An official website of the United States government
ABSTRACT Forty years ago Witten suggested that dark matter could be composed of macroscopic clusters of strange quark matter. This idea was very popular for several years, but it dropped out of fashion once lattice quantum chromodynamics calculations indicated that the confinement/deconfinement transition, at small baryonic chemical potential, is not first order, which seemed to be a crucial requirement in order to produce large clusters of quarks. Here, we revisit the conditions under which strangelets can be produced in the Early Universe. We discuss the impact of an instability in the hadronic phase separating a low density, positive-strange-charge phase from a high-density phase with a negative strange charge. This second phase can rapidly stabilize by forming colour-superconducting gaps. The strangelets then undergo partial evaporation. In this way, we obtain distributions of their sizes in agreement with the observational constraints and we discuss the many astrophysical and cosmological implications of these objects. Finally, we examine the most promising techniques to detect this type of strangelets. We also show that strangelets can exist with masses $$\lesssim $$1017 g, while primordial black holes are ruled out in that mass range, allowing us to distinguish between these two dark matter candidates.
more »
« less
Approaching the Conformal Limit of Quark Matter with Different Chemical Potentials
We study in detail the influence of different chemical potentials (baryon, electric charge, strange, and neutrino) on how and how fast a free gas of quarks in the zero-temperature limit reaches the conformal limit. We discuss the influence of non-zero masses, the inclusion of leptons, and different constraints, such as charge neutrality, zero-net strangeness, and fixed lepton fraction. We also investigate for the first time how the symmetry energy of the system under some of these conditions approaches the conformal limit. We find that the inclusion of all quark masses (even the light ones) can produce different results depending on the chemical potential values or constraints assumed. A positive or negative deviation of 10% from the pressure of free massless quarks with the same chemical potential was found to take place as low as μB=77 to as high as 48,897 MeV. This illustrates the fact that the “free” or conformal limit is not a unique description. Finally, we briefly discuss what kind of corrections are expected from perturbative QCD as one goes away from the conformal limit.
more »
« less
- Award ID(s):
- 1748621
- PAR ID:
- 10521523
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Symmetry
- Volume:
- 16
- Issue:
- 7
- ISSN:
- 2073-8994
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
A bstract We study operators with large charge j in the d -dimensional O ( N ) model with long range interactions that decrease with the distance as 1/ r d + s , where s is a continuous parameter. We consider the double scaling limit of large N , large j with $$ j/N=\hat{j} $$ j / N = j ̂ fixed, and identify the semiclassical saddle point that captures the two-point function of the large charge operators in this limit. The solution is given in terms of certain ladder conformal integrals that have recently appeared in the literature on fishnet models. We find that the scaling dimensions for general s interpolate between $$ {\Delta }_j\sim \frac{\left(d-s\right)}{2}j $$ ∆ j ∼ d − s 2 j at small $$ \hat{j} $$ j ̂ and $$ {\Delta }_j\sim \frac{\left(d+s\right)}{2}j $$ ∆ j ∼ d + s 2 j at large $$ \hat{j} $$ j ̂ , which is a qualitatively different behavior from the one found in the short range version of the O ( N ) model. We also derive results for the structure constants and 4-point functions with two large charge and one or two finite charge operators. Using a description of the long range models as defects in a higher dimensional local free field theory, we also obtain the scaling dimensions in a complementary way, by mapping the problem to a cylinder in the presence of a chemical potential for the conserved charge.more » « less
-
A bstract We study $$ \mathcal{N} $$ N = 2 supersymmetric Sachdev-Ye-Kitaev (SYK) models with com- plex fermions at non-zero background charge. Motivated by multi-charge supersymmetric black holes, we propose a new $$ \mathcal{N} $$ N = 2 SYK model with multiple U (1) symmetries, integer charges, and a non-vanishing supersymmetric index, realizing features not present in known SYK models. In both models, a conformal solution with a super-Schwarzian mode emerges at low temperatures, signalling the appearance of nearly AdS 2 /BPS physics. However, in contrast to complex SYK, the fermion scaling dimension depends on the background charge in the conformal limit. For a critical charge, we find a high to low entropy phase transition in which the conformal solution ceases to be valid. This transition has a simple interpretation– the fermion scaling dimension violates the unitarity bound. We offer some comments on a holographic interpretation for supersymmetric black holes.more » « less
-
A<sc>bstract</sc> Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We develop a customized approximation that fully accounts for the Landau-level quantization of electron states while neglecting such quantization for quarks. This approach is well-justified in dense quark matter, where the chemical potentials of up and down quarks significantly exceed those of electrons. Our analysis provides a detailed exploration of the influence of strong magnetic fields on neutrino emission, including both the modification of the total emission rate and the emergence of emission asymmetry relative to the magnetic field direction. We further examine the role of temperature in smoothing the oscillatory behavior of neutrino emission as a function of magnetic field strength. Additionally, we study the interplay between the Landau-level quantization of electrons and the Fermi-liquid effects of quarks in modifying the phase space of relevant weak processes. Finally, we briefly discuss the broader implications of magnetic fields on stellar cooling processes and the potential contribution of asymmetric neutrino emission to pulsar kicks.more » « less
-
The hadron mass can be obtained through the calculation of the trace of the energy-momentum tensor in the hadron which includes the trace anomaly and sigma terms. The anomaly due to conformal symmetry breaking is believed to be an important ingredient for hadron mass generation and confinement. In this work, we will present the calculation of the glue part of the trace anomaly form factors of the pion up to and the nucleon up to . The calculations are performed on a domain wall fermion ensemble with overlap valence quarks at seven valence pion masses varying from to , including the unitary point . We calculate the radius of the glue trace anomaly for the pion and the nucleon from the expansion. By performing a two-dimensional Fourier transform on the glue trace anomaly form factors in the infinite momentum frame with no energy transfer, we also obtain their spatial distributions for several valence quark masses. The results are qualitatively extrapolated to the physical valence pion mass with systematic errors from the unphysical sea quark mass, discretization effects in the renormalization sum rule, and finite-volume effects to be addressed in the future. We find the pion’s form factor changes sign, as does its spatial distribution, for light quark masses. This explains how the trace anomaly contribution to the pion mass approaches zero toward the chiral limit. Published by the American Physical Society2024more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/sym16070852
