arXiv subjects

Joydip Kundu

Publications and source records attributed to Joydip Kundu.

6 recordsLinked to original sources

arXiv2005

Constraint equations for heavy-to-light currents in SCET

A complete basis for the next-to-next-to leading order heavy-to-light currents in the soft-collinear effective theory is constructed. Reparameterization invariance is imposed by deriving constraint equations. Their solutions give the set of allowed Dirac structures as well as relations between the Wilson coefficients of operators that appear at different orders in the power expansion. The completeness of reparameterization invariance constraints derived on a projected surface is investigated. We also discuss the universality of the ultrasoft Wilson line with boundary conditions.

hep-ph↗

arXiv2005

A Hot Water Bottle for Aging Neutron Stars

The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat loss by neutrino emission L_ν. The gCFL phase is characterized by an unusual quasiparticle dispersion relation that makes both its specific heat c_V and its neutrino emissivity epsilon_νparametrically larger than in any other phase of nuclear or quark matter. During the epoch in which the cooling of the star is dominated by direct Urca neutrino emission, the presence of a gCFL region does not strongly alter the cooling history because the enhancements of C_V and L_νcancel against each other. At late times, however, the cooling is dominated by photon emission from the surface, so L_νis irrelevant, and the anomalously large heat capacity of the gCFL region keeps the star warm. The temperature drops with time as T\sim t^{-1.4} rather than the canonical T\sim t^{-5}. This provides a unique and potentially observable signature of gCFL quark matter.

astro-ph↗

arXiv2004

Neutrino scattering off pair-breaking and collective excitations in superfluid neutron matter and in color-flavor locked quark matter

We calculate the correlation functions needed to describe the linear response of superfluid matter, and go on to calculate the differential cross section for neutral-current neutrino scattering in superfluid neutron matter and in color-flavor locked quark matter (CFL). We report the first calculation of scattering rates that includes neutrino interactions with both pair-breaking excitations and low-lying collective excitations (Goldstone modes). Our results apply both above and below the critical temperature, allowing use in simulations of neutrino transport in supernovae and neutron stars.

nucl-th↗

arXiv2002

Mass-Induced Crystalline Color Superconductivity

We demonstrate that crystalline color superconductivity may arise as a result of pairing between massless quarks and quarks with nonzero mass m_s. Previous analyses of this phase of cold dense quark matter have all utilized a chemical potential difference δμto favor crystalline color superconductivity over ordinary BCS pairing. In any context in which crystalline color superconductivity occurs in nature, however, it will be m_s-induced. The effect of m_s is qualitatively different from that of δμin one crucial respect: m_s depresses the value of the BCS gap Δ_0 whereas δμleaves Δ_0 unchanged. This effect in the BCS phase must be taken into account before m_s-induced and δμ-induced crystalline color superconductivity can sensibly be compared.

hep-ph↗

arXiv2001

A Diagrammatic Approach to Crystalline Color Superconductivity

We present a derivation of the gap equation for the crystalline color superconducting phase of QCD which begins from a one-loop Schwinger-Dyson equation written using a Nambu-Gorkov propagator modified to describe the spatially varying condensate. Some aspects of previous variational calculations become more straightforward when rephrased beginning from a diagrammatic starting point. This derivation also provides a natural base from which to generalize the analysis to include quark masses, nontrivial crystal structures, gluon propagation at asymptotic densities, and nonzero temperature. In this paper, we analyze the effects of nonzero temperature on the crystalline color superconducting phase.

hep-ph↗

arXiv1999

Distributed Entanglement

Consider three qubits A, B, and C which may be entangled with each other. We show that there is a trade-off between A's entanglement with B and its entanglement with C. This relation is expressed in terms of a measure of entanglement called the "tangle," which is related to the entanglement of formation. Specifically, we show that the tangle between A and B, plus the tangle between A and C, cannot be greater than the tangle between A and the pair BC. This inequality is as strong as it could be, in the sense that for any values of the tangles satisfying the corresponding equality, one can find a quantum state consistent with those values. Further exploration of this result leads to a definition of the "three-way tangle" of the system, which is invariant under permutations of the qubits.

quant-ph↗