The h Bar - 2017-08-05 (page 1 of 5)

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12:00 AM

8 qbits is a big deal but dont see much in cyberspace on it via google...

Mithrandir24601

To clarify, I think the 8 qubit one is universal, but may suffer from the same problems as e.g. IBM when it comes to operations between arbitrary qubits - possible, but requiring the use of other qubits, which I believe the 3 qubit one wouldn't have

Here's the proof-of-concept: arxiv.org/pdf/1611.03511

@vzn and yes. Yes I have :)

12:35 AM

@Mithrandir24601 yeah saw that here, nice cio.com.au/article/599964/… can it be said to have some # of qubits? have noticed for yrs australia seems to be very strong in QC... natl govt priority...

@vzn I won't be happy until we live in absolute anarchy.

Hmm...libgen appears to be down

this is not good

3 hours later…

Anonymous

3:37 AM

@0celóñe7 It's not down!

Anonymous

Use .pw extension

@Blue what

Anonymous

@0celóñe7 libgen.pw

huh

thx

3:54 AM

@0celóñe7 lol so maybe mad max is your favorite movie? what is your fave movie anyway? you do watch movies right? ps you know how mel gibson turned out right? think about that a little sometime :P o_O

4:49 AM

@vzn mad max was good

my favorite movie is Shawshank

@JohnRennie Good morning/evening.

Hi :-)

@0celóñe7 lol think about the burn victim in mad max. now theres a nice metaphor for anarchy... o_O

I don't remember the burn victim

@JohnRennie Why is Windows crazy?

user image

Chrome thinks it's on Windows 7

Weird. Is it just Chrome displays the Win7 type title bar?

@JohnRennie Yeah, and just one instance of Chrome too

I have double Chrome for high efficiency

5:02 AM

Chrome draws its own title bar i.e. though it may look like a standard Windows title bar Chrome actually draws the bar itself and just makes it look standard.

So something in that window must have persuaded Chrome to draw the old style bar.

@0celóñe7 lol he was all wrapped up in bandages in a hospital bed dying and his cohorts swore to avenge him. selective memory? you forgot that part? for me its the most memorable. havent seen the movie in close to 3 decades, only watched snippets of it on tv, couldnt watch the whole thing, found it nearly unwatchable. if you liked mad max, try apocalypto! now theres a wild movie... o_O

@vzn I didn't watch the old one

I'm talking about the new one

@JohnRennie it's a conspiracy

@0celóñe7 ah the 1st is a (timeless?) classic. yeah latest one is quite a spectacle, havent seen it, read about it, its too dystopian for me. almost beyond dystopian. hellish!

@0celóñe7 I'm wondering if there's a setting somewhere in chrome://flags/

Gautham Shankar

@JohnRennie Will a magnet deflect if kept under electric supply lines ??

5:08 AM

frames-per-second.appspot.com

@JohnRennie ^ very useful

@0celóñe7 for testin your new GSYNC monitor :-)

Why did you bold that

@GauthamShankar Hi Gautham

@JohnRennie Yes, it is actually useful for testing if 120 fps is a placebo or not.

I can definitely tell the difference.

@0celóñe7 just to make sure the world knows you have a new gsync monitor :-)

I think there are two separate questions there:
(a) does a magnet deflect in a magnetic field
(b) do power lines generate a magnetic field

5:10 AM

@JohnRennie Well, sure, but I thought you might be interested to see what 30 fps vs. 60 fps looks like.

Gautham Shankar

@JohnRennie I have doubts on the (b ) question.

@0celóñe7 It's interesting to compare the two balls at the same fps, one with motion blur off and one with motion blur on

At 60 fps I struggle to see a difference, but at 30 fps the difference is obvious.

@0celóñe7 your favorite line is back, I guess

@GauthamShankar I don't know if electricity transmission lines have a magnetic field. Obviously a current in a wire produces a magnetic field, but transmission lines are a lot more complicated than simply a current in wire.

@0celóñe7 This is the only related flag I could see

user image

@JohnRennie wait, how did you reply without an automatic ping being shown?

5:19 AM

@Sid I used shift-enter to split the post onto several lines. If you do that it hides the (at)username for some reason.

@Sid what?

@JohnRennie I certainly didn't do that

should I do a virus scan?

@GauthamShankar have a look at this. The article explains how to calculate the magnetic fields generated by transmission lines.

@0celóñe7 no, it's just Chrome being freaky.

No virus I've ever seen restricts itself to changing Chrome title bars

9 mins ago, by Gautham Shankar

@JohnRennie I have doubts on the (b ) question.

Have you got any Chrome add-ons? Maybe one of those is responsible.

Just ad block pro

maybe I should benchmark my SSD just to make sure...

5:22 AM

You have a serious case of computer paranoia :-)

Gautham Shankar

@JohnRennie Thank :) Also , I should probably test it real time.

@GauthamShankar you'll need a magnetometer, though you could probably build one with a little effort ...

There are no transmission lines near my house otherwise I might be tempted to try it myself.

Gautham Shankar

@JohnRennie Wouldn't an ordinary compass work?

@GauthamShankar That would tell there was a magnetic field present, but it's not quantitative. And the needle would be stable under the line so you'd need to measure the change as you walked towards and away from the line.

It would be more interesting to make a proper magnetometer.

@JohnRennie ::pours bourbon:: It's not paranoia if it's true

Gautham Shankar

5:28 AM

@JohnRennie OK !

@0celóñe7 Just because you're paranoid it doesn't mean they aren't out to get you!

@JohnRennie Score is up from yesterday

The little guy seems to be doing somewhat better

@0celóñe7 they'll find your emaciated corpse slumped over the keyboard running just one last benchmark :-)

Gautham Shankar

Hi all! I thought i would introduce myself being a newcomer to the chatbox. I am Gautham , a high school student from India and a future physicist ( maybe!) :)

@JohnRennie Hey, I actually managed to enjoy a game at 144 fps

5:32 AM

Allegedly the new Doom will play at up to 200fps on top end hardware

Though where you can find a 200 fps display I don't know ...

@JohnRennie The game I am currently playing goes at 230, but I capped my system to 144 so I'm not creating extra heat.

It's an old-ish game

What game?

Metro 2033 Redux

user image

@GauthamShankar senior in high school?

It's not amazingly optimized, it's doing strange things with my GPU's boost

5:34 AM

Based on the Dmitry Glukhovsky book?

@JohnRennie yeah

It's a good game

Smooth as butter at 144 fps

Gautham Shankar

@Sid Yup.

Ah, that's been on my reading list for ages

@JohnRennie It's one of the few games that are optimized for > 60 fps

Apparently lots of games are not, so the main utility of Gsync is to make < 60 better

@GauthamShankar okay. Good luck. So.. you want to be ~~like JR~~ a physicist. Good idea

Gautham Shankar

5:37 AM

@Sid 12th grade(17 yo) . Just to make sure , doesn't high school senior mean the same?

Same thing.

@JohnRennie I spent many hours trying to get Skyrim to run consistently at 60fps. My GPU util was like 50% and none of my cores were maxing out. The consenus seems to be that the engine is just crap.

Although some people can run it at 144Hz, not sure what is going on there

@Sid I'm a colloid scientist. I just pretend to be a physicist :-)

Metro 2033 Redux - 15 Minutes of Gameplay

@0celóñe7 sorry, I was just looking to see what the Metro 2033 gameplay was like.

@JohnRennie It's a very minimalist shooter. The emphasis is on the atmosphere and visuals.

It's always dangerous to judge your system by how well it plays any one game because, as you say, it might just be that the game is crap.

Anonymous

5:40 AM

@JohnRennie Are colloid scientists supposed to know GR ? =P

@JohnRennie Right, and I have some fundamental modifications on Skyrim.

Complete graphics overhauls, complete retextures, complete weather overhauls, etc.

@Blue I spent decades wondering exactly how GR worked, and when I finally sat down and started to learn it I found it amazingly interesting.

Anonymous

@JohnRennie Wow, you learnt it yourself?

@Blue It really isn't hard

@Blue the basic ideas are not that hard.

Anonymous

5:43 AM

@0celóñe7 Good to know. I can get started then. =P :D

@Blue it uses maths that you probably didn't get taught unless you're a theoretical physicist or a mathematician, and it is hard to get to grips with the maths when you've never seen it before. But once you get the hang of it the rest isn't that hard.

@Blue I understood significant parts of GR books for physicists in high school

I found GR for physicists much easier than QM or QFT for physicists

Anonymous

@0celóñe7 Which books did you use ?

Anonymous

I'm was doing a bit of SR few days back

Anonymous

I don't know if I know enough maths to get started with GR

5:46 AM

@Blue Zee, online lectures by Susskind

Cahill, "Physical Mathematics"

Anonymous

This semester I'll be taking Vector Calculus, Tensors, Fourier Transforms, ODE, PDE and Complex Analysis. What else do I need to get started ?

@Blue For what you want, you only need to know multivariable calculus and linear algebra

@Blue What kind of class is "tensors"

Also how are you taking 6 math classes

Anonymous

@0celóñe7 Basic tensor calculus

Anonymous

@0celóñe7 Here is the syllabus and I've decided to study Tensor calculus and ODE/PDE on my own.

Anonymous

We have linear algebra in the next semester

5:48 AM

@Blue Ok, that makes more sense.

Anonymous

So I think from next April-June I can start :)

@Blue I am conflicted in giving advice because I am a mathematical physicist

I can either give mathematics or physics advice :P

Anonymous

@0celóñe7 I'll check Zee. Susskind's lectures are not very rigorous from what I've seen. Anyway, thanks!

@Blue Rigorous in what sense?

Anonymous

@0celóñe7 Do you mean this lecture series by Susskind (theoreticalminimum.com/courses/general-relativity/2012/fall) ?

Anonymous

5:51 AM

The Theoritical Minimum series was made for general public I think

Those lectures are not for the general public.

But the amount of math used by physicists for GR (broadly speaking) is trivial.

You really shouldn't be worried if you have a very good understanding of vector calculus.

Anonymous

@0celóñe7 Ah, okhay !

Anonymous

@0celóñe7 I'll try to do so this semester. Using Schaums outline book for VC

@Blue I would encourage you to read Zee and note what parts trip you up so you can focus on them

I learned vector calculus in that way

I got Zee's book after taking calculus 1 in high school

Anonymous

blau.itp.unibe.ch/GREX/hs16.html

Anonymous

5:55 AM

Looks nice

Anonymous

I'll try!

Anonymous

@0celóñe7 BTW do you identify yourself as a nuclear engineer or a mathematician? =P

@Blue Depends on who I am talking to and about what

I will be able to give a more precise answer in two years

Anonymous

Hehe. I'm sure you don't like to be called a physicist XD :-)

@Blue GR is as much physics as it is geometric analysis

Well, maybe not

But I'm definitely not a physicist

Anonymous

6:02 AM

@0celóñe7 You'll complete your UG degree in another 2 years? Is it a 5 years course?

@Blue No

Anonymous

@0celóñe7 ?

@Blue Yes, then no

Anonymous

@0celóñe7 Okay. Then I deduce that you are in 3rd year of your UG which is a 4 years course =P

6:20 AM

@Blue yes

Anonymous

Sounds cool. I've never heard of a Nuclear Engineering+Mathematics double major (or major+minor). The only dual degrees that are available in some colleges here are 5 year courses. Actually we don't have any Nuclear Engineering UG course in any Indian university.

Undergraduate courses were only three years in my day, but they've discovered more physics since then :-)

Anonymous

@JohnRennie Undergraduate science courses are 3 years here also. Engineering courses are 4 years or 5 years (for major+minor or BTech+MTech).

Anonymous

Your UG degree was in Natural Sciences iirc :)

yrc

Anonymous

6:26 AM

:D

Though the Natural Sciences degree at Cambridge is now four years.

Anonymous

Ooo. Didn't know that

The cynic might suggest it's a way of squeezing more money out of students ...

Anonymous

I'm considering Cambridge for my MS. Getting selected seems quite tough though (esp. for international students).

Anonymous

@JohnRennie hehe...well, it's effing Cambridge! It's worth the money XD

6:29 AM

Really? I was under the impression all the major universities loved foreign students because they're so profitable.

Anonymous

I guess they do give scholarships

Anonymous

@JohnRennie The MS by research degree is supposed to be fully funded. I need to check. Not very sure

I got a scholarship but it wasn't very much. I don't remember the exact figure, but it was small.

Who gets an MS these days besides Germans?

Cambridge is a wonderful place to study. The atmosphere is fantastic and Cambridge is a beautiful city. But I'm not convinced it's that much better than any of the other good universities in the UK. I guess it has a cachet that is worth a lot.

Anonymous

6:32 AM

Anyways I am saving my money in case I need it for my graduate degree. My current university degree costs less that 160 $ for 4 years! :P However, afaik MS by research and PhD degrees are supposed to be funded by the university

Anonymous

@JohnRennie Of course it's a beautiful city :) Yeah, I'll try the others too like Imperial College London and Oxford

Funded by professors, not the university

Anonymous

@0celóñe7 Well, yeah

I think Mithrandir is, or was, at Cambridge. He'd be the one to ask what it's like now.

I do wonder about the value of a Masters if you're studying science.

For a scientist an MS on its own is pretty useless, except possibly to get you into a PhD programme somewhere else.

Anonymous

@JohnRennie I want to get into MS to actually get to know what a research career looks like and whether I want to pursue a full-fledged PhD or an MBA/economics degree. I'm interested in entrepreneurship in the areas of science and technology.

6:39 AM

The intelligent choice is to get an MBA

It is simple savagery to pursue a basic research PhD

Anonymous

Also some universities like Stanford offer dual MS+MBA. I'll try to apply to those also

@0celóñe7 It is? My PhD was the most enjoyable time of my life!

@JohnRennie Some people here also enjoy eating with their hands

Anonymous

Individual tastes man....

@0celóñe7 As non sequiturs go that's quite a non sequitur

6:42 AM

@JohnRennie I've been non sequituring the chat for years

Has anyone seen Dunkirk?

Anonymous

Me

Anonymous

Jul 30 at 17:14, by Blue

Watched Dunkirk today. The visuals were stunning. But it felt like the movie ended too fast and that too without any definite climax. :/

Should I go and watch it? Caution- I am trying hard to save money for another week at least

Curiously, that's what I think is a problem in most of the Nolan movies I have watched

shit gets real quickly, and then it all ends

think about

say interstellar

Anonymous

6:50 AM

Not worth spending your money on. But perhaps I had set the bar too high after watching Interstellar and Inception.

Anonymous

@BalarkaSen Interstellar was a movie that kept you thinking for at-least a week about the intricacies. Dunkirk was more forgettable.

Anonymous

@BalarkaSen Hehe, that's true

@Blue I didn't think Interstellar was particularly cerebral. It is visually dazzling, but I have watched too many space movies to say it's high up on my list of those

GR is trivial for @BalarkaSen

I don't mean to say it's a bad movie. It's good, just not as good as people claim

Anonymous

6:52 AM

@BalarkaSen Probably I agree

Right, this is a Physics chatroom. I have a question on Physics. (gasp)

Are you sure it's not a doubt?

Anonymous

Obviously it is a doubt

lol

Where exactly do we use Lorentz transformation?

Anonymous

6:56 AM

@Sid SR

Those are isometries of the Minkowski 4-space aren't they

@BalarkaSen time to read GMT bedtime story

@BalarkaSen Yes, but why do you have to make things complicated?

Eh, I mean, the whole thing that time is not absolute is not quite intuitive to me.

@Sid Suppose you set up a reference frame with yourself at the origin.

You have a ruler that you can use for measuring distances in the x, y and z directions, and you have a clock that you can use for meauring time.

@0celóñe7 you're particularly edgy today.

also ugh GMT

6:58 AM

@BalarkaSen what?

@Sid With me so far?

Yep.

@Sid OK, and I do the same. Now ignore relativity for now and assume Newtonian mechanics applies. Assume also that I'm moving relative to you with some speed $v$.

And we'll assume we synchronise our clocks and set both to zero at the instant we pass each other.

Actually, does the asymmetry between neutrinos and antineutrinos enough to account for all the matter antimatter asymmetry?

@JohnRennie I am stationary, right? And you are not at origin?

7:00 AM

@Sid In your frame you are stationary at the origin.

@BalarkaSen He goes into way more depth for general measure theory than I like

I should learn epsilon measure theory at some point

right now I know 0

@Sid I'm moving relative to you with some velocity v, and at the moment I passed you, i.e. at the instant we were at the same point in space, we both set our clocks to zero.

@BalarkaSen Do you have a need

Okay.

7:02 AM

@Sid you measure the coordinates of some event as (t,x,y,z). The question is what are the coordinates of that point in my reference frame?

@0celóñe7 vOv, maybe. I want to learn more analysis in general.

do you know Arnol'd ODE book by the way?

I know of it

I can't imagine it being very rigorous

excellent

i am supposed to read it

Anonymous

user image

@Sid you can calculate the position of the event in my coordinates using a Galilean transformation:

Galilean transformation

In physics, a Galilean transformation is used to transform between the coordinates of two reference frames which differ only by constant relative motion within the constructs of Newtonian physics. These transformations together with spatial rotations and translations in space and time form the inhomogeneous Galilean group (assumed throughout below). Without the translations in space and time the group is the homogeneous Galilean group. The Galilean group is the group of motions of Galilean relativity action on the four dimensions of space and time, forming the Galilean geometry. This is the passive...

7:04 AM

@JohnRennie I think it depends along which direction you passed me? Since, we are talking about 2 different reference frames in relative motion

@Sid you're free to arrange your x, y and z axes in any direction you want, so you can choose my direction of motion to be your x coordinate.

That's what we usually do so in your coordinates my velocity looks like $(v_x, 0, 0)$.

The reason we do this is we can then ignore the y and z directions and just consider t and x.

In which case, the co-ordinates of y and z will remain same

@Sid Yes

And because this is Newtonian mechanics time is absolute so our t coordinates also always agree.

@BalarkaSen Measure theory basically tells you what you already know

And your x-co-ordinates should be my x-coordinate -vt

7:08 AM

Yes, exactly.

So the transformation rules are:
t' = t
x' = x - vt
y' = y
z' = z

Yes. I am with you so far

where t', x', y' and z' are my coordinates for the event and t, x, y and z are your coordinates for the event

So though Galilean transformation sounds complicated it's actually really simple. It tells you how I see the event. With me so far?

Yep.

Good night all

A Lorentz transformation does the same thing as the Galilean transformation i.e. it tells you how I see the event.

7:11 AM

@0celóñe7 night

It's just that the rules for the transformation are different because, well, relativity!

Hmm.. But how is time relative?

Also, can we discuss this a little bit later?. Canteen closes in 15 minutes. I need to go eat

Anonymous

Food is more important than Relativity. Run =P!

OK I need to get back to work anyway

In Galilean transformations, the time in both reference frames is the same $t$. In Lorentz transformations, the time measured in different frames, is different. Some $t_1$ and some $t_2$

7:17 AM

(I didn't have breakfast in the morning either. So, a tad hungry

@Balarka youtu.be/WhPvJOnHotE

2

7:43 AM

@Avantgarde lol

this is good

8:13 AM

0

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8:37 AM

@Blue Did you try some IDEs in the meantime? Or did you decide to find and watch some intro to programming (in C) course first?

now I am realising that different compilers in programming languages mess things up badly.

All the time, I had done coding with a turbo C++ compiler. Codechef uses gcc I think.

As long as it works for you, a turbo C++ compiler is good enough.

@Sid still interested in Lorentz transformations?

Yep. Continue where we left.

OK. Go back to Newtonian mechanics again for a moment, and consider moving a small distance dx in the x direction, dy in the y direction and dz in the z direction.

8:50 AM

Okay...

So your displacement is the vector (dx, dy, dz)

It is.

And the total distance moved $ds$ is just given by Pythagoras: $$ds^2 = dx^2 + dy^2 + dz^2 $$

Okay.

This distance ds is called the norm or the magnitude of the vector (dx,dy,dz) and in Galilean transformations it is an invariant

i.e. no matter how I am moving reltive to you we will both agree on the value os $ds$.

So a Galilean transformation does not change $ds$

Make sense so far?

8:53 AM

Yes, it does.

Well this is where it's gets weird ...

Because in special relativity we have to treat displacements in 4D spacetime so we get vectors like $(dt,dx,dy,dz)$.

Hmm... okaaay..

And just like in Galilean relativity the norm of the vector is an invariant. Which makes sense because the vector shoudn't change just because I'm moving.

But ... would you like to have a guess at how we calculate the norm of the vector $(dt,dx,dy,dz)$ in relativity?

No, I am blanking. I don't think Pythagoras will help anymore.

You're quite correct that the Pythagoras' theorem doesn't work. The norm of a four vector $(dt,dx,dy,dz)$ is given by: $$ ds^2 = -c^2dt^2 + dx^2 + dy^2 + dz^2 $$

8:58 AM

what is -c^2?

You can't add time to distance because they have different units - you can't add seconds to metres.

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