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Jes Madsen

Publications and source records attributed to Jes Madsen.

At least 19 recordsLinked to original sources
arXiv2009

Cavitation from bulk viscosity in neutron stars and quark stars

The bulk viscosity in quark matter is sufficiently high to reduce the effective pressure below the corresponding vapor pressure during density perturbations in neutron stars and strange stars. This leads to mechanical instability where the quark matter breaks apart into fragments comparable to cavitation scenarios discussed for ultra-relativistic heavy-ion collisions. Similar phenomena may take place in kaon-condensed stellar cores. Possible applications to compact star phenomenology include a new mechanism for damping oscillations and instabilities, triggering of phase transitions, changes in gravitational wave signatures of binary star inspiral, and astrophysical formation of strangelets. At a more fundamental level it points to the possible inadequacy of a hydrodynamical treatment of these processes in compact stars.

astro-ph.SR↗
arXiv2009

Signature of deconfinement with spin down compression in cooling hybrid stars

The thermal evolution of neutron stars is coupled to their spin down and the resulting changes in structure and chemical composition. This coupling correlates stellar surface temperatures with rotational state as well as time. We report an extensive investigation of the coupling between spin down and cooling for hybrid stars which undergo a phase transition to deconfined quark matter at the high densities present in stars at low rotation frequencies. The thermal balance of neutron stars is re-analyzed to incorporate phase transitions and the related latent heat self-consistently, and numerical calculations are undertaken to simultaneously evolve the stellar structure and temperature distribution. We find that the changes in stellar structure and chemical composition with the introduction of a pure quark matter phase in the core delay the cooling and produce a period of increasing surface temperature for strongly superfluid stars of strong and intermediate magnetic field strength. The latent heat of deconfinement is found to reinforce this signature if quark matter is superfluid and it can dominate the thermal balance during the formation of a pure quark matter core. At other times it is less important and does not significantly change the thermal evolution.

astro-ph↗
arXiv2009

Search for stable Strange Quark Matter in lunar soil

We report results from a search for strangelets (small chunks of Strange Quark Matter) in lunar soil using the Yale WNSL accelerator as a mass spectrometer. We have searched over a range in mass from A=42 to A=70 amu for nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the experiment. For strangelets with nuclear charge 8, a concentration in lunar soil higher than $10^{-16}$ is excluded at the 95% confidence level. The implied limit on the strangelet flux in cosmic rays is the most sensitive to date for the covered range and is relevant to both recent theoretical flux predictions and a strangelet candidate event found by the AMS-01 experiment.

nucl-ex↗
arXiv2008

Universal Charge-Radius Relation for Subatomic and Astrophysical Compact Objects

Electron-positron pair creation in supercritical electric fields limits the net charge of any static, spherical object, such as superheavy nuclei, strangelets, and Q-balls, or compact stars like neutron stars, quark stars, and black holes. For radii between $4\times10^2$ fm and $10^4$ fm the upper bound on the net charge is given by the universal relation $Z=0.71R_{fm}$, and for larger radii (measured in fm or km) $Z = 7 \times 10^{-5} R_{fm}^2 = 7 \times 10^{31} R_{km}^2$. For objects with nuclear density the relation corresponds to $Z \approx 0.7 A^{1/3}$ ($10^{8} < A < 10^{12}$) and $Z \approx 7\times10^{-5} A^{2/3}$ ($A > 10^{12}$), where $A$ is the baryon number. For some systems this universal upper bound improves existing charge limits in the literature.

hep-ph↗
arXiv2006

Strangelets in Cosmic Rays

The properties of strangelets are reviewed and two experiments searching for them in cosmic rays are described. The prospects for strangelets as ultra-high energy cosmic rays beyond the classical GZK-cutoff are discussed.

astro-ph↗
arXiv2006

Strangelets, Nuclearites, Q-balls--A Brief Overview

Astrophysical bounds on the properties and abundances of primordial quark nuggets and cosmic ray strangelets are reviewed. New experiments to search for cosmic ray strangelets in lunar soil and from the International Space Station are described. Analogies with baryonic and supersymmetric Q-balls are briefly mentioned, as are prospects for strangelets as ultra-high energy cosmic rays.

astro-ph↗
arXiv2006

Consistency between deep crustal heating of strange stars in superbursters and soft X-ray transients

Both superbursters and soft X-ray transients probe the process of deep crustal heating in compact stars. It was recently shown that the transfer of matter from crust to core in a strange star can heat the crust and ignite superbursts provided certain constraints on the strange quark matter equation of state are fulfilled. We derive corresponding constraints on the equation of state for soft X-ray transients assuming their quiescent emission is powered in the same way, and further discuss the time dependence of this heating mechanism in transient systems. We approach this using a simple parametrized model for deep crustal heating in strange stars assuming slow neutrino cooling in the core and blackbody photon emission from the surface.The constraints derived for hot frequently accreting soft X-ray transients are always consistent with those for superbursters. The colder sources are consistent for low values of the quark matter binding energy, heat conductivity and neutrino emissivity. The heating mechanism is very time dependent which may help to explain cold sources with long recurrence times. Thus deep crustal heating in strange stars can provide a consistent explanation for superbursters and soft X-ray transients.

astro-ph↗
arXiv2005

Stable quark matter in cosmic rays?

Stable lumps of quark matter may be present in cosmic rays at a flux level, which can be detected by high precision cosmic ray experiments sensitive to anomalous "nuclei" with high mass-to-charge ratio. The properties of these lumps, called strangelets, are described, and so is the production and propagation of strangelets in cosmic rays. Two experiments underway which are sensitive to a strangelet flux in the predicted range are briefly described. Finally it is summarized how strangelets circumvent the acceleration problem encountered by conventional candidates for ultra-high energy cosmic rays and move the Greisen-Zatsepin-Kuzmin cutoff to energies well above the observed maximum energies.

astro-ph↗
arXiv2005

Gaps below strange star crusts

The gap caused by a strong electric field between the quark surface and nuclear crust of a strange star is studied in an improved model including gravity and pressure as well as electrostatic forces. The transition from gap to crust is followed in detail. The properties of the gap are investigated for a wide range of parameters assuming both color-flavor locked and non color-flavor locked strange star cores. The maximally allowed crust density is generally lower than that of neutron drip. Finite temperature is shown to increase the gap width, but the effect is significant only at extreme temperatures. Analytical approximations are derived and shown to provide useful fits to the numerical results.

astro-ph↗
arXiv2005

Strangelet propagation and cosmic ray flux

The galactic propagation of cosmic ray strangelets is described and the resulting flux is calculated for a wide range of parameters as a prerequisite for strangelet searches in lunar soil and with an Earth orbiting magnetic spectrometer, AMS-02. While the inherent uncertainties are large, flux predictions at a measurable level are obtained for reasonable choices of parameters if strange quark matter is absolutely stable. This allows a direct test of the strange matter hypothesis.

astro-ph↗
arXiv2004

Cosmic ray strangelets

Searching for strangelets in cosmic rays may be the best way to test the possible stability of strange quark matter. I review calculations of the astrophysical strangelet flux in the GV--TV rigidity range, which will be investigated from the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station, and discuss the merits of strangelets as ultra-high energy cosmic rays at EeV--ZeV energies, beyond the Greisen-Zatsepin-Kuzmin cutoff. I also address some ``counter-arguments'' sometimes raised against the possibility of stable strangelets. It will be argued that stability of strange quark matter remains a viable possibility, which must be tested by experiments.

astro-ph↗
arXiv2003

Strangelets as Cosmic Rays beyond the Greisen-Zatsepin-Kuzmin Cutoff

Strangelets (stable lumps of quark matter) can have masses and charges much higher than those of nuclei, but have very low charge-to-mass ratios. This is confirmed in a relativistic Thomas-Fermi model. The high charge allows astrophysical strangelet acceleration to energies orders of magnitude higher than for protons. In addition, strangelets are much less susceptible to the interactions with the cosmic microwave background that suppress the flux of cosmic ray protons and nuclei above energies of $10^{19}$--$10^{20}$ eV (the GZK-cutoff). This makes strangelets an interesting possibility for explaining ultra-high energy cosmic rays.

astro-ph↗
arXiv2001

Color-flavor locked strangelets and their detection

Strange quark matter in a color-flavor locked state is significantly more bound than ``ordinary'' strange quark matter. This increases the likelihood of strangelet metastability or even absolute stability. Properties of color-flavor locked strangelets are discussed and compared to ordinary strangelets. Apart from differences in binding energy, the main difference is related to the charge. A statistical sample of strangelets may allow experimental distinction of the two. Preliminary estimates indicate that the flux of strangelets in galactic cosmic rays could be sufficient to allow for strangelet discovery and study in the upcoming Alpha Magnetic Spectrometer AMS-02 cosmic ray experiment on the International Space Station.

hep-ph↗
arXiv2001

Color-flavor locking in strange stars, strangelets, and cosmic rays

Three topics with relation to color superconductivity in strange quark matter are discussed. 1) The r-mode instability in strange stars, which is consistent with the existence of ``ordinary'' strange quark matter stars but inconsistent with strange stars in a pure color-flavor locked state. 2) Color-flavor locked strangelets, which are more bound than normal strangelets, and have a different charge-mass relation. 3) Estimates of the strangelet flux in cosmic rays, which is relevant for strangelet detections in upcoming cosmic ray space experiments.

hep-ph↗
arXiv2001

Color-flavor locked strangelets

Finite lumps of color-flavor locked strange quark matter (CFL-strangelets) are significantly more stable than strangelets without color-flavor locking for wide ranges of parameters, increasing the likelihood of strangelet metastability, or even absolute stability beyond some minimum baryon number $A_{min}$. Whereas bulk CFL strange quark matter is electrically neutral, CFL-strangelets are positively charged, with $Z\approx 0.3 A^{2/3}$. This is quite different from ``ordinary'' strangelets and may provide a possible test of color-flavor locking if strangelets are detected in upcoming cosmic-ray space experiments.

hep-ph↗
arXiv2001

Dark matter phase space densities

The low velocity part of a kinetic equilibrium dark matter distribution has higher phase space density and is more easily incorporated in formation of a low mass galaxy than the high velocity part. For relativistically decoupling fermions (bosons), this explains one (two) orders of magnitude of the observed trend, that phase space densities in dark matter halo cores are highest in the smallest systems, and loosens constraints on particle masses significantly. For non-relativistic decoupling and/or finite chemical potentials even larger effects may occur. It is therefore premature to dismiss dissipationless particle distributions as dark matter on the basis of phase space arguments.

astro-ph↗