Research

# Shoucheng Zhang, 1963-2018

In Memoriam I never had the good fortune of meeting or personally knowing Shoucheng Zhang. Nevertheless he has had a profound influence on my academic career. As the world learned sometime last week, Zhang passed away suddenly on December 1 “after fighting a battle with depression” 1. He was one of the world’s greatest theoretical… Continue reading Shoucheng Zhang, 1963-2018

Research

# Negative Temperatures

The thermodynamic concept of temperature is defined by the following equation: $$T = \frac{\partial E}{\partial S}$$ where $E$ is the energy of the system and $S$ is the entropy. Now usually when the energy of a system increases or decreases it’s disorder, and hence it’s entropy, also increases or… Continue reading Negative Temperatures

# Social Relevance of Quantum Gravity

Other 1 than all the other very good theoretical reasons for wanting a theory of quantum gravity, there are some very good practical reasons for wanting such a theory. Ultimately the fate of scientists, theorists and experimentalists alike, rests in the hands of the general public and its elected or appointed political representatives. Why, after… Continue reading Social Relevance of Quantum Gravity

Research

# The Planck Scale May Be Closer Than It Appears

Objects in the rearview mirror may be closer than they seem. This statutory warning is familiar to anyone who has ever ridden in a passenger vehicle. Its intent is to warn the driver and the passengers to beĀ careful while backing up in case the car collides with something which is closer than it actually seemsĀ in… Continue reading The Planck Scale May Be Closer Than It Appears

Research

# Euler’s Homogenous Function Theorem

Homogenous Functions A homogenous function of order $n$ satisfies: $$f(\lambda x_1, \lambda x_2, \ldots, \lambda x_m) =\lambda^n f(x_1, x_2, \ldots, x_m)$$ For e.g. $$f(x,y) = \sqrt{x} y^2$$ is homogenous of order $n = 3/2$ . However: $$f(x,y) = \sqrt x y^2 + x^2 y^2$$ is not a homogenous function… Continue reading Euler’s Homogenous Function Theorem

Research

# Euler’s Theorem and the Smarr Relation

The area of a charged rotating (Kerr) black hole is given by $$\label{eqn:kerr-area-relation} A = 4\pi \left[ 2 M^2 + 2 (M^4 – L^2 – M^2 Q^2)^{1/2} – Q^2 \right]$$ This relation can be inverted to express the mass $M$ as a function of charge $Q$, area $A$ and angular momentum $L$: … Continue reading Euler’s Theorem and the Smarr Relation

Research

# 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… Continue reading EVONET18 – Tensor Networks for One and All

# 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… Continue reading Theoretical Physicists in India

Research

# 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… Continue reading Fluctuation Dissipation in Quantum Gravity

Research

# 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… Continue reading Spacetime Geometry as Information Geometry