Paulo Bedaque | University of Maryland (original) (raw)
Papers by Paulo Bedaque
Physical Review C, 2015
Neutron matter at densities of the order of the nuclear saturation density is believed to have ne... more Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3 P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking of rotational symmetry as well as three other, gapped modes. We compute their masses at arbitrary temperatures.
We show that ions at the low densities and high magnetic fields relevant to the outer crust of ma... more We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longerranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field strength, different lattice structures (fcc, hcp or bcc oriented in different ways in relation to the magnetic field) are favored.
Physical Review C, 2015
Neutron matter at densities of the order of the nuclear saturation density is believed to have ne... more Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3 P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking of rotational symmetry as well as three other, gapped modes. We compute their masses at arbitrary temperatures.
Nuclear Physics A
In this work we outline a program for lattice QCD that would provide a first step toward understa... more In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Λ's, and Σ's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P −wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Lüscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for ΛN scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone, appropriate for lattice calculations, is constructed.
We show that in the limit of large and positive atom-atom scattering length the properties of an ... more We show that in the limit of large and positive atom-atom scattering length the properties of an atomic-molecular Bose-Einstein Condensate (amBEC) are determined by an universal energy density functional (EDF). We find that the optimal conditions for the formation of a stable amBEC are in the regime where there are no shallow trimers and the atomdimer scattering length is negative and comparable in magnitude with the atom-atom scattering length. At temperatures lower than Tc the chemical potentials for the atoms and molecules can be specified independently. Besides three-body recombinations processes into dimers of large size, inelastic processes involving the formation of deeply bound small size molecular states are possible. These inelastic processes do not lead to an efficient heating of the amBEC and can be used for its mostly non-destructive monitoring.
The exponentially decreasing signal to noise ratio in multibaryon correlators is the main obstacl... more The exponentially decreasing signal to noise ratio in multibaryon correlators is the main obstacle to a first principles, QCD-based calculation of the nuclear force. Recently, we have proposed an orbifold boundary condition ("restless pions") that can dramatically improve this matter. Here we develop the idea further by proposing an explicit algorithm that can be used with purely periodic, "off the shelf" gauge configurations. We also discuss finite volume corrections with the new boundary conditions and the use of the "Lüscher formula" for the phase shifts.
We review the recent advances in the calculation of the forces between hadron using lattice QCD. ... more We review the recent advances in the calculation of the forces between hadron using lattice QCD. Particular attention is payed to the case of nuclear forces. The issues facing this project and some of the ideas put forward to solve them are briefly discussed.
We show that a dilute atomic Fermi system at sufficiently low temperatures, can display fermionic... more We show that a dilute atomic Fermi system at sufficiently low temperatures, can display fermionic superfluidity, even in the case of a repulsive atom-atom interaction, when the scattering length is positive. The attraction leading to the formation of Cooper pairs is provided by the exchange of Bogoliubov phonons if a fraction of the atoms form a BEC of weakly bound
Physical review letters, Jan 23, 2015
It has been conjectured that the velocity of sound in any medium is smaller than the velocity of ... more It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by sqrt[3]. Simple arguments support this bound in nonrelativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.
We show that ions at the low densities and high magnetic fields relevant to the outer crust of ma... more We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longerranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field strength, different lattice structures (fcc, hcp or bcc oriented in different ways in relation to the magnetic field) are favored.
The possibility that ions in a helium white dwarf star are in a Bose-Einstein condensed state has... more The possibility that ions in a helium white dwarf star are in a Bose-Einstein condensed state has been explored recently. In particular, it has been argued that the resulting novel quantum liquid has a new kind of quasiparticle excitation with a phonon-like dispersion relation. We investigate the neutrino emission rate due to this gapless state and the resulting impact on the total luminosity of helium white dwarf stars, as a possible observable way of detecting this exotic phase. If the condensation temperature for the quantum liquid state, which is currently not known very precisely, turns out to be high enough, our calculations indicate that neutrino emission due to the gapless mode would make a large contribution to the total luminosity of the helium white dwarf stars.
Physical Review A, 2001
We show that a central 1/r n singular potential (with n ≥ 2) is renormalized by a one-parameter s... more We show that a central 1/r n singular potential (with n ≥ 2) is renormalized by a one-parameter square-well counterterm; low-energy observables are made independent of the square-well width by adjusting the square-well strength. We find a closed form expression for the renormalization-group evolution of the square-well counterterm.
Physical Review Letters, 1999
We discuss renormalization of the non-relativistic threebody problem with short-range forces. The... more We discuss renormalization of the non-relativistic threebody problem with short-range forces. The problem becomes non-perturbative at momenta of the order of the inverse of the two-body scattering length, and an infinite number of graphs must be summed. This summation leads to a cutoff dependence that does not appear in any order in perturbation theory. We argue that this cutoff dependence can be absorbed in a single three-body counterterm and compute the running of the three-body force with the cutoff. We comment on relevance of this result for the effective field theory program in nuclear and molecular physics.
Physical Review D, 2007
We compute the ratio of pseudoscalar decay constants f K /f π using domain-wall valence quarks an... more We compute the ratio of pseudoscalar decay constants f K /f π using domain-wall valence quarks and rooted improved Kogut-Susskind sea quarks. By employing continuum chiral perturbation theory, we extract the Gasser-Leutwyler low-energy constant L 5 , and extrapolate f K /f π to the physical point. We find: f K /f π = 1.218 ± 0.002 +0.011 −0.024 where the first error is statistical and the second error is an estimate of the systematic due to chiral extrapolation and fitting procedures. This value agrees within the uncertainties with the determination by the MILC collaboration, calculated using Kogut-Susskind valence quarks, indicating that systematic errors arising from the choice of lattice valence quark are small.
Nuclear Physics A, 2000
We apply the effective field theory approach to the three-nucleon system. In particular, we consi... more We apply the effective field theory approach to the three-nucleon system. In particular, we consider S = 1/2 neutron-deuteron scattering and the triton. We show that in this channel a unique nonperturbative renormalization takes place which requires the introduction of a single three-body force at leading order. With one fitted parameter we find a good description of low-energy data. Invariance under the renormalization group explains some universal features of the three-nucleon system -such as the Thomas and Efimov effects and the Phillips line-and the origin of SU (4) symmetry in nuclei.
Handbook of QCD(In 3 Volumes), 2001
Physical Review C, 2015
Neutron matter at densities of the order of the nuclear saturation density is believed to have ne... more Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3 P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking of rotational symmetry as well as three other, gapped modes. We compute their masses at arbitrary temperatures.
We show that ions at the low densities and high magnetic fields relevant to the outer crust of ma... more We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longerranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field strength, different lattice structures (fcc, hcp or bcc oriented in different ways in relation to the magnetic field) are favored.
Physical Review C, 2015
Neutron matter at densities of the order of the nuclear saturation density is believed to have ne... more Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3 P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking of rotational symmetry as well as three other, gapped modes. We compute their masses at arbitrary temperatures.
Nuclear Physics A
In this work we outline a program for lattice QCD that would provide a first step toward understa... more In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Λ's, and Σ's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P −wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Lüscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for ΛN scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone, appropriate for lattice calculations, is constructed.
We show that in the limit of large and positive atom-atom scattering length the properties of an ... more We show that in the limit of large and positive atom-atom scattering length the properties of an atomic-molecular Bose-Einstein Condensate (amBEC) are determined by an universal energy density functional (EDF). We find that the optimal conditions for the formation of a stable amBEC are in the regime where there are no shallow trimers and the atomdimer scattering length is negative and comparable in magnitude with the atom-atom scattering length. At temperatures lower than Tc the chemical potentials for the atoms and molecules can be specified independently. Besides three-body recombinations processes into dimers of large size, inelastic processes involving the formation of deeply bound small size molecular states are possible. These inelastic processes do not lead to an efficient heating of the amBEC and can be used for its mostly non-destructive monitoring.
The exponentially decreasing signal to noise ratio in multibaryon correlators is the main obstacl... more The exponentially decreasing signal to noise ratio in multibaryon correlators is the main obstacle to a first principles, QCD-based calculation of the nuclear force. Recently, we have proposed an orbifold boundary condition ("restless pions") that can dramatically improve this matter. Here we develop the idea further by proposing an explicit algorithm that can be used with purely periodic, "off the shelf" gauge configurations. We also discuss finite volume corrections with the new boundary conditions and the use of the "Lüscher formula" for the phase shifts.
We review the recent advances in the calculation of the forces between hadron using lattice QCD. ... more We review the recent advances in the calculation of the forces between hadron using lattice QCD. Particular attention is payed to the case of nuclear forces. The issues facing this project and some of the ideas put forward to solve them are briefly discussed.
We show that a dilute atomic Fermi system at sufficiently low temperatures, can display fermionic... more We show that a dilute atomic Fermi system at sufficiently low temperatures, can display fermionic superfluidity, even in the case of a repulsive atom-atom interaction, when the scattering length is positive. The attraction leading to the formation of Cooper pairs is provided by the exchange of Bogoliubov phonons if a fraction of the atoms form a BEC of weakly bound
Physical review letters, Jan 23, 2015
It has been conjectured that the velocity of sound in any medium is smaller than the velocity of ... more It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by sqrt[3]. Simple arguments support this bound in nonrelativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.
We show that ions at the low densities and high magnetic fields relevant to the outer crust of ma... more We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longerranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field strength, different lattice structures (fcc, hcp or bcc oriented in different ways in relation to the magnetic field) are favored.
The possibility that ions in a helium white dwarf star are in a Bose-Einstein condensed state has... more The possibility that ions in a helium white dwarf star are in a Bose-Einstein condensed state has been explored recently. In particular, it has been argued that the resulting novel quantum liquid has a new kind of quasiparticle excitation with a phonon-like dispersion relation. We investigate the neutrino emission rate due to this gapless state and the resulting impact on the total luminosity of helium white dwarf stars, as a possible observable way of detecting this exotic phase. If the condensation temperature for the quantum liquid state, which is currently not known very precisely, turns out to be high enough, our calculations indicate that neutrino emission due to the gapless mode would make a large contribution to the total luminosity of the helium white dwarf stars.
Physical Review A, 2001
We show that a central 1/r n singular potential (with n ≥ 2) is renormalized by a one-parameter s... more We show that a central 1/r n singular potential (with n ≥ 2) is renormalized by a one-parameter square-well counterterm; low-energy observables are made independent of the square-well width by adjusting the square-well strength. We find a closed form expression for the renormalization-group evolution of the square-well counterterm.
Physical Review Letters, 1999
We discuss renormalization of the non-relativistic threebody problem with short-range forces. The... more We discuss renormalization of the non-relativistic threebody problem with short-range forces. The problem becomes non-perturbative at momenta of the order of the inverse of the two-body scattering length, and an infinite number of graphs must be summed. This summation leads to a cutoff dependence that does not appear in any order in perturbation theory. We argue that this cutoff dependence can be absorbed in a single three-body counterterm and compute the running of the three-body force with the cutoff. We comment on relevance of this result for the effective field theory program in nuclear and molecular physics.
Physical Review D, 2007
We compute the ratio of pseudoscalar decay constants f K /f π using domain-wall valence quarks an... more We compute the ratio of pseudoscalar decay constants f K /f π using domain-wall valence quarks and rooted improved Kogut-Susskind sea quarks. By employing continuum chiral perturbation theory, we extract the Gasser-Leutwyler low-energy constant L 5 , and extrapolate f K /f π to the physical point. We find: f K /f π = 1.218 ± 0.002 +0.011 −0.024 where the first error is statistical and the second error is an estimate of the systematic due to chiral extrapolation and fitting procedures. This value agrees within the uncertainties with the determination by the MILC collaboration, calculated using Kogut-Susskind valence quarks, indicating that systematic errors arising from the choice of lattice valence quark are small.
Nuclear Physics A, 2000
We apply the effective field theory approach to the three-nucleon system. In particular, we consi... more We apply the effective field theory approach to the three-nucleon system. In particular, we consider S = 1/2 neutron-deuteron scattering and the triton. We show that in this channel a unique nonperturbative renormalization takes place which requires the introduction of a single three-body force at leading order. With one fitted parameter we find a good description of low-energy data. Invariance under the renormalization group explains some universal features of the three-nucleon system -such as the Thomas and Efimov effects and the Phillips line-and the origin of SU (4) symmetry in nuclei.
Handbook of QCD(In 3 Volumes), 2001