Nemanja Kaloper
We show that Maxwell theory with a codimension-$1$ Chern-Simons interface supports chiral electromagnetic surface waves on the interface, even when the bulk theory on both sides is conventional vacuum electrodynamics in infinite space.…
Hints of cosmic microwave background polarization rotation ($\Delta\vartheta \sim 10^{-3}$ rad) are commonly attributed to late-time dynamics of ultralight axions. We show that such ultralight degrees of freedom are not required.…
We propose a mechanism for relaxing a gauge theory CP violating phase in discrete steps to very small values. The idea is that the CP violating phase includes the magnetic dual of a $4$-form flux which can discharge by the nucleation of…
Light crossing dark domain walls that source a top form coupled to gauge Chern--Simons terms mixing visible and dark $U(1)$ gauge fields generically converts into dark photons. The effect is entirely localized on the wall and requires no…
We extend Maxwell electrodynamics with a Chern--Simons coupling to a dark sector top form sourced by domain walls. Electromagnetic fields which cross such domain walls exhibit optical activity. We outline the parameter space where the…
We show that in multi-stage axion monodromy inflation an interruption near the end of the penultimate stage can lead to a spike in the gravitational wave background. These gravitational waves are in the frequency range and with an amplitude…
The $U(1)$ CP-violating phase which arises below chiral symmetry breaking in a non-Abelian gauge theory is ``secretly" the magnetic dual of the flux of a $U(1)$ $4$-form gauge field. Thus the discharge of this $4$-form flux by Schwinger…
We propose a new UV-complete dark energy model which is \underbar{\it neither} a cosmological constant nor a slowly rolling scalar field. Our dark energy is the flux of a top form in a hidden sector gauge theory similar to QCD. The top form…
We propose using fuzzy axion dark matter to test the anthropic principle. A very light axion can be directly detectable, at least by black hole superradiance effects. The idea then is that gravitational and astrophysical observations can…
We consider a conformally coupled scalar QFT on $2+1$ dimensional static Einstein universe $R \times S^2$, and write down the free theory Hilbert space. We explain that this theory is secretly a QFT in $2+1$ de Sitter space because all the…
We point out that time's arrow is naturally induced by quantum mechanical evolution, whenever the systems have a very large number ${\cal N}$ of non-degenerate states and a Hamiltonian bounded from below. When ${\cal N}$ is finite, the…
We examine implications of the weak gravity conjecture for the mechanisms for discharging cosmological constant via membrane nucleations. Once screening fluxes and membranes which source them enter, and weak gravity bounds are enforced, a…
Linear axion monodromy models modulated with higher powers of fields naturally realize the quantum-mechanical flux discharge mechanism for relaxing the cosmological constant toward zero. Working with multiple copies of superposed linear and…
General covariant unimodular gravity frameworks, based on the Henneaux-Teitelboim formulation, are, in disguise, precisely $4$-form field theories corrected with higher dimension operators. In the presence of charged tensional membranes,…
We exhibit a mechanism which dynamically adjusts cosmological constant toward $0^+$. The adjustment is quantum-mechanical, discharging cosmological constant in random discrete steps. It renders de Sitter space unstable, and triggers its…
Based on entropy considerations and the arrow of time Penrose argued that the universe must have started in a special initial singularity with vanishing Weyl curvature. This is often interpreted to be at odds with inflation. Here we argue…
We extend General Relativity by promoting Planck scale and the cosmological constant into integration constants, interpreted as fluxes of $4$-forms hiding in the theory. When we include the charges of the $4$-forms, these `constants' can…
We define `third derivative' General Relativity, by promoting the integration measure in Einstein-Hilbert action to be an arbitrary $4$-form field strength. We project out its local fluctuations by coupling it to another $4$-form field…
(Abridged) Does inflation have to happen all in one go? The answer is a resounding no! All cosmological problems can be solved by a sequence of short bursts of cosmic acceleration, interrupted by short epochs of decelerated expansion. The…
The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white…