Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

The azimuthal correlation, $$\Delta \phi _{12}$$ Δ ϕ 12 , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ s = 13 TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ Δ ϕ 12 is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi $$ Δ ϕ 12 → π , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ α s , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ Δ ϕ 12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution.

Generalized Gibbs Phase Rule and Multicriticality Applied to Magnetic Systems

A generalization of the original Gibbs phase rule is proposed in order to study the presence of single phases, multiphase coexistence, and multicritical phenomena in lattice spin magnetic models. The rule is based on counting the thermodynamic number of degrees of freedom, which strongly depends on the external fields needed to break the ground state degeneracy of the model. The phase diagrams of some spin Hamiltonians are analyzed according to this general phase rule, including general spin Ising and Blume–Capel models, as well as q-state Potts models. It is shown that by properly taking into account the intensive fields of the model in study, the generalized Gibbs phase rule furnishes a good description of the possible topology of the corresponding phase diagram. Although this scheme is unfortunately not able to locate the phase boundaries, it is quite useful to at least provide a good description regarding the possible presence of critical and multicritical surfaces, as well as isolated multicritical points.

The Masses of Heavy Pentaquarks in Non-Relativistic Bethe-Salpeter Quark Model

The exotic particles such as the pentaquarks are to strengthen understanding of important interactions and the principle of QCD in which pentaquarks contain two heavy- valence quarks. The structure of two bodies including an antiquark and two-diquark is introduced. A new potential for quark interaction is suggested which includes the logarithm potential, the linear potential, and the spin-spin interaction. The suggested potential is included in the framework of spinless of Bethe-Salpeter equation. A comparison with other works is presented which provides a good description of pentaquarks.

NICER Study of Pulsed Thermal X-Rays from Calvera: A Neutron Star Born in the Galactic Halo?

Calvera (1RXS J141256.0+792204) is an isolated neutron star detected only through its thermal X-ray emission. Its location at high Galactic latitude (b = +37°) is unusual if Calvera is a relatively young pulsar, as suggested by its spin period (59 ms) and period derivative (3.2 × 10−15 s s−1). Using the Neutron Star Interior Composition Explorer, we obtained a phase-connected timing solution spanning four years, which allowed us to measure the second derivative of the frequency ν ̈ = − 2.5 × 10 − 23 Hz s−2 and to reveal timing noise consistent with that of normal radio pulsars. A magnetized hydrogen atmosphere model, covering the entire star surface, provides a good description of the phase-resolved spectra and energy-dependent pulsed fraction. However, we found that a temperature map more anisotropic than that produced by a dipole field is required, with a hotter zone concentrated toward the poles. By adding two small polar caps, we found that the surface effective temperature and that of the caps are ∼0.1 and ∼0.36 keV, respectively. The inferred distance is ∼3.3 kpc. We confirmed the presence of an absorption line at 0.7 keV associated with the emission from the whole star surface, difficult to interpret as a cyclotron feature and more likely originating from atomic transitions. We searched for pulsed γ-ray emission by folding seven years of Fermi-LAT data using the X-ray ephemeris, but no evidence for pulsations was found. Our results favor the hypothesis that Calvera is a normal rotation-powered pulsar, with the only peculiarity of being born at a large height above the Galactic disk.

Accurate prediction of the Drell-Yan φ∗ η distribution in wide dilepton mass and rapidity ranges in pp collisions through NNLO+N3LL

This paper presents high-accuracy predictions for the differential cross sections as a function of the key observable φ*η of the neutral-current Drell-Yan (DY) dilepton production in proton-proton (pp) collisions. The differential distributions for the φ*η are presented by using the state-of-the-art predictions from the combined calculations of fixed-order perturbative QCD corrections at next-to-next-to-leading order (NNLO) accuracy and resummation of large logarithmic terms at next-to-next-to-leading logarithmic (NNLL) and next-to-NNLL (N3LL) accuracies, i.e., NNLO+NNLL and NNLO+N3LL, respectively. The predicted distributions are reported for a thorough set of the DY dilepton invariant mass mll ranges, spanning a wide kinematic region of 50 < mll< 1000 GeV both near and away from the Z-boson mass peak, and rapidity yll ranges in the central detector acceptance region of |yll| < 2.4. The differential φ*η distributions in the wide mll and yll ranges offer stringent tests to assess the reliability of the predictions, where the mll and yll are closely correlated with the parton distribution functions (PDFs) of the incoming partons. The merged predictions through NNLO+N3LL are observed to provide good description of the 13 TeV pp collision data for the φ*η (including the dilepton transverse momentum pll T as well) distributions in almost the entire mll and yll ranges, apart from the intermediate- to high-φ*η region in the lowest mass range 50–76 GeV which is assessed to constitute a challenge for the presented predictions. The merged predictions at NNLO+N3LL are also reported at 14 TeV for the upcoming high-luminosity running era of the LHC, in which increasing amount of data is expected to require more accurate and precise theoretical description. The most recent PDF models MSHT20 and CT18 are tested for the first time in addition to the NNPDF3.1 exploiting the merged φ*η predictions.

Minimal Realism about ordinary objects

<p>In 2015 Daniel Korman published an incredibly important book called Objects: Nothing out of the ordinary, in which he defends a position known as conservatism about ordinary objects. He contrasts this position with two other positions – eliminativism and permissivism – and provides comprehensive arguments against these two positions. Korman takes eliminativism to be the view that ordinary objects do not exist. Even though this is indeed one of the claims eliminativists make, by itself it is not a good description of what eliminativism entails. For eliminativism, as ordinarily conceived, contains three main claims: i) the anti-realist claim that certain entities do not exist, ii) the claim that we are making an error when we assert that those entities do exist, and iii) the prescriptive claim that we should eliminate talking and thinking about those entities. These three claims together entail eliminativism. Korman, however, identifies eliminativism merely with the first anti-realist claim. Since Korman‟s focus is on the anti-realist claim, this thesis departs from Korman‟s tripartite division and instead frames the debate in terms of Minimal Realism and Minimal Anti-Realism about ordinary objects. Minimal Realism is simply the view that ordinary objects exist, and includes views such as conservatism and permissivism. Minimal Anti-Realism, by contrast, is the view that ordinary objects do not exist, such as eliminativism as Korman defines it. By refocussing the debate in terms of Minimal Realism and Minimal Anti-Realism, it becomes apparent that there are a variety of Minimal Realist positions which claim that ordinary objects do indeed exist, but which have been left out by Korman. My goal is to supplement Korman‟s arguments with literature published since the publication of his book, and to show how Minimal Realism responds to the arguments for eliminativism. In particular, I focus on the Debunking Argument, the Argument from Arbitrariness, the Overdetermination Argument, the Argument from Vagueness, the Argument from Material Constitution, and the Problem of the Many. After setting out these arguments, I discuss some recent objections, and show how Minimal Realism can respond to the proposed arguments and objections.</p>

Minimal Realism about ordinary objects

<p>In 2015 Daniel Korman published an incredibly important book called Objects: Nothing out of the ordinary, in which he defends a position known as conservatism about ordinary objects. He contrasts this position with two other positions – eliminativism and permissivism – and provides comprehensive arguments against these two positions. Korman takes eliminativism to be the view that ordinary objects do not exist. Even though this is indeed one of the claims eliminativists make, by itself it is not a good description of what eliminativism entails. For eliminativism, as ordinarily conceived, contains three main claims: i) the anti-realist claim that certain entities do not exist, ii) the claim that we are making an error when we assert that those entities do exist, and iii) the prescriptive claim that we should eliminate talking and thinking about those entities. These three claims together entail eliminativism. Korman, however, identifies eliminativism merely with the first anti-realist claim. Since Korman‟s focus is on the anti-realist claim, this thesis departs from Korman‟s tripartite division and instead frames the debate in terms of Minimal Realism and Minimal Anti-Realism about ordinary objects. Minimal Realism is simply the view that ordinary objects exist, and includes views such as conservatism and permissivism. Minimal Anti-Realism, by contrast, is the view that ordinary objects do not exist, such as eliminativism as Korman defines it. By refocussing the debate in terms of Minimal Realism and Minimal Anti-Realism, it becomes apparent that there are a variety of Minimal Realist positions which claim that ordinary objects do indeed exist, but which have been left out by Korman. My goal is to supplement Korman‟s arguments with literature published since the publication of his book, and to show how Minimal Realism responds to the arguments for eliminativism. In particular, I focus on the Debunking Argument, the Argument from Arbitrariness, the Overdetermination Argument, the Argument from Vagueness, the Argument from Material Constitution, and the Problem of the Many. After setting out these arguments, I discuss some recent objections, and show how Minimal Realism can respond to the proposed arguments and objections.</p>

Quantum Many-Body Theory

<p>This thesis is a collection of theoretical investigations into different aspects of the broad subject of quantum many-body theory. The results are grouped into three main parts, which in turn are divided into separate self-contained sections. Some of the work is presented in the form of published papers and papers that have been submitted for publication. The first section of Part A introduces some of the concepts involved in many-body problems, by developing methods to evaluate expectation values of the form . In the rest of Part A I consider collective excitations of finite quantum systems. The calculations are confined to nuclei because the results can then be compared with the extensive investigations that have been made into collective nuclear modes. In Section AII, wavefunctions are proposed for rotational excitations of even-even nuclei. Both isoscalar and isovector nuclear modes are discussed. In particular, the l2,m> isoscalar states are investigated for both spherical and deformed even-even nuclei, and the simplest isovector wavefunction is shown to give a good description of the giant dipole resonance. In section AIII wavefunctions are proposed for compressional vibrational states of spherical nuclei. Section AIV discusses sum rules for nuclear transitions of a given electric multipolarity. It is found that the 2+ and 1- states investigated in section AII and all but one of the vibrational states discussed in AIII each exhaust a large part of the appropriate sum rule. In Part B I consider the problem of how to describe flow in quantum fluids. In particular, we want to be able to identify the physical motion represented by any given many-body wavefunction. Section BI derives a guantum mechanical velocity field for a many-body system, paying special attention to the need for a quantum continuity equation. It is found that when the wavefunction has the usual time dependence e-iwt , that the quantum velocity formula averages over all oscillatory motion, so that much of the physical nature of the flow field is lost. In section BII a particular wavefunction is proposed to represent the quantum excitation corresponding to any given potential flow field. The results obtained by considering specific examples are very encouraging. In Part C I investigate the properties of surfaces. Section CI presents a theoretical description of the tension, energy and thickness of a classical liquid-vapour interface. In section CII the classical results are extended to describe the surface of a quantum system, namely superfluid helium four. Problems occur for the quantum system if the correlations arising from the zero-point-motion of the phonon modes are included in the ground state wavefunction. Finally, in section CIII discuss generalized virial theorems that give the change in the free energy of a system undergoing an infinitesimal deformation. For example, a particular deformation gives the expression used in CII, for the surface tension of a plane quantum surface.</p>

Quantum Many-Body Theory

<p>This thesis is a collection of theoretical investigations into different aspects of the broad subject of quantum many-body theory. The results are grouped into three main parts, which in turn are divided into separate self-contained sections. Some of the work is presented in the form of published papers and papers that have been submitted for publication. The first section of Part A introduces some of the concepts involved in many-body problems, by developing methods to evaluate expectation values of the form . In the rest of Part A I consider collective excitations of finite quantum systems. The calculations are confined to nuclei because the results can then be compared with the extensive investigations that have been made into collective nuclear modes. In Section AII, wavefunctions are proposed for rotational excitations of even-even nuclei. Both isoscalar and isovector nuclear modes are discussed. In particular, the l2,m> isoscalar states are investigated for both spherical and deformed even-even nuclei, and the simplest isovector wavefunction is shown to give a good description of the giant dipole resonance. In section AIII wavefunctions are proposed for compressional vibrational states of spherical nuclei. Section AIV discusses sum rules for nuclear transitions of a given electric multipolarity. It is found that the 2+ and 1- states investigated in section AII and all but one of the vibrational states discussed in AIII each exhaust a large part of the appropriate sum rule. In Part B I consider the problem of how to describe flow in quantum fluids. In particular, we want to be able to identify the physical motion represented by any given many-body wavefunction. Section BI derives a guantum mechanical velocity field for a many-body system, paying special attention to the need for a quantum continuity equation. It is found that when the wavefunction has the usual time dependence e-iwt , that the quantum velocity formula averages over all oscillatory motion, so that much of the physical nature of the flow field is lost. In section BII a particular wavefunction is proposed to represent the quantum excitation corresponding to any given potential flow field. The results obtained by considering specific examples are very encouraging. In Part C I investigate the properties of surfaces. Section CI presents a theoretical description of the tension, energy and thickness of a classical liquid-vapour interface. In section CII the classical results are extended to describe the surface of a quantum system, namely superfluid helium four. Problems occur for the quantum system if the correlations arising from the zero-point-motion of the phonon modes are included in the ground state wavefunction. Finally, in section CIII discuss generalized virial theorems that give the change in the free energy of a system undergoing an infinitesimal deformation. For example, a particular deformation gives the expression used in CII, for the surface tension of a plane quantum surface.</p>

Minimal-active-space multistate density functional theory for excitation energy involving local and charge transfer states

Multistate density functional theory (MSDFT) employing a minimum active space (MAS) is presented to determine charge transfer (CT) and local excited states of bimolecular complexes. MSDFT is a hybrid wave function theory (WFT) and density functional theory, in which dynamic correlation is first incorporated in individual determinant configurations using a Kohn–Sham exchange-correlation functional. Then, nonorthogonal configuration-state interaction is performed to treat static correlation. Because molecular orbitals are optimized separately for each determinant by including Kohn–Sham dynamic correlation, a minimal number of configurations in the active space, essential to representing low-lying excited and CT states of interest, is sufficient to yield the adiabatic states. We found that the present MAS-MSDFT method provides a good description of covalent and CT excited states in comparison with experiments and high-level computational results. Because of the simplicity and interpretive capability through diabatic configuration weights, the method may be useful in dynamic simulations of CT and nonadiabatic processes.