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Category: Research

EVONET18 – Tensor Networks for One and All

EVONET18 – Tensor Networks for One and All

So one month ago there was this wonderful workshop on “Optimising, Renormalising, Evolving and Quantising Tensor Networks” – or EVONET18 – organized by the Max Planck Institute for Complex Systems (MPIPKS) in Dresden, Germany. I was fortunate enough to be selected for a poster presentation and had the great privilege of mingling and discussing physics with some great minds such as Javier Molina-Vilaplana, Shinsei Ryu, Thorsten Wahl, Andrew Green, Zohar Ringel, Andrej Gendiar and some very talented graduate students including…

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Theoretical Physicists in India

Theoretical Physicists in India

There are many research centers and researchers in India working in hep-th (High Energy Physics, Theory), gr-qc (General Relativity/Quantum Cosmology) and quant-ph (Quantum Physics). However they are scattered all over the place and I have not been able to find a place which lists the names of places and individuals working in these fields in India. So, I figured, why not make a list! Here is my attempt at making one. It is, hopefully, a continuing work to be expanded…

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Fluctuation Dissipation in Quantum Gravity

Fluctuation Dissipation in Quantum Gravity

In statistical mechanics we are mostly concerned with the statistical averages of various physical quantities when the system is in equilibrium. Fluctuation is a common phenomenon in nature. Fluctuation means how much a quantity deviates from its average value. The average value of the thermodynamic observables and the size of their fluctuation about their equilibrium values can be predicted by equilibrium statistical mechanics.

Spacetime Geometry as Information Geometry

Spacetime Geometry as Information Geometry

In an entry to the 2013 FQXi essay contest and in an accompanying paper, Jonathan Heckman, a postdoc at Harvard, put forward a scintillating new idea – that one can derive the theory of strings and of gravity starting from nothing more but a Bayesian statistical inference model in which a collective of $N$ agents (representing by points on a $d$-dimensional grid) sample a probability distribution in order to obtain the best fits to a set of parameters $\{y_1,\ldots,y_M\}$. In…

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Multiverse, multiverse, where art thou?

Multiverse, multiverse, where art thou?

As I understand it, the multiverse concept arises as a consequence of the standard inflationary scenario which involves one or more scalar fields “rolling down” the side of a potential hill, causing an exponential increase in the “size” of the Universe soon after the Big Bang. Now the form of the potential itself varies from place to place. Though what “place to place” means, when you are talking about the time when the geometric exoskeleton of the Universe is still…

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The Measurement Problem, Part 1

The Measurement Problem, Part 1

The Problem The measurement problem becomes a problem only when we neglect to specify the nature of the observer’s Hilbert space. Postulates I (Systems are described by vectors in a Hilbert space) and II (Time evolution occurs via some given Hamiltonian for a particular system) are fine in that regard. These two postulates deal only with the description of a quantum system. It is the third postulate (Measurement leads to collapse of state vector to an eigenstate) where there is…

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Thermal Time and Kepler’s Second Law

Thermal Time and Kepler’s Second Law

In a fascinating recent paper (arXiv:1302.0724), Haggard and Rovelli (HR) discuss the relationship between the concept of thermal time, the Tolman-Ehrenfest effect and the rate of dynamical evolution of a system – i.e., the number of distinguishable (orthogonal) states a given system transitions through in each unit of time. The last of these is also the subject of the Margolus-Levitin theorem (arXiv:quant-ph/9710043v2) according to which the rate of dynamical evolution of a macroscopic system with fixed average energy (E), has…

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Some things … cannot be learned quickly

Some things … cannot be learned quickly

There are some things which cannot be learned quickly, and time, which is all we have, must be paid heavily for their acquiring. They are the very simplest things, and because it takes a man’s life to know them the little new that each man gets from life is very costly and the only heritage he has to leave. – Ernest Hemingway (From A. E. Hotchner, Papa Hemingway, Random House, NY, 1966)

Elementary particles and quantum geometry

Elementary particles and quantum geometry

Black holes are formed due to the gravitational collapse of matter – ordinary matter, consisting of the particles and excitations of the Standard Model that we know and love. These include electrons, photons, neutrinos, quarks, mesons etc, and their respective anti-particles. General Relativity tells us that the properties of (macroscopic) black holes are universal, in that they do not depend on the precise fraction of each particle species in the initial “mixture”. A black hole formed from the collapse of…

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… and so it begins

… and so it begins

Welcome to my blog, gentle readers. Here you will be exposed to all manner of speculation and conjecture on my part. Those with an enhanced sensitivity to non-rigorous reasoning might occasionally experience a feeling akin to motion sickness. I urge such rigor-bound passengers to depart at the earliest exit. To the rest, welcome aboard. Happy trails!