I am an physics undergrad in my pre-final year. Recently, I tried learning some QFT (from the likes of Peskin and Schroeder’s 1st 4 chapters, David tong etc.) and got interested in it’s working in a condensed matter setting. As it happens, listening to broad applications of QFT in CMP got me interested in learning about Keldysh field theory and am curious to see how it handles non-eqm situations. Currently I am stuck about charting a  proper path/topics list that can help me reach Keldysh field theory in a proper manner. The only resource I have seen as such are ArviX articles which are quite inaccessible for me.  So I am asking about the necessary topics/chapters required to learn Keldysh Field theory. I’ve done some path integrals and am starting to know about imaginary time calculations. But I’ve no idea how exactly to proceed (another answer on  regd the resources is quite useful, but that assumes some pre-requisite, I wanted if a broad list of topics could be highlighted to reach there). Any resources/specific topics would be highly welcome.  As per my background - I have taken course work in Quantum mechanics (scattering/perturbation and relativistic) and am currently taking a course in solid state physics and stat mech. Ig some understanding of material here (i.e. coursework) would be pre-requisite, but till now following Negele and Orland’s book for the 1st couple of chapters, I’ve managed to build up whatever I need on the go. Hoping for suggestions!
I'd like some suggestions for good reading materials on the Keldysh formalism in the condensed matter physics community. I'm familiar with the imaginary time, coherent state, and path integral formalisms, but lately, I've been seeing Keldysh more and more in papers. My understanding is that it is superior to the imaginary time formalism at least in that one can evaluate non-equilibrium expectations.
How can I invert a 'clip' selection within TikZ? I wish to draw an arc for a reflex angle on the outside of a triangle with coordinates (A), (B) and (C).  If I wanted to draw the arc inside the triangle I could use something like  \begin{scope} \path[clip] (A) -- (B) -- (C) -- cycle; \draw (B) circle (2mm);    % this is the little angle marker \end{scope}   Is there a straightforward way to exclude the part of the circle that's in the triangle, as in the pseudo-code below?  \begin{scope} \path[magicalinverseclipcommand] (A) -- (B) -- (C) -- cycle; \draw (B) circle (2mm);    % this is the little angle marker \end{scope}   EDIT: Although I included the code above as a motivating example of what an inverse clip would do, I would prefer a general solution that works systematically with any closed path, and not just in the particular example of a triangle with a circle clipped out of it. Looking at my question, I realise this isn't clear, and I will be happy with the best solution to my particular problem, but wonder if there is a less ad hoc solution than those listed so far. Can Blender render animated gifs? I'd like to put some shared Javascript to Resource file to reuse it between several components. This Javascript is general purpose set of utility functions. However, functions from my resource file are not available from the Components. Static resource (named TestScript):  function helloWorld() {      return 42; }   Component:  &lt;ltng:require scripts="{!$Resource.TestScript}" &lt;ui:button label="Do job" press="{!c.doJob}"/&gt;   Controller:  doJob: function(cmp, event, helper) {      var i = helloWorld();      // failed with Uncaught ReferenceError: helloWorld is not defined }   I don't like to use  &lt;ltng:require scripts="{!$Resource.***resourceName***}" afterScriptsLoaded="{!c.afterScriptsLoaded}" /&gt;   because my static resource is a set of functions and I'd like just use them as functions later in my controllers. How can I achieve that (if possible)? If not, what's the suggested solution? Ubuntu 18.04 No WiFi adapter found [Dell Inspiron 3542.] Just installed Ubuntu 18.04 but my WiFi adapter Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter doesn't work or even appear in the system settings.  output of lspci -knn | grep Net -A3:  &gt; rahul@rahul-Inspiron-3542:~$ lspci -knn | grep Net -A3 06:00.0 Network controller [0280]: Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter [168c:0036] (rev 01)     Subsystem: Dell QCA9565 / AR9565 Wireless Network Adapter [1028:020c]     Kernel driver in use: ath9k     Kernel modules: ath9k 07:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller [10ec:8136] (rev 07)   output of lspci -knn | grep Net -A2  rahul@rahul-Inspiron-3542:~$ lspci -knn | grep Net -A2 06:00.0 Network controller [0280]: Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter [168c:0036] (rev 01)     Subsystem: Dell QCA9565 / AR9565 Wireless Network Adapter [1028:020c]     Kernel driver in use: ath9k     Kernel modules: ath9k   output of sudo rfkill list  rahul@rahul-Inspiron-3542:~$ sudo rfkill list [sudo] password for rahul:  0: dell-rbtn: Wireless LAN     Soft blocked: yes     Hard blocked: yes 1: phy0: Wireless LAN     Soft blocked: no     Hard blocked: no 2: hci0: Bluetooth     Soft blocked: yes     Hard blocked: no   output of sudo lshw -C network  rahul@rahul-Inspiron-3542:~$ sudo lshw -C network   *-network DISABLED                description: Wireless interface        product: QCA9565 / AR9565 Wireless Network Adapter        vendor: Qualcomm Atheros        physical id: 0        bus info: pci@0000:06:00.0        logical name: wlp6s0        version: 01        serial: 4c:bb:58:30:aa:07        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical wireless        configuration: broadcast=yes driver=ath9k driverversion=4.17.11-041711-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11        resources: irq:18 memory:f7900000-f797ffff memory:f7980000-f798ffff   *-network        description: Ethernet interface        product: RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:07:00.0        logical name: enp7s0        version: 07        serial: 74:e6:e2:14:2a:c8        size: 10Mbit/s        capacity: 100Mbit/s        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl8106e-1_0.0.1 06/29/12 latency=0 link=no multicast=yes port=MII speed=10Mbit/s        resources: irq:19 ioport:e000(size=256) memory:f7800000-f7800fff memory:f2100000-f2103fff   *-network        description: Ethernet interface        physical id: 2        logical name: enp0s20u1        serial: 7a:14:5b:44:b4:96        capabilities: ethernet physical        configuration: broadcast=yes driver=rndis_host driverversion=22-Aug-2005 firmware=RNDIS device ip=192.168.42.109 link=yes multicast=yes   output of dmesg | grep ath9k  rahul@rahul-Inspiron-3542:~$ dmesg | grep ath9k [   23.712505] ath9k 0000:06:00.0 wlp6s0: renamed from wlan0   output of sudo iw dev  rahul@rahul-Inspiron-3542:~$ sudo iw dev [sudo] password for rahul:  phy#0     Interface wlp6s0         ifindex 3         wdev 0x1         addr 4c:bb:58:30:aa:07         type managed         txpower 0.00 dBm   output of dmesg   I already tried so many solutions but nothing works for me , I'm looking for answer from so many days. Please Someone solve my issue . If anyone want any other information please let me know.  Any help would be greatly appreciated. For many of my datasets I have the same imported data duplicated numerous times, each iteration displaying the data values for a different column (in my case it's fish catch weight per gridded cell per year, so lots of iterations of the same grid, with a different pattern of values per year).  For presentation purposes, it strikes me as helpful to use the same scale for each year, so I go to the original data and divide the maximum value into (arbitrarily) 10 classes and manually input the values and labels after setting the desired colour ramp and input data field:   This is extremely tedious, not just the manual excel calculation part, but also the input interface for the values &amp; labels*, hence my intention to make use of the 'save style' option. HOWEVER: when I save the style as QML and load it for the next layer, it saves everything - including the data field (in my case, year). When I change this field, QGis automatically generates the values &amp; labels based on the data for that field, ditching all of the values &amp; labels I set.   Is there any way to avoid this happening &amp; thereby duplicate class number, values and labels for each field by simply loading a style? (somewhat meta) Am I going around this the wrong way, OR, is there a different face I could use to climb this mountain? Trying to install Steam ERROR: You are missing the following 32-bit libraries, and Steam may not run: not I've already installed Steam, but when I click on the program I get this message  ERROR- You are missing the following 32-bit libraries, and Steam may not run: not   I don't know what to install or even do. Pass by Reference / Value in C++ I would like to clarify the differences between by value and by reference.  I drew a picture     So, for passing by value,  a copy of an identical object is created with a different reference, and the local variable is assigned the new reference, so to point to the new copy  How to understand the words: " If the function modifies that value, the modifications appear also within the scope of the calling function for both passing by value and by reference "  Thanks! Looking at the questions and answer to these two questions.  &amp;  and neither mentions the longevity of magic. I recall several instances of magic failing to last; the money that was spread at the  and the broken  on.  If I recall correctly when Voldemort died, the curses on several people were lifted.  I don't recall if any other spells fell apart with his death.  Is there any canon evidence on the the length of time a spell will live? How to run some code only when the rails console starts, kind of like an rc file? I'm using a  freely downloadable latex class file and the style is set to \bibliographystyle{ieeetr}. But when I cite something with \cite{} I get it inside ().   For example I get it as abc et al. (1) but what I want to get is abc et al. [1].   Please tell me how to get my citations inside [ ] ? Here is a fun integral I am trying to evaluate:  $$\int_{0}^{\infty}\frac{\sin^{2n+1}(x)}{x} \ dx=\frac{\pi \binom{2n}{n}}{2^{2n+1}}.$$  I thought about integrating by parts $2n$ times and then using the binomial theorem for $\sin(x)$, that is, using $\dfrac{e^{ix}-e^{-ix}}{2i}$ form in the binomial series.  But, I am having a rough time getting it set up correctly. Then, again, there is probably a better approach.   $$\frac{1}{(2n)!}\int_{0}^{\infty}\frac{1}{(2i)^{2n}}\sum_{k=0}^{n}(-1)^{2n+1-k}\binom{2n}{k}\frac{d^{2n}}{dx^{2n}}(e^{i(2k-2n-1)x})\frac{dx}{x^{1-2n}}$$  or something like that. I doubt if that is anywhere close, but is my initial idea of using the binomial series for sin valid or is there a better way?.  Thanks everyone. Proof that $V = \sum_k U_k$ and $\dim V=\sum_k \dim U_k$ implies $V=\oplus_k U_k$ I need to prove that there are infinitely many numbers  of the form $x = 111....1$ such that $31\mid x$  what I tried - I wrote x as   $\sum_0^{n-1} 10^i$  I know that $(10,31) = 1 $  now I'm stuck .. any help will be appreciated Tensor product in dual-space I am a bid confused regarding the notation for tensor products when going into dual-space  If $\left| \Psi \rangle \right. = \left| A \rangle \right. \left| B \rangle \right.$ is $ \left. \langle \Psi \right| = \left. \langle A \right| \left. \langle B \right|$ or $\left. \langle B  \right| \left. \langle A \right|$?  My guess is the last choice, since operators should act on   $\left| 0 \rangle \right. = \left( \begin{matrix}   1 \\   0  \end{matrix} \right) $  $\left| 1 \rangle \right. = \left( \begin{matrix}   0 \\   1  \end{matrix} \right) $  so  $\left| 01 \rangle \right. = \left| 0 \rangle \right. \left| 1 \rangle \right. = \left( \begin{matrix}   0 \\   1 \\   0 \\   0  \end{matrix} \right) $  But then, for me, it should be  $\left( \begin{matrix}   0 &amp; 1 &amp; 0 &amp; 0  \end{matrix} \right) = \left \langle 10 \right|$ But this is not correct if i calculate the tensor product, since   $\left \langle 1 \right| \left \langle 0 \right| = \left( \begin{matrix}   0 &amp; 0 &amp; 1 &amp; 0  \end{matrix} \right)$  For instance, shoulden't it be  $\left| 01 \rangle \right. \left \langle 10 \right| = \left( \begin{matrix}   0 &amp; 0 &amp; 0 &amp; 0\\   0 &amp; 1 &amp; 0 &amp; 0\\   0 &amp; 0 &amp; 0 &amp; 0\\   0 &amp; 0 &amp; 0 &amp; 0\\  \end{matrix} \right) $ ?  I hope I have made my confusion clear I’m a newbie in Python. I’m learning regexes, but I need help here.  Here comes the HTML source:  &lt;a href="http://www.ptop.se" target="_blank"&gt;http://www.ptop.se&lt;/a&gt;   I’m trying to code a tool that only prints out http://ptop.se. Can you help me please? Are fractions with prime numerator and denominator dense? How do I determine whether a drive is an HDD or SSD in Windows 8? I've recently received an assembled PC. I don't know if the disk is an SSD or old HDD (whether SATA or other technologies).  I can't find a way to tell if the disk is SSD or not, apart from the size of the disk. However, now that the sizes of SSDs are getting close to that of HDDs, checking the size is not a good and robust way to distinguish drive type. Is there some other way to determine if the disk is an SSD? Divergence of $\frac{ \hat {\bf r}}{r^2} \equiv \frac{{\bf r}}{r^3}$, what is the 'paradox'? I just started in Griffith's Introduction to electrodynamics and I stumbled upon the divergence of $\frac{ \hat r}{r^2} \equiv \frac{{\bf r}}{r^3}$, now from the book, Griffiths says:  Now what is the paradox, exactly? Ignoring any physical intuition behind this (point charge at the origin) how are we supposed to believe that the source of $\vec v$ is concentrated at the origin mathematically? Or are we forced to believe that because there was a contradiction with the divergence theorem? Also how would the situation differ if $\vec v$ was the same vector function but not for a point charge? Or is it impossible? To all the 'sed' doctors out there:  How can you get 'sed' to extract a regular expression it has matched in a  line?   In other words words, I want just the string corresponding to the regular  expression with all the non-matching characters from the containing line stripped away.  I tried using the back-reference feature like below  regular expression to be isolated           gets `inserted`                here                     |                v    sed -n 's/.*\( \).*/\1/p    this works for some expressions like   sed -n 's/.*\(CONFIG_[a-zA-Z0-9_]*\).*/\1/p    which neatly extracts all macro names starting with 'CONFIG_ ....' ( found in some '*.h' file ) and prints them all out line by line             CONFIG_AT91_GPIO           CONFIG_DRIVER_AT91EMAC                    .                    .              CONFIG_USB_ATMEL           CONFIG_USB_OHCI_NEW                    .                  e.t.c.    BUT the above breaks down for something like    sed -n 's/.*\([0-9][0-9]*\).*/\1/p    this always returns single digits like                    7                  9                  .                  .                    6   rather than extracting a contiguous number field such as.                 8908078               89670890                    .                  .                    .                23019                     .                e.t.c.     P.S.: I would be grateful to feedback on how this is achieved in 'sed'.        I know how to do this with 'grep' and 'awk'       I would like to find out if my - albeit limited - understanding of        'sed' has holes in it and if there is way to do this in 'sed' which I       have simply overlooked. When should I use \input vs. \include?