Asymptotic critical behavior of holographic superconductor phase transition — the spectrum of excited states becomes continuous at T = 0

A multidimensional least-squares analysis of transient Raman data acquired during a single laser pulse is used to resolve the spectra of excited-state species from the spectra of ground-state and solvent species. The kinetics of optical excitation produce a higher order dependence on laser intensity for Raman spectra of the excited states. In the absence of saturation of the ground- or excited-state populations, the excited-state spectrum increases quadratically with laser intensity. In cases where excited states cause significant absorption of the excitation source, the scattering from a solvent band may be used as an in situ intensity reference to correct the measured laser energies for the analysis. Saturation of excited-state populations causes deviations from the sample quadratic dependence of Raman intensities on laser energy. Least-squares regression analysis with a model describing the saturation kinetics allows the spectrum of the excited state to be resolved. The method is introduced in this work and applied to the detection of the Raman spectrum of benzophenone excited triplet states. A kinetic model describing the loss of triplet states through dissociation of upper triplet states of benzophenone produced during the laser pulse explains the results observed with 316 nm excitation

We study thermodynamics of charged AdS black hole surrounded by quintessence in a new formalism which is called the restricted phase space thermodynamics. This context is based on Visser’s holographic thermodynamics with a fixed anti-de Sitter radius and a variable Newton constant. The conjugate variables, central charge C and the chemical potential μ, are introduced as a new pair of thermodynamic variables. We find that the iso-e-charge T–S curve becomes non-monotonic when Q ^ < Q ^ c . Correspondingly, the F–T curve exhibits a swallow tail structure. This behavior is considered as a van der Waals-like phase transition. As the value of b ^ related to the energy density of Kiselev’s fluid becomes larger, the critical temperature T c will decrease. Thus, the van der Waals-like phase transition will occur at lower temperature. There is always a non-quilibrium transition from a small unstable black hole to a large stable black hole state in the isocoltage T–S process. There exist a maximum and a Hawking–Page phase transition points in the μ–C plane. As the value of b ^ related to Kiselev’s fluid becomes larger, the Hawking–Page phase transition will occur at lower temperature in the isovoltage μ–T process. For other values of the state parameter ω, there also exists van der Waals-like phase transition.

Allophycocyanin (APC) is a light-harvesting protein found in cyanobacteria and red algae. APC along with other phycobiliproteins such as phycocyanin (PC) and phycoerythrin (PE) constitutes phycobilisome and plays an important role in collecting light and cascading the excitation energy into a reaction center where the light energy is converted into chemical potential. Thus it is important to understand how excitation energy is transferred between the phycobiliproteins and inside them. APC is a trimer of αβ subunit, each of which contains a linear tetrapyrrole chromophore, phycocyanobilin (PCB), covalently bound to a cystein residue (Fig. 1). Close proximity (~20 A) between α-84 and nearby β-84 in APC can cause the electronic states of the chromophores to interact to form split exciton states. In this case, interexciton dynamics mediates the energy transfer. On the other hand, it is also possible that energy transfer from α-84 to β-84 occurs via dipole-dipole coupling between the two chromophores (Forster model). The intermediate range of distance between the PCBs in APC makes both models quite feasible for an energy transfer mechanism and has generated much controversy. Here we report on the excited state dynamics of APC measured by femtosecond stimulated Raman spectroscopy. Femtosecond stimulated Raman spectroscopy (FSRS) reveals the structure of fast-evolving molecules by providing vibrational spectra with excellent spectral resolution on a femtosecond time scale. We prepare the electronic excited state of APC by 40 nJ, 30 fs actinic pump pulse at 1 kHz, centered at 610 nm. The femtosecond stimulated Raman spectra of the excited state APC are obtained at a series of time delays by coupling 0.5 μJ/pulse, 2 ps, 800 nm Raman pump pulse and 4 nJ/pulse, 20 fs, broadband continuum Raman probe pulse. The detailed description of the detection system and how to generate the laser pulses has been published elsewhere. APC was isolated from the filamentous cyanobacterium Anabaena variabilis and used in phosphate buffer solution. Figure 2 presents the FSRS spectra of the ground state and the excited state APC at selected time delays. The excited state spectra were obtained by subtracting the spectra of buffer solution and the ground state APC which accounts for the unexcited 85% of APC. The ground state FSRS spectrum is in excellent agreement with the resonance Raman spectra previously reported at UV wavelengths. The excited state spectra show broad and dispersive features without any well-defined peaks. The amplitude of the dispersive features increases up to ~80 fs and decreases gradually, completely gone by 5 ps (not shown). McCamant et al. found that dispersive lineshapes appear when the Raman pump and probe pulses drive resonant stimulated emission from the excited state and create vibrational coherence on the electronic ground state surface, which they termed the Raman initiated by nonlinear emission (RINE). The RINE spectra contain the information on the vibrational frequencies of the electronic ground state whose dynamics is determined by the evolution of the excited state population. From this model, McCamant et al. successfully extracted the vibrational spectra of the ground state bacteriorhodopsin, which evolve with the population changes in the excited state. Adopting a similar method described in ref. 14, we fit the excited state FSRS spectra of APC to the RINE model. From

The excited singlet state absorption spectrum of 1,4-diphenylnaphthalene

A strong S1−S2 vibronic coupling effect is observed in the time-resolved coherent anti-Stokes Raman spectroscopy (CARS) spectra originating from the first excited singlet state of diphenylhexatriene. As determined from picosecond CARS measurements, the excited state spectrum appears on a subpicosecond time scale. An extremely high excited state hyperpolarizability |γ|excited state ≅ 3 ×10-31 is derived from a CARS line shape analysis and is attributed to the increased delocalization after excitation in accordance with semiempirical calculations of bond lengths. We observe two strongly frequency-broadened vibrations being upshifted with respect to the CC double bond stretching region of the ground state and assign them to the totally symmetric CC stretching motion of the chain. Both frequencies depend on the solvent polarizability, giving evidence of strong S1−S2 vibronic coupling in the lowest excited singlet states. We discuss a model of S1−S2 vibronic coupling via an asymmetric low frequency mode. According to this model a double-well potential for the respective vibrational coordinate is generated in the first excited singlet state, resulting in two frequencies originating from the same type of vibration.

In this paper, we extend the study of the relationship between the photon sphere and the thermodynamic phase transition, especially the reentrant phase transition, to this black hole background. According to the number of the thermodynamic critical points, the black hole systems are divided into four cases with different values of Born-Infeld parameter b, where the black hole systems can have no phase transition, reentrant phase transition, or Van der Waals-like phase transition. For these different cases, we obtain the corresponding phase structures in pressure-temperature diagram and temperature-specific volume diagram. The tiny differences between these cases are clearly displayed. On the other hand, the radius rps and the minimal impact parameter ups of the photon sphere are calculated via the effective potential of the radial motion of photons. For different cases, rps and ups are found to have different behaviors. In particular, with the increase of rps or ups, the temperature possesses a decrease-increase-decrease-increase behavior for fixed pressure if there exists the reentrant phase transition. While for fixed temperature, the pressure will show an increase-decrease-increase-decrease behavior instead. These behaviors are quite different from that of the Van der Waals-like phase transition. Near the critical point, the changes of rps and ups among the black hole phase transition confirm an universal critical exponent 12. Therefore, all the results indicate that, for the charged Born-Infeld-AdS black holes, not only the Van der Waals-like phase transition, but also the reentrant phase transition can be reflected through the photon sphere.

With motivation by holography, employing black hole entropy, two-point connection function and entanglement entropy, we show that, for the higher-dimensional Anti-de Sitter charged hairy black hole in the fixed charged ensemble, a Van der Waals-like phase transition can be observed. Furthermore, based on the Maxwell equal-area construction, we check numerically the equal-area law for a first order phase transition in order to further characterize the Van der Waals-like phase transition.

The ultrafast structural changes during the photoinduced isomerization of the retinal-protonated Schiff base (RPSB) is still a poorly understood aspect in the retinal's photochemistry. In this work, we apply pump-degenerate four-wave mixing (pump-DFWM) to all- trans retinal (ATR) and retinal Schiff bases (RSB) to resolve coherent high- and low-frequency vibrational signatures from excited electronic states. We show that the vibrational spectra of excited singlet states in these samples exhibit pronounced differences compared to the relaxed ground state. Pump-DFWM results indicate three major features for ATR and RSB. (i) Excited state vibrational spectra of ATR and RSB consist predominately of low-frequency modes in the energetic range 100-500 cm-1. (ii) Excited state vibrational spectra show distinct differences for excitation in specific regions of electronic transitions of excited state absorption and emission. (iii) Low-frequency modes in ATR and RSB are inducible during the entire lifetime of the excited electronic states. This latter effect points to a transient molecular structure that, following initial relaxation between different excited electronic states, does not change anymore over the lifetime of the finally populated excited electronic state.

We report the first optical dephasing study of an inorganic impurity system possessing sharp, low frequency mode structure in its ground and excited state spectra. The total dephasing times T2 and population relaxation times T1 for the 1T2g and 1Eg d9s excited states of NaF:Cu+ are determined at a series of temperatures between 1.8 and 296 K. The T2 values are determined by extracting the Lorentzian components from one- and two-photon excitation line shapes. The T1 values caused by nonradiative decay rates are obtained by detecting very low quantum yield emission from the fast-relaxing excited states and applying the formula tnr=Qtr, where t’s are radiative and nonradiative lifetimes and Q is the quantum yield. T1(1T2g)=4.6 ps and T1(1Eg )=2.0 ps at 8 K. Significantly, these are very similar to the T1 values calculated from lowest temperature Lorentzian linewidths by the relationship 1/T2=1/T′2 +1/(2T1). The T1 values stay approximately constant over the temperature range 1.8–45 K, while the linewidths rapidly increase indicating that pure dephasing dominates. Using ground and excited state information on the low frequency modes, we test optical Redfield theory and the nonperturbative harmonic theory for pure dephasing by pseudolocal phonons against data for this system which displays strongly anhamonic progressions. The nonperturbative theory fits the line broadening data to higher temperatures than optical Redfield theory for the least anharmonic excited state potential, 1T2g. Both theories underpredict the broadening with temperature of the extremely anharmonic 1Eg state. A simple anharmonic theory including scattering to overtone levels also fails to predict the observed linewidth temperature behavior, although it is demonstrated these processes should be occurring.

Two-flavor QCD at finite temperature and chemical potential in a functional approach

In characterizing the chiral phase-structure of pseudoscalar ( ), scalar ( ), vector ( ) and axial-vector ( t) meson states and their dependence on temperature, chemical potential, and magnetic field, we utilize the SU(3) Polyakov linear-sigma model (PLSM) in the mean-field approximation. We first determine the chiral (non)strange quark condensates, and , and the corresponding deconfinement order parameters, and , in thermal and dense (finite chemical potential) medium and finite magnetic field. The temperature and the chemical potential characteristics of nonet meson states normalized to the lowest bosonic Matsubara frequency are analyzed. We note that all normalized meson masses become temperature independent at different critical temperatures. We observe that the chiral and deconfinement phase transitions are shifted to lower quasicritical temperatures with increasing chemical potential and magnetic field. Thus, we conclude that the magnetic field seems to have almost the same effect as the chemical potential, especially on accelerating the phase transition, i.e. inverse magnetic catalysis. We also find that increasing the chemical potential enhances the mass degeneracy of the various meson masses, while increasing the magnetic field seems to reduce the critical chemical potential, at which the chiral phase transition takes place. Our mass spectrum calculations agree well with the recent PDG compilations and PNJL, lattice QCD calculations, and QMD/UrQMD simulations.

We have considered the interference spectra arising from the competition between a spontaneous process and one induced by a laser field in a two-level atom. Expressions for the spectral functions have been derived describing the spectra of the excited and ground states of the atom in the low- and high-intensity limit of the laser field. For the excited-state spectra in the low-intensity limit, the frequency profiles of the two peaks, which arise from the spontaneous and the induced processes, cancel each other out completely near the center of the line, while for the ground state the induced process dominates. For finite values of the detuning, the spectra of the excited state consist of two peaks, which have positive and negative frequency profiles, respectively. The computed spectra have been graphically presented and discussed. In the high-intensity limit, the dynamic Stark effect dominates the spectra of the excited and ground states of the atom. Expressions for the correlation functions have been derived that describe the emission or the absorption of a laser photon at two different times. The derived expressions for the corresponding delay functions in the low- and high-intensity limits have been found to be identical to those recently proposed in the literature. The laser field has been treated as a classical as well as a quantized entity.

In our everyday lives, we experience three spatial dimensions and a fourth dimension of time. Neverthe-less, several intricate problems of modern physics may be mastered with the introduction of additional dimensions, including the hierarchy problem and the unification of the fundamental forces. Furthermore, dualities between certain strongly coupled quantum field theories and particular gravitational theories in higher dimensions were conjectured based on string theory, which generically comes with the premise of extra dimensions. Specifically, the AdS/CFT correspondence or rather gauge/gravity duality motivated the study of a wide variety of higher dimensional gravitational theories with additional matter. The first part of this thesis covers the numerical construction of localized black holes in five, six and ten dimensional Kaluza-Klein theories. We focus on static, asymptotically flat vacuum solutions of Einsteins field equations with one periodic compact dimension. Our study concentrates on the critical regime, where the poles of the localized black holes are about to merge. We utilize a well adapted multi-domain pseudo-spectral scheme for obtaining high accuracy results and investigate the phase diagram of the localized solutions far beyond previous results. A spiral phase space structure is found for the five and six dimensional setups which matches to the results that were recently obtained for non-uniform black strings. On the contrary, the phase space structure of the ten dimensional configuration exhibits no spiraling behavior of the thermodynamical quantities. These critical exponents were extracted from the numerical data of the aforementioned configurations and show an excellent agreement with the theoretical predictions. In the second part of this thesis, the AdS/CFT correspondence is employed for studying strongly coupled Weyl semimetals. More concretely, we numerically investigate the effects of inhomogenities within a holographic Weyl semimetal by using a pseudo-spectral scheme, including interfaces of Weyl semimetals and the impact of time independent disorder. When studying interfaces between differentWeyl semimetal phases, we observe the appearance of an electric current, that is restricted to the interface in the presence of an electric chemical potential. The related integrated current is universal in the sense that it only depends on the topology of the phases. These results may shed some light on anomalous transport for inhomogeneous magnetic fields. As another point, we study the effects of time independent one-dimensional disorder on the holographic Weyl semimetal quantum phase transition (QPT), with a particular focus on the quantum critical region. We observe the smearing of the sharp QPT linked to the appearance of rare regions where the order parameter is locally non-zero. We discuss the role of the disorder correlation and we compare our results to expectations from condensed matter theory at weak coupling. We also analyze the interplay of finite temperature and disorder.

As a model system for the photoinduced/photoswitched spin alignment in a purely organic pi-conjugated spin system, 9-[4-(4,4,5,5-tetramethyl-1-yloxyimidazolin-2-yl)phenyl]anthracene (1a), 9-[3-(4,4,5,5-tetramethyl-1-yloxyimidazolin-2-yl)phenyl]anthracene (1b), 9,10-bis[4-(4,4,5,5-tetramethyl-1-yloxyimidazolin-2-yl)phenyl]anthracene (2a), and 9,10-bis[3-(4,4,5,5-tetramethyl-1-yloxyimidazolin-2-yl)phenyl]anthracene (2b) were designed and synthesized. In these spin systems, 9-phenylanthracene and 9,10-diphenylanthracene were chosen as photo spin couplers and iminonitroxide was chosen as a dangling stable radical. Time-resolved electron spin resonance (TRESR) spectra of the first excited states with resolved fine-structure splittings were observed for 1a and 2a in an EPA or a 2-MTHF rigid glass matrix. Using the spectral simulation based on the eigenfield method, the observed TRESR spectra for 1a and 2a were unambiguously assigned as an excited quartet (S = 3/2) spin state (Q) and an excited quintet (S = 2) spin state (Qu), respectively. The g value and fine-structure splitting for the quartet state of 1a were determined to be g(Q) = 2.0043, D(Q) = 0.0235 cm(-1), and E(Q) = 0.0 cm(-1). The relative populations (polarization) of each M(S)() sublevel in Q were determined to be P(+1/2') = P(-1/2') = 0.5 and P(+3/2') = P(-3/2') = 0.0 with an increasing order of energy in zero magnetic field. The spin Hamiltonian parameters for Qu are g = 2.0043, D = 0.0130 cm(-1), and E = 0.0 cm(-1), and the relative populations in Qu were determined to be P(0') = 0.30, P(-1') = P(+1') = 0.35 and P(-2') = P(+2') = 0.0. These are the first observations of a photoexcited quartet and a quintet high-spin state in pi-conjugated triplet-radical pair systems. In contrast high-spin excited states were not observed for 1b and 2b, the pi-topological isomers of 1a and 2a, showing the role of pi-topology in the spin alignment of the excited states. Since a weak antiferromagnetic exchange interaction was observed in the ground state of 2a, the clear detection of the excited quintet high-spin state shows that the effective exchange coupling between the two dangling radicals through the diphenylanthracene spin coupler has been changed from antiferromagnetic to ferromagnetic upon photoexcitation. Thus, a photoinduced spin alignment utilizing the excited triplet molecular field was realized for the first time in the purely organic pi-conjugated spin system. Furthermore, the mechanism for the generation of dynamic electron spin polarization was investigated for the observed quartet and quintet states, and a plausible mechanism of the enhanced selective intersystem crossing was proposed. Ab initio molecular orbital calculations based on density functional theory were carried out to determine the electronic structures of the excited high-spin states and to understand the mechanism of the spin alignment utilizing the excited molecular field. The role of the spin delocalization and the spin polarization mechanisms were revealed on the photoexcited state.

We investigate the spectrum of excited electronic states of various systems by a combination of three ab-initio techniques: density-functional theory, GW quasiparticle calculations, and the Bethe-Salpeter equation for coupled electronhole excited states. Results for three different materials are discussed: the optical spectrum of quartz, the optical response of the Ge(111)-(2×1) surface, and excited states of methane. The particular focus is on the interrelation of the excitations with the atomic geometry. In the case of Ge(111)-(2×l), the calculated spectra allow to distinguish between two nearly isoenergetic isomers of the surface. In the case of methane, it is shown that the geometry changes drastically during the transition from the ground state to the excited state.