColumn'. The statement has been terminated. How to use the SSD for caching in Windows without Intel Smart Response? My motherboard is Asus P8B75-M. It doesn't have Intel Smart Response. But recently I bought a SSD. Since I mostly use linux I have Linux installed in it. But can I use it to speed up Windows also? How? I don't have Smart Response... (I run Windows 8.1). The SSD is only 64GB. dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) nginx The Software up-to-date Option automatically download the upgrade for nginx. but While installing it's giving me the following error:  Reading package lists... Done Building dependency tree        Reading state information... Done The following NEW packages will be installed:   nginx 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/434 kB of archives. After this operation, 977 kB of additional disk space will be used. (Reading database ... 291344 files and directories currently installed.) Unpacking nginx (from .../nginx_1.4.7-1~precise_amd64.deb) ... ----------------------------------------------------------------------  Thanks for using nginx!  Please find the official documentation for nginx here: * http://nginx.org/en/docs/  Commercial subscriptions for nginx are available on: * http://nginx.com/products/  ---------------------------------------------------------------------- dpkg: error processing /var/cache/apt/archives/nginx_1.4.7-1~precise_amd64.deb (--unpack):  trying to overwrite '/etc/logrotate.d/nginx', which is also in package nginx-common 1.4.6-1+precise0 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing:  /var/cache/apt/archives/nginx_1.4.7-1~precise_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   Actually that file /etc/logrotate.d/nginx does not exist in this folder. My java code has an obvious error. Why does it compile and run? I am relatively new to Blender so please excuse me if this is rather amateur!   The bottom of my torus has poor surface quality, I have scaled the vertices down for a smaller (variable) tubular radius all the way around the torus and at the bottom the surface quality is awful, with inaccurate shading. Any ideas as to what is wrong and/or how I could fix this?  Thanks, itsanate Let $A$ be a non-empty set and $n$ be the number of elements in $A$, i.e. $n:=|A|$.  I know that the number of elements of the power set of $A$ is $2^n$, i.e.  $|\mathcal{P}(A)|=2^n$.  I came across the fact that exactly half of the elements of $\mathcal{P}(A)$ contain an odd number of elements, and half of them an even number of elements.  Can someone prove this? Or hint at a proof? What are the rules for China's visa-free transit programs? What is the syntax for IF/ELSE in bash? I am trying to pull logs and doing few others things directly. written a small line BASH but not working. I am sure thats with IF Condition.    sed -rne '/21:25:07/,/21:50:07/ p'  server.log.2015-04-21 &gt; /tmp/filename.log ; du -sh  /tmp/filename.log ;  if [`du -sh  /tmp/filename.log` -gt 0] then gzip /tmp/filename.log ; I have an internal microphone in my laptop. I think it uses Intel High Definition Audio. But I can't get it to work with Ubuntu. It doesn't work with either the Sound Recorder or Skype.  On the Input tab in 'Sound Preferences', I just see Internal Analog Input Device...