## Profile

Sean Carroll
Works at Caltech
Attended Harvard University
Lives in Los Angeles
66,373 followers|2,872,052 views

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### Sean Carroll

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Check out physicist Bob Scherrer's new blog -- Cosmic Yarns: Exploring the Science in Science Fiction.
http://www.cosmicyarns.com/﻿
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I initially misread the title as cosmic yams.﻿

### Sean Carroll

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Very pleased to learn that I've been awarded a Guggenheim Fellowship. Here's my "career narrative."
http://www.preposterousuniverse.com/blog/2015/04/09/a-personal-narrative/﻿
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congrats!!!﻿

### Sean Carroll

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Billie Holiday’s name has been in the news lately for some reasons that remind us of the tragedies she sang about and those she endured.
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Love you, Billie!﻿

### Sean Carroll

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"Time" is the most-used noun in the English Language. Does it denote something real and central?
http://www.preposterousuniverse.com/blog/2015/04/03/the-reality-of-time/﻿
The idea that time isn't “real” is an ancient one — if we're allowed to refer to things as “ancient” under the supposition that time isn't real. You will recall the humorous debate we had at our Setting Time Aright conference a few years ago, in which Julian Barbour (the world's most famous ...
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Another notion of time...

Time is a concept predicated on the idea for the potential of change. The moment there is no potential for change is the moment there is no time.

I am claiming this as a universal, since, if we could observe a universe from our universe which had completely stopped, I would still claim time as "present", since, there is a universe that hasn't "stopped". ﻿

### Sean Carroll

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Ah, those kooky kids and their April Fool's physics papers.
http://arxiv.org/abs/1504.00108﻿
Abstract: Some of the most obviously correct physical theories - namely string theory and the multiverse - make no testable predictions, leading many to question whether we should accept something as scientific even if it makes no testable predictions and hence is not refutable.
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That was a fun read...I like what they did with the Sean, not Lewis citation haha﻿

### Sean Carroll

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The classical limit of quantum mechanics should yield probability distributions, not individual trajectories.
[latexpage] One of the great crimes against humanity occurs each year in introductory quantum mechanics courses when students are introduced to an $\hbar \to 0$ limit, sometimes decorated with word...
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The classical "trajectory" is simply the mean of the distribution. No big deal.﻿
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### Sean Carroll

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How quantum field theory allows us to distinguish between the known knowns and the known unknowns.
http://www.preposterousuniverse.com/blog/2015/04/21/quantum-field-theory-and-the-limits-of-knowledge/﻿
Last week I had the pleasure of giving a seminar to the philosophy department at the University of North Carolina. Ordinarily I would have talked about the only really philosophical work I've done recently (or arguably ever), deriving the Born Rule in the Everett approach to quantum mechanics.
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black holes might sound dark, but have nothing to do with dark matter. Dark matter and even more, dark energy, are kind of scattered everywhere in the universe.﻿

### Sean Carroll

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Virtually Speaking Science tonight:@JenLucPiquant talks with @ShaunMaguire about quantum information & emergence.
Tensor networks, quantum information, emergent space-time, black hole firewallsJ ennifer talks with Shaun Maguire, a mathematical physicist with expertise in control theory, statistics and quantum computing. PhD student working in quantum information at Caltech. Founding member of Escape Dynamics
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### Sean Carroll

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Jonah Nolan and Kip Thorne relaunch Interstellar at the Jet Propulsion Laboratory. We were there...
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Can I ask why all the talk about this movie right now? Press releases? Marketing? Screen to disc and streaming transition? You have stock in this venture? A financial iron in this fire?﻿

### Sean Carroll

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Why it's hard (impossible?) to get a positive cosmological constant in heterotic string theory.
http://arxiv.org/abs/1504.00056﻿
Abstract: We argue that the heterotic string does not have classical vacua corresponding to de Sitter space-times of dimension four or higher. The same conclusion applies to type II vacua in the absence of RR fluxes. Our argument extends prior supergravity no-go results to regimes of high ...
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The paper at _"In the case of the heterotic string, we are not aware of any simple background that requires a mixing of ghost and matter sectors. It would be very interesting to find other ways to
evade our constraint."_ challenges me to reveal the wonderful French Pun that the heterotic string inspired to me scores of years ago.

314159
BIAISq

Which in such nutshell is overly terse... but features in parallel D=10 vs D=26, allusion to the idea that sex sells (the why not of erotic in heterotic) because q reads in French as cul - butt, slang for both sex and luck. The local π rotation along the length of the string to swap distinct left- and right- moving components, that's figured by the decimals of π. BIAIS means bias, but also means to an end. Arabic digits are mapped to latin capital for the purpose of facilitating left-to-right reading off as latin capital glyphs, what are really intended as glyphs of digits, while electing ingredients of the mapping by examining digits in natural order 0123456789... what obviously fixes OIRBASG before any need for tweaking the next choice.﻿

### Sean Carroll

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I use Github for science collaborations. China is trying to take it down, afraid of anti-censorship projects.
http://www.vox.com/2015/3/30/8315281/github-chinese-ddos-attacks﻿
The attacks are designed to pressure the popular programming website Github to take down content censored by the Chinese government.
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Chinese don't deserve Open source.﻿

### Sean Carroll

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Angelina Jolie Pitt on her cancer-prevention surgeries: "this is a part of life."
http://www.3quarksdaily.com/3quarksdaily/2015/03/diary-of-a-surgery.html﻿
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We live in an age of beating the quantum possibility theory﻿
People
In his circles
405 people
Have him in circles
66,373 people
Work
Occupation
Scientist
Employment
• Caltech
Scientist, present
Places
Currently
Los Angeles
Contact Information
Work
 Email carroll@cosmicvariance.comseancarroll@gmail.com
Story
Tagline
Physicist at Caltech. Master of time and space.
Introduction
I think about things that are smaller than atoms and/or bigger than galaxies.  Everything in between scares me.

Links on right will lead you to awesome things to read and think about.

Disclaimer: my opinions are the ones everyone should have.
Bragging rights
Married to +Jennifer Ouellette.
Education
• Harvard University
Astronomy (PhD), 1988 - 1993
• Villanova University
Astronomy (BA), 1984 - 1988
• Pennsbury High School
1980 - 1984
Basic Information
Gender
Male