Unitary Fermi gas at finite temperature in the epsilon expansion

Thermodynamics of the unitary Fermi gas at finite temperature is investigated from the perspective of the expansion over epsilon=4-d with d being the dimensionality of space. We show that the thermodynamics is dominated by bosonic excitations in the low temperature region T<<Tc. Analytic formulas for the thermodynamic functions as functions of the temperature are derived to the lowest order in epsilon in this region. In the high temperature region where T Tc, bosonic and fermionic quasiparticles are excited. We determine the critical temperature Tc of the superfluid phase transition and the thermodynamic functions around Tc to the leading and next-to-leading orders in epsilon.Comment: 13 pages, 7 figures, revtex4; version to appear in Phys. Rev.

Capacity-constrained renewable power generation development in light of storage cost uncertainty. ESRI Working Paper No. 647 December 2019

The development of sustainable energy sources and their enabling infrastructures are often met by public opposition, resulting in lengthy planning processes. One proposed means of reducing public opposition is constraining the capacity of renewable energy projects onshore, leading to more small-scale, decentralised and possibly community-driven developments. This work computes the effects of same by performing a medium- and long-term generation expansion planning exercise considering two renewable development cases, in which renewable power expansion is spatially constrained to certain degrees, under high and low storage cost regimes. We employ an appropriately designed optimisation model, accounting for network effects, which are largely neglected in previous studies. We apply our study to the future Irish power system under a range of demand and policy scenarios. Irrespective of storage costs, the unconstrained portfolio is marginally cheaper than the constrained one. However, there are substantial differences in the final generation expansion portfolios. The network reinforcement requirements are also greater under the unconstrained approach. Lower storage costs only slightly mitigate the costs of capacity constraints but significantly alter the spatial distribution of generation investments. The differential in costs between the unconstrained and constrained cases increases non-linearly with renewable generation targets

The Spectral Line Shape of Exotic Nuclei

The quadrupole strength function of $^{28}O$ is calculated making use of the SIII interaction, within the framework of continuum-RPA and taking into account collisions among the nucleons (doorway coupling). The centroid of the giant resonance is predicted at $\approx 14$ MeV, that is much below the energy expected for both isoscalar and isovector quadrupole resonances in nuclei along the stability valley. About half of this width arises from the coupling of the resonance to the continuum and about half is due to doorway coupling. This result is similar to that obtained in the study of giant resonances in light, $\beta$-stable nuclei, and shows the lack of basis for the expectation, entertained until now in the literature, that continuum decay was the main damping mechanism of giant resonances in halo nuclei.Comment: LaTeX file, 7 pages, figures not included but available if requested at [email protected], accepted for publication in Phys. Rev.

Demand response within the energy-for-water-nexus - A review. ESRI WP637, October 2019

A promising tool to achieve more flexibility within power systems is demand re-sponse (DR). End-users in many strands of industry have been subject to research up to now regarding the opportunities for implementing DR programmes. One sector that has received little attention from the literature so far, is wastewater treatment. However, case studies indicate that the potential for wastewater treatment plants to provide DR services might be significant. This review presents and categorises recent modelling approaches for industrial demand response as well as for the wastewater treatment plant operation. Furthermore, the main sources of flexibility from wastewater treatment plants are presented: a potential for variable electricity use in aeration, the time-shifting operation of pumps, the exploitation of built-in redundan-cy in the system and flexibility in the sludge processing. Although case studies con-note the potential for DR from individual WWTPs, no study acknowledges the en-dogeneity of energy prices which arises from a large-scale utilisation of DR. There-fore, an integrated energy systems approach is required to quantify system and market effects effectively

Spin-triplet pairing in large nuclei

The nuclear pairing condensate is expected to change character from spin-singlet to spin-triplet when the nucleus is very large and the neutron and proton numbers $Z,N$ are equal. We investigate the transition between these two phases within the framework of the Hartree-Fock-Bogoliubov equations, using a zero-range interaction to generate the pairing. We confirm that extremely large nucleus would indeed favor triplet pairing condensates, with the Hamiltonian parameters taken from known systematics. The favored phase is found to depend on the specific orbitals at the Fermi energy. The smallest nuclei with a well-developed spin-triplet condensate are in the mass region A ~ 130-140.Comment: 8 pages, 2 figures, 2 table

How harmonic is dipole resonance of metal clusters?

We discuss the degree of anharmonicity of dipole plasmon resonances in metal clusters. We employ the time-dependent variational principle and show that the relative shift of the second phonon scales as $N^{-4/3}$ in energy, $N$ being the number of particles. This scaling property coincides with that for nuclear giant resonances. Contrary to the previous study based on the boson-expansion method, the deviation from the harmonic limit is found to be almost negligible for Na clusters, the result being consistent with the recent experimental observation.Comment: RevTex, 8 page

Electromagnetic transition strengths in soft deformed nuclei

Spectroscopic observables such as electromagnetic transitions strengths can be related to the properties of the intrinsic mean-field wave function when the latter are strongly deformed, but the standard rotational formulas break down when the deformation decreases. Nevertheless there is a well-defined, non-zero, spherical limit that can be evaluated in terms of overlaps of mean-field intrinsic deformed wave functions. We examine the transition between the spherical limit and strongly deformed one for a range of nuclei comparing the two limiting formulas with exact projection results. We find a simple criterion for the validity of the rotational formula depending on $$, the mean square fluctuation in the angular momentum of the intrinsic state. We also propose an interpolation formula which describes the transition strengths over the entire range of deformations, reducing to the two simple expressions in the appropriate limits.Comment: 16 pages, 5 figures, supplemental material include