Congratulations to Dr. Nosiphiwo Zwane!

Congratulations to Dr. Nosiphiwo Zwane on successfully defending her PhD thesis, entitled:

“Cosmological Tests of Causal Set Phenomenology”

Here is a picture of Nosiphiwo (right) with her two supervisors, me and Rafael Sorkin …


… and a close-up of the cake we’re holding, featuring a colorful causal set, with Nosiphiwo’s work on causal set predictions for dark energy history featured in the middle.  Hopefully, I will write about it later here, but in summary, it is an amazing result that shows dark energy might have been stochastic but fluctuating (i.e. everpresent) throughout cosmic history, and this is consistent with all the cosmological observations.

We wish Nosiphiwo all the best in her grand new adventures!


Congratulations to Dr. Yasaman Yazdi!


Congratulations to Dr. Yasaman Yazdi on successfully defending her thesis, entitled: “Entanglement Entropy of Scalar Fields in Causal Set Theory”

Featured above is the most photogenic celebratory cake that you’ll ever see, featuring Yasman’s seminal recovery of entropy “area” law for 2D causal sets, as well as a tale of our foray into firewall territory with high energy neutrinos!


Featured above, from left to right are: Don Page (Yasaman’s future postdoc advisor at Univ. of Alberta), Steve Carlip (External Examiner at Yasaman’s PhD defence), Yasman herself, myself and Rafael Sorkin (Yasman’s PhD co-supervisors), and Bill Unruh (Yasaman’s former undergraduate supervisor at Univ. of British Columbia).

To find out more about Yasaman’s impressive body of work during her PhD and MSc, ranging from Astrophysical Accretion to Entanglement Entropy and Causal Sets, check out her papers on arXiv.

Reflections on Spacetime

Last week, I attended the conference “Cosmology and the Future of Spacetime”. It brought together physicists and philosophers to discuss foundational theoretical and observational issues about emergence of spacetime and cosmology.  I talked about my  Reflections on Spacetime (find slides here), with a prelude on the continuous spectrum between Science and Religion, and how we can make Quantum Gravity more scientific.


I was pleasantly surprised to see  interpreted my talk as work of art:

Now, a video of my talk is also available below:

Life of a Lover (Rumi)

گر جان عاشق دم زند آتش در این عالم زند        وین عالم بی‌اصل را چون ذره‌ها برهم زند

بشکافد آن دم آسمان نی کون ماند نی مکان         شوری درافتد در جهان، وین سور بر ماتم زند

خورشید افتد در کمی از نور جان آدمی            کم پرس از نامحرمان آن جا که محرم کم زن

نی درد ماند نی دوا نی خصم ماند نی گوا           نی نای ماند نی نوا نی چنگ زیر و بم زند

حق آتشی افروخته تا هر چه ناحق سوخته         آتش بسوزد قلب را بر قلب آن عالم زند

Fire showers down, if Love ever speaks … Burning the ruthless Fate, razing all the peaks!
The Sky will burst, Eviscerate time and space …  A passion fills the world, Joy over the death.
The Sun will fall short, as the inner light glows … The uninitiated can’t know, where the love flows.
No pains or cures, No friends or foes … Only the murmurs of the harp as the flute blows.
Lord made this fire to burn the unjust … It burns through the heart, The world into the dust.

Our universe out of a hologram: Big Bang without a story

Universe out of a Hologram!

Here is a new story, with a novel twist on an old story: Let’s throw out the story!

And that’s my take on Holographic Cosmology, first developed by Paul McFadden and Kostas Skenderis, as a way to understand big bang. In short we can use the properties of a quantum field theory in 3 dimensions (without time),  to understand the outcome of our 3+1 dimensional big bang.

What’s new is that, working with my PhD student Beth and other collaborators, we find observational evidence for a holographic description of our Universe by analyzing the cosmic microwave background, the afterglow of the big bag. The origin of structures in the universe is one of the deepest mysteries in modern physics, and at the heart of empirical efforts to understand the big bang. It is often believed that quantum fluctuations during an early period of accelerated expansion, or cosmic inflation, have seeded these structures but the physics and origins of inflation have remained illusive. Modern advances in quantum gravity have provided strong support for a holographic conjecture, which suggests gravitational physics within a volume contains the same information as a quantum field theory on its boundary. We apply this powerful conjecture to the early universe, rewriting the observable implications of a 4-dimensional big bang, in terms of a 3-dimensional quantum field theory. Surprisingly, we discovered that some of the simplest field theories in 3 dimensions can successfully explain (nearly) all cosmological observations of the early universe. New techniques are necessary to understand the correlations in the cosmic microwave background on angles larger than 10 degrees, which is where tantalizing hints for new physics have been seen over the past 20 years.

Read our paper on Physical Review Letters or arXiv.

Or some press coverage, with seemingly contradictory statements (!):

Can you hear the echoes from the abyss? If not, come to my talk!

Image Credit: NASA/Ames Research Center/C. Henze

Recently, with Jahed Abedi and Hannah Dykaar, we found gravitational wave signatures for quantum gravity effects near black hole horizons. If you’d like to hear more about this, and you’re in Waterloo, come to my seminar tomorrow:


Our original paper can be found here, with additional press coverage (in various languages):

In a second paper, which just appeared on arXiv, we clarify some of the misunderstandings about our finding.

Delayed echoes from Planck-scale structure near black hole horizons predict a peak at x=1 in this plot. As can be seen, analysis of LIGO gravitational wave data indeed shows such a peak with >99% confidence level (from arXiv:1701.03485)

He will be eternally lost in his hopeless oblivion!


Today, a friend on facebook was asking for a translation of the famous Persian poem by Ibn Yamin:

آن کس که بداند و بداند که بداند
اسب خرد از گنبد گردون بجهاند
آن کس که بداند و نداند که بداند
آگاه نمایید که بس خفته نماند
آن کس که نداند و بداند که نداند
لنگان خرک خویش به منزل برساند
آن کس که نداند و نداند که نداند
در جهل مرکب ابدالدهر بماند
It turns out that back in Sep. 2011, my colleague Kris Sigurdson wanted to use this in one of his talks. He had found it originally on the “There are known knowns” entry on wikipedia, which reflects on Donald Rumsfeld’s words of wisdom. Back in 2011, the page quoted Ib Yamin’s poem as an older version  of a similar philosophy, but provided a very poor English translation. So, I gave Kris a much better translation (in my opinion), and updated the wikipedia entry:
One who knows and knows that he knows…
His horse of wisdom will reach the skies.
One who knows, but doesn’t know that he knows…
He is fast asleep, so you should wake him up!
One who doesn’t know, but knows that he doesn’t know…
His limping mule will eventually get him home.
One who doesn’t know and doesn’t know that he doesn’t know…
He will be eternally lost in his hopeless oblivion! 
However, when I checked today, the wikipedia page had lost all the reference to the poem. In fact, Ibn Yamin doesn’t even have any English wikipedia entry. However, my translation had lived on, with more than 1300 hits on Google as of now, which use it verbatim, either with no reference, or citing the now non-existent wikipedia page.
That’s why I decided to write this and set the record straight, so that the next time you wanted a more eloquent and original version of Rumsfeld’s wisdom, you know where to find it.

Battle for the heart of democracy: The case for Bernie Sanders


There is a battle brewing less than a hundred miles from where I’m sitting right now. On the face of it, it’s just a political campaign the likes of which happen every four years in the US, and frequently across the world. But on closer examination, I argue, it is something much more significant and unique. It is a battle for the heart and soul of democracy; do people have a right or desire for self-determination, or do they ultimately opt to give up that right, and be subjects to the elite ruling class, to the rich and powerful, to the Oligarchy?

But let’s start with a naive question: How are the liberal democracies of the 21st century different from the dynasties that have governed our civilizations for millennia?

There are, of course, the civil rights and liberties of the citizenry, but they have existed in some shape or form, albeit imperfectly, in various authoritarian governments of the past. Rather, the most characteristic trait of a democracy must be the people’s right to self-determination through the ballot box, either directly or via their elected representatives.

In a dynasty, a family is entrusted with ensuring the good of a country. The children are groomed from an early age to be effective leaders, and then are trusted to maintain a happy and prosperous nation. In contrast, in a liberal democracy, citizens can freely elect the representatives who most closely represent their interests, and keep them in power, or kick them out, depending on their performance.

Or can they?!  In fact, is there any reason to believe that the authoritarian systems that have evolved and perfected within our societies over millennia would suddenly and spontaneously change in any fundamental way? Could it be that, instead of citizens picking their leaders in a democracy, the ruling class “manufactures our consent” through money and media, with the ultimate goal of keeping themselves in power?  

If this vision is too dystopian for your taste, you may feel comfort in the fact that the answer to this question is not written yet. People of New York are to decide in a few days whether they prefer a decades-old dynasty, entangled and paid for by the world’s biggest banks and corporations, to rule them. Or may they opt for the much more radical alternative, to elect someone who represents the people not the billionaires, the big money, and the political establishment?  

Bernie Sanders 2016 logo

So, this is the gist of why I support Senator Bernie Sanders’ bid for the presidency of the United States, against Secretary Hillary Clinton. It is because he has always supported the rights of ordinary people across the world, from the US to Central America, Iran, Iraq, or Palestine, over dogma and ambitions of the ruling elite, moneyed influence, and political expediency. It is because I think the most powerful military in the world can only be entrusted with someone who believes the state “should not be in the business of killing people“, in the US or anywhere else.  It is because he appreciates that bringing back the power from the top 1% to the people, via universal healthcare, free public education, and a healthy campaign finance system, while uncharted territory, is worth fighting for and the true cost of a democracy. It is because his proudest foreign policy accomplishment IS NOT putting in place brutal sanctions on poor people of a 3rd world country.

So, there are still a few days left to save the biggest democracy on this side of the world. But that all depends on who wins the Battle of New York 🙂



Critical geometry of a thermal big bang (and how it exactly matches CMB with no fine-tuning)


Here is something bizarre that Joao Magueijo and I have discovered. You can have a purely thermal big bang, all the way through,  and reproduce the exact same deviation from scale-invariant primordial power spectrum, as observed in CMB data, without ANY fine-tuning or free parameters! This is more predictive (and falsifiable) than ANY inflationary (or non-inflationary) theory of early universe.

What’s the catch? The acoustic speed in the primordial plasma should suddenly diverge (i.e. become much faster than speed of light) at 4 orders of magnitude below Planck temperature. This is what my student and I had called Thermal Tachyacoustic Cosmology (TTC) before. What’s new is that there is a unique critical version of this model, with a geometric interpretation involving a membrane moving in a very special geometry (with two times 😜). Amazingly, it has a very sharp prediction for deviation from scale-invariance (n=0.9648) which matches CMB observations (n=0.9667 +/- 0.0040) to 3 significant digits!

So, there you have it! The most predictive theory of early universe, but it costs you a new time dimension 😀