Katherine Freese - Academia.edu (original) (raw)
Papers by Katherine Freese
Physics Letters B, 2003
The ultimate fate of life in a universe with accelerated expansion is considered. Previous work s... more The ultimate fate of life in a universe with accelerated expansion is considered. Previous work showed that life cannot go on indefinitely in a universe dominated by a cosmological constant. In this paper we consider instead other models of acceleration (including quintessence and Cardassian expansion). We find that it is possible in these cosmologies for life to persist indefinitely. As an example we study potentials of the form V ∝ φ n and find the requirement n < −2.
Annals of the New York Academy of Sciences, Jan 11, 2015
The holy grail of physics has been to merge each of its fundamental branches into a unified "... more The holy grail of physics has been to merge each of its fundamental branches into a unified "theory of everything" that would explain the functioning and existence of the universe. The last step toward this goal is to reconcile general relativity with the principles of quantum mechanics, a quest that has thus far eluded physicists. Will physics ever be able to develop an all-encompassing theory, or should we simply acknowledge that science will always have inherent limitations as to what can be known? Should new theories be validated solely on the basis of calculations that can never be empirically tested? Can we ever truly grasp the implications of modern physics when the basic laws of nature do not always operate according to our standard paradigms? These and other questions are discussed in this paper.
The Arrows of Time, 2011
An oscillating universe cycles through a series of expansions and contractions. We propose a mode... more An oscillating universe cycles through a series of expansions and contractions. We propose a model in which "phantom" energy with a supernegative pressure (p < −ρ) grows rapidly and dominates the late-time expanding phase. The universe's energy density is so large that the effects of quantum gravity are important at both the beginning and the end of each expansion (or contraction). The bounce can be caused by high energy modifications to the Friedmann equation, which make the cosmology nonsingular. The classic black hole overproduction of oscillating universes is resolved due to their destruction by the phantom energy.
Physical Review D, 2005
Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto ... more Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing ∼(0.3-23)% of the local density of our Galactic Halo. If the Sagittarius galaxy contains WIMP dark matter, the extra contribution from the stream gives rise to a step-like feature in the energy recoil spectrum in direct dark matter detection. For our best estimate of stream velocity (300 km/sec) and direction (the plane containing the Sgr dwarf and its debris), the count rate is maximum on June 28 and minimum on December 27 (for most recoil energies), and the location of the step oscillates yearly with a phase opposite to that of the count rate. In the CDMS experiment, for 60 GeV WIMPs, the location of the step oscillates between 35 and 42 keV, and for the most favorable stream density, the stream should be detectable at the 11σ level in four years of data with 10 keV energy bins. Planned large detectors like XENON, CryoArray and the directional detector DRIFT may also be able to identify the Sgr stream.
Physics Letters B, 1986
Scalar neutrinos and massive Dirac neutrinos in the mass range 2-20 GeV have been proposed as can... more Scalar neutrinos and massive Dirac neutrinos in the mass range 2-20 GeV have been proposed as candidates to provide the dark matter in the halo of our galaxy. If so, the particles are captured inthe Earth with an efficiency of 10-10 - 10-7. For Dirac neutrinos more massive than about 9 GeV and scalar neutrinos more massive than abour 12
Physical Review D, 2011
We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-indepe... more We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-independent (SI) dark matter Weakly Interacting Massive Particles (WIMPs), particularly at low masses (∼10 GeV), assuming a standard dark matter halo. The XENON bounds depend on the scintillation efficiency factor L eff for which there is considerable uncertainty. Thus we consider various extrapolations for L eff at low energy. With the L eff measurements we consider, XENON100 results are found to be insensitive to the low energy extrapolation. We find the strongest bounds are from XENON10, rather than XENON100, due to the lower energy threshold. For reasonable choices of L eff and for the case of SI elastic scattering, XENON10 is incompatible with the DAMA/LIBRA 3σ region and severely constrains the 7-12 GeV WIMP mass region of interest published by the CoGeNT collaboration.
Proceedings of the International Astronomical Union, 2008
The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by... more The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (∼ 800M ), cool (6000 K), bright (∼ 10 6 L ), long-lived (∼ 10 6 years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that a Dark Star is born again.
Nuclear Physics B, 1985
Abstract We develop a manifestly, generally coordinate-covariant functional Schrödinger formalism... more Abstract We develop a manifestly, generally coordinate-covariant functional Schrödinger formalism. We study the usual problem of Hawking radiation in the Rindler coordinate system. The Hawking effect appears as a shift in the width of the ground-state wave ...
The Identification of Dark Matter - Proceedings of the Third International Workshop, 2001
The nature of the dark matter in the haloes of galaxies is one of the outstanding questions in as... more The nature of the dark matter in the haloes of galaxies is one of the outstanding questions in astrophysics. All stellar candidates, until recently thought to be likely baryonic contributions to the Halo of our Galaxy, are shown to be ruled out. Faint stars and brown dwarfs are found to constitute only a few percent of the mass of the Galaxy. Stellar remnants, including white dwarfs and neutron stars, are shown to be very constrained as well. High energy gamma-rays observed in HEGRA data place the strongest constraints, ΩW D < 3 × 10 −3 h −1 , where h is the Hubble constant in units of 100 km s −1 Mpc −1 . Hence one is left with several unanswered questions: 1) What are MACHOs seen in microlensing surveys? 2) What is the dark matter in our Galaxy? Indeed a nonbaryonic component in the Halo seems to be required.
The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presente... more The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that the dark matter does not consist of ordinary stellar or substellar objects, i.e., the dark matter is not made of faint stars, brown dwarfs, white dwarfs, or neutron stars. In fact, faint stars and brown dwarfs constitute no more than a
Physical Review D, 2012
We calculate the limits on the fraction of viable dark matter minihalos in the early universe to ... more We calculate the limits on the fraction of viable dark matter minihalos in the early universe to host Population III.1 stars, surviving today as dark matter spikes in our Milky Way halo. Motivated by potential hints of light dark matter from the DAMA and CoGeNT direct dark matter searches, we consider thermal relic WIMP dark matter with masses of 5, 10, and 20 GeV, and annihilation to µ + µ − , τ + τ − , and qq. From this brief study we conclude that, if dark matter is light, either the typical black hole size is 100M ⊙ (i.e. there is no significant Dark Star phase), and/or dark matter annihilates primarily to µ + µ − or other final states that result in low gamma-ray luminosity, and/or that an extremely small fraction of minihalos in the early universe that seem suitable to host the formation of the first stars actually did. spikes is made of Weakly Interacting Massive Particles (WIMPs), typically these are their own antiparticles, and they annihilate with one another inside the spikes surrounding the black holes. This paper focuses on the gamma-ray flux from the annihilation, and compares it to data from the Fermi Gamma-Ray Space Telescope (FGST). In previous work , hereafter SDFS, we considered WIMPS with masses in the range 100 GeV to 2 TeV and used the FGST data to constrain models of Population III.1 star formation and/or dark matter annihilation for these WIMP masses. Subsequently, the possibility that WIMP dark matter is non-thermal in origin was also investigated . In this paper, we return to the thermal WIMP paradigm, but consider WIMP masses of 5, 10, and 20 GeV.
Physical Review D, 1993
A pseudo-Nambu-Goldstone boson, with a potential of the form V (φ) = Λ 4 [1 ± cos(φ/f )], can nat... more A pseudo-Nambu-Goldstone boson, with a potential of the form V (φ) = Λ 4 [1 ± cos(φ/f )], can naturally give rise to an epoch of inflation in the early universe, if f ∼ M P l and Λ ∼ M GU T . Such mass scales arise in particle physics models with a gauge group that becomes strongly interacting at the GUT scale. We explore the particle physics basis for these models, focusing on technicolor and superstring theories, and work out a specific example based on the multiple gaugino condensation scenario in string/supergravity theory. We study the cosmological evolution of and constraints upon these models numerically and analytically. To obtain a sufficiently high post-inflation reheat temperature for baryosynthesis to occur we require f ∼ > 0.3M pl . The primordial density fluctuation spectrum generated by quantum fluctuations in φ is a non-scale-invariant power law, P (k) ∝ k n s , with n s ≃ 1 − (M 2 P l /8πf 2 ), leading to more power on large length scales than the n s = 1 Harrison-Zeldovich spectrum. We pay special attention to the prospects of using the enhanced power to explain the otherwise puzzling large-scale clustering of galaxies and clusters and their flows. We find that the standard cold dark matter model with 0 ∼ < n s ∼ < 0.6 could in principle explain this data. However, the microwave background anisotropies recently detected by COBE imply such low primordial amplitudes (that is, bias factors b 8 ∼ > 2) for these CDM models that galaxy formation would occur too late to be viable and the large-scale galaxy flows would be too small; when combined with COBE, these each lead to the constraint n s ∼ > 0.6, hence f > 0.3M P l , comparable to the bound from baryogenesis. For other inflation models which give rise to initial fluctuation spectra that are power laws through the 3 decades in wavelength During the inflationary epoch, the energy density of the universe is dominated by the (nearly constant) potential energy density V (φ) associated with a slowly rolling scalar field φ, the inflaton . To satisfy cosmic microwave background radiation (CMBR) anisotropy limits on the generation of density fluctuations, the potential of the inflaton must be very flat. Consequently, the field φ must be extremely weakly self-coupled, with effective quartic self-coupling constant satisfying λ φ < 10 −12 − 10 −14 in most models .
Journal of High Energy Physics, 2003
We consider some consequences of describing the gauge and matter degrees of freedom in our univer... more We consider some consequences of describing the gauge and matter degrees of freedom in our universe by open strings, as suggested by the braneworld scenario. We focus on the geometric effects described by the open string metric and investigate their observational implications. The causal structure of spacetime on the brane is altered; it is described not by the usual metric g µν , but instead by the open string metric,
Journal of High Energy Physics, 2011
We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Su... more We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos,
The Astrophysical Journal, 2008
Dark Stars are the very first phase of stellar evolution in the history of the universe: the firs... more Dark Stars are the very first phase of stellar evolution in the history of the universe: the first stars to form (typically at redshifts z ∼ 10 − 50) are powered by heating from dark matter (DM) annihilation instead of fusion (if the DM is made of particles which are their own antiparticles). We find equilibrium polytropic configurations for these stars; we start from the time DM heating becomes important (M ∼ 1 − 10 M ⊙ ) and build up the star via accretion up to 1000 M ⊙ . The dark stars, with an assumed particle mass of 100 GeV, are found to have luminosities of a few times 10 6 L ⊙ , surface temperatures of 4000-10,000 K, radii ∼ 10 14 cm, lifetimes of at least 0.5 Myr, and are predicted to show lines of atomic and molecular hydrogen. Dark stars look quite different from standard metal-free stars without DM heating: they are far more massive (e.g. ∼ 800M ⊙ for 100 GeV WIMPs), cooler, and larger, and can be distinguished in future observations, possibly even by JWST or TMT.
The Astrophysical Journal, 1985
Certain currently proposed weakly interacting elementary particles can have a high probability of... more Certain currently proposed weakly interacting elementary particles can have a high probability of solar capture if they make up the Galactic halo. Their present abundance in the Sun is here determined by balancing capture rates against annihilation rates. Both particle physics and cosmological considerations impose constraints on scattering and annihilation cross sections. In general, for the candidate particles here discussed
The Astrophysical Journal, 2000
We examine the chemical abundance constraints on a population of white dwarfs in the halo of our ... more We examine the chemical abundance constraints on a population of white dwarfs in the halo of our Galaxy. We are motivated by microlensing experiments that have reported evidence for massive compact halo objects (MACHOs) in the halo of our Galaxy, with an estimated mass of 0.1-1 Msolar the only conventional dark astrophysical candidates for objects in this mass range are
![Research paper thumbnail of Constraining the Cosmic Abundance of Stellar Remnants with Multi-T[CLC]e[/CLC]V Gamma Rays](https://attachments.academia-assets.com/40019789/thumbnails/1.jpg)
](The Astrophysical Journal, 1999
If galactic halos contain stellar remnants, the infra-red flux from the remnant progenitors would... more If galactic halos contain stellar remnants, the infra-red flux from the remnant progenitors would contribute to the opacity of multi-TeV γ-rays. The multi-TeV γ-ray horizon is established to be at a redshift z > 0.034 by the observation of the blazar Mkn501 . By requiring that the optical depth due to γγ −→ e + e − be less than one for a source at z = 0.034 we limit the cosmological density of stellar remnants, Ω rm ≤ (2 − 4) × 10 −3 h −1
Physics Letters B, 2003
The ultimate fate of life in a universe with accelerated expansion is considered. Previous work s... more The ultimate fate of life in a universe with accelerated expansion is considered. Previous work showed that life cannot go on indefinitely in a universe dominated by a cosmological constant. In this paper we consider instead other models of acceleration (including quintessence and Cardassian expansion). We find that it is possible in these cosmologies for life to persist indefinitely. As an example we study potentials of the form V ∝ φ n and find the requirement n < −2.
Annals of the New York Academy of Sciences, Jan 11, 2015
The holy grail of physics has been to merge each of its fundamental branches into a unified "... more The holy grail of physics has been to merge each of its fundamental branches into a unified "theory of everything" that would explain the functioning and existence of the universe. The last step toward this goal is to reconcile general relativity with the principles of quantum mechanics, a quest that has thus far eluded physicists. Will physics ever be able to develop an all-encompassing theory, or should we simply acknowledge that science will always have inherent limitations as to what can be known? Should new theories be validated solely on the basis of calculations that can never be empirically tested? Can we ever truly grasp the implications of modern physics when the basic laws of nature do not always operate according to our standard paradigms? These and other questions are discussed in this paper.
The Arrows of Time, 2011
An oscillating universe cycles through a series of expansions and contractions. We propose a mode... more An oscillating universe cycles through a series of expansions and contractions. We propose a model in which "phantom" energy with a supernegative pressure (p < −ρ) grows rapidly and dominates the late-time expanding phase. The universe's energy density is so large that the effects of quantum gravity are important at both the beginning and the end of each expansion (or contraction). The bounce can be caused by high energy modifications to the Friedmann equation, which make the cosmology nonsingular. The classic black hole overproduction of oscillating universes is resolved due to their destruction by the phantom energy.
Physical Review D, 2005
Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto ... more Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing ∼(0.3-23)% of the local density of our Galactic Halo. If the Sagittarius galaxy contains WIMP dark matter, the extra contribution from the stream gives rise to a step-like feature in the energy recoil spectrum in direct dark matter detection. For our best estimate of stream velocity (300 km/sec) and direction (the plane containing the Sgr dwarf and its debris), the count rate is maximum on June 28 and minimum on December 27 (for most recoil energies), and the location of the step oscillates yearly with a phase opposite to that of the count rate. In the CDMS experiment, for 60 GeV WIMPs, the location of the step oscillates between 35 and 42 keV, and for the most favorable stream density, the stream should be detectable at the 11σ level in four years of data with 10 keV energy bins. Planned large detectors like XENON, CryoArray and the directional detector DRIFT may also be able to identify the Sgr stream.
Physics Letters B, 1986
Scalar neutrinos and massive Dirac neutrinos in the mass range 2-20 GeV have been proposed as can... more Scalar neutrinos and massive Dirac neutrinos in the mass range 2-20 GeV have been proposed as candidates to provide the dark matter in the halo of our galaxy. If so, the particles are captured inthe Earth with an efficiency of 10-10 - 10-7. For Dirac neutrinos more massive than about 9 GeV and scalar neutrinos more massive than abour 12
Physical Review D, 2011
We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-indepe... more We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-independent (SI) dark matter Weakly Interacting Massive Particles (WIMPs), particularly at low masses (∼10 GeV), assuming a standard dark matter halo. The XENON bounds depend on the scintillation efficiency factor L eff for which there is considerable uncertainty. Thus we consider various extrapolations for L eff at low energy. With the L eff measurements we consider, XENON100 results are found to be insensitive to the low energy extrapolation. We find the strongest bounds are from XENON10, rather than XENON100, due to the lower energy threshold. For reasonable choices of L eff and for the case of SI elastic scattering, XENON10 is incompatible with the DAMA/LIBRA 3σ region and severely constrains the 7-12 GeV WIMP mass region of interest published by the CoGeNT collaboration.
Proceedings of the International Astronomical Union, 2008
The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by... more The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (∼ 800M ), cool (6000 K), bright (∼ 10 6 L ), long-lived (∼ 10 6 years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that a Dark Star is born again.
Nuclear Physics B, 1985
Abstract We develop a manifestly, generally coordinate-covariant functional Schrödinger formalism... more Abstract We develop a manifestly, generally coordinate-covariant functional Schrödinger formalism. We study the usual problem of Hawking radiation in the Rindler coordinate system. The Hawking effect appears as a shift in the width of the ground-state wave ...
The Identification of Dark Matter - Proceedings of the Third International Workshop, 2001
The nature of the dark matter in the haloes of galaxies is one of the outstanding questions in as... more The nature of the dark matter in the haloes of galaxies is one of the outstanding questions in astrophysics. All stellar candidates, until recently thought to be likely baryonic contributions to the Halo of our Galaxy, are shown to be ruled out. Faint stars and brown dwarfs are found to constitute only a few percent of the mass of the Galaxy. Stellar remnants, including white dwarfs and neutron stars, are shown to be very constrained as well. High energy gamma-rays observed in HEGRA data place the strongest constraints, ΩW D < 3 × 10 −3 h −1 , where h is the Hubble constant in units of 100 km s −1 Mpc −1 . Hence one is left with several unanswered questions: 1) What are MACHOs seen in microlensing surveys? 2) What is the dark matter in our Galaxy? Indeed a nonbaryonic component in the Halo seems to be required.
The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presente... more The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that the dark matter does not consist of ordinary stellar or substellar objects, i.e., the dark matter is not made of faint stars, brown dwarfs, white dwarfs, or neutron stars. In fact, faint stars and brown dwarfs constitute no more than a
Physical Review D, 2012
We calculate the limits on the fraction of viable dark matter minihalos in the early universe to ... more We calculate the limits on the fraction of viable dark matter minihalos in the early universe to host Population III.1 stars, surviving today as dark matter spikes in our Milky Way halo. Motivated by potential hints of light dark matter from the DAMA and CoGeNT direct dark matter searches, we consider thermal relic WIMP dark matter with masses of 5, 10, and 20 GeV, and annihilation to µ + µ − , τ + τ − , and qq. From this brief study we conclude that, if dark matter is light, either the typical black hole size is 100M ⊙ (i.e. there is no significant Dark Star phase), and/or dark matter annihilates primarily to µ + µ − or other final states that result in low gamma-ray luminosity, and/or that an extremely small fraction of minihalos in the early universe that seem suitable to host the formation of the first stars actually did. spikes is made of Weakly Interacting Massive Particles (WIMPs), typically these are their own antiparticles, and they annihilate with one another inside the spikes surrounding the black holes. This paper focuses on the gamma-ray flux from the annihilation, and compares it to data from the Fermi Gamma-Ray Space Telescope (FGST). In previous work , hereafter SDFS, we considered WIMPS with masses in the range 100 GeV to 2 TeV and used the FGST data to constrain models of Population III.1 star formation and/or dark matter annihilation for these WIMP masses. Subsequently, the possibility that WIMP dark matter is non-thermal in origin was also investigated . In this paper, we return to the thermal WIMP paradigm, but consider WIMP masses of 5, 10, and 20 GeV.
Physical Review D, 1993
A pseudo-Nambu-Goldstone boson, with a potential of the form V (φ) = Λ 4 [1 ± cos(φ/f )], can nat... more A pseudo-Nambu-Goldstone boson, with a potential of the form V (φ) = Λ 4 [1 ± cos(φ/f )], can naturally give rise to an epoch of inflation in the early universe, if f ∼ M P l and Λ ∼ M GU T . Such mass scales arise in particle physics models with a gauge group that becomes strongly interacting at the GUT scale. We explore the particle physics basis for these models, focusing on technicolor and superstring theories, and work out a specific example based on the multiple gaugino condensation scenario in string/supergravity theory. We study the cosmological evolution of and constraints upon these models numerically and analytically. To obtain a sufficiently high post-inflation reheat temperature for baryosynthesis to occur we require f ∼ > 0.3M pl . The primordial density fluctuation spectrum generated by quantum fluctuations in φ is a non-scale-invariant power law, P (k) ∝ k n s , with n s ≃ 1 − (M 2 P l /8πf 2 ), leading to more power on large length scales than the n s = 1 Harrison-Zeldovich spectrum. We pay special attention to the prospects of using the enhanced power to explain the otherwise puzzling large-scale clustering of galaxies and clusters and their flows. We find that the standard cold dark matter model with 0 ∼ < n s ∼ < 0.6 could in principle explain this data. However, the microwave background anisotropies recently detected by COBE imply such low primordial amplitudes (that is, bias factors b 8 ∼ > 2) for these CDM models that galaxy formation would occur too late to be viable and the large-scale galaxy flows would be too small; when combined with COBE, these each lead to the constraint n s ∼ > 0.6, hence f > 0.3M P l , comparable to the bound from baryogenesis. For other inflation models which give rise to initial fluctuation spectra that are power laws through the 3 decades in wavelength During the inflationary epoch, the energy density of the universe is dominated by the (nearly constant) potential energy density V (φ) associated with a slowly rolling scalar field φ, the inflaton . To satisfy cosmic microwave background radiation (CMBR) anisotropy limits on the generation of density fluctuations, the potential of the inflaton must be very flat. Consequently, the field φ must be extremely weakly self-coupled, with effective quartic self-coupling constant satisfying λ φ < 10 −12 − 10 −14 in most models .
Journal of High Energy Physics, 2003
We consider some consequences of describing the gauge and matter degrees of freedom in our univer... more We consider some consequences of describing the gauge and matter degrees of freedom in our universe by open strings, as suggested by the braneworld scenario. We focus on the geometric effects described by the open string metric and investigate their observational implications. The causal structure of spacetime on the brane is altered; it is described not by the usual metric g µν , but instead by the open string metric,
Journal of High Energy Physics, 2011
We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Su... more We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos,
The Astrophysical Journal, 2008
Dark Stars are the very first phase of stellar evolution in the history of the universe: the firs... more Dark Stars are the very first phase of stellar evolution in the history of the universe: the first stars to form (typically at redshifts z ∼ 10 − 50) are powered by heating from dark matter (DM) annihilation instead of fusion (if the DM is made of particles which are their own antiparticles). We find equilibrium polytropic configurations for these stars; we start from the time DM heating becomes important (M ∼ 1 − 10 M ⊙ ) and build up the star via accretion up to 1000 M ⊙ . The dark stars, with an assumed particle mass of 100 GeV, are found to have luminosities of a few times 10 6 L ⊙ , surface temperatures of 4000-10,000 K, radii ∼ 10 14 cm, lifetimes of at least 0.5 Myr, and are predicted to show lines of atomic and molecular hydrogen. Dark stars look quite different from standard metal-free stars without DM heating: they are far more massive (e.g. ∼ 800M ⊙ for 100 GeV WIMPs), cooler, and larger, and can be distinguished in future observations, possibly even by JWST or TMT.
The Astrophysical Journal, 1985
Certain currently proposed weakly interacting elementary particles can have a high probability of... more Certain currently proposed weakly interacting elementary particles can have a high probability of solar capture if they make up the Galactic halo. Their present abundance in the Sun is here determined by balancing capture rates against annihilation rates. Both particle physics and cosmological considerations impose constraints on scattering and annihilation cross sections. In general, for the candidate particles here discussed
The Astrophysical Journal, 2000
We examine the chemical abundance constraints on a population of white dwarfs in the halo of our ... more We examine the chemical abundance constraints on a population of white dwarfs in the halo of our Galaxy. We are motivated by microlensing experiments that have reported evidence for massive compact halo objects (MACHOs) in the halo of our Galaxy, with an estimated mass of 0.1-1 Msolar the only conventional dark astrophysical candidates for objects in this mass range are
The Astrophysical Journal, 1999
If galactic halos contain stellar remnants, the infra-red flux from the remnant progenitors would... more If galactic halos contain stellar remnants, the infra-red flux from the remnant progenitors would contribute to the opacity of multi-TeV γ-rays. The multi-TeV γ-ray horizon is established to be at a redshift z > 0.034 by the observation of the blazar Mkn501 . By requiring that the optical depth due to γγ −→ e + e − be less than one for a source at z = 0.034 we limit the cosmological density of stellar remnants, Ω rm ≤ (2 − 4) × 10 −3 h −1