The h Bar

I recently set up a new laptop with W10 and no AV, just the built in Windows Defender, and Windows Defender was making quite a big difference to disk speed. When I installed AVG (which disables Defender) there was a considerable improvement.

MalwareBytes will also affect speed. AV apps works by inserting themselves in the disk driver chain and scanning data as it's read/written. That always causes a performance hit.

You could try temporarily disabling the Defender services:

And I don't think it's necessary to have MalwareBytes installed.

0celóñe7

@JohnRennie I trust it because it's found stuff on my laptop that Defender has missed

Unless you want to suggest a better AV altogether?

@Slereah morning

Slereah

tips hat

John Rennie

For speed the best option would be to use no AV at all and only use the PC for gaming i.e. don't surf on it.

0celóñe7

@JohnRennie that's ridiculous :P

I won't be gaming for a while

this now a work pc

John Rennie

5:08 AM

Then the disk speed isn't an issue

0celóñe7

@JohnRennie I've said a billion times that the speed is not an issue

What is an issue is that I paid a premium price for an M.2 SSD and am not getting M.2 speeds

John Rennie

Well you're the one who brought up the subject :-)

0celóñe7

It's a matter of principle

John Rennie

The disk benchmarks are still miles better than my SanDisk Ultra II, that is supposed to be a fast disk.

0celóñe7

@JohnRennie I can't end the defender services

John Rennie

5:10 AM

Are they not allowing you to stop them?

0celóñe7

mhm, there is simply no option for it

it's grayed out

John Rennie

Let me look at my test installation ...

0celóñe7

John Rennie

Hmm, MS really don't want you to stop the Defender services. There's probably a way to do it if you Google.

@0celóñe7 The sequential speeds look about right.

0celóñe7

@JohnRennie Should I disconnect from the internet if I somehow turn off defender?

John Rennie

5:15 AM

No, just don't open any attachments purporting to be from young ladies with large busts

skullpatrol

Hello hello.

0celóñe7

@JohnRennie the Microsoft website apparently has no clue what the Windows 10 menus look like

none of their instructions are ever helpful

@JohnRennie turning off real-time protection for defender has no effect

@Slereah want to check a proof for me?

Slereah

I can try

But y'know

John Rennie

if you're serious about this what you need to do is wipe the disk completely i.e. clean off all the partition info and do a clean W10 install. Then benchmark and check the speeds are back to those advertised.

Slereah

I'm not gr8 at analysis

John Rennie

5:26 AM

Then one by one add back the apps you use and rerun the benckmarks each time.

That should identify what is causing the performance issue.

But, obviously this is a massive balls ache. The question is how much you care.

0celóñe7

@JohnRennie Not sure. There are rumors of new SSDs coming out

I might get a PCI SSD

Although I could just burn my money at this point

John Rennie

M.2 is PCIe

0celóñe7

the PC works fine

@JohnRennie I don't have another M.2 slot

skullpatrol

How's your vacation going? @Slereah

Slereah

5:57 AM

It reaches its end

Going back to the coalmine wednesday

0celóñe7

@ACuriousMind @BalarkaSen @Blue apparently measuring kills the cat

4

Anonymous

Is that a cat or wool ? :P

Anonymous

cute

Anonymous

Actually that cat is quite big :D I've seen only much smaller cats

Anonymous

@0celóñe7 It's just tired after completing the whole book. Let it rest ;)

0celóñe7

6:08 AM

@Blue we're a third through and really only read a half of that ;)

Anonymous

6:21 AM

Ugh, analysis involves so much manipulation. If a function $f$ is such that its derivative is continuous in $[a,b]$ and derivable in $]a,b[$. Then prove that there exists a number $c$ $(a<c<b)$ such that $f(b)=f(a)+(b-a)f'(a)+\frac{1}{2}(b-a)^2f''(c)$. This looks like Taylor's theorem

The Raiders of Las Vegas

"Herbert Federer" on @Wikipedia: "Nevertheless, the book's unique style exhibits a rare and artistic economy that still inspires admiration, respect—and exasperation."
https://en.wikipedia.org/wiki/Herbert_Federer?wprov=sfti1

Why is Einstein sleeping on a zebra? @0celóñe7

and where is The Evidence?

The Raiders of Las Vegas

7:06 AM

> ::prepares for life-long ban::

John Rennie

7:29 AM

By Dr. Seuss? Well, it has a good pedigree :-)

The Raiders of Las Vegas

7:40 AM

Dr. Seuss was married for 40 and 23 years?

rob

-2

A: Why geologist do not consider molten iron in the magma to be the source of Earth's magnetic field?

Earth was hypothesized to have an iron core solely because it was needed to explain the strong magnetism of the earth. Now that we realize that molten iron isn't magnetic, I think the composition of the center of the earth needs to be re visioned in a way that might not include iron as the cause ...

2

This post is in the review queue flagged as "not an answer." My understanding of our policy is that questions based on non-mainstream physics get closed (since they may not have any answers) but that answers based on non-mainstream physics should be voted on based on their (in)correctness, not removed. Perhaps other reviewers could take a look.

John Rennie

7:54 AM

Whether to delete questions is somewhat controversial, and reasonably so since it veers dangerously close to censorship. But if I would be embarrassed to have someone whose views I respect read an answer on our site then I will vote to delete that answer.

The Raiders of Las Vegas

Your usage of words is inspirational sometimes :-)

David Z

8:37 AM

@rob Yep, I believe that's correct

Loong

@rob BTW: I asked a related question on meta chemistry: chemistry.meta.stackexchange.com/q/3484/7951

ACuriousMind

@rob Yup. downvote it to oblivion, but don't delete it.

@JohnRennie Did you mean "answers" not "questions"?

John Rennie

@ACuriousMind ah yes, oops.

CooperCape

9:54 AM

that moment when you log into +415rep like woah

Mithrandir24601

@0celóñe7 I take back what I said last night about Baelish not being a main character...

ACuriousMind

10:12 AM

No spoilers for the current season, please

CooperCape

I'm on like season 4 I've given up with avoiding spoilers now...

CooperCape

10:41 AM

@JohnRennie (or anyone with any authority) on questions such as this one can we put comments such as "Think of Snell's Law etc." or is it just a no go.

John Rennie

@CooperCape as homework questions go that's an egregious one. The OP hasn't made even the slightest effort to think about it themself. No, don't comment.

CooperCape

Okay, sure.

John Rennie

I will sometimes try to provide helpful comments if I think the OP is genuinely interested and trying to learn, but there's no evidence from that post that the OP is anything other than lazy and dishonest.

CooperCape

that makes sense...

Rumplestillskin

Does anyone have any experience with deriving the post newtonian approximate solution to the Einstein field equations?

Mithrandir24601

10:58 AM

@ACuriousMind spoiler: It's absolutely fantastic

Balarka Sen

11:22 AM

@0celóñe7 Beautiful.

0celóñe7

1:03 PM

@Mithrandir24601 really? Last night's episode was not exciting

@ACuriousMind why no spoilers

ACuriousMind

@0celóñe7 Because I haven't watched it yet

0celóñe7

@ACuriousMind ...why?

ACuriousMind

@0celóñe7 I like to binge-watch more than the one-episode-per-week pace. Also, all ways I could watch it are either expensive or illegal, which you surely don't approve of :P

CooperCape

@ACuriousMind Apologies on that answer you deleted. Just in my mind he'd basically done the question anyway :/

The Raiders of Las Vegas

1:43 PM

What is a "Cooper Cape"? @CooperCape

CooperCape

Mario Kart Star Cup Koopa Cape

but that username was taken when I signed up for runescape like eight years ago

so...

coopercape

The Raiders of Las Vegas

thnx

CooperCape

Yeah it's a bit odd

but nevvverr taken

winwin

AccidentalFourierTransform

1:58 PM

good afternoon peeps

0celóñe7

@ACuriousMind I want to discuss S7 with @Mithrandir24601

Close your eyes

The Raiders of Las Vegas

Heya

AccidentalFourierTransform

@0celóñe7 you two get a room

The Raiders of Las Vegas

^

AccidentalFourierTransform

spoilers shall be flagged

ACuriousMind

2:01 PM

@0celóñe7 Yeah, what AFT said - if you want to discuss it, make your own room (or look at the SFF chat rooms, I wouldn't be surprised if they already had their own room for discussing GoT

The Raiders of Las Vegas

@0celóñe7 chat.stackexchange.com/rooms/63794/0celone7-and-mithrandir24601

AccidentalFourierTransform

oh you were talking about GoT? I thought you ment grey's anatomy

you can discuss GoT here if you want

ACuriousMind

@AccidentalFourierTransform You could at least have picked another series that actually had a 7th season coming up :P

0celóñe7

GA is a great show

AccidentalFourierTransform

I couldnt think of any :-P

The Raiders of Las Vegas

2:04 PM

For premed students...it's great

AccidentalFourierTransform

I actually know several premed students that love the show

so much better than house, apparently

The Raiders of Las Vegas

The textbook is a classic

0celóñe7

House is the best show ever though

House is my role model

@ACuriousMind link to such a chat?

On mobile

ACuriousMind

@0celóñe7 chat.stackexchange.com/rooms/info/39179/the-quill-and-tankard

CooperCape

The Quill and Tankard

General discussion of "A Song of Ice and Fire", (and that TV s...

I don't know how active it is

but it was on scifi SE

Sid

2:08 PM

Oh, GoT is on my list to watch soon.

ACuriousMind

Last discussiony activity in that room seems to have been around Aug 11

CooperCape

that's fair

just people linkin stuff

Sid

My only problem with such TV series is that they are too long

ACuriousMind

@CooperCape Not people - the posts there with the questions are from a bot that posts stuff tagged game-of-thrones on the movies and SFF SEs

CooperCape

oh eww I didn't look into it past the words phrase 'GoT'

The Raiders of Las Vegas

2:10 PM

A bot trap!

0celóñe7

@ACuriousMind seems to be dead

Reddit has some good threads

Anonymous

That reminds me.....the Reddit UI looks so outdated! It's time they should improve it

CooperCape

better than 4chan...

then again... it's 4chan.

Anonymous

Don't even mention 4chan...lol

The Raiders of Las Vegas

4chan :P

0celóñe7

2:13 PM

Why should 4chan be updated

It works

CooperCape

I spent a regrettable evening going through each of their /*/ sections

AccidentalFourierTransform

4chan is the blog of the hacker anonymous, right?

CooperCape

god....

0celóñe7

@ACuriousMind people are uber salty about people dying in this show

AccidentalFourierTransform

i miss natalie :-(

a couple of weeks ago I visited the cathedral where she died

0celóñe7

2:15 PM

Is that a spoiler

AccidentalFourierTransform

yiss

ACuriousMind

@0celóñe7 I can imagine

0celóñe7

@ACuriousMind without too much spoilers, they put many fan favorites in a situation where half of them will die next week

Unless plot armor.

Danu

1

Q: Dressing vs. renormalization

In the past, my understanding was always that the processes of dressing a bare quantity (such as mass or charge) and renormalizing these same properties are different things. Dressing, as far as I had come to learn, was the result of switching on interactions in a formerly free theory and obs...

AccidentalFourierTransform

@ACuriousMind do you know of any reference (aimed eg at mathematicians) that discusses feynman diagrams and the associated combinatorics? for example, how the expression $Z[j]=\mathrm e^{iS_\mathrm{int}[\frac{\delta}{\delta j}]}\mathrm e^{i\int j(x)\Delta(x-y)j(y)}$ leads to the Feynman rules?

Danu

2:16 PM

That moment when you wake up and you know you should get dressed and go to uni but you just wanna renormalize

AccidentalFourierTransform

it seems intuitively clear, but Id like to find a semi-rigorous discussion

0celóñe7

@AccidentalFourierTransform Weinberg

AccidentalFourierTransform

Weinberg is not bad, but his approach is rather non-standard

he doesnt mention my formula above anywhere

the expansion is in terms of ladder operators

Id like to find something more "path-integral" oriented

no operators, no commutators, just my formula above

Srednicki, chapter 9 is very close to what I want

but he only discusses scalar theories, and not in much depth

Anonymous

Currently I'm reading "Quantum Physics for Dummies". It's the only QM book which I could comprehend so far without getting stuck for long :P (2 chapters over XD)

AccidentalFourierTransform

would this be a reasonable question for main?

ACuriousMind

2:21 PM

@AccidentalFourierTransform Yes, but I have to find it. I'm sure it was a reference from the "Constructive Fermionic Field Theory" course I took

AccidentalFourierTransform

well if you find it let me know pls

I recall a set of lecture notes from the MIT that were nice, but I cant find them anywhere

Prathyush Poduval

@Blue Have you tried griffiths? Its quite a wonderful book, I liked it very much

AccidentalFourierTransform

the best intro to QM is the book by the nobel laureate dr Cohen-Tannoudji

0celóñe7

No, either Shankar or Hall

Anonymous

@PrathyushPoduval I did. But Griffiths is handwavy in many places. Not that the book I'm reading is not hand-wavy, but I am being able to grasp it better than Griffiths. For example in Griffiths they mention things like the Hamiltonian is Hermitian without explaining why. Many more such examples

0celóñe7

2:25 PM

Hall if you like a little spice in your QM

@PrathyushPoduval I think we concluded that @Blue didn't have the background for proper QM

Anonymous

@0celóñe7 Wouldn't suit a dummy like me =P I did try starting with Shankar. Got stuck. Left it.

Prathyush Poduval

@Blue Oh no

Thats quite high

But the mathematical intro in shankar is wonderful

Anonymous

@0celóñe7 I agree, man. I'm learning Linear Algebra so that I can start with rigorous QM soon

Prathyush Poduval

@0celóñe7 Not like I have a perfect understanding :P

AccidentalFourierTransform

the best intro to QM is to take DeWitt's "the global approach to quantum field theory" and to take the non-relativistic limit

Anonymous

2:30 PM

Balarka is teaching me btw :P

Prathyush Poduval

Ah, nice

Its always good to have a teacher. when youre learning on your own, there's always a risk you may go wrong without knowing it

ACuriousMind

@AccidentalFourierTransform I think "Renormalization: An introduction" by Salmhofer should have what you want, it was his course that I was talking about.

0celóñe7

@Blue rigorous?

You need more than linear algebra

Prathyush Poduval

@AccidentalFourierTransform So shouldn't you have a good understanding to relativity then?

AccidentalFourierTransform

lets give it a look

Prathyush Poduval

2:32 PM

for that book?

Anonymous

@0celóñe7 Do tell me

ACuriousMind

I think it were some notes from his Oberwolfach seminar I was remembering, but they seem to be gone from the Oberwolfach website and I can't figure out where I put them

@Blue If you are interested in how physicists do QM, you don't want to do rigorous QM. It involves a load of functional analysis most physicists have never heard of.

Prathyush Poduval

@Blue Look at anthony Zee, Einstien gravity in a nutshell. He goes from f=ma to the field equations with reasonable and fun hand-waving :P

Anonymous

We formally will have a QM course in our 3rd year I suppose. (As an elective)

AccidentalFourierTransform

Zee is a clown

Prathyush Poduval

2:34 PM

Only 3rd year?

@AccidentalFourierTransform Agree with that, his books are quite funny

ACuriousMind

@AccidentalFourierTransform Most educational clown in the business, though

AccidentalFourierTransform

I meant clown in a pejorative sense

Anonymous

@PrathyushPoduval We are having a basic QM class in our 1 st sem which deals only the parts required for solid state...but I'm turned off by the hand-waviness in the course :P

ACuriousMind

@AccidentalFourierTransform In that case: Please be nice also to people who are not present here.

Prathyush Poduval

@Blue Ah okay. Most of the colleges have basic Qmech in the 1st or 2nd year

AccidentalFourierTransform

2:36 PM

my sincere apologies mr @Zee

Anonymous

We started with Schrodinger's equation directly. lol

Prathyush Poduval

@Blue Yeah, there should atleast be some inspiration for it

ACuriousMind

@Blue Ahahahaha...Some parts of solid state physics are basically QFT, so "required for solid state" is certainly not what you're learning :P

0celóñe7

@AccidentalFourierTransform Zee's gravity book is perhaps the best in the business

Prathyush Poduval

@Blue wtf thats too much. They should do it like Allan Adams, the way he "derives" the wave equation is awesome

AccidentalFourierTransform

2:37 PM

@0celóñe7 sad business it is, then

ACuriousMind

Since the Schrödinger equation is a postulate anyway, there's nothing wrong with starting with it.

AccidentalFourierTransform

and there is a lot wrong with not stating with it

ACuriousMind

One should start with the other postulates - states are rays in Hilbert space, Born rule, etc. - before that, though :P

AccidentalFourierTransform

de Broglie was a clown too

Prathyush Poduval

@ACuriousMind But one should have some intuition as to how the postulate is arrived at

Anonymous

2:38 PM

@ACuriousMind I don't know what that means. But anyway, you can have a look at the book "Semiconductor Physics" by Neamen and Biswas. We are following exactly that (It has a few chapters on QM)

AccidentalFourierTransform

@PrathyushPoduval no, one should not

intuition is the most useless thing you can have

fools gold

Prathyush Poduval

@AccidentalFourierTransform Blasphemy!!

dmckee

Arrggghhhh!

The problem with

Anonymous

@PrathyushPoduval I liked Allan Adam's lectures. Hope to continue with it. I saw the first few

dmckee

4

Q: Using a diffraction grating to view the sun

As part of the eclipse 2017 festivities, I plan on constructing a home made pinhole camera. Is there a good technique to incorporate a diffraction grating in order to look at the Sun's spectrum during the eclipse in this kind of setup? Assume that I'm already going to have the materials to setu...

astronomy diffraction home-experiment

Prathyush Poduval

2:39 PM

@Blue Yeah do continue

dmckee

has nothing to do with engineering! It has everything to do with being a open-ended "give me a list of ideas" shot in the dark!

ACuriousMind

@PrathyushPoduval I disagree. Or at least, I think it's vastly overrated and leads many people to believe that the SE can be "derived" or is "intuitive", when it really is an axiom of quantum mechanics. It's like pretending one can derive Newton's laws.

Prathyush Poduval

@ACuriousMind But then how did schroodinger and the others arrive with that postulate?

AccidentalFourierTransform

sheer luck

ACuriousMind

@PrathyushPoduval The question of how it was historically arrived at is distinct from how things should be taught.

Prathyush Poduval

2:40 PM

Its not like they woke up some day and decided to make it a postulate

@ACuriousMind How was it historically arrived at?

dmckee

@ACuriousMind You can, of course, motivate it from the Hamiltonian of a particle and hand waving on Planck and de Broglie.

ACuriousMind

@PrathyushPoduval Historically? I'm not sure. I imagine Schrödinger looked at the double-slit and tried to write down some "wavy" equation that matched it

Prathyush Poduval

:39405994 Shouldn't it be flagged?

ACuriousMind

And I don't care precisely because I think knowing the old and confusing ways quantum mechanics was done contributes little to actually understanding the modern formalism

dmckee

^ That.

0celóñe7

2:44 PM

On the flip side, I think @ACuriousMind 's attitude is ok for someone who's been doing it for years, but is a bewildering thought to beginners

Prathyush Poduval

@ACuriousMind I do agree with that

dmckee

There are an increasing number of introductory QM books that don't start with the historical development of a lot of ad hoceries and instead just present the real theory in a series of less confined boxes.

@0celóñe7 I disagree from classroom observation.

0celóñe7

Newton's equation can be checked somewhat easily for lots of circumstances

ACuriousMind

@0celóñe7 The list of postulates - with little in the way of motivation except a bit of double-slit - was precisely how my first formal QM course went when I was a "beginner"

dmckee

Starting with the ad hoc stuff developed between 1905 and 1925 generates confusion. Starting with the pure theory lets you learn that theory without a lot of half-baked ideas getting in the way.

0celóñe7

2:46 PM

I like the way that Sakurai does it. The Hamiltonian is the infinitesimal generator of time translations, then get the equation from that.

ACuriousMind

And I liked it a lot better than the handwavy deBroglie wavelength/wave-particle duality/uncertainty principle stuff that had been done before when we needed to invoke QM without actually having learned the formalism

0celóñe7

That seems much more reasonable than randomly throwing down the Schroedinger equation.

At least there you start with a principle and derive the equation.

Putting the equation down as a principle is cheating.

Anonymous

Personally I'd hate it if somebody told me: SE is a postulate. Learn it and solve questions using it. XD

0celóñe7

@Blue Exactly, but that is what people do

ACuriousMind

@0celóñe7 Yes, I completely agree.

0celóñe7

2:47 PM

In GR, we spend lots of time motivating the equations

Lots of time discussing why they shouldn't be anything else, in fact

Prathyush Poduval

@ACuriousMind @Blue en.wikipedia.org/wiki/… has the reasoning made by schrodinger, and i think it would only help the learner if they were told this(It certainly did help me)

0celóñe7

@ACuriousMind Does this look right to you? The paper said it follows from a "standard covering argument" and I thought that meant Vitali/Besicovitch. I just covered with balls and it works, I think.

ACuriousMind

@Blue That's...not exactly what I'm proposing. I'm not saying we should postulate the SE so that the students can go solve stupid exercises with it. But I am saying that it is a postulate of the theory (or equivalent to one, like the postulate that the Hamiltonian generates time-evolution that 0celo7 is talking about), and that we should not pretend that it can be "derived" from anything.

Prathyush Poduval

Its much better remembering it as "something vaguely related to conservation of energy but not it" than "some random wave equation made up by schroodinger"

ACuriousMind

Well, if you know both classical Hamiltonian mechanics and the concept of generators, then the easiest mnemonic is that the Hamiltonian generates time-translation. That gives you both the classical Hamilton's equations and the Schrödinger equation if you apply what it means to "generate" time translation in the respective formalisms.

Anonymous

2:51 PM

@ACuriousMind That's reasonable. Similar to saying that Newton's laws are not derived from anything (but found as a result of experiments/observations).

Prathyush Poduval

Anyways, I got to go for dinner. It was nice discussing with all of you.

0celóñe7

@Blue Actually I saw an old paper by Laplace that tried to derive Newton's equations

ACuriousMind

@0celóñe7 I have no idea what "Vitali/Besicovitch" is, but it looks fine to me.

Anonymous

Laplace came a lot after Newton I guess :P Well, it's possible. For example: I don't even know why charges are attracted or repelled. I heard advanced QFT proves it mathematically or something like that

ACuriousMind

@Blue Yes, QFT can derive the sign of the force - that it can be both attractive and repusive depending on the sign of the charge - from the postulate that EM comes from a vector potential (rather than a scalar or 2-tensor).

0celóñe7

2:56 PM

@ACuriousMind Vitali states that if $\mathcal B=\{B(x,r)\}$ is a collection of closed balls in a metric space $X$, and $\sup r<\infty$, then there is a countable collection of disjoint balls $\{B(x_i,r_i)\}$ such that $$\bigcup \mathcal B\subset \bigcup_{i\ge 1}B(x_i,5r_i)$$

In short: Cover something by balls, then you can take a countable disjoint subset and increase the radii by 5 to get another cover.

Anonymous

@ACuriousMind One thing: Isn't QFT also based on some "assumptions" which are thought of as "inherent" properties of nature? I don't think anything in Physics can be proven without taking some "assumptions" .

ACuriousMind

@Blue Sure

Anonymous

That makes sense :P

0celóñe7

ah, here is his wonderful proof

The Quill and Tankard

Transcript for